Grout Sealing

• Penetrating (impregnating) sealers: Soak into the grout or stone and line the pores. They do not change the look much and do not form a film that can peel. This is what we normally use in showers and on floors.
• Surface or film-forming sealers: Leave a coating on top. Some are used on stone for a sheen or "wet look", but they can wear and peel on busy floors and in showers.
• Colour sealers: Tinted coatings that refresh and seal grout in one step. They suit sound grout that is stained, not cracked.

A sealer is only as good as the grout under it. If the grout is cracked, crumbling or missing, it needs re-grouting tiled surfaces first.

No, not fully. Products sold as a waterproof grout sealer make grout highly water-resistant: it slows water down, keeps stains and mould on the surface, and makes cleaning far easier. It is not a waterproof barrier. The waterproofing in a shower should be the tanking membrane behind the tiles, applied before they were fixed. Sealer protects the grout; tanking protects the wall. If your shower was never tanked, sealing will help but will not make it watertight, and retiling through our installing kitchen and bathroom tiles service is the lasting fix.

Epoxy grout is different: it is already waterproof and does not need sealing.

Yes, if it is cement-based grout. A shower is the wettest place in the home, and unsealed cement grout there absorbs water every day, so it stays damp, discolours and grows mould. Sealing keeps it cleaner for longer and reduces the water reaching the background. Shower tile sealing is also worth doing on the shower floor or tray surround, where water sits longest.

Marble, limestone, travertine and slate are porous, so the tiles need sealing as well as the joints:

• Before grouting: Many stones are pre-sealed so grout pigment does not stain the surface.
• After grouting: A full coat of penetrating sealer over the tiles and joints.
• Cleaning: Marble, limestone and travertine are damaged by acidic cleaners, including many bathroom products and vinegar. Use a pH-neutral stone cleaner.

Glazed ceramic and most glazed porcelain do not need sealing, but unglazed and polished porcelain sometimes do. We follow the tile manufacturer's advice.

It depends on the sealer, how much the area is used and how it is cleaned. Harsh cleaners wear sealer away faster. The simple check is a water drop test: put a few drops of water on the grout. If they bead up, the seal is working; if the grout darkens quickly, it is time to reseal. Showers and kitchen floors need resealing more often than a splashback or bathroom wall. Always follow the sealer manufacturer's guidance.

1. 1

   Inspect: we check the grout, tiles and silicone, and look for signs of water behind the tiles.

2. 2

   Deep clean: grout and tiles are cleaned, and mould treated, using a cleaner that suits the tile.

3. 3

   Dry: the grout must be completely dry, or the sealer will not soak in. New grout must be fully cured first.

4. 4

   Apply: sealer is brushed into the joints, or over the whole surface on stone, in as many coats as the product needs.

5. 5

   Wipe off: excess sealer is removed from glazed tiles before it dries, so there is no haze.

6. 6

   Cure: the area stays dry until the sealer has cured, following the manufacturer's instructions.

Find the route the water is taking first, because sealing only fixes one of them:

Damp patches on the other side of the wall, stains on the ceiling below or loose tiles are signs that water is already behind the tiles. That needs investigating before sealing.