Treat mould behind furniture on outside walls

Clean and treat mould behind furniture on a cold outside wall, then improve airflow so it doesn't return.

MO-01Prepare the roomOpen a window for ventilation and lay a dust sheet on the floor. Pull the furniture at least 300mm away from the wall so you can reach the whole mouldy patch. Put on disposable gloves and a mask, as mould spores are unpleasant to breathe in.

1 each · Dust sheet

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1 pack · Disposable gloves (pack)

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1 each · FFP3 face mask

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MO-02Check what you're dealing withFluffy black or green spots on the surface, worst on cold corners or behind bulky furniture, is usually condensation mould. A damp patch that stays cold and wet, or spreads up from the skirting, may be rising or penetrating damp instead. If it looks like that, or there's a musty smell with no obvious cause, get the source checked before you just clean and repaint over it.

MO-03Wash off the mouldMix a mould and mildew remover, or dilute bleach 1 part to 4 parts water, in a bucket. Scrub the mouldy area with a stiff brush, working from the top down so drips don't restart the patch further down. Wipe clean with a damp cloth, then dry the wall thoroughly with a dry cloth or paper towel.

1 bottle · Mould & mildew remover spray

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1 each · Bucket

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1 each · Stiff scrubbing brush

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1 pack · Cloths (pack)

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MO-04Let the wall dry out fullyKeep the window open and, if you have one, run a dehumidifier or small fan heater near the wall for a few hours. Don't move the furniture back until the wall feels properly dry to the touch, not just dry on the surface.

1 each · Mini dehumidifier (optional)

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MO-05Apply a mould-resistant treatmentOnce the wall is dry, brush on a fungicidal wash over the treated area and leave it for the dwell time stated on the tin. If the paint underneath is flaking or badly stained, repaint once the wash has fully dried, using an anti-condensation or moisture-resistant paint.

1 bottle · Fungicidal wash

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1 tin · Anti-condensation paint (1L)

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1 each · Paintbrush

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MO-06Improve airflow behind the furnitureWhen you put the furniture back, leave a gap of at least 50mm between it and the wall — more for a large wardrobe or sofa. Fit small self-adhesive rubber feet or risers under the legs so air can move underneath as well as behind.

1 pack · Self-adhesive rubber feet/risers (pack)

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MO-07Keep the room ventilated going forwardOpen a window for 10-15 minutes daily, even in winter, and run the extractor fan when cooking or showering nearby. Keep the room at a steady low background heat rather than switching the heating on and off, and wipe away any condensation on windows each morning.

MO-08Tidy upBin the used cloths and gloves, and rinse the bucket and brush under a tap. Ventilate the room for another hour to clear any fumes from the treatment. Store any leftover fungicidal wash or paint out of reach of children, following the label.

1 pack · Bin bags

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