Clear blocked airbricks

Clear blocked airbricks safely and restore underfloor airflow to stop damp building up.

AB-01Find every airbrick and check which are blockedWalk right round the outside of the house at ground level. Airbricks are the small grilled bricks near the base of the wall, usually just above ground level, letting air into the space under a suspended timber floor. Shine a torch through each one — if you can't see daylight or clear space behind it, it's blocked. Note down how many need clearing before you start.

1 each · Torch

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1 pair · Work gloves

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AB-02Check for nesting birds or bees before you touch anythingLook and listen for activity — bees going in and out, or a bird's nest just inside the grille. Do not clear or disturb an airbrick with an active bird's nest. Wild bird nests are protected by law while in use, so wait until the birds have finished nesting before clearing that airbrick. If it's bees rather than birds, leave that one alone and call a local pest or bee removal service.

RULES

KNOW THE RULES

The Wildlife and Countryside Act 1981 makes it an offence to damage or destroy the nest of a wild bird while it's being built or used. Leave an occupied nest alone until the birds have fledged.

AB-03Clear soil, plants and debris from outside the airbrickCut back any plants, ivy or grass growing over the airbrick. Dig away soil, mulch, gravel or paving that has built up in front of it — the ground level outside should sit at least 150mm below the bottom of the airbrick, so air can flow freely. Bag up everything you remove as you go.

1 each · Garden trowel

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1 each · Secateurs

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2 each · Refuse sacks

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AB-04Clear the grille itselfUse a stiff brush to sweep leaves, cobwebs and dirt out of the grille slots. Pick out any solid lumps of soil or debris with a small trowel or an old screwdriver. Finish with a vacuum on a narrow nozzle if you have one, holding it close to draw out fine dust and grit.

1 each · Stiff masonry brush

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1 each · Old flat-head screwdriver

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AB-05Check the airway is clear on the inside tooIf you have easy access to the underfloor void — for example, a removable floorboard or hatch nearby — lift it and shine a torch across to the airbrick from inside. Make sure nothing (insulation, old newspaper, a plastic bag stuffed in years ago) is blocking it from this side. Skip this step if you have no safe access; clearing the outside is usually enough on its own.

1 each · Torch

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AB-06Replace a broken, rusted or missing airbrick grilleIf the grille itself is cracked, crumbling or missing, fit a new one rather than trying to repair it — they're cheap. This means drilling into solid brick or block, so use a cable and pipe detector first and still work carefully: pipework for an outside tap or a mains water feed sometimes runs near ground level. Find your stopcock (usually under the kitchen sink) and check it turns before you start, so you can shut the water off fast if you nick a pipe. Drill fixing holes with a 6mm or 7mm masonry bit to match your wall plugs, push in the plugs, and screw the new grille into place.

1 each · Replacement airbrick grille (clay or plastic, 215 x 65mm)

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4 each · Masonry wall plugs, 6-7mm

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4 each · Screws, 40mm

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1 each · Masonry drill bit, 6mm or 7mm

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1 each · Cable and pipe detector

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AB-07Tidy up and check ground levels stay clearSweep up any soil, brick dust or leaves left on the path or patio. If you've dug back soil or gravel to expose the airbrick, consider adding a small gravel-filled trench or a shallow drop in level so it doesn't build up again. Keep an eye on it after heavy rain or when plants regrow.

1 each · Yard brush

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AB-08Check the results over the next few weeksHold your hand near the airbrick on a breezy day — you should feel a faint draught if the underfloor space is ventilating properly. If you'd noticed a musty smell or damp patches near skirting boards before, check whether these ease off over the following weeks now air is moving freely again.

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