Grout Turning Black
Grout between tiles turning dark grey, black, or developing visible mould spots, especially in wet areas.
What Is Causing This?
- 1Mould and mildew growing in damp conditions
- 2Grout not sealed after installation
- 3Poor ventilation in bathrooms and shower areas
How Urgent Is This?
This is a cosmetic issue. It is not causing damage and can be addressed in your own time.
What Needs to Be Done
A tiler will clean the grout with a mould treatment, and if too far gone, rake out the old grout and regrout with a mould-resistant product.
How Much Will It Cost?
National average estimate
Labour: £233 – £688 | Materials: £113 – £475
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Prices are estimates based on typical UK rates. Actual costs depend on the specific issue, accessibility, and your location. All quotes from tradespeople on Tradesfolk are completely free.
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Ask a QuestionHow to Prevent This
Seal grout after installation and reseal annually. Wipe down tiles after showering. Run the extractor fan to reduce moisture.
Related Problems
Black or dark green spots spreading across the bathroom ceiling, sometimes extending down the walls.
Dark mould growing on ceiling, walls, grout, sealant, or around the window in the bathroom.
Signs of water getting behind wall tiles, such as damp patches on the other side of the wall or loose tiles.
Other Tiler Problems
A crack running through one or more wall or floor tiles in the bathroom, sometimes with pieces missing.
One or more floor tiles that rock, click, or move underfoot, sometimes with hollow sounds when tapped.
Floor tiles tenting upward or popping off the substrate, sometimes with a cracking sound.
Tiles in the shower enclosure loosening, bulging, or falling off the wall, often with damp behind them.