When people hear the term waterproof, they often imagine a material that never absorbs water at all. In building construction, however, the definition is more practical: a material is considered waterproof if it prevents water from passing through it into the structure, even if the material itself absorbs some moisture. This distinction is key when talking about non‑vitrified clay tiles.
Do Clay Tiles Absorb Water?
Yes, non‑vitrified clay tiles can have a water absorption rate from 10% to 15%, depending on the specific clay body, firing temperature, and density. Gopuram brand clay tiles absorb around 12% water. This means if you immerse the tile in water, some water will enter its pores.
But here’s the important point: water absorption is not the same as water leakage.
Why Are Clay Tiles Still Considered Waterproof in Building Use?
In practical construction terms, clay tiles serve as the exposed layer of a roofing or open terrace. Their job is to prevent rainwater from reaching the inner structure. They do this through:
- Overlapping installation – In sloped roofs, tiles are laid so water runs off without finding a path inward.
- Roof slope drainage – Water flows away quickly, minimizing time in contact with the tile surface.
- Capillarity limits – While moisture may enter surface pores, it does not pass entirely through the tile at a rate or volume that would cause structural wetting.
- Drying ability – Once wet, clay tiles dry out naturally in ambient air and sunlight without losing strength or performance.
This combination means that even non‑vitrified clay tiles, though porous, function effectively as a waterproofing layer for roofs and walls.
How Are Clay Tiles Tested to be Considered Waterproof?
Annex B (Clause 8.2) of IS 654 Clay Roofing Tiles, Mangalore Pattern (India Standard) describes the procedure for testing Permeability of clay tiles. All Gopuram Brand tiles pass this test.