Brick Bat Coba is a traditional waterproofing technique used in building construction, especially for flat roofs. It involves laying brick bats (broken pieces of bricks) over a layer of cement mortar in a systematic manner to create a slope that facilitates water drainage.
This is followed by applying a layer of waterproof plaster over the brick bats to seal the surface and prevent water seepage. The method is valued for its durability, thermal insulation properties, and cost-effectiveness.
Commonly used in Indian architecture, Brick Bat Coba is particularly effective in regions with heavy rainfall, providing a robust and time-tested solution for roof waterproofing.
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Image of Brick bat coba detail and downloadable (in DWG) link below
Brick bat coba detail drawing – 1
A Brick Bat Coba detail drawing in construction illustrates how this waterproofing method is applied on flat roofs.
Here’s a description of what a typical detail drawing includes and how it’s constructed:
Brick Bat Coba Waterproofing – Detail Drawing Description
Base Slab (RCC Roof Slab)
- The process starts with the structural reinforced concrete (RCC) roof slab.
- The surface is cleaned and roughened for better adhesion.
Bonding/Slurry Coat
- A cement slurry or bonding agent is applied over the slab to ensure good adhesion of the waterproofing layers.
Brick Bat Layer
- Brick bats (typically 40–70 mm thick) are laid in 1:4 cement mortar (1 part cement, 4 parts sand).
- Laid with a minimum slope of 1:100 to 1:150 for proper drainage.
- The brick bats are spaced with gaps filled with mortar to form a solid, sloping base.
Cement Mortar Plaster (Top Coat)
- Over the brick bats, a top plaster layer of 1:3 cement mortar (about 20–25 mm thick) is applied.
- This is finished smooth and sloped towards the drainage outlets.
Curing
- The entire surface is cured properly for at least 7 to 14 days to prevent cracks and ensure long-term durability.
Optional Finishes
- Some may add a protective coating (e.g., acrylic waterproof coating) or a tile finish on top for aesthetics and additional waterproofing.
Drainage Outlets
- Proper detailing around drainage pipes, ensuring smooth water flow and sealing to avoid leakage.
Key Notes in the Drawing
- Indicate slopes using arrows.
- Show cross-sections with materials labeled: RCC, mortar, brick bats, plaster.
- Add dimensions for each layer (e.g., slab thickness, coba thickness).
- Highlight expansion joints, if used.
- Mark parapet wall junctions where waterproofing continues up the wall (~150–300 mm).
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