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Airbricks, Flooding and Cavity Wall Insulation

Posted by Jason Ramsdale on 6 January 2016 at 4:45 pm

Airbricks are hollow, vented blocks that are placed into walls to allow for air circulation in the subfloor of houses with suspended timber floor. This air circulation is designed to prevent the underfloor space becoming damp and stale. Damp problems can occur if airbricks are blocked, flooded, covered or subject to soil ingress particularly if outside ground levels are raised. Failure to address a build-up in damp beneath your floor can lead to rotting floor joists and rising damp which can be expensive and disruptive to repair.

Airbricks in flood risk areas:

If your airbricks are at risk of flooding, or are too close to the ground, telescopic airbricks can be used to raise the height of the ventilation. In addition, flood bricks can be replaced with specially designed flood-proof bricks that allow for ventilation under normal conditions but close automatically as water levels rise preventing your walls and floors from being flooded.

Cavity Wall Insulation (CWI) and airbricks:

For those of you with both airbricks and cavity walls, a duct can be fitted inside the cavity between the internal and external airbrick to allow for cavity wall insulation (CWI) without blocking ventilation to the subfloor. These ducts can be made like a periscope to allow for a raised external airbrick.


Cavity Wall Insulation in flood risk areas:

In the event of a flood CWI can retain high levels of moisture leading to potential damp problems after the visible areas of your home have dried out. Flooding can often lead to areas of CWI clumping and sagging leaving cold spots vulnerable to developing condensation and damp. If your cavity has been flooded the insulation may need to be removed to allow your walls to properly dry out. When installing CWI there is the possibility of injecting polyurethane foam e.g. Technitherm, which is flood resilient and non-absorbent. Polyurethane foam is also extremely sticky and can replace corroded wall ties, holding your outer and inner walls in place.


Airbrick by steve p2008

Telescopic vent by Timloc


More information about ventilation and draughts on YouGen.

More information about Insulation on YouGen.

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2 comments - read them below or add one

Tom Bragg

Tom BraggComment left on: 31 January 2016 at 10:09 am

Our flood-risk has risen to 1 yr in 1,000 on the Environment Agency Map, which, with climate change, I take as a rising risk, worth preparing for. I've made plywood air-brick covers, with fixings, ready for installing if there's a flood warning. Ready-made plastic ones are available too. Automatic ones, as in the video above, requiring no fitting during flood-risk and removal after, would be better, but a bit pricey.

I found Richard Simmons' practical advice helpful on preparing for a flood and "You have been flooded", which I hope you don't need!

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Cavity Insulation Guarantee Agency

Cavity Insulation Guarantee AgencyComment left on: 7 January 2016 at 10:48 am

It is heart-breaking to listen to the stories of families affected by the recent floods.

When a home is flooded significant remedial work needs to be undertaken to make the house liveable once again.

Homes fitted with retro-fitted cavity wall insulation are no exception.

That is why CIGA has issued technical advice to households on what to do if their home is flooded and they have retro fit cavity wall insulation installed.

To receive a copy of the advice, homeowners are asked to email Gerry Miller, CEO, CIGA

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