Air-brick covers and automatic air bricks

Why air bricks matter

Air bricks are the perforated bricks or grilles set low in external walls, usually just above ground level. In homes with suspended timber floors, they ventilate the space beneath the floor, keeping the timbers dry and preventing rot. They are also found at higher levels ventilating cavities, rooms and appliances.

Because they sit close to the ground and are open by design, air bricks are one of the most common routes for floodwater to enter a property. Even a few centimetres of water outside can flow through them into the underfloor void and then up through gaps in the floorboards. A flood door on its own will not stop this.

Covers

Air-brick covers are plates that fit over or into the air brick when flooding is expected. They usually clip into a permanently fixed frame or screw into position and seal against the wall. They are inexpensive and simple, but like all deployable measures they rely on someone fitting them in time and remembering to remove them afterwards. Leaving covers in place for long periods blocks ventilation and can lead to damp and timber decay.

Automatic air bricks

Automatic or self-closing air bricks replace the existing air brick with a unit that allows air to pass normally but seals itself when water arrives. Most use a float mechanism: as water rises into the unit, a buoyant flap lifts and closes against a seal. When the water recedes, the flap drops and ventilation resumes.

Because they work without intervention, automatic air bricks are a strong choice for homes where occupants may be away, where warnings are short, or where many air bricks would otherwise need covering. They are fitted by removing the existing brick and building the new unit into the wall, which usually takes a short time per unit.

Keeping ventilation working

Ventilation beneath suspended floors is important for the health of the building. Any flood measure must preserve adequate airflow in normal conditions. When replacing air bricks, the installer should check that the new units provide at least equivalent ventilation, and that the underfloor void is not blocked by debris or soil that could reduce airflow.

If you have a solid floor, low-level air bricks may be ventilating something else, such as a cavity or an appliance flue. Always establish their purpose before sealing or replacing them.

Standards and installation

Look for covers and automatic air bricks that have been tested for flood resistance, for example under the BSI Kitemark scheme. Installation matters: the unit must be properly bedded and sealed into the wall so that water cannot pass around it. The surrounding brickwork should be in good condition and well pointed.

Air bricks are rarely the only route water can take. Other openings in the wall, such as weep vents, overflow pipes and service entries, may also need sealing. A property flood survey will identify them all.

Maintenance

Automatic air bricks should be checked periodically to make sure the mechanism moves freely and is not blocked by leaves, soil, insects or paint. Some manufacturers recommend a simple test by pouring water into the unit. Covers should be stored with their fixings, and seals inspected before each season.

Finding an installer

Many flood-protection installers fit air-brick solutions as part of a wider package. Use Flood Protection Finder to search by postcode, compare specialists and request quotations for a complete set of measures rather than a single product.