If your grout is visibly cracked or crumbling, it's likely going to be letting water behind your tiles. Even if your grout doesn't appear to be damaged, if it's not water-resistant it could potentially be the source of the leak.
Most showers leak when water enters the substrate of the property through cracks in the tiles, damaged grout or broken sealant barriers. It goes without saying, but these concealed parts of the home don't cope well with moisture.
If you do not seal your grout at the right intervals, then water may seep through. Your tile floor may sustain water damage due to this leakage. Not only will this damage tiles, but it will also harm the underlying subfloor.
ANSWER - Water coming up through your tile grout joints is an indication that you have a high water table on your property or that water is being directed towards your house, and you don't have a vapor retarder under the concrete slab to prevent water from migrating through the concrete.
Moisture that gets behind tiles can cause all sorts of problems. It can destroy the drywall backing, it can cause rot, and it can cause the tiles to begin to fall off if left too long. Worst-case scenario, water damage behind your tiles can lead to mold problems. Mold can be a serious health risk to your family.
Starting with a dry shower, splash water on one area of one wall at a time, working your way around the shower. Look for missing grout along the tiles as you go, as it's easy to spot when wet. If you happen to locate a spot with missing grout, simply re-apply some fresh grout in its spot.
All cement-based grouts are water resistant so they all allow the passage of water through them without breaking down. The more polymer that is in the grout the greater the resistance to water penetration.
MAPEI offers Penetrating Plus Stone, Tile & Grout Sealer which is a water-based sealer and Penetrating Plus SB Stone & Porcelain Tile Sealer a solvent-based sealer. Let's be clear, sealing does not make grout stain or waterproof.
No matter what, moisture - steam and water - eventually will get through the grout, or through a crack in your tile.
The grout in your shower should always be sealed; this will block any moisture that could easily enter the very porous material. A sealer will prevent water from becoming stuck behind the tile and grout, forming mold and mildew.
Many authorities recommend sealing shower grout at least once a year as a rule of thumb.
Every time you turn on the shower, the grout gets wet. If you don't dry it off right away (and let's be honest, we aren't exactly wiping our showers down with a towel), the grout absorbs that water. That water then works its way behind the tiles and into the wall.
How Does Water Get Behind the Tiles in My Shower? Most homeowners think of the shower as a waterproof environment. Ceramic tiles don't absorb moisture, but the grout that fills tile joints is a cement-based product. If it isn't sealed properly, grout allows condensation to form behind tiles.
When grout is not sealed in time, grime and water can seep into it, causing cracks on your tiles and forcing them to break at a certain point. By sealing your grout, you get to prolong your tile surface's lifespan and minimize damage to a considerable extent.
In general, grout is a great option for shower tiles but if you're sealing the joint of a bath or a shower tray, you need the flexibility and the anti-fungal properties of a good watertight silicone.
Grout needs to be sealed. It's naturally porous and will stain easily. Most installers of tile floors do not seal them because grout has to cure first. It's something you should do to keep your grout looking its best.
The only type of grout that doesn't need sealer is epoxy, which is inherently pre-sealed.
The answer to the question is, surprisingly, no. Tile and grout is not totally waterproof and neither is cement board, backer board, sealers and cement adhesives, they absorb water but do not block penetration.
Bathroom waterproofing with liquid membranes is perhaps the easiest and cheapest modern method of waterproofing, which can be applied to any surfaces that come into contact with water or moisture.
Pin holes, large holes, cracks or missing grout ruin the beauty and aesthetics of your showers. The missing grout spaces accumulate water and the cracks absorb moisture, further leading to mold and mildew breeding. Mold and mildew occur in places that are constantly damp.
One of the tell-tale signs of a water leak coming from a shower valve behind the wall is water stains. If you have an upstairs bathroom, you may notice dried water stains on the ceiling below the shower. Most times shower valve leaks behind the wall are very slow.
Signs you have a shower leak
Tiles or flooring are loose or curling near the shower. Paint is peeling or flaking. Wood finishes look chalky. Mold spots appear on the shower wall or the floor near the shower.
At this point you may wonder if a complete re-grout is necessary or if it would be possible to simply put new grout over old grout. The answer is, yes, it is possible to put new grout over old grout.