How to clean, remove and renew discoloured grout

Grout that turns grey, yellow, black or green: almost everyone has seen it in a bathroom, kitchen or on a floor. The good news: discoloured grout is not always broken grout. Often it is simply dirty, and cleaning is enough. If the grout really is at the end of its life, you can rake it out and renew it yourself in a few hours with the right products. This blog takes you through the whole route: causes, cleaning with products such as Fila Fuganet, when to replace, raking out, regrouting, protecting and choosing the right colour. As a concrete example we use colour code KK47.

Note: raking out grout releases fine dust and cleaners are chemical. Wear an FFP2 dust mask, safety glasses, gloves and knee pads (see the PPE overview below). For leaks, cracks, damp problems, natural stone or expensive tiles, call in a professional: a professional is never superfluous.

Why does grout discolour?

Grout is porous and sits a few millimetres below the tile. So everything that passes through the air, water and your hands in a bathroom or kitchen sticks to it. Find the cause first, because it decides what helps.

Try first: clean the grout

Cleaning is quick and can be undone. So always try it first, especially if the grout is still hard and intact.

1. Test on a trial piece first. Try each cleaner on a small, inconspicuous piece of grout and tile. Read the product information on the packaging.
2. Wet the grout. That stops the cleaner soaking too deep.
3. Apply the cleaner. Fila Fuganet is meant for the joints of wall and floor tiles: a ready-to-use cleaner for ceramic and porcelain tiles. Spray it on the joint and leave it to work according to the packaging. For stubborn grease on a floor, Fila PS87 Pro fits. For limescale in the bathroom, Fila Deepclean fits.
4. Brush the grout. Use a hand brush and work the joint briefly and gently. A hard wire brush roughens the grout and makes it dirtier later.
5. Rinse well with clean water and wipe off with a sponge or microfibre cloth. Cleaner residue leaves a haze itself.
6. Let the grout dry fully and judge the result in daylight.

Never mix different cleaners and ventilate well. If you use an acid product, for example for limescale, do not use it on polished marble or other acid-sensitive materials: according to the Deepclean product information it can damage the surface. For natural stone, ask a professional for advice.

When should grout be replaced?

Cleaning does not always help. Replace the grout if:

• the discolouration comes back or does not go after two or three rounds of cleaning (mould is then often deep in the grout);
• the grout is powdery, soft, cracked or loose, or falls out of the joint;
• grout is missing or tiles are starting to move;
• the colour no longer suits, for example after a new wall or floor;
• a cement grout in a wet room stains again and again.

Are tiles loose, is there a leak, are cracks running through tiles and grout, or is the substrate damp? Then replacing only the grout is not enough. Have a professional assess the cause before you rake anything out.

What do you need?

Materials

• Grout in the colour you want: Fugabella (cement-based resin-cement) or Fugalite (waterproof, stain-proof grout resin). Which grout suits which use is explained in our blog choosing between Fugalite and Fugabella.
• A concrete example in colour KK47: Fugabella Color KK47 or Fugalite Color KK47.
• Cleaners: Fila Fuganet, and optionally Fila PS87 Pro or Fila Deepclean.
• Protection afterwards: Fila Fuga Proof.
• More maintenance and cleaning products are in the maintenance and cleaning chemicals category and on the Fila brand page.

Tools

• A grout rake or hand scraper for raking out, or an oscillating multi-tool with a carbide grout segment blade. A multifunction scraper helps with loose residue.
• A construction vacuum cleaner with HEPA filter to remove dust straight away.
• A grout float or rubber grout spreader for applying the grout.
• A sponge, a microfibre cloth and clean buckets for wiping off; a grout wash bucket is handy on larger areas.
• A hand brush for cleaner and dust.

Personal protection (mandatory)

• An FFP2 dust mask: raking out releases fine dust that you must not breathe in.
• Safety glasses against dust, splinters and splashes.
• Work gloves for raking and rubber gloves for cleaners and grout.
• Knee pads for working on the floor.
• More about protection is in our workwear and safety category and in working safely on the construction site.

Raking out and removing the grout

1. Put on your PPE: FFP2 mask, glasses, gloves and knee pads. Ventilate the room.
2. Protect the surroundings. Cover the bath, basin and drain so no dust or debris gets in.
3. Rake out the grout with the grout rake. Work slowly and keep the rake in the middle of the joint so you do not damage the tile edge. With a multi-tool and grout segment blade it goes faster, but needs a steady hand. With porcelain and glass mosaic, extra care is needed.
4. Work deep enough. Remove the old grout to a depth of a few millimetres (roughly 3 to 5 mm, or as the data sheet of your grout says) so the new grout bonds well. Scraping only the surface is not enough.
5. Vacuum the dust straight away with the construction vacuum cleaner and remove loose residue with the scraper and a brush.
6. Clean the substrate. Clean the open joints and tile edges with a damp sponge, and with a suitable cleaner for grease or mould. Rinse afterwards.
7. Let everything dry completely. Grout on a wet substrate comes loose. How long that takes depends on the room and ventilation; check that the joints are really dry before you continue.

Applying new grout

1. Choose the grout. In wet or greasy rooms and where stains show quickly, a waterproof, stain-proof grout such as Fugalite is an option. Fugabella is a decorative resin-cement grout for ceramic tiles, mosaics and natural stone, among other things. If in doubt, read our comparison of the two.
2. Mix according to the packaging. Keep to the ratio and resting time. Do not mix too liquid, because that causes colour differences and shrinkage.
3. Apply the grout. Work diagonally across the tiles with the grout float or rubber spreader and press the grout well into the joint. Work in small areas.
4. Remove the excess with the float, diagonally across the joints.
5. Wipe off with the sponge. Wait until the grout has begun to set, then wipe off with a slightly damp sponge. Rinse the sponge often, preferably in a grout wash bucket or clean bucket. A wet sponge washes the binder out of the grout and causes colour differences.
6. Polish with a microfibre cloth once the grout has cured enough, and remove any haze following the product information.
7. Let it cure. Follow the curing time of your grout before you wet or load the joint.

You can read more about tiling and grouting in our blogs how to tile a wall and how to tile a floor, and about the final clean in how to clean while tiling.

Protect: keep the grout looking good for longer

Cement-based grout is porous. A grout protector such as Fila Fuga Proof makes dirt easier to remove according to the product information and stops water and stains soaking into the grout. Apply it to dry, clean joints, after cleaning with Fila Fuganet, and keep the surface dry for the first 24 hours. For a daily bathroom routine: ventilate, wipe the tiles after showering and clean regularly, and discolouration comes back far less quickly.

Colour choice and trial piece: example KK47

The grout colour has a big effect on the end result. Light grout makes tiles look larger and cleaner, but shows dirt sooner. Grout in the tile colour makes a surface calmer; contrasting grout brings out the tile pattern.

A concrete example is colour code KK47. According to the product pages it is a natural green shade, available as Fugabella Color KK47 (resin-cement grout), as Fugalite Color KK47 (waterproof grout resin) and as Silicone Color KK47 (sealant). That is handy: if you choose KK47 for the grout, you can finish the sealant joints in the same colour code. That way grout and sealant match neatly.

• Choose in daylight and artificial light. A colour looks different on a screen or in a shop than on your wall.
• Always make a trial piece. Grout a small, inconspicuous area and let it dry fully, because grout often dries lighter or darker than it looks wet.
• If in doubt, choose a shade that shows dirt less, especially on the floor.
• Use one batch per room and mix everything in the same ratio: colour differences between mixes are otherwise visible.

Sealant joints are a different story

Where tile meets bath, shower, basin or a corner there is sealant, not grout. It moves with the building and is replaced differently: first remove the old sealant completely, clean and degrease the substrate and then apply new sealant. Sealant residue on tiles can be removed with, for example, Fila Zero Sil, following the product information. For applying, use a sealant gun and a sealant in the same colour code, such as Silicone Color KK47. The whole method is in our blog how to reseal your bathroom with new silicone.

When do you call in a professional?

For ordinary ceramic tiles this is doable. Call in a professional for:

• Leaks or damp problems: the grout is then a symptom, not the cause.
• Cracks in grout and tiles, or tiles that sound hollow or come loose.
• Natural stone and marble: acids and scraping can cause permanent damage.
• Expensive, polished or special tiles where a mistake cannot be put right.
• Large areas or grouting work you are not sure about.

A professional assesses cause, substrate and execution. That is experience no step-by-step plan replaces. A good professional is never superfluous, even if you do a lot yourself.

Common mistakes

• Raking without PPE. Grout dust is not healthy to breathe: always wear an FFP2 mask.
• Not raking out deep enough. The new grout then bonds poorly and comes loose.
• Grouting on a damp substrate. Let everything dry fully first.
• Wiping off too wet. That causes colour differences and weak grout.
• No trial piece. Always test colour and cleaner first.
• Mixing cleaners. Never do it.
• Ignoring the cause. With damp or a leak, the discolouration simply comes back.

💡 Tip: renew the worst joints first as a trial and watch for a few days how the colour dries before you tackle the whole wall.

Where do you find everything for your job?

At Saniso, the online store for DIYers and professionals, you will find grout, cleaners, tools and personal protective equipment.

• See the Fila brand page, our maintenance and cleaning chemicals and workwear and safety.
• Create a customer account and order easily.
• Working on a larger project or want to hand the job over? Request a project quote.
• Book a showroom visit, at least 24 hours in advance.
• Unsure about the grout or the approach? Contact us.

Unsure about the cause, the tiles or the substrate? Feel free to call in a professional: a good professional is never superfluous.

Saniso – Build your home with Saniso.

Read also: How to repair broken wall or floor tiles

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Read also: Resina-cemento explained: why Fugabella Color gives an even grout colour