BRICK WORK



BRICK WORK

6. SPECIFICATIONS FOR BRICKS / BRICK TILES / BRICK BATS

6.1. Bricks / Brick tiles / Brick bats - Bricks used in the masonry may be of the following type:

a) Common burnt clay bricks - Shall be hand moulded or machine moulded.  They shall be free from nodules of free lime; visible cracks, flaws warpage and organic matter have a frog 100mm to 20 mm deep on one of its flat sides.  Bricks made by extrusion process and brick tiles may not be marked with frogs.  Each brick shall be marked (in the frog where provided) with the manufacturer’s identification mark or initials.

b) Fly ash lime brick - Shall be sound, compact and uniform in shape free from visible cracks, war pages flaws and organic matter, have a frog 100 mm in length, 40mm width and 10 to 20 mm deep on one of its flat side.  The shape and size of the frog shall conform to   IS: 12894.

Fly Ash: Flay ash shall conform to grade I or Grade 2 of IS: 3812.

Bottom ash used as replacement of sand shall not have more than 12% loss on ignition when tested.

Sand: Deleterious materials, such as clay and silt in the sand shall preferably be less than 5%.

Lime: Lime shall conform to Class ‘C‘hydrated lime of IS: 712.

Additives: Any Suitable additive considered not detrimental to the durability of bricks may be used.

c) Clay fly ash bricks - The clay fly ash brick shall be sound, compact and uniform in shape and colour.  Bricks shall have smooth rectangular faces with sharp and square corners.  The bricks shall be free from visible cracks, flaws, warpage, nodules of free lime and organic matter.  The bricks shall be hand or machine moulded.  The bricks shall have frog of 100 mm in length 40 mm width and 10 to 20 mm deep on one of its flat sides.

d) Fly ash shall conform to grade I of II of IS: 3812

Calcium silicate bricks - Calcium silicate bricks shall be sound, compact and uniform in shape –bricks shall be free from visible cracks, warpage organic matter, large pebbles and nodules of free lime.  Bricks shall be solid and with or without frog.  The bricks shall be made of finely grounded sand siliceous rock and lime.  In addition limited quantity of fly ash conforming to IS: 3812 may be used in the mix.

e) Tile brick - The bricks of 4 cm height shall be moulded without frogs.  Where modular tiles are not freely available in the market, the tile bricks of F.P.S. thickness 44mm (1-3/4”) shall be used unless otherwise specified.

f) Brick bats - Brick bats shall be obtained from well burnt bricks.

6.1.1. Dimensions - The brick may be modular or non-modular.  Size for both types of bricks/ tiles shall be as per Table 1.  While use of modular brick tiles is recommended, non-modular (FPS) bricks/tiles can also be used where so specified.  Non–modular bricks / tiles of sizes other than the sizes mentioned in Table 1 may also be used where specified.

Table -1

Type of Bricks / tiles

Nominal size (mm)

Actual size (mm)

Modular Bricks

200x100x100mm

190x90x90mm

Modular Tile Bricks

200x100x40mm

190x90x40mm

Non-Modular Tile Bricks

229x114x44mm

225x111x44mm

Non-Modular Bricks

229x114x70mm

 

225x111x70mm

225x112.5x65mm

 6.1.2. Classification - Bricks / Brick tiles shall be classified on the basis of their minimum compressive strength as given below.

Table -2

Class Designation

Average compressive strength

Not less than

Less than

N/mm²

(kgf/cm²)

N/mm²

(kgf/cm²)

10(100)

10

(100)

12.5

125

7.5(75)

7.5

(75)

10

100

5(50)

5

(50)

7.5

75

3.5(35)

3.5

(35)

5.0

50

the bricks shall have smooth rectangular faces with sharp corner and shall be uniform in colour and emit clear ringing sound when struck.(Note: Upper limits specified in Table 2 are for calculating the average compressive strength in accordance with Annexure 6-A.2.)

6.1.3. Sampling and tests - Sampling of bricks shall be subjected to the following tests 

(a)Dimensional tolerance (b) Water absorption (c) Efflorescence (d) Compressive strength

6.1.3.1. Sampling - For carrying out compressive strength, water absorption, efflorescence and dimensional tests, the samples of bricks shall be taken at random according to the size of lot as given in table 3 below.  The sample thus taken shall be stored in a dry place until tests are made.  For the purpose of sampling the following definition shall apply.

a) Lot - A collection of same class and size, manufactured under relatively similar conditions of production.  For the purpose of sampling a lot shall contain a maximum of 50,000 bricks

In case a consignment has bricks more than 50,000 of the same classification and size and manufactured under relatively similar conditions of production , it shall be divided into lots of 50,000 bricks or part there of.

(b) Sample - A collection of bricks selected for inspection and/ or testing from a lot to reach the decision regarding the acceptance or rejection of the lot.

(c)Defective - A brick failing to meet one or more of the specified requirements.

6.1.3.2. The samples shall be taken as below:

(i) Sampling from a stack - When it is necessary to take a sample from a stack, the stack shall be divided into a number of real or imaginary sections and the required number of bricks drawn from each section.  For this purpose bricks in the upper layers of the stack shall be removed to enable units to be sampled from places within the stack.

Note: For other methods of sampling i.e. sampling in motion and sampling from lorries or trucks, IS: 5454 may be referred. Scale of sampling and criteria for conformity for visual and dimensional characteristics: -

Visual characteristics - The bricks shall be selected and inspected for ascertaining their conformity to the requirements of the relevant specification.

The number of bricks to be selected from a lot shall depend on the size of lot and shall in accordance of col. 1 and 2 of Table 3 for visual characteristics in all case and dimensional characteristics if specified for individual bricks.

(ii) Visual characteristics - All the bricks selected above in accordance with col. 1 and 2 of Table 3 shall be examined for visual characteristics.  If the number of defective bricks found in the sample is less than or equal to the corresponding number as specified in col.3 of table 3 the lot shall be considered as satisfying the requirements of visual characteristics, otherwise the lot shall be deemed as not having met the visual requirements.

(iii) Dimensional characteristics - The number of bricks to be selected for inspecting the dimensions and tolerance shall be in accordance with col.1. and 4 of Table 3.  These bricks will be divided into groups of 20 bricks at random and each of 20 bricks thus formed will be tested for all the dimensions and tolerances.  A lot shall be considered having found meeting the requirements of dimensions and tolerance, if none of the groups of bricks inspected fails to meet the specified requirements.

Table 3 Scale of sampling and permissible number of defectives for visual and dimensional characteristics

No. of bricks in the lot

For characteristics specified for individual bricks

For dimensional characteristics for group of 20 bricks- No. of bricks to be selected

No. of bricks to be selected

Permissible no of defectives in the sample

2001-10000

20

1

40

10001-35000

32

2

60

35001-50000

50

3

80

Note: In case the lot contains 2000 or less bricks the sampling shall be as per decision of the engineer.

iv)Scale of sampling and criteria for physical characteristics - The lot which has been found satisfactory in respect of visual and dimensional requirements shall be next tested for physical characteristics like compressive strength water absorption, efflorescence as specified in relevant material specification.  The bricks for this purpose shall be taken at random from those already selected above.  The number of bricks to be selected for each of these characteristics shall be in accordance with relevant columns of Table 4.

Table -4

Lot Size

Sample size for compressive strength, water absorption and efflorescence

Permissible No. of defectives for efflorescence

2001-10000

5

0

10001-35000

10

0

35001-50000

15

1

Note: In case the lot contains 2000 or less bricks, the sampling shall be as per decision of engineer.

v) A lot shall be considered having satisfied the requirements of physical characteristics if the condition stipulated here in are all satisfied.

(a) From the test results for compressive strength the average shall be calculated and shall satisfy the requirements specified in relevant material specification.

Note: In case any of the test results for compressive strength exceeds the upper limit for the class of bricks, the same shall be limited to the upper limit of the class for the purpose of average

(b) Where specified in the material specification, the compressive strength of any individual bricks tested in the sample shall not fall below the minimum average compressive strength specified for the corresponding class of brick by more than 20 per cent. (c) From the test results for water absorption, the average for the bricks in the sample shall be calculated and shall satisfy the relevant requirements shall satisfy the relevant requirements specification in material specification. (d) The number of bricks failing to satisfy the requirements of the efflorescence specified in the relevant specification should not be more than the permissible no. of defectives given in col. 3 of Table 4.

6.1.3.3. Dimensional tolerances - The dimensions of modular bricks when tested as described above as per procedure described in Annexure 6-A.1 shall be within the following limits per 20 bricks.

Length 372 to 388 cm (380 ± 8 cm)

Width 176 to 184 cm (180 ± 4 cm)

Height 176 to 184 cm (180 ± 4 cm) for 90 cm high bricks

Brick tiles

76 to 84 cm (80 ± 4) for 40 mm high brick tiles. In case of non–modular bricks, %age tolerance will be ± 2% for group of 20 numbers of classes, 10 bricks and ± 4% for other class of bricks.

6.1.3.4. Compressive strength - The bricks when tested in accordance with the procedure laid down in Annexure 6-A.2 shall have a minimum average compressive strength for various classes as given in Table 2 the compressive strength of any individual brick tested shall not fall below the min average compressive strength specified for the corresponding class of brick by more than 20%.  In case compressive strength of any individual brick tested exceeds the upper limit specified in Table 2 for the corresponding class of bricks, the same shall be limited to upper limit of the class as specified in Table 2 for the purpose of calculating the average compressive strength.

6.1.3.5. Water absorption - The average water absorption of bricks when tested in accordance with the procedure laid down in Annexure 6-A.3 shall be not more than 20% by weight.

6.1.3.6. Efflorescence - The rating of efflorescence of bricks when tested in accordance with the procedure laid in Annexure 6-A.4 shall be not more than moderate.

6.2. SPECIFICATIONS FOR BRICK WORK

6.2.1. Classification - The brick work shall be classified according to the class designation of bricks used.

6.2.2. Mortar - The mortar for the brick work shall be as specified, and conform to accepted standards. Lime shall not be used where reinforcement is provided in brickwork.

6.2.3. Soaking of bricks - Bricks shall be soaked in water before use for a period for the water to just penetrate the whole depth of the bricks.  Alternatively bricks may be adequately soaked in stacks by profusely spraying with clean water at regular intervals for a period not less than six hours.  The bricks required for masonry work using mud mortar shall not be soaked.  When the bricks are soaked they shall be removed from the tank sufficiently early so that at the time of laying they are skin-dry.  Such soaked bricks shall be stacked on a clean place where they are not again spoiled by dirt earth etc.

Note: 1. The period of soaking be easily found at site by a field test in which the bricks are soaked in water for extent of water penetration.  The least period that corresponds to complete soaking will be the one to be allowed for in construction work.

Note: 2. If the bricks are soaked for the required time in water that is frequently changed the soluble salt in the bricks will be leached out, and subsequently efflorescence will be reduced.

6.2.4. Laying

6.2.4.1. Bricks shall be laid in English bond (fig.2.3.) unless otherwise specified.  For brick work in half brick wall, bricks shall be laid in stretcher bond. Half or cut bricks shall not be used except as closer where necessary to complete the bond.  Closers in such cases shall be cut to the required size and used near the ends of the wall.  Header bond shall be used preferably in all courses in curved plan for ensuring better alignment.

Note: Header bond shall also be used in foundation footings unless thickness of walls (width of footing) makes the use of headers impracticable, where thickness of footing is uniform for a number of courses the top course of footing shall be headers.

6.2.4.2. All loose materials, dirt and set lumps of mortar which may be lying over the surface on which brick work is to be freshly started, shall be removed with a wire brush and surface wetted.  Bricks shall be laid on a full bed of mortar when laying each brick shall, be properly bedded and set in position by gently pressing with the handle of a trowel.  Its inside face shall be buttered with mortar before the next brick is laid and pressed against it.  Joints shall be fully filled and packed with mortar such that no hollow spaces are left inside the joints.

6.2.4.3. The walls shall be taken up truly in plumb or true to the required batter where specified.  All courses shall be laid truly horizontal and all vertical joints shall be truly vertical.  Vertical joints in the alternate course shall come directly one over the other.  Quoin, jambs and other angles shall be properly plumbed as the work proceeds.  Care shall be taken to keep the propounds properly aligned within following maximum permissible tolerances:

(a) Deviation from vertical within a storey shall not exceed 6 mm per 3m height.

(b) Deviation in verticality in total height of any wall of building more than one storey in height shall not exceed 12.5. mm (c) Deviation from position shown on plan of any brickwork shall not exceed 12.5. mm (d) Relative displacement between load bearing wall in adjacent storey intended to be vertical alignments all not exceed 6 mm. (e) A set of tools comprising of wooden straight edge, masonic spirit levels, square, 1 meter rule line and plumb shall be kept on the site of work for every 3 masons for every 3 masons for proper check during the progress of work.

6.2.4.4. All quoins shall be accurately contracted and the height of brick courses shall be kept uniform.  This will be checked using graduated wooden straight edge or storey rod indicating height of each course including thickness of joints.  The position of damp proof course, windowsills, bottom of lintels top of the wall etc, along the height of the wall shall be marked on the graduated straight edge or storey rod.  Acute and obtuse quoins shall be bonded, where practicable in the same way as square quoins.  Obtuse quoins shall be formed with squint showing three quarters brick on one face and quarter brick on the other.

6.2.4.5. The brickwork shall be built in uniform layers.  No part of the wall during its construction shall rise more than one meter above the general construction level.  Parts of wall left at different levels shall be raked back at an angle of 45 degrees or less with the horizontal.  Toothing shall not be permitted as an alternative to raking back.  For half brick partition to be keyed into main walls, indents shall be left in the main walls.

6.2.4.6. All pipe fittings and specials, spouts hold fasts and other fixtures which are required to be built into the walls shall be embedded, as specified in their correct position as the work proceeds unless otherwise directed by the engineer.

6.2.4.7. Top courses of all plinths, parapets, steps and top of walls below floor and roof slabs shall be laid with brick on edge, unless specified otherwise.  Brick on edge laid in the top courses at corner of walls shall be properly radiated and keyed into position to form cut   corners as shown in Fig. 4.   Where bricks cannot be cut to the required shape to from cut corners, cement concrete 1:2:4(1 cement: 2 coarse sand: 4 graded stone aggregate 20 mm nominal size) equal to thickness of course shall be provided in lieu of cut bricks.

6.2.4.8. Bricks shall be laid with frog (where provided) up.  However, when top course is exposed bricks shall be laid with frog down.  For the bricks to be laid with frog down, the frog shall be filled with mortar before placing the brick in position.

6.2.4.9. In case of walls one brick thick and under one face shall be kept even and in proper plane, which the other face may be slightly rough.  In case of walls more than one brick thick, both the faces shall be kept even and in proper plane.

6.2.4.10. To facilitate taking service lines later without excessive cutting of completed work, sleeves (to be paid separately) shall be provided, where specified, while raising the brick work. Such sleeves in external walls shall be sloped down outward so as to avoid passage of water inside.

6.2.4.11. Top of the brickwork in coping and sills in external walls shall be slightly tilted.  Where brick coping and sills are projecting beyond the face of the wall drip course/ throating (to be paid separately) shall be provided where indicated.

6.2.4.12. Care shall be taken during construction that edges of jambs sills and projections are not damaged in case of rain.  New built work shall be covered with gunny bags or tarpaulin so as to prevent the mortar from being washed away.  Damage if any, shall be made good to the satisfaction of the engineer.

6.2.4.13. Vertical reinforcement in the form of bars (MS or high strength deformed bars) considered necessary at the corners and junction of walls and jamb opening doors, windows etc., shall be encased with cement mortar not leaner than 1:4 (1 Cement 4 coarse sand) or cement concrete mix as specified.  The reinforcement shall be suitably tied, properly embedded in the foundation and at roof level.  The Dai of bars shall not be less than 8 mm and concrete grade shall be minimum 1:3:6 (1 cement 3 coarse sand: 6 graded stone aggregate 20 mm nominal size).

6.2.4.14. In retaining walls and the like where water is likely to accumulate weep holes, 50 to 75 mm square shall be provided at 2 m vertically and horizontally unless otherwise specified.  The lowest weep hole shall be at about 30 cm above the ground level.  All weep helps shall be surrounded by loose stones and shall have sufficient fall to drain of the water quickly.

(Note: Work of providing loose stone will be payable extra).

6.2.4.15.  Work of cutting chases, where required to be made in the walls for housing G.I pipe, CI pipe or any other fixtures shall be carried out in various locations as per guidelines given below:

(a) Cutting of chases in one brick thick and above load bearing walls

(i) As far as possible services should be planned with the help of vertical chases.  Horizontal chases should be avoided. (ii) The depths of vertical chases and horizontal chases shall not exceed one third and one sixth of the thickness of the masonry respectively. (iii) When narrow stretches of masonry (or short length of walls) such as between doors and windows, cannot be avoided they should not be pierced with openings for soil or waste pipes or possibility of load concentration such narrow lengths of walls shall be checked for stresses and high strength bricks in mortar or concrete walls provided if required. (iv) Horizontal chases when unavoidable should be located in the upper or lower one third or height of storey and not more than three chases should be permitted in any stretch of a wall No. continuous horizontal chase shall exceed one meter in length.  Where unavoidable stresses in the affected area should be checked and kept within the permissible limits.(v) Vertical chases should not be closer than 2 m in any stretch of a wall.  These shall be kept away from bearings of beams and lintels.  If unavoidable stresses in the affected area should be checked and kept within permissible limits, (vi) Masonry directly above a recess, if wider than 30 cm horizontal dimension should be supported on lintel. Holes are masonry may be provided upto to cm width and 30 cm height without any lintel.  In the case of circular holes in the masonry, no lintel need be provided for holes upto 40 cm in diameter.

(b) Cutting of chases in half brick load bearing walls -       

No chase shall be permitted in half brick load bearing walls and as such no recessed conduits and concealed pipes shall be provided with half thick load bearing walls.

(c) Cutting of chases in half brick non-load bearing wall - Services should be planned with the help of vertical chases.  Horizontal chase should be provided only when unavoidable.

6.2.5. Joints - The thickness of all types of joints including brick wall joints shall be such that four course and three joints taken consecutively shall measure as follows:

(i)In case of modular bricks conforming to IS: 1077 specification for common burnt clay buildings bricks, equal to 39 cm.  (ii) In case of non–modular bricks, it shall be equal to 31 cm.

Note: Specified thickness of joints shall be of 1 cm.  Deviation from the specified thickness of all joints shall not exceed one – fifth of specified thickness.

6.2.5.1. Finishing of joints - The face of brickwork be finished flush or by pointing.  In flush finishing either the face joints of mortar shall be worked out while still green to give a finished surface flush with the face of the brick work or the joints shall be squarely raked out to a depth of 1 cm while the mortar is till green for subsequently plastering.  The faces of brickwork shall be cleaned with wire brush so as to remove any splashes of mortar during the course of raising the brickwork.  In pointing the joints shall be squarely raked out to a depth of 1.5 cm while the mortar is still green and raked joints shall be brushed to remove dust and loose particles and well wetted and shall be later refilled with mortar to give ruled finish some such finishes are "flush" " weathered" "ruled" etc.,

6.2.6. Curing - The brickwork shall be constantly kept moist on all faces for a minimum period of seven days.  Brickwork done during the day shall be suitably marked indicating the date on which the work is done so as of keep a watch on the curing period.

6.2.7. Scaffolding - Scaffolding shall be strong to withstand all dead, live and impact loads, which are likely to come on them.  Scaffolding shall be provided to allow easy approach to every part of the work.

6.2.7.1. Single scaffolding - Where plastering pointing or any finishing has been indicated for brickwork single scaffolding may be provided unless otherwise specified.  In single scaffolding one end of the put –logs / pole shall rest in the hole provided in the header course of brick masonry.  Not more than one header for each put – log / pole rest in the hole provided in the header course of brick masonry.  Not more than one header for each put log / pole shall be left out.  Such holes shall not be allowed in the case of pillars, brick work less than one metre in length between the openings or near the skewbacks of arches or immediately under or near the structural member supported by the walls.  The holes for putlogs / poles shall be made good with brickwork and wall finishing as specified.

6.2.7.2. Double Scaffolding - Where the brick work or tile work is to be exposed and not to be finished with plastering etc., double scaffolding having two independent supports clear of the work, shall be provided.

6.2.8. Measurements

6.2.8.1. Brickwork shall be measured in cubic meters unless otherwise specified.  Any extra work over the specified dimensions shall be ignored.  Dimensions shall be measured correct to the nearest 0.01-m i.e. 1 cm.  Areas shall be calculated to the nearest 0.01 sq.mtrs and the cubic contents shall be worked out to the nearest 0.01 cubic meters.

6.2.8.2. Brickwork shall be measured separately in the following stages

(a) From foundation to floor one level (Plinth level)

(b) Plinth (floor one) level to floor two level

(c) Between two specified floor levels above floor two level

Note: (1) Brick work in parapet walls, mumty, lift machine room and water tanks constructed on the roof upto 1.2 m height above roof shall be measured together with the corresponding work of the floor next below.

6.2.8.3. No deductions or additions shall be done and no extra payment made for the following:

Note: Where minimum area is defined for deduction of an opening or void or both such areas shall refer only to opening or void the space measured.

a) Ends of dissimilar materials (that is, joints beams, lintels, posts, girders, rafters, purlins trusses, corbels, steps etc.,) up to 0.1 m² in section.

b) Opening up to 0.1.m² in area (see Note)

c) Wall plates, bed plates and bearing of slabs chejjas and the like, where thickness does not exceed 10 cm and bearing does not extend over the full thickness of wall:

d) Cement concrete blocks as for holdfasts and holding down bolts:

e) Iron fixtures such as wall ties pipes upto 300 mm diameter and hold fasts for doors and windows; and f) Chases of section not exceeding 50 cm in girth g) Bearing portion drip course bearing of moulding and cornice.

Note: In calculating area of an opening any separate lintel or sills shall be included with the size of the opening but end portions of lintel shall be excluded.  Extra width of rebated reveals, if any shall also be excluded.

6.2.8.4. Walls half brick and less shall each be measured separately in square meters stating thickness.

6.2.8.5. Walls beyond half brick thickness shall be measured in multiples of half brick, which shall be deemed to be inclusive of mortar joints for the sizes of bricks specified in 6.1.1. half brick thickness  shall mean 100 mm for modular and 115 mm for non – modular bricks.

Where fractions of half brick occur due to architectural or other reasons, measurement shall be as follows: a) upto 1/4th brick – actual measurements and b) exceeding ¼ brick- full half bricks.

6.2.8.6. String courses, projecting pilasters, aprons sills and other projections shall be fully described and measure separately in running meters stating dimensions of each projection.

6.2.8.7. Square or rectangular pillars shall be measured separately in cubic meters in multiple of half brick.

6.2.8.8. Circular pillars shall be measured separately in cubic meters as per actual dimensions.

6.2.8.9. Brick work curved on plan shall be measured like the brick in straight walls and shall include all cutting and wastage of bricks tapered, vertical joints and use of extra mortar, if any.  Brick work curved on plan to a mean radius not exceeding six meters shall be measured separately and extra shall be payable over the rates for brick work in straight walls.  Nothing extra shall be payable if the mean radius of the brickwork curved in plan exceeds six meters.

6.2.8.10. Tapered walls shall be measured net as walls and extra payment shall be allowed for making tapered surface for brickwork in walls.

6.2.8.11. Brick work with brick tiles shall be measured and paid for separately.

6.2.9. Rate - The rate shall include the cost of materials and labour required for all the operations described above except the vertical reinforcement and its encasement in cement mortar or cement concrete the rate shall also include the following:

a) Raking out joints or finishing joints flush as the work proceeds;

b) Preparing tops of existing walls and the like for raising further new brick work.

c) Rough cutting and waste for forming gables splays at eaves and the like.

d) Leaving holes for pipes upto 150 mm dia and encasing hold fasts etc.

e) Rough cutting and waste for brick work curved in plan and for backing to stone or other types of facing.

f) Embedding in ends of beams, joints slabs, lintels, sills, trusses etc.

g) Bedding wall plates lintels, sills, roof tiles corrugated sheets etc in or on walls if not covered in respective items and

h) Leaving chases of section not exceeding 50 cm in girth or 350 sq in cross-section.

I) Brick on edge courses, cut brick corners, splays reveal, cavity walls, brick works, curved on plan to a mean radius exceeding six meters.

6.3. SPECIFICATIONS FOR BRICK WORK IN ARCHES (Fig 5)

6.3.0. The detailed specifications for brick work mentioned in 6.2 shall apply, in so far as these are applicable.  Arch work shall include masonry for both gauged as well as plain arches.  In gauged arches, cut or moulded bricks shall be used.  In plain arches uncut bricks shall be used.

Brick forming skew – backs shall be dressed or cut so as give proper radials to the end voussiors.  Defects in dressing of bricks shall not be permitted by extravagant use of mortar, nor shall the use of chips or bats etc., be permitted.

The bricks of the spandrel wall at their junction with the extrudes of the arch shall be cut fit the curvature of the arch.

6.3.1. Circular arches - These shall be either (a) plain arches, and shall be built in half brick concentric rings with break joints, or (b) gauged arches built with bricks cut or moulded to proper shape.  The arch work shall be carried up from both ends extraneously and keyed in the centre.  The bricks shall be flush with mortar and well pressed into their positions so as to squeeze out a part of their mortar and leave the joints thin and compact.  All joints shall be full of mortar and thickness of joints shall be full of mortar and thickness of joints shall not be less than 5 mm nor more than 15 mm.

After the arch is completed, the haunches shall be loaded by filling up the spandrels upto the crown level of the arch.  Care shall be taken to load the haunches on two sides of the spandrels.

When the arch face is to be pointed (and not plastered), the face bricks shall be cut to proper shape or moulded so as to have the joints not more than 5 mm thick These shall be laid with radial joints to the full depth of the arch.  The voussiors shall break joints to the full depth of the arch.

6.3.2. Flat arches - These shall be gauged arches of brick cut or moulded to proper shape.  The extrudes shall be kept horizontal and the  intrudes shall be given slight camber of 1 in 100 of the span.  The center of the arch from which joints shall radiate shall be determined by the point of the inter – section of the two lines drawn from the ends of the arch at the springing level and at 60 to horizontal. In flat arches bricks shall be laid with radial joints to the full depth of arch and voussiors breaking joints with each other.  The arch work shall be carried up from both ends simultaneously and keyed in the center.  The thickness of the joints shall not exceed 5 mm.  Flat arches may be used for the sake of appearance but for purpose of carrying loads of the wall above these shall be used in conjunction with relieving arches, lintels placed below.

6.3.3. Centering and shuttering - The centering and shuttering for the arch shall be got approved by the engineer before the arch work is started.  It shall be strong enough to bear the dead load of the arch and the live loads that are likely to come upon it during construction, without any appreciable deflections.

The shuttering shall be tightened with hard wood wedged or sandboxes, so that the same could be eased without jerks being transmitted to the arch.  The sequence of easing the shuttering shall be got approved from the engineer.  The shuttering shall be struck within 48 hours.  This shall be done after the spandrel has been filled in and the arch loaded.

6.3.4. Measurements - The length of the arch shall be measured as the mean of the extrudes and intrudes of the arch correct to a cm.  The thickness of the arch shall be measured in multiples of the half brick. The breadth in the direction of the thickness of wall shall be measured as specified.

The cubical contents shall be calculated in cubic meter correct to two places of decimal.

For arches exceeding 6 m in spans extra payment shall be made on the actual area of the soffit for additional cost of centering including all strutting, bolting, wedging, easing, striking and its removal.

6.3.5. Rate - The rate is inclusive of the cost of the materials and labour for all the operations described above.

6.4. Half brickwork - Brick work in half brick walls shall be done in the same manner as described above in 6.2.4 except that the bricks shall be laid in stretcher bond.  When the half brick work is to be reinforced 2Nos. M.S. bars of 6mm dia, shall be embedded in every third course as given in the item (the dia of bars shall not exceed 8 mm).  These shall be securely anchored at their end where the partitions end.  The free ends of the reinforcement shall be keyed into the mortar of the main brickwork to which the half brickwork is joined.  The mortar used for reinforced brickwork shall be rich dense cement mortar of mix 1:4.  Lime mortar shall not be used.  Over laps in reinforcement if any shall not be less than 30 cm. The mortar interposed between the reinforcement bars and the brick shall not be less than 5mm.  The mortar covering in the direction of joints shall not be less than 15 mm.

6.4.1. Measurements - The length and height of the wall shall be measured correct to a cm.  The area shall be calculated in sqm where half brick wall is joined to the main walls of one brick or greater thickness and measurements for half brick wall shall be taken for its clear length from the face of the thicker wall.

6.4.2. Rate - The rate includes the cost of the materials and labour involved in all the operations described above except reinforcement which is to be paid for separately.

6.5. SPECIFICATIONS FOR BRICK TILE WORK

The work shall be done in the same manner as described in 6.2.4 except that brick tile shall be used instead of bricks.  The measurements and rate shall be same as specified under 6.2.

6.6. SPECIFICATIONS FOR HONEYCOMB BRICKWORK 

The brick honeycomb work shall be done with specified class of brick, laid in specified mortar. All joints and edges shall be struck flush to given an even surface. The thickness of the brick honeycomb works shall be half-brick only, unless otherwise specified.  Openings shall be equal and alternate with half brick laid with a bearing of 2cm on either side.

6.6.1. Measurements - The length and height shall be measure correct to a cm.  Area shall be calculated in square meters correct to two places of decimal.  Honeycomb openings shall not be deducted.

6.6.2. Rate - The rate includes the cost of materials and labour involved in all the operations described above.

6.7. SPECIFICATIONS FOR JOINING OLD BRICK WORK WITH NEW BRICK WORK.

6.7.1.  In case the height of the bricks of old as well as new work is same, the old work shall be toothed to the full width of the new wall and to the depth of a quarter of brick in alternate courses.  In case the height of the bricks is unequal, the height of each course of new work shall be made equal to the height of the old work by adjusting thickness of horizontal mortar joints in the new wall.  Where necessary adjustment shall be made equal to thickness of old wall by adjusting the thickness of vertical joints.

6.7.2. For joining new cross wall to old main walls a number of rectangular recesses of width equal to the thickness of cross wall, there courses in height and half a brick in depth shall be cut in the main walls.  A space of the three courses shall be left between two consecutive recesses.  The new cross wall shall be bonded into the recesses to avoid settlement.

6.7.3. Joining of old brickwork with the new brickwork shall be done in such a way that there shall not be any hump r projection at the joint.

6.7.4. Measurement - The height and thickness of vertical face in contact with new work shall be measured to the nearest 0.01 m and the area shall be calculated to the nearest 0.01 sqm.

6.7.5. Rate - The rate includes the cost of labour and material involved in all the operations described above.

6.8. SPECIFICATIONS FOR MOULDING AND CORNICES.

The specifications described under 6.2 shall apply in so far these are applicable.  Moulding and cornices shall be made with bricks as specified for brickwork.  The bricks shall be cut and dressed to the required shape as shown in the architectural drawings.

6.8.1. Cornices shall not ordinarily project by more than 15 cm to 20 cm and this projection shall be obtained by projecting each brick course by not more than one fourth of the brick length.  For cornices projecting more than 20cm projection metal cramps shall be used and paid for separately.

6.8.2. Corbelling shall be brought roughly to shape by plastering with the specified mortar.  When the mortar is still green, the moldings shall be finished straight and true with the help of metal templates.

6.8.3. Curing and protection - The moulding and cornices shall be cured for at least seven days.  These shall be protected from the effects of sun and rain by suitable covering and also from damage during the execution of the work.

6.8.4. Measurements - For the purpose of measurements the sectional periphery of moulding and cornices (excluding the portion in contact with wall shall be measured in centimeters and length in meters (fig below).  The girth and length shall be measured correct to cm.  No deduction shall be made from the masonry of wall for the bearing of the moulding and cornices.

6.8.5. Rate - The rate includes the cost of materials and labour involved in all the operations described above

6.9. SPECIFICATIONS FOR BRICK WORK UNDER WATER OF FOUL POSITIONS.

Brick work under following conditions: (1) Work in or under water / or liquid mud (2) Work in or under foul positions shall be measured separately for payment of extra rate over and above the quantity measured and paid under para 6.2.8.

6.10. SPECIFICATIONS FOR EXPOSED BRICK WORK

6.10.1. Facing bricks - The facing bricks made from suitable soils shall be free from cracks, flaws, and nodules of free lime warpage and organic matter.  These shall be thoroughly burnt and shall have plane rectangular faces with parallel sides and sharp straight right angled edges.  Facing bricks shall have uniform colour and even texture.  Unless otherwise specified, facing bricks shall be machine moulded.  Selected hand moulded bricks may also be used as facing bricks where specified.  As far as possible, total requirements of facing bricks for a work shall be arranged from the same kiln.  Bricks with chipped edges and broken corners shall not be used.

6.10.2. Dimensions and tolerances - The standard sizes of machine moulded facing bricks shall be as specified in 6.1.1.

The permissible tolerances shall be as under:

 

Dimension (mm)

Tolerance (for Machine moulded bricks)  mm

Length

190 or 225

± 3

Width

90 or 111

± 1.5

Thickness

40 or 44

± 1.5

Notes: (1) The sectional periphery curve ABCDEF (2) Length FA shall not be measured

Note: Tolerance and dimensions for selected had moulded bricks ± 4mm in length and ± 3 mm in width and thickness

6.10.3. Sampling:  As per para 6.1.3 and 6.1.3.2.

6.10.4. Physical requirements - Facing bricks shall be of class designation 75 unless otherwise specified.  Average compressive strength shall not be less than 7.5.N/mn².  Water absorption shall not exceed 20 per cent by weight and efflorescence rating shall be nil when tested in accordance with procedure laid down and tolerance in dimensions shall be checked as per the procedure laid down.

Mortar, soaking of bricks and laying shall be as specified in para 6.2.2., 6.2.3. and 6.2.4 respectively.

6.10.5. Joints in the exposed brickwork shall be truly horizontal and vertical and kept uniform with the help of wooden or steel strips. The thickness of joints shall be as per 6.2.5.0.

6.10.6. Curing and scaffolding shall be as specified in 6.2.6 and 6.2.7 to 6.2.7.2 respectively.

6.10.7. Measurements - Exposed brick work in face using machine moulded bricks and selected hand moulded bricks shall be measured separately and the measurement shall be as specified in 6.2.8.

6.10.8. Rate - The rates shall be as specified in 6.2.9 and shall also include the following;

a) Labour for selecting bricks and wastage of bricks where use of selected hand moulded brick is specified (b) Leaving uniform horizontal and vertical grooves of specified depth and providing joints of required thickness using wooden or steel strips as the proceeds.

6.11. SPECIFICATIONS FOR CAVITY WALL.

It is a wall comprising of two leaves, each leaf being built of masonry units and separated by a cavity so as to provide an air space within the wall and tied together with metal ties or bonding units to ensure that two leaves act as one structural unit.  The width of the cavity shall not be less than 50 mm and not more than 115mm.  Each leaf of the cavity wall shall not be less than 75mm.  The space between the leaves being either left as cavity of filled with non-load bearing insulating and water proofing materials.

6.11.1. Metal ties - These may be of galvanized iron wrought iron, gun metal brass, copper, stainless steel or any such corrosion resistant metal made of flats 20x5 mm cranked or twisted at their mid point with ends split and fish tailed.  They shall be built into horizontal bed joints during erection, placed sloping towards the exterior side to prevent water from flowing along it from outer to inner leaf side.  (Refer fig 6)

6.11.2. Bonding units - These shall be preferably precast R.C.C. units having cross – section as per Fig. No 6.

Length of the bonding units will be sum of thickness of both leaves plus width of cavity if the leaves are 75 mm or 115 mm.  If the leaves are more than 115 mm thick, then length of a unit will be2 x 115 + width of cavity as shown in fig.6.  Precast  RCC units shall be provided with 2 no. 8mm Torsteel reinforcement bars tied with 2 no. 3mm dia M.S hard drawn wire cross bars (as shown in Fig. 6) placed in the center of units.

Cement concrete used in the bonding units shall not be leaner than 1:3:6 (1 Cement: 3 coarse sand: 6 graded stone aggregate 20mm nominal size).

6.11.3. Spacing - Metal ties/bonding units shall be spaced not more than 90 cm apart horizontally and 45 cm vertically and staggered in each course.  Additional ties shall be used near openings.

6.11.4. Restrictions - Cavity walls shall not normally be built more than 7.5 meters in height and 9 meters in length.  Where large lengths and heights are desired, the wall shall be divided into panels with strengthening measures such as pillars etc., cavity shall be covered at the top with at least two courses of masonry unit and/ or coping over it.

Adoption of cavity walls is not recommended when heavy concentrated load from beam etc are to be supported by walls:

6.11.5. Measurements and rate

(a) Brickwork in walls shall be included and measured with general brickwork.  The width of the cavity shall not be measured skin of cavity wall, half brick thickness shall be measured as and paid as described in para 6.2.8 and 6.4.(b) The forming of the cavity shall be given in square meters stating the width of the cavity and shall include the metal ties / bonding unit specifying the numbers per square metre.(c) Labour and material for closing cavities at the jambs, sills and heads of opening shall be as described and measured separately in running meters.(d) The item shall include use of device for keeping cavity clear and forming the requisite weep and vent holes and nothing extra on this account shall be payable.

THE BREADTH SHALL NOT EXCEED

THREE TIMES THE THICKNESS AND

THICKNESS ITSELF SHALL NOT

EXCEED MORE THAN THREE BRICKS

Fig. 1

ENGLISH BOND

Fig. 2

Fig. 3

Fig. 4

CIRCULAR ARCH

FLAT GAUGED ARCH

Fig. 5

Annexure 6-A.1.

TEST FOR DIMENSIONAL TOLERANCE   (Para 6.1.3.3.)

1. Sampling - As per para 6.1.3.1 and 6.1.3.2.

2. Procedure - All the blisters loose particles of clay and small projections shall be removed from the surface of bricks.  Each specimen of 20 bricks shall them be arranged upon a level surface successively as indicated in fig. A  contact with each other and in straight line.  The overall length of the assembled bricks (20 Nos.) shall be measured with a steel tape sufficiently long to measure the whole row at one stretch.

3. Tolerance - The actual dimensions of bricks when tested as described in A-2 shall be with in the following limits per 20 bricks.

Modular bricks

Length 372 to 388 cm (380 ± 8 cm)

Width 176 to 184 cm (180 ± 4 cm)

Heights 176 to 184cm (180 ± 4 cm) for 90 mm high brick.

“A “ Measurement of Length

“B “ Measurement of Width

“C “ Measurement of Height

76 to 84 cm( 80 ± 4) for 40 mm high brick.

Non - Modular bricks

For class 10

Length 441 to 459cm

Width 218 to 226 cm

Height 138 to 142 cm (for 70 mm high bricks)

86 to 90 cm (for high bricks)

For other classes

Length 432 to 468

Width 213 to 231

Height 134 to 146 cm (for 70 mm high bricks)

84 to 92 cm (for 44 mm high bricks)

A.4. Criteria for conformity - A lot shall be considered conforming to the requirements of dimensions and tolerances if all the groups of bricks are tested to meet the specified requirements.

Annexure 6-A.2.

TEST FOR COMPRESSIVE STRENGTH   (Para 6.1.3.4.)

1. Specimen - Five whole bricks shall be taken from the samples as specimens for this test.  Length and width of each specimen shall be measured correct to 1 mm.

2. Apparatus - The apparatus consists of compression testing machine, the compression plate of which shall have a ball seating in the form of portion of a sphere the center of which shall co-incide with the center of the plate.

3. Procedure

(a) Pre-conditioning - The specimen shall be immersed in the water for 24 hours at 25°to 29°C.  Any surplus moisture shall be allowed to drain at room temperature.  The frog of the bricks should be filled flush with mortar 1:3 (1 cement: 3 clean coarse sand of grade 3mm and down) and shall be kept under damp jute bags for 24 hours after that these shall be immersed in clean water for three days. After removal from water, the bricks shall be wiped lean without of any traces of moisture.

(b) Actual testing - Specimen shall be placed with flat faces horizontal and mortar filled face upward between three 3-ply plywood sheets each of thickness 3 mm and carefully centered between plates of the testing machine.  Plaster of Paris can also be used in place of plywood sheets to ensure a uniform surface. Load shall be applied carefully axially at uniform rate of 14 N. mm² per minute till the failure of the specimen occurs.

4. Reporting the test results - The compressive strength of each specimen shall be calculated in N/mm² as under:

                              Maximum load at failure (in N)

Compressive strength =  ------------------------------

                             Area of specimen (in sq. mm)

In case the compressive strength of any individual brick tested exceeds the upper limit of the average compressive strength the same shall be limited to the upper limit of the class specified in 6.1.1. for the purpose of calculating the average compressive strength.  Compressive strength of all the individual bricks comprising the sample shall be averaged and reported.

5. Criteria for conformity - A lot shall be considered having satisfied the requirements of average compressive strength if the average compressive strength specified in 6.1.2. for the corresponding class of brick tested is not below the minimum average compressive strength specified for the corresponding class of bricks by more than 20 percent.

Annexure 6-A.3

TEST FOR WATER ABSORPTION   (Para 6.1.3.5.)

1. No. of specimen - Five whole bricks shall be taken from samples as specimen for this test.

2. Apparatus - A balance required for this test shall be sensitive to weigh 0.1 per cent of the weight of the specimen

3. Procedure:

(a)  Pre–conditioning -  The specimen shall be allowed to dry in a ventilated oven at a 110°C to 115°C till it attains a substantially constant weight.  If the specimen is known to be relatively dry this would be accomplished in 48 hours, if the specimen is wet several additional hours may be required to attain a constant weight.  it shall be allowed to cool at room temperature.  In a ventilated room, properly separated bricks will require four hours for cooling unless electric fan passes air over them continuously in which case two hours may suffice.  The cooled specimen shall be weigh (WI) a warm specimen shall not be used for this purpose.

(b) Actual testing - Specimen shall be completely dried before immersion in the water.  It shall be kept in clean water at a temperature of 27°C±2°C for 24 hours.  Specimen shall be wiped out of the treaces of water with a damp cloth after removing from the water and then shall be weighed within three minutes after removing from water (W2).

4. Reporting the test results -The water absorption of each specimen shall be calculated as follows and the average of five tests shall be reported.

                         W2-w1

Water Absorption =    ----------- X 100

                         W1

5. Criteria for conformity - A lot shall be considered having statified the requirements of water absorption if the average water absorption is not more than 20% by weight.

Annexure 6-A.4.

TEST FOR EFFLORESCENCE (Para 6.1.3.6.)

1. No. of Specimen - Five whole bricks shall be taken as specimen for this test.

2. Apparatus - Apparatus required for this test shall be a shallow flat bottom dish containing distilled water.

3. Procedure (actual testing) - The brick shall be placed vertically in the dish with 2.5. cm immersed in the water.  The room shall be warm (18°C to 30°C) and well ventilated.  The bricks should not be removed until it absorbs whole water.  When the whole water is absorbed and the brick appears to be dry places a similar quantity of water in that dish and allow it to evaporate as before.  The brick shall be examined after the second evaporation.

D.4. Reporting the test results - The rating to efflorescence in ascending order shall be reported as ‘NIL', ‘ SLIGHT ', 'MODERATE', ‘ HEAVY ‘ OR  ‘ SERIOUS ' in accordance with the following:

(a) Nil - when there is no perceptible deposit of efflorescence,

(b) Slight - When not more than 10percent of the area of the brick is covered with a thin deposit of salts.

(c) Moderate - When there is heavier deposit and covering upto 50% of the area of the brick surface but unaccompanied by powdering or flaking of the surface.

(d) Heavy - When there is a heavy deposit of salts covering 50% or more of the brick surface be unaccompanied by powdering or faking of the surface.

(e) Serious - When there is heavy deposit of salts accompanied powdering and/ or flaking of the surface and tending to increase in the repeated wetting of the specimen.

5. Criteria for conformity - A lot be considered having satisfied the requirements of efflorescence if for 4 out of the specimen of 5 bricks, the rating of efflorescence is not beyond “moderate”.

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