Luigi’s Answer:
All tiles absorb water to some degree, even low porosity porcelain tiles. The problem here is that the biscuit or body of the tiles have become saturated with water.
As the biscuit soaks up water it becomes darker and if the glaze on the tile is white or a very light in colour it tends to be translucent or see through. The wet tiles then appear darker than the ones that have remained dry.
What causes the problem?
Most tiles are not intended to be continuously emmersed or exposed to moisture. Somehow water has got behind or under the tiles in sufficient quantity to soak into the biscuit. The glazed surface of a tile is impervious but there are a number of ways water can get behind the tiles or be allowed to accumulate:
- Grout penetration; most grouts are not impervious and it only takes a pinhole for water to find its way. - Poorly grouted tiles eg joints not fully compacted, edges of tiles left exposed.
- Cracked or damaged grout
- Internal corners and bottom row of tiles not siliconed properly or at all.
- Tiles wernt bedded into the adhesive fully. Wet areas require 100% adhesive coverage.No voids please.
- Poorly formed shower base , inadequate or partially blocked fall causing ponding on top of or under the tiles. - Puddle flange not or incorrectly fitted around waste.
- Taps not sealed and waterproofed where they meet the tiles.
- Shower recess was never waterproofed or waterproofing has failed.
- Leaky waterpipe behind the wall.
What can I do?
The tile discolouration could be the sympton of a serious problem so needs to be attended to promptly.
It is not a problem with the tile, but the installation or perhaps a serious water leak.
If your shower is covered by warranty call your Builder or waterproofer,
If not:
- Get a plumber to test for leaks in the pipewater or water service.
- If the watermarkng is not very bad, and the grout and silicone look to be in good order you might be able to dry the tiles out without removing the grout and silicon sealer and hopefully solve the problem by applying a penetrating sealer to the grout.
However drying the tiles until they revert back to normal colour may not be possible without removing the grout as even then it will take some time as the moisture can only escape from the edges of the tiles. If the grout & silicone is removed, take care not to damage the waterproof membrane. Drying can be sped up by the use of a fan heater. Then regrout the tiles with grout mixed with an additive instead of water taking care to fully pack the joints and leaving no edges exposed.
Once the grout is dry apply a penetrating sealer to further reduce the grouts porosity.
Unfortunatly if this does not solve the problem there is no option but to retile the whole shower enclosure, making sure the correct installation procedures are followed.