Air bricks & Cavity insulation

What did your HIP say?

No. They should have been lined. Wooden floors can rot *very* quickly when not properly ventilated and I would get them cleard ASAP.

Andy

On Tue, 16 Oct 2007 09:41:37 +0100 someone who may be Another Dave wrote this:-

The work was done by cowboys. Check any paperwork you may have, there is generally a ten year "guarantee" and then chase this up with Uncle Tom Cobbleigh and all.

If you leave it you will find your floors rotting remarkably quickly.

Thanks for the reply.

The company is Miller Pattison. I haven't attempted to contact them yet, but if they're out of business or unco-operative what sort of remedial work is involved? Do I simply scrape out the gunge to clear the airways or what? I'm reasonably handy.

Another Dave

Normally there is a nylon brush (looks like the end of a toilet brush but longer) fitted up into the cavity via the outside airbrick to stop the insulation blocking the airbrick. Unfortunately over time and the weight of insulation this can fall down and block the airbrick completely. Ideally you need to take the floorboards up to get at the inside, and push rolled up chicken wire up into the cavity like ^ around the inside air slot, doing it this way will give you a chance to inspect joists and sleeper plates for the first signs of Rot ! Alternatively take the outside airbrick out and fit a plastic cavity sleeve, and hope for no rot.

When we had ours done the company replaced our airbricks with plastic sleeved versions that stopped the filling blocking them.

Pete

From the look of things no attempt was made to stop the insulation simply exiting the cavity via the air brick at the time of installation. I'm sure it's not a later event.

Fortunately the ground floors are concrete so hopefully rot won't be too much of a problem. Removing the air brick seems to be the solution.

Thanks

Another Dave

Hmm.. 1930 house with air bricks and concrete floors ? Not originally I would have thought Were do you live.

I live in NE Staffordshire (near Ashbourne)

According to neighbours the house was renovated about 15 years ago by a developer and an extension built on the back housing the kitchen amongst other things. There's evidence of a chemical damp-proof course down one side of the original part.

Are you saying a house with a concrete floor doesn't need air bricks?

Didn't they have concrete floors in 1930 or didn't they have air bricks?

Is it just the combination of the two that's unusual?

Sorry about all the questions.

Another Dave

Concrete will have no air gap underneath it so doesn't need ventilating. If you have a part concrete and part wooden floor with gap underneath) you need to still ventilate the wooden floor bit. You might need additional ventilation with new style airbricks which might give better airflow or more airbricks. If the extension has covered exits of old airvents rather than them being tunneled through you might need more ventilation at the sides and front.

Australia is miles ahead and have some solar fan vents which look very funky and would increase air flow

Well the purpose of low level airbricks is to ventilate the underfloor void and to a lesser extent the cavity space. Modern houses with solid floors have much smaller trickle vents higher up. I have seen lots of Victorian and later houses with concrete kitchen-scullery floors but none had air bricks at this location. I have seen 30s houses with _suspended_ concrete floors which did have air bricks, but these are quite rare down south. Which is partly why I asked were you were. I have also seen many Victorian and later houses were the ground floor void has been filled in with concrete for whatever daft reason, they usually suffer chronic damp problems as the internal DPC is inevitably breached.

They may have had both, though it is unusual: the airbricks would be there to ventilate the cavity. As previously pointed out here, the original reason for cavity walls was to keep out damp, not for thermal insulation. IIRC in Scotland cavity walls are still ventilated.

If the original suspended floor was replaced with a solid floor then the airbricks would be superfluous.

Is the upshot of all this that Miller Pattison were correct in blocking the air bricks and that I have no claim on the guarantee?

Another Dave