How to clean grout between bathroom tiles

You can clean the grout between tiles with warm water and a mild cleaning product of neutral to slightly alkaline pH, using a stiff-bristled brush run along the whole length of the joint, then rinse everything with clean water and dry. Acidic descalers do not belong on cement grout, as they erode it. Mould that has grown into grout or silicone usually cannot be removed by cleaning, and it is better to renew the joint.

What type of grout you have

• Cement grout is the most common in flats. It is slightly absorbent, so dirt, soap and moisture get into it easily.
• Epoxy grout is more chemically resistant and less absorbent. Manufacturers recommend it where aggressive cleaning products are used often or where the grout is permanently in water.
• Silicone joints are found in corners and around the bath and shower tray. They are not grout in the true sense but a flexible sealant, which is cleaned and renewed differently.

If you do not know which grout the tiler used, assume it is cement-based and choose the gentler method.

What to clean grout with and what to avoid

The technical data sheet for the cement grout Ceresit CE 40 Plus recommends mild cleaning products of neutral to alkaline pH for routine maintenance and states that the grout is not compatible with cleaning products containing acids in a concentration above 2%. For places where aggressive cleaning products are used often, the manufacturer refers to a chemically resistant epoxy grout.

• Suitable: warm water, a mild all-purpose or bathroom product with neutral pH, a mildly alkaline baking soda solution.
• Unsuitable for cement grout: acidic descalers, vinegar, citric acid, acid-based toilet cleaners.
• Mind the colour: the technical data sheet for Ceresit CE 43 grout warns against cleaning products with an intense colour, which can stain the grout.
• Tools: a brush with stiff plastic bristles. A metal brush and sharp scrapers damage and roughen the grout, so it then gets dirty faster.

If you are fighting limescale in the bathroom, apply descaler specifically to glass and taps and make sure it does not run into the grout. You will find tips in the article Jak odstranit vodní kámen.

Cleaning step by step

1. First dampen the grout with clean warm water. Damp grout absorbs less of the dirty solution.
2. Apply a solution of the mild product and leave it to work for a few minutes.
3. Scrub along the grout line, not across it. Clean vertical grout lines from the bottom up, so that dirty water does not run down the clean surface.
4. Wipe off the loosened dirt with a cloth or sponge and rinse it out in clean water.
5. Rinse the surface with clean water so that no product residue remains in the grout, as further dirt sticks to it.
6. Wipe the tiles and grout dry and ventilate the room.

On the floor, work in smaller sections and change the dirty water regularly. If the grout stays grey even after cleaning, the dirt is most likely inside the material, and only sealing or regrouting will help.

Mould in grout and on silicone

Black spots in the grout and on the silicone around the bath or shower are usually mould. Before you start, protect yourself: the CDC recommends rubber, nitrile or vinyl gloves, protective goggles and an open window or door, and warns that bleach must never be mixed with ammonia or any other cleaning product.

1. Scrub surface mould with water and a cleaning product and dry the area completely. This method for hard surfaces is given by the US agency EPA.
2. If you use a mould remover, follow the label and test it first in an inconspicuous spot on coloured grout.
3. If stains remain after cleaning, the mould has grown into the material. The EPA warns that mouldy surfaces should not be painted over or caulked over. Therefore cut out the silicone and replace it with new, scrape out the damaged grout and regrout.
4. Remove the cause: ventilate the bathroom after showering, wipe water off glass and tiles with a squeegee and check whether there is a leak somewhere.

When replacing silicone, bear in mind that, according to the technical data sheet for Ceresit CS 25 sanitary silicone, acetic acid is released during curing, so protect your skin and eyes and ventilate. According to the same data sheet, cured silicone can only be removed mechanically. Mould on walls and ceilings is covered in the article Plíseň na zdi: jak ji odstranit.

How often to clean grout

The more often you go over the grout, the less you have to scrub it later. A tried-and-tested routine in a normal household:

• After every shower: wipe water off the tiles with a squeegee and ventilate, so that the grout in the shower dries quickly.
• Once a week: wash the tiles in the shower and the bathroom floor with a mild product and rinse.
• About once a month: go over the grout with a brush following the method above, especially in the shower, around the bath and by the toilet.
• During deep cleaning: check the condition of the grout and silicone and decide whether cleaning is enough or whether it is time for sealing or replacement.

On a kitchen floor, it is mainly grease that clings to the grout. Even there, warm water and a product with neutral pH are enough; just leave the solution to work a little longer and change the water more often.

Sealing: how to protect grout

After cleaning, cement grout can be treated with a transparent sealer, which reduces absorbency and the build-up of dirt. For this purpose, the manufacturers of CE 40 and CE 43 grouts recommend the silicone sealer Ceresit CT 10. Its technical data sheet indicates the following:

• the substrate must be firm, clean and dry or only slightly damp,
• work at a temperature from +5 °C to +25 °C,
• on the grout itself, the sealer is applied with a brush and one coat is generally sufficient,
• on very absorbent substrates, a test must first be done to check that the shade does not change,
• ventilation is necessary in enclosed spaces,
• fresh residues can be washed off with water, dried coating only with a solvent.

Apply the sealer only to perfectly cleaned and dried grout. If mould or dirt remained in the grout, the sealer would trap it inside.

New grout and grout after renovation

A freshly grouted bathroom needs gentle care. The technical data sheet for CE 43 grout states that for the first five days it should be washed with clean water only, without cleaning products, and that the grout reaches full resistance to water penetration after five days. Cement in grout reacts alkaline, so protect your skin and eyes when working.

The grey film of grout on tiles left by tradespeople is best removed immediately. According to the CE 40 Plus data sheet, fresh residues can be washed off with water, and hardened material only mechanically. The overall procedure for cleaning after building work is covered in the article Úklid po rekonstrukci: postup.

When to regrout

• the grout is crumbling, cracking or is eroded in places,
• mould returns even after thorough cleaning and drying,
• the grout is dark and saturated even after cleaning and sealing,
• the tile next to the grout moves or sounds hollow.

The last two points may mean water is leaking under the tiles. In that case cleaning is not enough, and it is advisable to have a tiler assess the condition. Regular care of the whole shower is described in the article Jak vyčistit sprchový kout.