Terrace tiles are a wearing surface, not a waterproof layer. Water passes through the joints — every joint, on every tiled terrace, always. That is normal and expected. The waterproofing is what sits underneath, and when a tiled terrace leaks it is almost never the tiles that failed.
The layers, bottom to top
- Structural slab, sound and repaired. Cracks cut out and filled first — see repairing roof cracks.
- Waterproofing, applied directly to the prepared slab, coved at every parapet and upstand and carried into every drain outlet.
- Protection, so the following trades do not damage what you just laid.
- Screed to falls — the layer that makes water run to the outlets instead of standing.
- Tiles and joints.
Notice where the waterproofing sits: under the screed, on the slab. That is the point of the whole arrangement. Water that gets through the tiles and joints lands on the waterproofing, runs down the slope built into the screed, and leaves through the outlet. The system is designed to be wet inside. It only fails when that drainage path is broken.
The four things that break it
The falls are wrong
If the screed does not fall consistently to the outlets, water stands. Standing water on a terrace finds every weakness eventually, and freeze-free Indian conditions do not save you — sustained standing water plus summer heat is its own stress. Check by pouring a bucket out and watching where it goes. Any pool that stays after an hour is a fall problem, and re-tiling will not fix it.
Water gets in but cannot get out
The commonest and least obvious failure. The waterproofing works, the water arrives on it as designed — and then the outlet detail traps it. If the drain is set at screed level rather than at membrane level, the water sitting on the membrane has nowhere to go. It ponds inside the build-up, permanently, invisibly, until it finds a pinhole. Outlets should drain at the waterproofing level, not only at the surface.
Something punctured it
Tiling over fresh waterproofing without a protection layer, dropping tools, wheeling barrows, cutting on the deck, later fixing a dish antenna or water tank base straight through the whole build-up. Every fixing that penetrates is a leak unless it is detailed.
The edges were never done
Same story as everywhere else — the treatment stops where the parapet begins. See parapet wall waterproofing.
If your tiled terrace is already leaking
You have three routes, and they cost very different amounts:
- Regrouting and joint sealing. Cheapest. Reduces how much water gets in but does not repair the layer below. Worth doing if the joints are visibly open and the leak is minor. It is a slowing measure, not a cure, and anyone presenting it as a cure is overselling it.
- A surface treatment over the tiles. A coating applied on top of the existing tiled surface, turning the wearing course itself into the barrier. Faster and far cheaper than stripping. It has to bond to a glazed or dense tile — surface preparation is the whole game here — and it changes the look and the feel underfoot. A reasonable answer where stripping is impractical.
- Strip and rebuild the layers. Expensive, disruptive, and the only route that actually restores the design. Correct when the falls are wrong, when the outlets are set at the wrong level, or when the terrace has been patched repeatedly without result.
Which is right depends on what is actually wrong. If water stands on your terrace after rain, no amount of grouting or coating will hold for long — the falls are the fault, and the falls are under the tiles.
Before you tile a new terrace
Two things that cost nothing at the right moment and a great deal later:
- Flood-test before the screed goes on. Block the outlets, hold water on the waterproofing overnight, inspect the ceiling below. Find the pinhole now, not through 100 mm of screed and tile.
- Photograph the layers. Every stage, with the outlets and parapet junctions clearly visible. Whoever investigates a leak in ten years will be able to see how it was built instead of guessing.