WATER PROOFING WORK



  DAMP-PROOFING AND WATER-PROOFING WORK

10.1 General

10.1.1 Damp proofing of basements and floors and waterproofing of roofs is necessary for protection against entry of moisture either from ground capillary action or from rainwater. These aspects are covered by Indian Standards which can be grouped as below:

a)General preparatory work – IS: 3067-1988 covering general details and preparatory work for damp proofing and waterproofing of buildings.

b)  Damp-proofing treatment

IS: 13182-1991

Covering waterproofing and damp-proofing of wet  areas in building.

IS: 1609-1991

Covering laying of damp-proofing treatment using bitumen felts.

IS: 7198-1974

Covering damp-proofing using bitumen mastic.

IS: 9918-1981

Covering in-situ waterproofing and damp-proofing treatments with glass fibre tissue reinforced bitumen.

c) Waterproofing treatment

IS: 3036-1992

Covering laying of lime concrete for a waterproofed roof finish.

IS: 1346-1991

Covering waterproofing of roofs with bitumen felts.

IS: 4365-1967

Covering application of bitumen mastic for waterproofing of roofs.

IS: 7290-1979

Covering recommendations for use of polyethylene film for waterproofing of roofs.

IS: 9918-1981

In-situ waterproofing and damp-proofing using glass fibre  tissue reinforced bitumen.

IS: 6494-1988

Covering waterproofing of underground water reservoirs and swimming pools.

IS: 12054-1987

Covering application of silicone based water repellent.

10.1.2 The materials generally used for damp proofing and waterproofing are lime concrete, bitumen felts, bitumen mastic, glass fibre reinforced bitumen and polyethylene film; silicone based water repellents are also coming into vogue. However, whatever be the new materials, the construction practices would largely be as reflected in the standards for damp proofing and waterproofing.

10.2 SPECIFICATIONS FOR GENERAL PREPARATORY WORK FOR DAMP-PROOFING AND WATER PROOFING

10.2.1 General - Different types of damp proofing and waterproofing materials are used in the building industry.  In order to obtain satisfactory performance, it is essential that prior to the application of these materials for the damp-proofing and waterproofing treatment, special care has to be taken regarding the design details and carefully preparing the building surface (sub-floor) for receiving the treatment.  Thus this is an essential adjunct to construction details of damp-proofing and waterproofing treatment dealt with subsequently in this section both for Part 1 and Part 2, unless otherwise modified.

10.2.2 Preparatory work

a) Damp proofing and water proofing shall be taken up only when the sub-soil water level is at its lowest, that is, in the dry season.

b) For efficient design and construction of the treatment the following particulars among other would be of use.

 1) Anticipated highest water level;

 2) Anticipated water level in rainy season;

 3) Shape of roof, that is, flat, sloping or curved;

 4) Type of roof;

 5) Type of thermal insulation treatment, that is, mud phuska or polystyrene slab, etc;

 6) Projections through roofs;

 7) Drainage arrangements;

 8) Intensity of rainfall; and

 9) Drawings as needed.

c) For effective damp-proofing of basements the following be considered:

 1) Construction joints, as far as possible, shall be avoided;

 2) In case expansion joints are necessary, adequate supports shall be provided at the vertical and horizontal joints to support the damp-proofing treatment from bursting under water pressure.

 3) The wall faces, as far as possible, shall be free from obstruction to enable continuous laying of damp-proofing treatment;

 4) Damp proofing shall be external for all new buildings.  Sufficient working space shall always be provided which shall in no case be less than 600 mm suitably protected all-round the basement; and

 5) In the case of reinforced concrete work, dowels shall be used on underground structures subject to sub-soil water pressure, otherwise the damp-proofing gunite may be blown on the surface on which it is applied.

d) For waterproofing of roofs, its effectiveness will depend on the following:

 1) The expansion joint in the roof shall be so designed as not to impair the effectiveness of the treatment; the joint may be treated with non-absorbent, compressible, non-brittle and watertight sealant; and

 2) Adequate openings shall be provided to drain water from the roof; the design shall be such that waterproofing treatment may be easily applied to the openings.

Fig 1 Arrangement showing dewatering of small basement by drains and pumps

Fig. 2 Arrangement showing dewatering of large areas where it is necessary to dewater under the floor

Fig. 3 Cross section of land drain with details

10.2.3 Planning in relation to sub-soil drainage

10.2.3.1 Site and underground drainage

a) The site shall be drained during the entire period of laying the damp-proofing treatment. Typical arrangement of de-watering in some cases shown in Figures 1, 2, 3 and 4.

b) For existing structures, internal tanking for damp proofing has per force to be adopted.  Damp-proofing treatment has to be taken up when the water is not there in the basement; if there is any standing water it shall be drained out.  If percolation persists, de-watering by well-point system may be done. Where it is not possible to employ well point for de-watering and the pressure of water during the dry season is negligible, it is possible to carry out the work by pumping the water out, with a pump located on the floor.  In this case the damp-proofing treatment shall be carried out both on the floor and walls. When the treatment is completed, the pump shall be removed, and damp proofing done over the area occupied by the pump, after suitably plugging the area with cement concrete.

Note -For de-watering and lowering of water table by well point method reference may be made to IS: 9759-1981.

Fig. 4 Alternate arrangements of dewatering for laying damp proof treatment In basement where space is restricted

10.2.3.2 Time schedule - In damp-proofing operations of basement due consideration shall be given to economical utilization of pumps and other equipment by coordinating the activities of the general contractor and the damp-proofing contractor.

10.2.4 Preparation of surface

10.2.4.1 Damp-proofing of basement

a) For treatment above ground level – The rise of moisture due to capillary action has to be dealt with suitably.

1) In places where rise in sub-soil water is severe, typical details of treatment are as given in Fig 5.  The mortar bed on which the damp-proofing treatment is to be laid shall be levelled and made free from projections liable to cause damage to the damp-proofing treatment. The damp-proofing treatment shall cover the full thickness of wall and shall not be set back from wall face for pointing.  In the case of lime terracing, a cavity shall be left for insertion of lime concrete treatment, which shall act as a plastering.

2) When a horizontal damp-proofing treatment has to be carried over to a vertical face, a cement mortar (1:4) fillet 75mm in radius shall be provided at the junction. Both the horizontal and vertical surfaces shall be finished smooth.

3) For residential buildings, a cement mortar (1:4) or 1:2:4 concrete 12 mm thick with waterproofing compound (see IS: 2645-1975) added may be laid below the course of brick.

Fig. 5 Damp proof treatment above ground floor for new building

b) For treatment below ground level

1) For internal tanking of existing buildings the vertical walls shall be roughened for proper grip; the floor shall be cleaned and levelled; and a fillet of cement mortar (1:4) 75 mm in radius may be provided at the junction between vertical and horizontal faces.

2) For external tanking of new buildings, where space is available for excavation, details are as given in Fig 6 where space for excavation is limited, the external protective wall shall be constructed first and internal face plastered evenly but rough; details are as in Fig 7. The damp-proofing treatment shall be continuous over the wall and the floor; a space of around 100 mm should be left between the vertical external protective wall and internal protective wall, which shall be grouted after laying of damp-proofing treatment.

3) For external tanking of new building a base slab of lean cement concrete rendered to a smooth surface finish shall be constructed on the floor of the excavation.  The slab shall project 250 mm beyond the outer faces of the structural walls when completed. The exterior of the structural wall shall be true and free from protrusions, but shall be smooth or roughened as required. For vertical damp proofing to be laid continuous with horizontal one, a fillet 75 mm radius of 1:4 cement mortar shall be provided.

c) Gunite Work – Guniting may be done for damp-proofing of both masonry and concrete surfaces both below and above ground level. The surfaces shall be prepared by removing all loose and disintegrated material cleaned by compressed air and water ; the concrete surfaces may also be roughened and the joints in masonry walls be raked to a depth of 12mm.

Fig 6 Typical damp proof treatment for basement in new buildings under construction

10.2.4.2 Waterproofing of roofs - The preparations, where necessary, apply to the use of bitumen felts, bitumen mastic, lime concrete, guniting, use of films, etc.

10.2.4.2.1 Preparation of concrete and masonry roofs:

a) Well defined cracks, other than hair line cracks in the roof, shall be cut to a ‘V’ shape, cleaned and filled flush with cement sand slurry or with cold applied bituminous caulking compound conforming to IS: 1580-1991. The roof surface shall be re-graded and cured prior to application of waterproofing treatment.

Fig. 7 Alternate damp proof treatment for basement in new buildings under construction

Note: Sequence of work

A- Base slab   B- Outer protective wall  C-Horizontal damp proofing treatment

D- Vertical damp proofing treatment on the inside of outer protective walls

E- Brick flat or cement concrete 1:3

G- RCC structural wall or floor thickness and reinforcement will be designed according to the depth and maximum water pressure.

b) The surface of roof and related parts to receive the treatment shall be cleaned of all foreign matter by wire brushing and dusting.

c) In case of lime concrete treatment, the structural roof surface shall be finished rough to provide adequate bond.

d) Drain outlets shall be suitably placed with respect to roof drainage to prevent accumulation of water. Masonry drain mouths shall be widened sufficiently and rounded with cement mortar (1:4).  For cast iron drain outlets, a groove shall be cut all round to truck the treatment.

e)  For projections or pipes passing through a roof, treatment should be typically as shown in Fig. 8

Projecting pipe on flat roof    Projecting pipe on sloping roof

Fig. 8 Typical waterproofing treatment when a pipe passes through a concrete roof

Note – Regarding the junction of parapet wall and roof, improved treatment is as shown in Fig 11

f) In case of parapet walls over 450 mm in height, typical details are as given in Fig. 9A in case of low parapet wall typical details are as in Fig. 9 B. In case of existing RCC and stone parapet walls, typical details are as in Fig 10  

Fig. 9 Waterproofing treatment at junction on roof and parapet wall

g) At the drain mouths fillet (see Fig.9) shall be suitably cutback and rounded off for easy application of the treatment and easy flow of water.

Fig. 10 Details of waterproofing treatment in parapet wall where cutting of grooves is not possible

10.2.4.2.2.  Preparation of timber roofs

a) On boarded roofs where timber boards are not tongued and grooved, the gap at joints shall be caulked with hemp, hessian or other suitable fibre impregnated with bitumen or some other suitable filler. In case of boards joined by tongue and groove joints, it is necessary to caulk the gaps, if any (see Fig 12 for typical details).

Fig. 11 Details at the junction of the roof with wall

b) All the boards shall be nailed to minimize curling. All sharp edges and corners shall be rounded or chamfered.

c) When a timber roof meets a vertical wall, a timber fillet 75 mm x 75 mm shall be provided at the junction. For timber walls, wooden moulding shall be used to secure and seal the top edge of the bitumen felt at a height of 150 mm from the junction.

Fig. 12 Waterproofing treatment of timber roof

d) Where a projection or pipe passes through timber roof typical treatment should be as shown in Fig. 10.

Fig. 13  waterproofing treatment of sloping timber roof with pipe projection

10.3. SPECIFICATIONS FOR DAMP PROOFING

10.3.1. General: -

10.3.1.1 Preparatory work - The provisions of preparatory work and other details given in 2 at the beginning of the section shall apply.  In order to provide continuity in tanking, provision of openings for service, such as, pipes, cables, etc., in walls or floors should be avoided. Where unavoidable, special treatment as given in Fig. 14 shall be given.

Fig 14 Typical arrangement of damp proofing around a pipe through an opening 

De-watering shall be continued during the laying of the layers of damp-proofing materials until they have hardened and the surface has developed enough strength to resist full hydrostatic pressure.

The surface on which the material has to be laid may be first sprayed with bitumen primer conforming to IS: 3384-1986.

10.3.2. SPECIFICATIONS FOR BITUMEN FELT TREATMENT: -

10.3.2.1 Materials:

a) The bitumen felt shall conform to the requirements of IS: 1322-1993 and IS: 7193-1974; bitumen primer shall conform to IS 3384: 1986; blown bitumen shall conform to IS: 702-1988 of Grades 85/25 or 90/110.

b) For preparing the surface, cement mortar (1:4) be laid with cement conforming to IS 269- 1989 and sand to IS: 2116-1980.

10.3.2.2 Damp-proofing treatment above ground level - The damp-proofing treatment for floors and for walls above ground level shall be in layers as described below.  The bitumen primer, if prescribed, shall be first brushed over the roof surface and allowed to dry; generally 0.2 to 0.4 l/m2 is recommended.

a) For floors (one layer of felt)

1) Hot applied blown bitumen at the rate of 1.5 kg/m2;

2) Hessian base self-finished felt Type 3, Grade 2 or glass fibre base Type 2, Grade II; and

3) Hot applied blown bitumen at the rate of 1.5 kg/m2.

b) For walls (one or two layers of felt)

1) One or two layers of hessian base self finished felt Type 3, Grade 2, or glass fibre base felt Type 2, Grade II shall be laid according to the life of the building using the blown bitumen between the wall and felt.

Note – Adopt one layer of felt for an expected life of building up to 10 years and two layers for more than 10 years.

10.3.2.3. Damp-proofing treatment below ground level

10.3.2.3.1. A multiple layers, that is, more than two layer damp-proofing treatment shall be laid according to either of the three methods described below. It may be noted that fibre based self-finished felt in IS: 1322-1993 is not recommended for use in basements.

a) Normal treatment (two layers of felt)

1) Primer (for vertical faces only) at the rate of 0.271/m2;

2) Hot applied blown bitumen at the rate of 1.5 kg/m2;

3) Hessian base self-finished felt, Type 3 Grade 2 or glass fibre base felt Type 2 Grade II;

4) Hot applied blown bitumen at the rate of 1.5 kg/m2;

5) Hessian base self-finished felt, Type 3, Grade 2 or glass fibre base felt, Type 2 Grade II; and

6) Hot applied blown bitumen at the rate of 1.5 kg/m2. 

b) Heavy treatment (three layers of felt)

1) Primer (for vertical faces only) at the rate of 0.271/m2;

2) Hot applied blown bitumen at the rate of 1.5 kg/m2;

3) Hessian base self-finished felt, Type 3 Grade 2 or glass fibre felt, Type 2, Grade II;

4) Hot applied blown bitumen at the rate of 1.5 kg/m2;

5) Hessian base self-finished felt Type 3, Grade 2, or glass fibre base felt, Type 2 Grade II;

6) Hot applied blown bitumen at the rate of 1.5 kg/m2;

7) Hessian base self-finished felt, Type 3 Grade 2 or glass fibre base felt, Type 2 Grade II; and

8) Hot applied blown bitumen at the rate of 1.5 kg/m2.

c) Extra heavy treatment (four layers of felt)

1) Primer (for vertical faces only) at the rate of 0.271/m2;

2) Hot applied blown bitumen at the rate of 1.5 kg/m2;

3) Hessian base self-finished felt, Type 3 Grade 2, or glass fibre felt Type 2 Grade II;

4) Hot applied blown bitumen at the rate of 1.5 kg/m2;

5) Hessian base self-finished felt, Type 3 Grade 2 or glass fibre felt, Type 2 Grade II;

6) Hot applied blown bitumen at the rate of 1.5 kg/m2;

7) Hessian base self-finished felt, Type 3, Grade 2 or glass fibre base felt, Type 2 Grade II;

8) Hot applied blown bitumen at the rate of 1.5 kg/m2;

9) Hessian base self-finished felt, Type 3 Grade 2 or glass fibre base felt, Type 2 Grade II; and

10) Hot applied blown bitumen at the rate of 1.5 kg/m 2.

10.3.2.4. SPECIFICATIONS FOR DAMP-PROOFING TREATMENT

10.3.2.4.1 General - The damp-proofing treatment shall be continuous throughout and the overlap of joints in felts, wherever they exist, shall be correctly made.

10.3.2.4.2 Laying of felt - The felt shall be laid as mentioned below:

a) The felt shall be first cut to the required lengths and brushed clean of dusting materials and laid flat on a level dry and clean surface; then it may be rolled up.

b) The laying of felt shall commence on the floor first and shall be completed before it is applied to the wall. Hot bitumen is poured in front of the rolled up felt on the floor to the full width of felt.  The rolled felt is now gradually unrolled with a slight pressure to squeeze out the excess bitumen.

c) After the whole floor is thus covered and overlapping joints properly sealed, the felt is laid on the vertical face in a similar manner. In this case the roll of felt is held at the floor level and then gradually unrolled up the wall face as hot blown bitumen is poured between the roll and the wall face. The minimum overlap shall be 100 mm both at sides and ends.

d) The subsequent layers of felts shall break joint midway between the joints of the layer beneath it.

10.3.3. SPECIFICATIONS FOR BITUMEN MASTIC TREATMENT

10.3.3.1. Materials - The bitumen mastic shall conform to the requirements of IS: 5871-1987; bitumen, Primer shall conform to IS: 3384-1986.

10.3.3.2 Damp-proofing treatment above ground level - The damp proofing treatment shall be laid across the full thickness of walls excluding plaster or each of the base of cavity walls shall not be set back of pointing.  The damp proofing in the wall shall be continuous with the layer of bitumen mastic in adjacent floors; and where necessary, a vertical damp-proofing course shall be provided on the inner surface of the wall as in Fig 15.

Fig 15 Typical arrangement of continuous damp-proofing in wall and adjacent floor

10.3.3.3. External tanking - The following points shall be kept in view for externally applied tanking:

a) The working space outside the walls may be not less than 0.6 m.

b) The base concrete of 100 mm in thickness shall be structurally sound; it shall be extended at least 150 mm beyond the edges of wall to permit angle fillet to form at the junction of horizontal and vertical damp-proofing (see Fig.16).

Fig 16. Externally applied tanking

c) As soon as the horizontal layer of mastic asphalt has been laid, it shall be covered with a screed of cement and sand 50 mm thick, to prevent damage.  The horizontal coat of structural slab shall be laid as quickly as possible.  The 150 mm offset structurally protected by the screed.

d) Immediately after the vertical damp-proofing bitumen mastic is laid, the outside of the wall shall be protected against damage by erection of a brick wall.

10.3.3.3. Internal tanking - The following precautions shall be taken before applying bitumen mastic:

a) A space of 300 mm outside the wall shall be provided as far as possibles during excavation to keep the wall dry at the time of laying bitumen mastic.

b) The base slab shall be provided with an even surface and the walls shall be built to the full height before mastic asphalt laying is commenced.

c) Earth shall not be filled outside the wall until three coats of vertical mastic have been applied and the loading coats have been hardened as shown in Fig. 17.

Fig 17. Internally applied tanking

d) As in external tanking, protective layers of screed should be laid and then the structural floors and walls laid.

10.3.3.4.  Remelting of mastic - Remelting shall be done at site in a mechanical mixer ; the temperature of mastic shall not exceed 200 degree C during remelting. Blocks of bitumen mastic shall be broken into pieces and then stocked in layers first round the sides and then inwards towards the centre of the mixer.  The charge shall be gradually heated to about 200 degree C and when the mastic has attained a molten condition, it shall be agitated continuously to ensure a uniform consistency. The duration of heating shall be such that the properties of bitumen are not impaired.

10.3.3.5.  Thickness and method of laying

10.3.3.5.1. Thickness - Bitumen mastic shall be applied in one or three coats as stated below to all surfaces, whether sloping, horizontal or vertical.  The thickness shall be as follows:

a) For walls and floors above ground level the bitumen mastic shall be laid in one coat minimum of 10mm thickness.

b) For vertical surfaces and surfaces steeper than 30 degree to the horizontal below the ground level, the bitumen mastic shall be applied in three coats to a total thickness of not less than 20 mm.

c) For horizontal surfaces and sloping surfaces not steeper than 30 degree to be horizontal below the ground level, the bitumen mastic shall be applied in three coats to a total thickness of not less than 30 mm.

10.3.3.5.2. Method of laying

10.3.3.5.3. Chases - The top of the vertical mastic shall be turned into a chase in the wall not less than 25 mm x 25 mm unless it is being continued horizontally.

10.3.3.5.4 Fillet - Angle fillet not less than 50 mm wide shall be applied in two coats at the junction of two planes forming an internal angle.

10.3.3.5.5 Construction joints - Edges of the mastic already laid should be warmed with hot asphalt and then cut out with a metal trowel to remove any dust or dirt that may have collected. The fresh mastic should be poured before the warmed up surface of the joint cools off.

10.3.4. SPECIFICATIONS FOR GLASS FIBRE TISSUE REINFORCED BITUMEN TREATMENT

10.3.4.1 General - Glass fibre is more resistant to weathering and has come into use for waterproofing and damp proofing of buildings.

10.3.4.2. Materials

10.3.4.2.1 Glass fibre tissue - The glass fibre tissue shall conform to the requirements given in Appendix A of IS: 7193-1991.  It shall be a thin, flexible, uniformly bonded mat composed of chemically resistant borosilicate staple glass fibres distributed in a random open porous structure, bonded together with a thermosetting resin (phenolic type).

The minimum weight of the tissue shall be 40 gm/2 and the nominal thickness shall be 0.5 ± 0.1 mm.

10.3.4.2.2. Blown bitumen shall conform to IS: 702-1988 or residual bitumen conforming to IS: 73-1992 may be used as bonding material. The penetration of bitumen shall be not more than 40 when tested in accordance with IS: 1203-1978.  Bitumen primer shall conform to IS 3384-1986.

10.3.4.3 In-situ damp-proofing treatment above ground level a nd below ground level, the National Building Code 2005 may be referred.

10.3.4.4 Laying In-situ treatment

a) Cut the required length at glass fibre tissue and roll it.

b) Pour hot bitumen on the surface to the full width of soil and simultaneously embed the glass fibre into it.  Proceed in this manner throughout the length of the floor.

c) After the whole floor has been covered, the overlapping joints shall be sealed; the glass fibre is laid on the walls in the same way.  The roll of glass fibre is held at floor level, and then gradually unrolled as the hot bitumen is poured between the roll and the wall face.

d) The joints between successive layers of glass fibre tissue shall be staggered.

e) The minimum overlap of joints shall be 100 mm at both sides and ends.  All overlaps shall be firmly bonded with bitumen.

10.3.5. SPECIFICATIONS FOR WATERPROOFING AND DAMP-PROOFING OF WET AREAS IN BUILDING

10.3.5.1. General - Bathroom, kitchen, water closet and to lesser extent verandah, balconies and sunshades may be termed as wet areas of buildings which are more vulnerable to water due to their functional requirements. These wet areas are one of the main source of leakage and dampness in a building which leads to unhygienic conditions affecting badly the health and comfort of the inhabitants and seriously deteriorating the stability of the building. The causes of leakage and dampness material, improper execution and incorrect usage by the occupant.

10.3.5.2. Recommendations - IS: 13182-1991 give detailed recommendations for identifying sources of leakage and dampness and their prevention in a systematic fashion for water closets, bathrooms, kitchen, open verandah, balconies and sunshades, floor traps, pipe work, water tank, sanitary shaft and external wall.  These recommendations are copiously illustrated with sketches.

Reference may be made to IS: 13182-1991 for details.

 10.4. SPECIFICATIONS FOR WATERPROOFING

10.4.1. General

10.4.1.1 The preparatory work and general details given in 2 at the beginning of the section shall apply. Waterproofing treatment to be efficient and lasting has to be carefully carried out from the time the surface is prepared to receive the treatment, such as, membrane, film, lime concrete, etc., to the finishing of the treated surface. Special attention and strict supervision has to be paid to proper overlapping of joints, particularly in felts and film, treatment around drainage openings in the roof and treatment of parapets.  The sticking of membrane to the roof by means of hot bitumen also requires skill, if the job is to be done economically and to give good results. For roof finish reference may be made to Section 11, after laying the waterproofing treatment.

10.4.2. SPECIFICATIONS FOR LIME CONCRETE WATERPROOFED FINISH

10.4.2.1 General - Lime concrete, apart from its use as a structural material in several situations in building construction, is also used for waterproofed roof finish.  The introduction of Pozzolanic materials, such as burnt brick pozzolana in lime concrete and compaction to maximum density enhances the waterproofing effect.

10.4.2.2 Materials

a) Lime – As far as possible Class C (fat lime) in the form of hydrated lime conforming to IS:  712-1984 shall be used. Quick lime shall be slaked in accordance with IS: 1635-1992.

b) Pozzolanic material – Calcined clay pozzolana shall conform to LP 40 of IS: 4098-1992.

c) Coarse aggregate shall be of broken brick (burnt clay) and conform to IS: 3068-1986 or natural stone aggregates conforming to IS: 383-1970.

d) Waster shall be clean and free from injurious amounts of deleterious materials. Seawater shall not be used. Potable water is generally considered satisfactory for use.

10.4.2.3. Lime concrete - Lime concrete shall be prepared as per specification in Section 4 and IS: 2541-1991.  Lime concrete shall be used in the work within 36 h of its preparation if burnt clay pozzolana is incorporated.

Notes -1) The sugar solution is prepared by mixing about 3 kg of jaggery and ½ kg of BAEL fruit to 100 litres of water by boiling.

2) The solution of terminalia chebula (KADUKAI) may be prepared as follows - Dry nuts shall be broken to small pieces and allowed to soak in water; about 600 g of nuts; 200 g of jaggery and 40 l of water for 10m2 of work can be used. The solution is brewed for 12 to 24 h ; the resulting liquor, after decantation, is used for work.  Sometimes methi, jaggery and hemp are also added while preparing and laying lime concrete.

10.4.2.4.5 The lime concrete shall be cured for a minimum of 10 days or until it hardens.

10.4.2.4.6 Treatment of junction between roof finish and parapets is as shown in Fig 18 and Fig. 19. 

   

Fig 18A Structural roof slab and lime Fig. 18B Structural roof slab and lime

Concrete finish extending to     concrete finish not extending to        

the full width of wall                    full width of wall

Fig 18. Typical details at junction between lime concrete waterproofed roof finish and parapet wall

10.4.2.5 Finish - Roof finish should be as described in Section 11 using burnt clay flat terracing tiles to IS: 2690 (Part1)-1993 and IS: 2690 (Part 2)-1991.  However in extreme conditions where there is considerable expansion and contraction, two layers of tiles may be laid on the lime concrete; the tiles should be joined by non-shrinking impervious mortar by adding an integral waterproofing admixtures or 5 percent engine oil and finished neat.

To drain rainwater every 40 m2 area of roof shall have a 100 mm dia rain water pipe or as in Table 3 of IS: 2527-1984 depending on the rainfall intensities of the locality.

18C Detail showing arrangement of downpipe for 18A

10.4.3. SPECIFICATIONS FOR BITUMEN FELT

10.4.3.1. General - Bitumen felt is one of the materials used for waterproofing of roofs. Waterproofing treatment with bitumen felt is adopted not only in the case of buildings and structures, but also in railway coaches, bus bodies, etc.

10.4.3.2. Materials

a) Regarding of the roof surface shall be carried out with suitable cement mortar incorporating clean, medium coarse sand or with a lime-surkhi mortar or any other suitable material.

b) Bitumen primer shall conform to IS: 3384-1986.

c) Bitumen felt shall conform to IS: 1322-1993 and IS: 7193-1971.

d) Bonding material for use between successive felts and between roof surface and felt shall conform to industrial blown type bitumen of Grade 85/25 or 90/15 conforming to IS: 702-1988. For top dressing bitumen shall be industrial blown type to IS: 702-1988 of penetration not more than 40 when tested in accordance with IS: 1203-1978.

For vertical surfaces up to 1 m in height blown type bitumen to IS: 702-1988 of Grade 85/25 or 90/15 and above 1 m Grade 115/15 may be used.

10.4.3.3. Waterproofing treatment - In selecting a combination of layers and grades of felt to be used, consideration shall be given to the type and construction of buildings, climatic and atmospheric conditions and the degree of permanence required.

18D Junction of roof with parapet wall (alternate arrangement)

18E – Detail for Khurra for 18D

Fig. 19A Junction between RCC roof slab and parapet wall

10.4.3.4. Concrete and masonry roofs, flat or sloping - The following treatments are recommended:

a) Normal treatment – Five courses for moderate conditions:

1) Primer at the rate of 0.27 l/m2, Min;

2) Hot applied bitumen at the rate of 1.2 kg/m2, Min;

3) Hessian based self-finished felt, Type 3, Grade 1, or glass fibre base, Type 2, Grade 1;

4) Hot applied bitumen at the rate of 1.2 kg/m2, Min; and

Fig 19 B Detail of roof slab and rain water pipe

5) Pea-sized gravel or grit devoid of fine sand at the rate of 0.006 m3/m10.3.2.

a). Floating treatment

1) Fibre base felt bitumen saturated underlay; Type 1;

2) Hot applied bitumen at the rate of 1.2 kg/m2, Min;

3) Fibre base self-finished felt, Type 2 Grade 1 or Grade 2;

4) Hot applied bitumen at the rate of 1.2 kg/m2; and

5) Pea-sized gravel or grit devoid of fine sand at the rate of 0.008 m3/m2, Min.

b) Heavy treatment – Seven courses for severe conditions:

1) Primer at the rate of 0.27 l/m2, Min;

2) Hot applied bitumen at the rate of 1.2 kg/m2, Min;

3) Hessian base self-finished felt, Type 3 Grade 1 or glass fibre base felt, Type 2 Grade 1;

4) Hot applied bitumen at the rate of 1.2 kg/m2, Min;

5) Hessian base self-finished felt, Type 3 Grade 1 or glass fibre base felt, Type 2 Grade 1;

6) Hot applied bitumen at the rate of 1.2 kg/m2, Min; and

7) Pea-sized gravel or grit devoid of fine sand at the rate of 0.006 m3/m10.3.2.

OR

1) Primer at the rate of 0.27 l/m2, Min;

2) Hot applied bitumen at the rate of 1.2 kg/m2, Min;

3) Fibre base self-finished felt, Type 2 Grade 1 or Grade 2;

4) Hot applied bitumen at the rate of 1.2 kg/m2, Min;

5) Fibre base self-finished felt, Type 2 Grade 1 or Grade 2;

6) Hot applied bitumen at the rate of 2.5 kg/m2, Min; and

7) Pea-sized gravel or grit devoid of fine sand at the rate of 0.008 m3/m2.

OR      

 Floating treatment:

1) Fibre base bitumen saturated underlay, Type 1;

2) Hot applied bitumen at the rate of 1.2kg/m2, Min;

3) Fibre base self-finished felt, Type 2 Grade 1 or Grade 2;

4) Hot applied bitumen at the rate of 1.2 kg/m2, Min;

5) Fibre base self-finished felt, Type 2 Grade 1 or Grade 2;

6) Hot applied bitumen at the rate of 2.5 kg/m2, Min; and

7) Pea-sized gravel or grit devoid of fine sand at the rate of 0.008 m3/m2.

c) Extra heavy treatment – Nine courses for very severe conditions:

1) Primer at the rate of 0.27 l/m2, Min;

2) Hot applied bitumen at the rate of 1.2 kg/m2, Min;

3) Hessian base self-finished felt, Type 3 Grade 1 or glass fibre base felt, Type 2 Grade 1;

4) Hot applied bitumen at the rate of 1.2 kg/m2, Min;

6) Hessian base self-finished felt, Type 3 Grade 1 or glass fibre base felt, Type 2 Grade 1;

7) Hot applied bitumen at the rate of 1.2 kg/m2, Min;

8) Hessian base self-finished felt, Type 3 Grade 1 or glass fibre base felt, Type 2 Grade 1;

9) Hot applied bitumen at the rate of 1.2 kg/m2, Min; and

10) Pea-sized gravel or grit devoid of fine sand at the rate of 0.006 m3/m2.

OR

1) Primer at the rate of 0.27/m2; Min;

2) Hot applied bitumen at the rate of 1.2 kg/m2, Min;

3) Fibre base self-finished felt, Type 2 Grade 1 or Grade 2;

4) Hot applied bitumen at the rate of 1.2 kg/m2, Min;

5) Fibre base self-finished felt, Type 2 Grade 1 or Grade 2;

6) Hot applied at the rate of 1.2kg/m2, Min;

7) Fibre base self-finished felt, Type 2 Grade 1 or Grade 2;

8) Hot applied bitumen at the rate of 2.5 kg/m2, Min; and

9) Pea-sized gravel or grit devoid of fine sand at the rate of 0.008 m3/m2.

Note -  Where pea-sized gravel or grit is not available, coarse sand may be used.

10.4.3.4.1 Surface finish of pea-sized gravel or grit affords a protection to the treatment and its durability.  On the flashing and at the drain mouths, the gravel or grit may be omitted and instead two coats of bituminous paint at the minimum rate of 0.1 l/m2 per coat or a single coat of bituminous emulsion at the rate of 0.5 l/m2 may be applied.

a) Surface finish, when subjected to foot traffic, shall be cement concrete flooring tiles or burnt clay flat terracing tiles as described in section 9.

b) Alternatively, a screeding of 1:4 cement sand mix layer 45 mm thick may be laid over the roofing treatment and marked off into squares of 600 mm made with expansion joints at a distance of 3 m caulked with bituminous sealing compound (see Grade A of IS 1834 : 1984).

10.4.3.5 Timber roofs, sloping

a) Normal treatment

1) Fibre base bitumen saturated underlay Type 1, or hessian base felt, Type 3 Grade 1 or glass fibre base felt, Type 2 Grade 1;

2) Hot applied bitumen at the rate of 1.2 kg/m2, Min; and

3) Fibre base self-finished felt, Type 2 Grade 1, or hessian base felt Type 3 Grade 1, or glass fibre base felt, Type 2 Grade 1.

b) Heavy treatment

1) Fibre base self-finished felt, Type 2 Grade 1, or hessian base felt, Type 3 Grade 2, or glass fibre base felt, Type 2 Grade 2;

2) Hot applied bitumen at the rate of 1.2 kg/m2, Min;

3) Fibre base self-finished felt, Type 2 Grade 1 or Grade 2, or hessian base felt.  Type 3 Grade 2, or glass fibre base felt. Type 2 Grade 2.

10.4.3.5.1 Timber roofs shall be finished with hot applied bitumen at the rate of 1.2 kg/m2. Min; or with two coats of bituminous paint at the rate of 0.1 l/m2 per coat or a single coat of bituminous emulsion at the rate of 0.5 l/m2 over it.

10.4.3.6.  Laying of felt

10.4.3.6.1 Sequence of Operations for all Types of roofs

  1. Preparatory work (see 2 given in the beginning of the section) ;
  2. Cleaning roof surface of foreign matter;
  3. Treatment of main roof
  4. Treatment of flashing and projecting pipes;
  5. Treatment of gutters and drain mouths;
  6. Top dressing, that is gravel or grit, fixing and laying tile or concrete protection or applying paint or emulsion ; and
  7. Cleaning and removal of surplus materials.

10.4.3.6.2 Concrete and masonry roofs

a) The felt is normally laid in lengths at right angles to the direction of the run-off gradient, commencing at the lowest level and working up to the crest. In this way, the overlaps of the adjacent layers of felt offers minimum obstruction to the flow-off of water.

1) Bitumen primer shall be brushed over the roof surface and left to dry after the surface is thoroughly cleaned.

2) The felt shall be cut to the required lengths, brushed clean of dusting materials and laid out flat on the roof and allowed to soften. Each length of felt shall then be laid in position and rolled up for a distance of half its length.  The hot bonding material shall be poured on to the roof across the full length of the rolled felt as the latter is rolled out steadily and pressed down.  The excess bonding material is squeezed out at the ends and is removed as the laying proceeds.

3) When the first half of the strip of felt has been bonded to the roof, the other half shall be rolled up and then unrolled on the hot bending material in the same way.

4) Minimum overlaps of 100 and 75 mm shall be allowed at the end and sides of strips of felt respectively. All overlaps shall be firmly bonded with hot bitumen.

5) The laying of the second layer shall be so arranged that the joints are staggered with those of the layer beneath it.

6) In the case of pent roofs where the type of treatment consists of one layer of felt only as in normal treatment, an additional layer of felt shall be provided at the ridge which shall cover a minimum length of the slope of 250 mm on both sides of the ridge.

b) Junctions of parapet wall and roof – Felt shall be laid as a flashing with minimum overlaps of 100 mm. The lower edge of the flashing shall overlap the felt laid on the flat portion of the roof and the upper edge of the flashing shall be tucked into the groove made in the parapet on the vertical face of the wall. Each layer shall be so arranged that the joints are staggered with those of the layer beneath it. After the layers of felt are laid and bonded, the grooves shall be filled with cement mortar (1:4) or lime mortar (1:3) or cement concrete (1:3:6) which when set will satisfactorily secure the treatment to the wall. A fillet of cement mortar (1:4) shall be done at the junction of wall and roof.

b) Drain mouths – Drain mouths with a bell shaped entry shall be fixed and properly set to allow the water to flow into it.  Felt shall generally be laid on the other portion of the roof and the treatment shall be carried inside the drainpipes overlapping at least 100 mm. If possible a grating cap should be provided over the drain mouth to protect choking caused by leaves, stones, etc.

c) Gutter – The treatment to be laid in gutters shall provide for one layer of roofing felt more than is provided on the roof proper. A priming coat shall be first be applied. Over this, the first layer of felt shall be bonded with hot bitumen securely together and finally painted with a coat of hot bitumen at not less than 1.5 kg/m2.

1) The first layer laid separately in the gutters shall be overlapped with the corresponding layer on the roof proper. The felt layers in the gutter shall be carried down to the outlet pipes to a minimum depth of 100 mm.

2) For gutters in pent roofs the flashing shall be laid separately at the sides and carried well under the caves of the pent roofs.

3) Two coats of bituminous paint at the rate of 0.1 l/m2 per coat or a single coat of bituminous emulsion at the rate of 0.5 l/m2 shall be applied.

10.4.3.6.3 Timber roofs sloping (see Fig. 12) - The underlay or first layer of felt shall be secured by nails spaced at 100 to 150 mm centres along overlaps and at 20 mm from the exposed edges. In case of struck on treatment, the felt shall be bonded on timber roof in the same manner as in the case of masonry roof but with nailing strips and back nailing.

1) Where required, additional nailing may be provided between overlaps at 150mm centres.

2) The second and subsequent layers of felt shall then be applied with bonding materials as in concrete and masonry roofs.

3) In the case of gabled roof, one single strip of felt shall cover from gutter to gutter over the ridge. If the treatment consists of one layer of felt, additional layer of felt shall be provided at the ridge, which shall cover a length of slope of 250 mm on both sides of the ridge.

4) Flashings – If the parapet is of masonry construction, the flashings shall be treated in the same way.  In case the roof butts against a timber wall, the flashings shall be continuously bonded down over the felt turn up and angle fillet. Joints in the felt flashings shall be lapped 100 mm and sealed.  The upper end of the flashing shall be firmly secured to the timber wall by screwing down with a timber batten.

10.4.3.6.4. Shell roofs

a) In the case of shell roofs additional layer of felt shall be provided for the valley gutter for normal treatment and for other type of treatment; the number of felts in valley gutters shall be one layer extra. The treatment on the valley should be laid first and the height to which the felt is to be taken shall be at least 150 mm above the anticipated standing water in the gutter.  For normal treatment on pent roofs, the felt should be paid parallel to the direction of run-off gradient. The felt is in the case of shell roofs shall be laid from one edge of the valley gutter to the other, that is, around the curvature. In case of north light cylindrical shells, it can either start from the valley gutter or from the upper edge. The upper edge shall be securely anchored at the edge of the shell.

Note - Where insulation is specified, the insulating material shall be applied on top of the shell surface and plastered, if necessary, with cement mortar to provide adequate base for application of waterproofing treatment.

1) When the felt is laid parallel to the direction of run-off gradient, that is, around the curvature in the case of shell roof, the side overlap should be 100 mm minimum and end overlap should be 75 mm minimum this means that the overlap lengths are interchanged with those when felts are laid across the gradient.

2) For surface finish instead of the normal bituminous gravel finish, either two coats of bituminous aluminium paint at the rate of 0.1 l/m2 per coat or one coat colour bituminous emulsion at the rate of 0.5 l/m2 per coat, or one coat of acrylic based coating at the rate of 0.3 l/m2 shall be applied.

10.4.3.6.5 Expansion joints - Expansion joints coverings may be zinc or a lead sheet or of bitumen felt.  In the case of the latter, a minimum of two layers of bitumen felt, Type 2, Grade 2 as specified in IS 1322: 1993 or Type 2 Grade 1 of IS 7193: 1994 shall be used with top dressing of gravel or other suitable finish (see Fig. 20).

10.4.3.6.6 Treatment of bubble formation - If ballooning occurs, remove the gravel on the ballooned surface. Then cut open and squeeze out the trapped vapour by firm pressure applied by hand.  Seal the bitumen felt so lifted, back on to the surface by applying additional bitumen. Finally seal the cut with a piece of bitumen felt with bitumen application and re-apply the gravel finish over it to make the surface look uniform with the rest.

10.3.6.7. Roof gardens - Where it is required to create a roof garden the waterproofing shall be carried out as per the treatment of damp-proofing covered in 2, Part 1 of this section. As far as possible, plants should be planted in containers to avoid roof penetration into the roof below.

10.4.4. SPECIFICATIONS FOR BITUMEN MASTIC

10.4.4.1. Materials - Bitumen mastic shall conform to IS: 3037-1986.  Bonding bitumen shall conform to IS: 702-1988 or residual bitumen to IS: 73-1991.  The penetration of blown bitumen shall be limited to 45 when tested in accordance with IS: 1203-1978.  Expanded metal lathing with coating of bitumen may be used for reinforcement for laying bitumen to vertical sloping surfaces. The underlay may be bitumen felt to IS: 1322-1993.  Vapour barrier should be hessian based Type 3 felt to IS: 1322-1993.

10.4.4.2 Preparatory work - In addition to requirements of this Part, the following points may be considered.

a) Keying – Bitumen mastic will not adhere to vertical and sloping surfaces unless such surfaces afford an adequate key.

1) When bitumen mastic is applied to vertical surfaces including skirting the top of the mastic shall be tucked into a continuous groove or not less than 25 mm x 25 mm in the structure and its exposed part shall be formed with a splay to shed rain water.

2) Horizontal joints in brickwork should not be less than 10 mm wide and the mortar joint shall be raked out and brushed clean to form a key to the bitumen mastic (see Fig. 21). For vertical surfaces on concrete, the details are as in Fig.22 

3) For vertical timber surfaces, a layer of metal reinforcement shall be securely fixed by nails.  All vertical metal surfaces shall be primed with a rubber bitumen emulsion before the bitumen mastic is applied.

4) Other surfaces, wherever possible, shall be hacked to give key to bitumen mastic.

10.4.4.3 Number of coats and thickness  - The number of coats depends on the particular position of the surface and the maximum thickness of mastic that is possible to apply while it is a warm state.

a) On a horizontal surface and on slopes up 30 degree, two coats of equal thickness to a total thickness of 20 mm shall be applied, excluding horizontal treatment in walls.

b) On a horizontal roof subject to foot traffic, two coats of mastic shall be applied; the first coat shall be not less than 10 mm and the second coat not less than 15 mm.

c) On vertical surfaces other than timber, including skirting, up-stands and drips and slopes over 30 degree, two equal coats of total thickness of not less than 12 mm or three coats of total thickness not less than 20 mm shall be applied.

d) On vertical or sloping timber surfaces, three coats of bitumen mastic shall be applied to a total thickness of not less than 20 mm (see Fig. 23).

Fig. 22 Bitumen mastic laid on screed roof and bitumen mastic skirting to concrete wall

e) At the intersection of two planes forming an internal angle and after the bitumen mastic has been laid on the horizontal, sloping and vertical surfaces, a solid angle fillet of bitumen mastic, not less than 50 mm wide, shall be formed in two coat work (see Fig 22 and Fig. 23).

10.4.4.4 Movement of joints - Where it is considered necessary to provide movement of joints in the roof structure, details could be as in Fig. 24. 

Fig. 23 Bitumen mastic laid on timber roof and bitumen  mastic skirting on free standing kerb

10.4.4.5. Laying of bitumen mastic:

10.4.4.5.1. Spreading:

a) Each coat of bitumen mastic of each bay marked out, shall be spread evenly and uniformly by means of float to the recommended thickness, on to the previously prepared surface, the isolating membrane or the preceding coat.

b) Each coat of bitumen mastic shall be followed, without delay by the succeeding coat, since exposure to contamination might impair adhesion and cause blistering.

c) The junction between two contiguous bays of a coat of bitumen mastic shall be not less than 150 mm from a corresponding junction in a preceding coat.

d) When bitumen mastic is laid horizontally, timber gauges of specified thickness shall be used during the laying of each coat.

e) When bitumen mastic is laid over vertical or steeply sloping surfaces, the first coat is essentially an adhesive layer, which acts as a base to ensure complete bonding of subsequent coats.

Fig. 24 Expansion joint in flat roof twin kerb type

f) Any blows shall be pierced and the affected area made good while the bitumen mastic is still warm.

10.4.4.5.2. Surface finish - Immediately after completion of the laying of mastic, the surfaces shall be rubbed with a wood float using clean sharp sand passing 850 micron IS Sieve and retained on 300 micron IS Sieve, while the mastic is still warm.

10.4.4.5.3 Final finish

a) To avoid absorption of solar heat, light coloured mineral aggregates or pea-size gravel may be evenly spread shoulder to shoulder over the entire surface. The aggregates shall be stuck to the top of the surface with bituminous bonding material.

b) The bitumen mastic may also be finished with roofing materials as described in section 11 using light coloured tiles, etc.

c) Where decorative finish is necessary, aluminium paint free from material deleterious to bitumen mastic or any other coloured emulsion paint may be used.

10.4.4.5.4 Other details

a) Insulating materials – Where it is necessary to prevent fluctuation of temperature inside a building, additional thermal insulation is obtainable by placing a layer of insulating material immediately below the mastic roofing.  A vapour barrier as shown in Fig 25 shall be laid between the base and the insulation layer.

b) Skirting and up-stands – The exposed uppermost part of bitumen mastic skirting shall be formed with a splay to shed rain water, even though a metal flashing is laid to cover the exposed part.

A similar splay is formed when bitumen mastic is continued through the wall to form a horizontal damp-proofing treatment (see Fig. 26).

c) All internal angles shall be laid in two coats, as a separate operation. It is essential that the last coat of bitumen mastic of contiguous surfaces shall be warmed and cleared, before the solid fillets are formed, by hot bitumen.

d) Projecting pipes should be surrounded by mastic as shown in Fig. 27. The treatment is continued over the metal surface coated with bituminous paint up to a stipulated height.  The metallic reinforcements shall be placed vertically against the first layer of bitumen mastic.  The top layer shall be built over the reinforcement.  Neat bitumen or plastic bitumen shall be used as a grout at the joint. A metal collar shall be fixed over it.

Fig. 25 Bitumen mastic laid on thermal insulating material

Fig. 26 Bitumen mastic laid on screeded roof with bitumen mastic skirting and damp proofing treatment to wall

10.4.5. SPECIFICATIONS FOR POLYETHYLENE FILM

10.4.5.1 General  - Polyethylene film is one of the materials which are being used for waterproofing of roofs in buildings.  Experience gained so far indicates that when polyethylene film is laid on the roof as recommended, the treatment provides satisfactory performance against water penetration. Special care shall be taken for effective bonding of the polyethylene film to the background surface as well as in the overlaps. Proper precautions shall be taken against puncturing of the film and entrapping air while laying the treatment.

10.4.5.2 Material

a) Polyethylene film shall conform to IS: 2508-1981.  In addition it shall satisfy the following conditions:

1) The film may be natural or black in colour.  The black film shall contain not less than 2.0 per cent of carbon black of an average particle size not exceeding 0.06 micron, well dispersed in mass. The natural film shall be ultraviolet stabilized quality only.

2) Water vapour transmission through the film determined by the procedure described in Annexure 10-A.5 shall not be more than 10.3.5.33 g/24 h/m2.

b) Bitumen primer shall conform to IS: 3384-1986.

c) Bonding materials shall be straight run bitumen grades conforming to IS: 73-1992.  Over the film a cold cutback bitumen conforming to IS: 73-1992 may be used; the temperature of the cutback shall not be more than 50 degree C at the time of application.

Fig. 27 Treatment when a pipe passes through a roof slab

10.4.5.3. TYPES OF WATERPROOFING TREATMENT

10.4.5.3.1. SPECIFICATIONS FOR PRE-SLOPED ROOFS

a) Single layer treatment (see Fig. 28) finished with plaster or gravel

1) Primer at the rate of 0.3 to 0.5 kg/m2, where necessary, till the surface is impregnated and the solvent oil in the primer is allowed to evaporate completely.

2) Hot applied bitumen (straight-run bitumen) at the rate of 0.70 kg/m2 Min;

3) Polyethylene film with cold cutback adhesive in overlaps;

4) Cold cutback bitumen at the rate of 1.0 kg/m2.

5) Binding materials, such as fine sand in dry condition at the rate of 0.5 to 1.0 kg/m2 dusted over bitumen in (4) above; and

6) Finishing layer, such as gravel on the flat surface and cement plaster 1:6 or lime mortar 1:3 on all vertical surfaces; or cement plaster 1:6 or lime mortar 1:3 on the entire treated area.

Note - Where pea-size gravel or grit finish is required, the size of the gravel should be 3 to 6 mm properly impregnated at 0.006 m3/m.

b) Single layer treatment finished with tiles or patent stone or cement concrete -

1) Primer at 0.3 to 0.5 kg/m2, till the surface is properly impregnated, where necessary;

2) Hot applied bitumen (straight-run grade) at the rate of 0.7 kg/m2, Min;

3) Polyethylene film with cold cutback adhesive in overlaps;

4) 100-g brown craft paper laminated in-situ over the film with semi-hot layer of straight-run bitumen. The technique of fixing craft paper to polyethylene film is to paint semi-hot bitumen on the paper, reverse it and laminate over the film;

5) Semi-hot applied bitumen (straight-run grade) at the rate of 0.7 kg/m2 dusted with fine sand; and

6) Finishing layer of tiles or patent stones (see section 10).

Fig. 28 Single layer film treatment over the thermal insulation on the roof

c) Multi-layer treatment – In severe conditions of exposure, such as, heavy rainfall or important structures it is advisable to provide multi-layer treatment. Normally, a two layer treatment is sufficient to obtain adequate resistance to rain penetration.

1. Lower Layer – Items (1) to (4) as in 5.3.1 (b).

2. Upper layer – Items (2) to (5) as in 5.3.1 (a) or items (2) as in 5.3.1 (b).

3. Finish – Item (6) of 5.3.1 (b) or item (6) as in 5.3.1 (a).

Fig 29 Treatment laid below thermal protection

10.4.5.3.2 Flat roofs with mud ‘Phuska’ finish or lime terracing:

a) Treatment laid below mud phuska (see Fig. 29) as in 5.3.1 (a) items (1) to (4) or 5.3.1 (b) items (1) to (5) and protective treatment, such as mud phuska and one or two layers of tiles.

b) Treatment laid below lime terracing – As in 10.4.5.10.3.1 (b) items (1) to (5) and protective treatment, such as lime terracing.

10.4.5.4 Laying

10.4.5.4.1 Sequence of operations shall be as in 10.4.6.1.

10.4.5.4.2 Laying 

a) The number of laps shall be minimized by selecting film of suitable width; the minimum width of laps shall be 100 mm both at ends and sides.

b) The primer shall be applied on the prepared roof surface by brushing and allowing it to dry for 6 to 12 h.

c) Hot bitumen shall be spread over the roof surface and allowed to cool to a temperature so that the film may be laid without any damage to it.

d) The polyethylene film shall be carefully laid on the bituminous layer and firmly but carefully pressed down with the help of a gunny cloth so as to prevent any damage to the film.

1) The next length of the film shall be similarly laid down on the roof with proper longitudinal and end overlaps and firmly pressed down on the bituminous layer. The joints and overlaps shall be carefully sealed with the help of cutback bitumen applied over the upper surface of the lower layer of the film.

2) As far as possible, the polyethylene film shall be laid as in Fig. 30-A for flat roofs; as in Fig. 30-B for sloping roofs and as in Fig. 30-C for curved shell roofs.

e) As far as possible, laps shall be avoided in the troughs or valleys; where unavoidable, they shall be covered with an additional filmstrip of adequate width.

Fig 30A Flat roof

10.4.5.4.3 Precautions to be taken into account in laying film treatment are as follows:

a) Excessive bitumen should not be used for bonding the film to the prepared surface, which may result in the film sliding and wrinkling.

b) The film should not be over-stretched, which otherwise leads to wrinkles when the film retracts. These wrinkles may get reproduced in the final treatment and are liable to get eroded and cause failure of treatment.

c) The laying of film should be immediately followed by subsequent operations of covering with bituminous compositions. If the film is left exposed, it can lead to softening of bitumen layer underneath causing wrinkles leading to damage. The work therefore should not be carried out when the temperature is high.

d) It is necessary to hold the film high and finally pressed in position by cloth pad, so that the film sets securely on bituminous underlay. Otherwise this will result in the formation of air bubbles below the film, which will lead to poor bonding.

Fig. 30B Sloping roof

Fig. 30C Shell roof Typical arrangement for laying polyethylene film

e) The workmen should preferably walk barefooted or with canvas shoes in order to prevent damage to the film.

f) If the polyethylene film is to be carried over from horizontal to vertical surface, it should be over a fillet and protected with cement plaster or any other treatment.

10.4.5.4.4 Projections - Typical details for treatment of roof projections, projection through roofs, etc are as given in Fig, 31, 32 and 310.3..

Fig 31 Typica

Fig. 31 Typical detail of waterproofing treatment in case of

Fig. 31 Typical detail of waterproofing treatment in case of roof projecting beyond the wall

For roof drainage, extra piece of polyethylene film shall be provided in the opening covering the edge of the down pipe and covered with cement plaster 1:6.

Fig 32 Typical details of  waterproofing treatment in case of roofs abutting against the parapet wall

10.4.6. SPECIFICATIONS FOR GLASS FIBRE TISSUE REINFORCED BITUMEN

10.4.6.1 General - Information on use of glass fibre tissue reinforced bitumen as damp-proofing material is covered in Part 1 of this section. This material is also used for waterproofing of roofs.

10.4.6.2 Materials

a) Bitumen primer shall conform to IS: 3384-1986.

b) Glass fibre tissue shall conform to IS: 719-1994. Other details of glass fibre shall be as in 4.2.1 of Part 1 of this section.

c) Bonding material shall be blown bitumen to IS: 702-1988 or residual bitumen to IS: 73- 1992, or a mixture thereof selected to suit local conditions. The penetration of bitumen shall not be more than 40 when tested in accordance with IS: 1203-1978.

10.4.6.3. In-situ – Waterproofing treatment of roofs

10.4.6.3.1. In selecting the combination of layers of glass the type and construction of buildings, climatic and atmospheric conditions in the degree of permanence required.

Fig. 33 Typical details of waterproofing treatment for roof with projecting features

10.4.6.3.2. For concrete, masonry and metallic roofs, flat or sloping, the following treatments are recommended:

Normal treatment:

  1. Bitumen primer at the rate of 0.4 kg/m2 ;
  2. Hot bitumen at the rate of 1.6 kg/m2, Min;
  3. Glass fibre tissue ;
  4. Hot bitumen at the rate of 1.6 kg/m2, Min; and
  5. Pea-sized gravel or grit devoid of fine sand at the rate of 0.006 m3/m2.

Heavy treatment

1 to 4) Same as in 10.6.3.2 (a) items (1) to (4) ;

  1. Second layer of glass fibre tissue laid perpendicular to previous layer;
  2. Hot applied bitumen at the rate of 1.6 kg/m2, Min; and
  3. Finish as in 10.6.3.2 (a), item 5.

Extra heavy treatment

1 to 6) Same as in 10.4.6.3..2 (b) item 1 to 6 ;

  1. Third layer of glass fibre tissue laid perpendicular to previous layer;
  2. Hot applied bitumen at the rate of 1.6 kg/m2, Min; and
  3. Finish as in 10.4.6.3.2. (a), item (5).

Note - 1) Five course treatment is recommended for moderate conditions (about 50 cm) of rainfall. Seven course treatment is suggested for severe conditions (between 50 to 150 cm) of rainfall. Nine course treatment is recommended for very severe condition (150 cm and above) of rainfall.

2) Where pea-size gravel is not available, course sand may be used.  Also tiles, finish, etc, shall be done in section 7.

3) In the case of flat roofs with precast slabs, where the roof is graded with lime concrete and surfaces plastered, normal treatment as in 10.4.6.3.2(a) can be adopted. In case of sloping roofs, heavy treatment as in 10.4.6.3.2 (b) can be adopted. In case of too much of structural movements, an additional layer of glass fibre tissue embedded in hot bitumen may be provided.

10.4.6.3.3 Junction of parapet wall and roof shall be treated as shown in Fig 34 and  Fig 35.

Fig 34 Waterproofing on a flat roof with brick parapet over 450 mm in height

10.4.6.3.4. For expansion joints two layers of glass fibre base felt, Type 2 Grade 1 shall be laid loose overlapping one and other with one end of the felt stuck with bitumen alternately and finally covered with a layer of glass fibre tissue impregnated with hot bitumen.  Typical arrangement is shown in Fig. 36       

10.4.6.3.5. Sloping roofs - Typical details of special treatment of AC and G1 corrugated roofing at joints is given in Fig. 37      

Fig 37 Special treatment for AC/GI corrugated surface joints – Typical details

10.4.6.4 Laying

10.4.6.4.1 Sequence of operations shall be as in 10.3.6.1.

Fig. 35 Waterproofing on a flat roof with RCC parapet over 450 mm or less in height

Fig. 36 Waterproofing of expansion joint with glass fibre in-situ treatment on RCC slab – Typical details

10.4.6.4.2 Procedure

a) Clean the surface to be treated with wire brushes;

b) Prime the entire surface;

c) Cut the required length of glass fibre tissue and roll it ;

d) Pour hot bitumen on the surface to the extent of roll width and simultaneously embed the glass fibre tissue into it.  Proceed in this manner throughout the length of the roll. Precaution should be taken to ensure adequate sealing of overlaps;

Fig. 37 Special treatment for AC/GI corrugated surface joints-Typical details

e) Apply second coat of hot bitumen;

f) In case of multi layer treatments, the joints in the glass fibre tissue between successive layers should be staggered midway;

g) The minimum overlap at ends and sides shall be 100 mm. All overlaps shall be firmly bonded with hot bitumen; and

h) The finishing materials like pea-sized gravel or grit surface dry shall be embedded into hot bitumen while it is being poured, by applying minimum pressure.

10.4.7. SPECIFICATIONS FOR WATERPROOFING OF UNDERGROUND RESERVOIRS AND SWIMMING POOLS

10.4.7.1. General - During construction of underground water resources and concrete swimming pools and reservoirs, it is essential to ensure water tightness of the resulting structures so that the flow of water from inside the structure to outside and the infiltration of the water from the surrounding soil into the structure are effectively prevented.

10.4.7.2 Design features - Suitable precautions should be taken to avoid cracks and resulting leakages from the following:

a) Movements due to shrinkage and creep;

b) Movements due to variation of temperature and humidity;

c) Movements due to dissipation of heat generated by the concrete in the process of hydration;

d) Damage to concrete by the percolation of chemically aggressive liquids from outside;

e) Damage due to uneven settlement of foundations;

f) Cracking of concrete caused by rusting of bars;

g) Hydrostatic uplift force.

10.4.7.2.2 The design shall be according to IS: 3370(Part 1)-1965.

a) The concrete mix proportions should be so designed to give an impermeable structure; this depends on the choice of water cement ratio, concrete mix, curing, etc.

b) To reduce shrinkage stresses as far as possible, there should not be less than 0.3 percent of steel in any direction.

c) To avoid temperature changes, reservoirs, shall be partly built into the ground, so that soil is available to cover the roof and to enclose the reservoir completely in a covering of earth, if necessary; and

d) Lapping of reinforcement in circular tanks should be so arranged that not more than 25 percent of the bars are jointed at any one vertical section.

10.4.7.3 Materials

a) Bitumen mastic shall conform to IS: 5871-1987. Bitumen felt shall conform to IS: 1322-1993 Type 3 Grade 2; or IS: 7193-1974, Type 2 Grade 1.  Bitumen for bonding shall conform to IS: 702-1988.

b) Cement, steel, water shall conform to IS: 3370 (Part 1)-1965.

10.4.7.4 Waterproofing treatment

10..4.7.4.1 Preventive measures

a) The ground should slope away from the structure for a distance of about 3 m to divert the run-off. The surfaces near the side walls should be paved; drainage to divert the water away from the structure shall be provided.

b) Waterproofing shall be done as in 3 using bitumen felt or 6 using glass fibre tissue ; and damp-proofing treatment shall as in 3 Part 1 of this section using bitumen mastic.

c) The treatment mentioned in 7.10.3.4.1 (b) shall be covered with a cement screed of 1:3 adding integral waterproofing compound.  The surface of the screed should be levelled.

d) The inside of walls and floors should be plastered, with cement plaster 1:3 with waterproofing compound added in two coats ; the first coat being 12 mm thick and  the second coat 10 mm thick. The outside surface of walls should be rendered with waterproofing compound added in a similar manner.

e) A coat of hot bitumen shall be applied to the outside wall after the rendering has dried.

10.4.7.5. Construction details

a) In long walls, they may be divided into 15 m sections with a gap of about 30 cm left between sections so that shrinkage in the long sections may occur, as far as possible, before the gap is concreted and the longer this can be deferred the better.

b) Vibrators shall be used wherever possible, for compaction.

c) Construction joints should be perpendicular to the general direction of the member. As far as possible vertical joints should be avoided.

d) It is not practicable to provide expansion joints in small and medium reservoirs and swimming pools. In large reservoirs expansion joints shall be provided at not more than 35 m for underground structures and not more than 28 m for exposed structures.

e) Pipes and special fixtures should be fixed in position before concreting is done.

f) For testing and remedial treatment reference may be made to IS: 6494-1988.

10.4.8. SPECIFICATIONS FOR SILICONE BASED WATER REPELLENT

10.4.8.1 General - Application of the appropriate class of water repellent to all exterior surfaces free from cracks wider than 0.1 mm above ground level provides protection against absorption of water, salt and dirt. Applied over cement based paints, the repellent preserves the colour, brightness and appearance. Used as primers for oil based paints, the repellents minimize peeling and blistering caused by damp and salt from the masonry walls. The repellents should be applied to complete masonry rather than to individual units, in order to avoid inadvertent treatment of bedding faces which would be detrimental to bonding of mortar. Normally the repellent does not alter the dry appearance of the surface. Application of water repellent on exposed brickwork surfaces reduces the appearance of efflorescence of soluble sulphates.

10.4.8.2  Materials

a) The silicone water repellent shall conform IS: 12027-1987. They are three classes of the repellents as below :

Class A – Silicone solvent solution for clay brickwork, hydraulic cement – based materials, natural and cast stone masonry for a predominantly siliceous nature.

Class B – Silicone solvent solution for natural and cast stone masonry work of predominantly calcareous nature and calcium silicate brickwork.

Class C – Aqueous solution of sodium methyl siliconate for clay brickwork, natural and cast stone masonry of a predominantly calcareous nature.

Note - Where the type of masonry cannot be classified, Class B repellent may be used.

10.4.8.2.1 Preparation of water repellent

a) From Class A and Class B materials – The Class A and Class B material may be diluted with mineral spirit or xylene. The mineral spirit should have minimum flash point of 27 degree C, boiling range of 135 to 185 degree C and minimum Kauri-Butanol value of 310.3.4.  For best results these classes of materials should contain 5 percent solids.

b) From Class C, the material may be diluted with water to a concentration of 3 percent solids just prior to the application.

10.4.8.3. Preparation of the surface

a) Cracks wider than 0.1 m and defective mortar joints shall be repaired. Surfaces should be clean and dry.  Detergents and wetting agents should not be used.

b) When drying of surface is difficult, Class C material shall be used either as a full treatment or prior to application of Class A or Class B treatment.

c) Efflorescence, if visible, shall be washed with 5 to 10 percent muriatic acid (HCI) solution and then rinse it with clear water. If it re-appears in some places after drying, the repellent shall be applied and allowed to cure for 24 h and the surface be again washed with muriatic acid (HCI) and rinsed. Then the surface may be treated with the repellent.

d) The masonry, concrete, cement plaster and cement based painted surfaces shall be allowed to cure for 21 days before applying the repellent. If cement paint surfaces are treated with the repellent on a small area and if water repellency has not developed, such surface shall be cured for a longer period.

10.4.8.4 Application of repellant

a) Normally a single generous or flood coat by brush or spray would be sufficient.  The material should be applied liberally so that it runs down the surface freely to about 15 cm below the point of application.

b) When spraying, the solution should not be atomized or misted, but in a solid stream by maintaining a low nozzle pressure.

c) Safety instructions of manufacturer should be followed.

10.5. Tests on Acrylic based polymer waterproofing materials    

For methods of test of Acrylic based polymer water roofing materials,

(1). Determination of solid content,

(2). Determination of solid content,

(3). Determination of capillary water take

(4). Determination of ph value

(5). Determination of minimum film forming temperature and white point, and

(6). Measuring of water vapour transmission of polyethylene film

BIS: 13435(Part 1)-1992 may be referred.

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