How To Seal Grout

How do you seal bathroom grout?

Clean the grout, spray it liberally with Selleys White For Life Grout Sealer, let it penetrate for an hour, wipe the overspray off the tiles, apply a second coat, and leave it 24 hours before it meets water. Then repeat the whole thing every 12 months.

Grout is porous. Unsealed, it takes up water, oil-based stains, soil and mould, which is why grout lines discolour long before the tiles do. Sealing helps lock those out when used as a system — it does not make grout waterproof, it makes it far harder to stain and far slower to absorb.

What you will need

• Selleys White For Life Grout Sealer
• A scrubbing brush
• A dustpan
• A clean white cloth or paper towel

Step 1 — Get the grout clean and clear

Ensure the surface is clean. Using the scrubbing brush and dustpan, remove any debris from the dried grout line.

Sealer works by penetrating the grout. Anything sitting on the surface — dust, soap film, cleaning residue — blocks that penetration and gets sealed in place instead. This is the step that decides how well the rest works.

If you are sealing existing grout rather than new grout, clean the surfaces first with Selleys White For Life Tile & Grout Cleaner.

If there is mould, clean the affected surfaces thoroughly with Selleys Rapid Mould Killer and allow them to dry before applying sealer. Sealing over live mould locks the colony in against a permanent moisture source. Patch test first — staining may occur on some matt finish tiles or in hard water areas, and it is not suitable for fabric, mirror tiles, metallic surfaces, or older baths or basins.

Step 2 — Apply the first coat

Push the clear plastic lock on the Grout Sealer trigger clockwise to the open position. Spray liberally onto the grout, saturating the surface. Allow it to penetrate the grout for 1 hour.

Saturating is the instruction, but there is a limit — see the warning about puddles below.

Step 3 — Wipe the overspray off the tiles

Wipe off overspray from the face of the tiles, using a clean white cloth or paper towel.

A white cloth is specified for a reason: it lets you see what you are lifting. Sealer left on a tile face dries into a haze that is much harder to remove than it is to prevent.

Step 4 — Apply the second coat

Apply a second coat of sealer for maximum protection. Ensure that this overspray is wiped off within 2 hours of application to prevent the sealer drying on the tile surface.

Two hours is the outer limit, not a target. Wipe as you go, section by section, rather than spraying the whole bathroom and then starting to clean.

Step 5 — Let it dry

Allow it to dry for at least 24 hours before exposing sealed grout to water on shower walls.

Through that period, try to prevent spilling any liquids or getting any dirt or contaminants on the grout lines. A sealer that is still curing takes up contamination as readily as bare grout does.

Step 6 — Re-seal every 12 months

Re-seal grouted surfaces every 12 months for ongoing protection. A grout sealer is a consumable, not a permanent treatment — it wears with cleaning and traffic, and a bathroom that was sealed three years ago is effectively unsealed now.

Put it in the calendar. The whole re-application takes an afternoon and it is the cheapest maintenance in a bathroom.

The details that decide the result

Work in small sections. Always apply in small sections at a time. This keeps the one hour penetration window and the two hour wipe-off window manageable, and it stops sealer drying on tiles at one end of the room while you are still spraying at the other.

Start at the top. Start from the top of the wall and finish with the base and floor. Overspray and runs travel downwards, and you want to be cleaning them off surfaces you have not yet sealed rather than ones you have.

Do not leave puddles. Always ensure that there are no puddles of sealer left in the grout lines. Too much sealer may cause discolouration of some grout types. "Saturate" means wet through, not pooled.

Check from several angles. Look at the tiles from different angles to make sure there is no sealer residue or sealer haze left on the tile surfaces. Haze is nearly invisible face-on and obvious in raking light — which is how you will notice it a week later.

Temperature matters. Do not apply sealer below 10 °C. In an unheated bathroom in winter, that is a real constraint rather than a formality.

Sealing new grout

If you have just grouted, the grout has to complete its own curing first. After the initial 24 hour set, grout needs a further 3 days before exposure to water in a shower. Sealing goes after that, and adds its own 24 hours. See 6 steps to grouting tiles for the sequence, and how to tile your bathroom for the stage before that.

Common questions about sealing grout

How long does the sealer need to penetrate?

One hour for the first coat.

Do I need two coats?

A second coat is recommended for maximum protection.

How soon can the shower be used?

At least 24 hours after the sealer has been applied.

How often should I re-seal?

Every 12 months for ongoing protection.

What if sealer dries on the tiles?

Prevention is the plan — wipe overspray off with a clean white cloth or paper towel, and within 2 hours of the second coat. Check the tiles from different angles to catch any haze.

Why is my grout patchy after sealing?

Puddles. Too much sealer left sitting in the grout lines may cause discolouration of some grout types.

Can I seal mouldy grout?

Not until it has been treated. Clean mould-affected surfaces thoroughly with Selleys Rapid Mould Killer and allow them to dry before applying sealer.

Can I seal grout in a cold bathroom?

Not below 10 °C.

Where do I start?

At the top of the wall, finishing with the base and floor, working in small sections.

Does sealing make grout waterproof?

No. It helps lock out water and oil-based stains, soil and mould when used as a system. Waterproofing a wet area is a different job done behind the tiles.

Should I clean old grout before sealing it?

Yes — with Selleys White For Life Tile & Grout Cleaner, and let it dry first.