Is blocking airbricks ever a good idea?

With well over 2 million people in the UK living in fuel poverty it isn’t surprising that many people are desperately looking for ways to save on heating costs wherever they can.

We see many properties where owners or tenants have blocked vents and airbricks to prevent draughts and heat loss and frankly who can blame them? What is the sense in heating a home only for the precious warmth to be lost?

The issue is that airbricks are there for a reason. When cavity construction was introduced in the 1920’s and 30’s it was an attempt to stop once and for all the constant dampness issues caused by old solid wall construction. You see, bricks are not waterproof – if they are exposed to water for long enough it will soak it up like a sponge.

Cavity walls allow for this ‘sponge effect’ by keeping the inside wall away from the outside skin. In other words, the outer wall can soak up as much rain as it wants but it will never make it through to the inside. Airbricks and ventilation spaces in the loft keep a flow of air throughout the cavity itself to assist the drying process of the outer bricks. So far so good.

The problem comes when people block up the airbricks, reducing airflow and along damp air to stay in the cavity. It may not immediately cause an issue indoor but there’s a strong chance the stale air will cause floor timber to rot – an expensive problem to rectify.

Another related issue is if the cavity has been blocked with insulation – a great idea to save money but if incorrectly installed or if it’s put in an unsuitable property ie one exposed to rain or flooding, you guessed it – damp will find it’s way through as the insulation simply bridges the gap that the home’s designer left open to stop it.

Our advice?


  • Don’t block air-bricks or internal vents unless a flood is likely.
  • If you have dampness or mould growth, check gutters, rendering and pointing as it may be letting water in.
  • Check for slipped or missing slates or tiles.
  • If you have dampness and insulation, call out an extraction company for a free quote to see if it has become wet.


  • Don’t put up with problems – they rarely fix themselves.

If you need cavity wall insulation removal due to dampness then give Cavitech-UK a call on 01903 331 578 or drop us an email on

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Is blocking air-bricks ever a good idea?