Waterproofing of Common / Open Terrace (Brick Bat Coba / Mosaic finish)
Pre Waterproofing Procedures:
1) All surfaces to be waterproofed shall be cleaned off all loose materials, mortar, oil, grease, if any, thoroughly by wire brush. It shall be ensured that parapet plasters are completed prior to cleaning activity is undertaken. Plaster shall be cut at one level, i.e. 1’ above terrace slab top.
2) Injection grouting shall be adopted at all major honeycombed portions, if necessary, after physical observation of slab.
3) Terrace slab shall be cured for at least 2 days by ponding to test for leakages and to serve water hungry concrete surface.
4) Ponding shall be done in areas of 5 sq. m each by forming bunds of 2” in height and cast in cement mortar 1:10 approx.
5) In case of major leakages, gravity grouting or pressure grouting shall be resorted to, to stop leakage.
6) Levels of water-proofing shall be clearly mark on concrete surface, clearly defining ridge line and valley lines with level pads underneath, minimum slope being 1:100 or as that mentioned in drawing.
7) Holes for outlet pipes shall be marked clearly for size & locations and chasing shall be done thereafter. Hole
diameter shall not exceed pipe diameter. Rendering of holes shall be executed using compatible bonding agents, (SBR based) expansive grouts, waterproofing compound and M15 grade concrete.
8) Rain water pipes shall be fixed at the required locations as per drawing. In case of PVC pipes, surface of pipes shall be roughened and applied with sand for proper bonding and P.V.C. grating shall be provided at the pipe mouths.
9) It shall be ensured that no water carrying pipes are running over the slab, which is to be water-proofed.
10) Materials required for only 2 days of water-proofing works shall be carried to avoid unnecessary loading of terrace slab.
During Waterproofing Procedures:
1) Bricks selected for using as Brick Bat Coba shall be either full brick, or 3/4th brick made out of one complete brick by breaking into required size, using mallets.
2) Brick bat shall not be stored in the form of a heap at one place.
3) They shall be soaked thoroughly for about 15 minutes prior to their placing.
4) Glazed tile pieces for China Mosaic Type Water-proofing shall be soaked for about 15 minutes before fixing.
5) After cleaning the slab, a thin layer of cement slurry shall be laid on cleaned slab prior to laying of brick bats.
6) Over this, maximum 40 mm thick layer of cement sand mortar in the proportion 1:3 mixed with compatible water-proofing compound shall be laid.
7) Mortar shall be preferable mixed in mechanical mixer only. Also use of plasticizer is recommended to
increase workability. Mortar prepared shall be used within 1 Hour of preparation.
8) Presoaked brick-bats shall then be laid in radial, by inserting brick-bats to a depth of about 15mm by light tamping with the help of adjacent layers of brickbats shall not exceed 25mm.
9) Application of brickbats shall proceed from one corner and shall be laid in radial pattern to drain of any water which has seeped through. Thiyyas for the same shall be given by Site Engineer, considering into account adequate slope. For this purpose line doris shall be fixed at every 3’ to define the slope. Brick-bats shall be laid accordingly.
10) Edge roundings shall be done simultaneously so that bottom edge of parapet wall plaster serves as drip mould (Kani).
11) The entire brick bat layer should be cured of minimum 3 days.
11) After curing is over, the surface shall be applied with a finishing coat of cement sand mortar in the proportion 1:3 with water-proofing compound.
12) Top coat shall be of neat cement slurry of adequate consistency and shall be monolithic with brick-bats.
Surface shall be finished with 3’ long float, polish patra and line dori to mark grids of 1 X 1 sq. ft. markings.
13) Finished surface is then tested for leakage by ponding. Ponding is done making mortar bunds of height 1” at every 5 feet. Testing shall be carried out for 7 days.
For China Mosaic Type water-proofing, following procedure shall be adopted:
1) After curing of finishing coat (which is roughened) a layer of cement sand mortar 1:3 in proportion and 20mm thk mixed with approved water proofing compound shall be laid over it.
2) While the bed mortar is fresh, white/colored glass pieces shall be set closely by hand with glazed side keeping exposed.
3) Wooden mallets shall be used for tamping China Mosaic tile pieces into place.
4) Ponding (Wattas) shall be made with mortar bedding with glazed tile pieces on top.
5) Surface of tiles shall be lightly rolled with wooden roller taking care that no hollow pockets are left underneath glazed tile pieces.
6) Top surface shall be cleaned with saw dust or cotton waste and if necessary with weak acid solution to remove stains of cement. Due care is taken to see to it that cement in the joints does not dissolve in the acid solution.
7) Slope of finished top shall be 1:100 or as mentioned on the drawing.
8) Finished surface shall be cured for at least 7 days by flooding and checked for leakages/dampness, if any.
Post Waterproofing Procedures:
Date of finishing shall be marked on the surface for curing by ponding for about 7 days.
Important
1) Waterproofing once done, shall not be broken, or pierced. If waterproofing is to be punctured, due care shall be taken to limit the damage to the restricted area. The cracks due to hammering shall not spread over the large area.
2) Repairing of the punctured area shall be done by using bonding agent and expansive grout.
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