Slabs are constructed either by RCC or RC, which needs insulation for thermal comfort and waterproofing treatment to prevent leakage of water. Brick bat coba is very effective method used for waterproofing.

Procedure

A] Surface Preparation: All existing treatment, coating on the slab top is removed and surface cleaned by hard wire brush and washed with water. The surface should be free from any oil, grease, dust etc. Remedial measures must be taken to all structural cracks as per standard practice. All non-structural cracks more than 0.5 mm wide and construction joints if any should be cut in “V” shape , cleaned with wire brush and washed , the cracks are then filled by polymer modified cement or mortar using acrylic polymer , with addition slurry mix is spread upon cleaned SSD roof surface . Over this 15mm thick Cement sand mortar, 1:4 admixed with water proofer is laid.

B] BRICK BAT LAYING: On the above green mortar, a layer of brick bats , soaked overnight in water , is laid , having an average thickness of about 110mm, about 70mm near rain water pipe and 150mm at the ridge. The gaps between the brick bats are generally kept between 15 and 20mm. These gaps are filled with cement sand mortar, 1:4, admixed with water proofer. In hot and dry weather, the surface should be covered with wet gunny bags immediately after finishing. Curing should start next day and continued for 7 days.

C] FINISHING LAYER: The top surface is then finished smooth with 20mm thick cement sand mortar, 1:4, admixed with water proofer. All liquid admixtures should be mixed with the mixing water. The surface when green is mixed with 300mm false squares. Curing is to be done by ponding.

Brick bat coba waterproofing is usually done at terrace/roof and basements.