Keep airbricks and vents clear when draughtproofing

Clear blocked airbricks, fix any that are covered, then draughtproof the rest of the house without blocking essential ventilation.

AB-01Find every airbrick and vent in the houseWalk round the outside and spot the small grilled openings low down in the brickwork - these are airbricks that ventilate the space under a suspended timber floor. Inside, check for wall vents near gas fires, old boilers or chimneys, and trickle vents along the top of window frames. Make a quick list or take photos of each one before you start any draughtproofing.

1 each · Torch

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AB-02Understand which vents you must never blockUnderfloor airbricks stop damp building up under timber floors and keep the joists dry. Vents feeding an open fire, gas fire or older boiler flue supply combustion air - they are a safety feature, not just a source of draughts. Never seal, paint over or cover any vent connected to a heat-producing appliance.

RULES

KNOW THE RULES

Blocking air supply to an open flue or gas appliance can breach Building Regulations Approved Document J - the appliance needs that air to burn safely.

AB-03Clear blocked or clogged airbricksUse a stiff wire brush or an airbrick clearing rod to pull leaves, moss, cobwebs and old mortar snots out of the grille and the void behind it. Work from outside and brush debris out, not further in. If an airbrick is crumbling or badly corroded, mark it for replacement rather than trying to clean it up.

1 each · Wire brush

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1 each · Airbrick clearing rod set

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AB-04Check the clearance around each airbrickAirbricks need at least 150mm of clear space between the bottom of the grille and the ground, path, decking or flower bed outside. Dig back soil, mulch or paving that has crept up over the years, and never let a new path, deck or raised bed cover one. This gap keeps rain and pests out and keeps the underfloor void ventilated.

RULES

KNOW THE RULES

Building Regulations Approved Document C expects a minimum clearance below airbricks on suspended timber floors - covering one can cause long-term damp and rot.

AB-05Replace a damaged or crumbling airbrickChip out the old airbrick and surrounding mortar carefully with a bolster and hammer, working from outside. Fit a new terracotta or plastic airbrick of the same size, buttering the edges with mortar, and check it sits flush with the wall face. On a cavity wall, fit a telescopic vent liner to bridge the gap so debris can't fall into the cavity.

1 each · Replacement terracotta airbrick

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1 each · Telescopic cavity vent liner

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1 each · Bricklaying mortar (small bag)

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AB-06Fit a screw-fixed vent cover or pest guard safelyIf you're screwing on a vent cover, pest guard or louvre, run a cable and pipe detector over the spot first - but still treat the wall as if something could be there, since detectors miss deep or shielded cables and pipes. Find your stopcock, usually under the kitchen sink, and check it turns before you drill, so you can shut the water off fast if you hit a pipe; if you're at all unsure, isolate the circuit at the consumer unit too. Drill into solid brick or block with a 6mm masonry bit to about 40mm deep, push in a matching wall plug, and drive in a 40mm screw - never rely on a screw alone in a mortar joint, which crumbles over time. If the inside face has a layer of dot-and-dab plasterboard, use a longer fixing that reaches the solid masonry behind the dabs, not just the plaster skim.

1 each · Cable and pipe detector

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1 each · Masonry drill bit 6mm

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1 pack · Wall plugs (pack)

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1 pack · Screws 40mm (pack)

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1 each · Vent cover or pest guard

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AB-07Draughtproof the rest of the house without covering ventsFit foam or brush strip draught excluders around window sashes and door frames, keeping well clear of any trickle vent along the top of the frame - these must stay open for background ventilation. Use decorator's caulk on skirting and floorboard gaps away from any airbrick, never over one. Check extractor fan vents and cooker hood ducting are still unobstructed once you've finished.

1 each · Brush strip draught excluder

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1 roll · Self-adhesive foam draught strip

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1 tube · Decorators caulk

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AB-08Tidy up and do a final checkSweep up brick dust, mortar bits and old leaves from outside and inside. Walk round the house again and confirm every airbrick and vent on your list is clear, undamaged and unobstructed. Note the date so you remember to check them again next year, especially after autumn leaf fall.

1 each · Dustpan and brush

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PART OF A BIGGER PROJECT

Draughtproof your whole house before winter

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