Need to add airbrick channel under solid concrete extension - HELP!!!

27 Mar 2018
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United Kingdom
Hi All,

I have just bought an old 2 story singleskin (no cavity) mid-terraced house that has suspended wooden floors throughout.

Ive been hacking away at the ungodly amount of renovations that need doing and come across one that has me stumped...

A more recent extension has been built running the full width of the house at the rear and it has a concrete base. It seems that this was built by a real cowboy and is the cause of alot of pain for me atm!

I have pulled up the floorboards to the rear of the living room (where it joins the extension) and can see that the joists/noggins and boards all look OK (no signs of damp etc). However upon inspection I can see that the 2 original airbricks that were in the rear of the living room have been knocked out and one of them seems to have copper pipes running into the extension (radiator I assume) and nothing else and the other 1 has a length of pvc pipe (about 6 inches) running under the concrete floor and out to the rear airbrick.

I have checked the rear airbricks that were fitted on the extension and confirmed that the one with the copper pipes seems to be completely blocked (unsure as to why they would have fitted it in the new extension wall and not laid a pvc channel under the floor, and the other has most of the holes blocked besides the middle few that line up with the diameter of the pvc pipe (thank god it runs all the way!!).

So my questions are:
- Am I right to panic here? given there is no damp under the floor is it safe to assume the current ventilation is adequate? or is this a disaster waiting to happen?

My initial thoughts to remedy this (if needed) are:
- Kango out 1 or 2 channels in the extension floor, hopefully missing pipes and lay new channels.
- Kango out a small area near the living room wall and retrofit some ground vents so air can transfer into the extension rather than under it.
- Rip out the old airbrick with the pipe behind and fit some sort of pipe --> brick adapter (if needed)?

If I need to address this i'd rather go for 2nd option (less kangoing/concrete/mess) however I assume the original airbrick holes are below the DPM that is under the extension floor (will try and confirm tomorrow). If this is the case I assume there is no way I can breach the DPM with the kango, fit the vent and then somehow fix the DPM?
could I line the entire void under the vent with DPM to ensure any moisture couldn't penetrate into the concrete floor above the DPM?

Please send over any thoughts/ideas!

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I don't see the issue?

Plenty of people have solid floors with copper pipe encased, although nowadays people add protection against the concrete and copper reacting.
leave alone IMHO

If the air brick inside is connected to a 6" pipe, thence to an external air brick, there is no issue.
If it isn't blocked, great. Check by running a long pole/cane/rod through from outside.
It may be that the pipe moved slightly when the concrete was poured but so long as there is a reasonable flow it should be fine.
Far easier to move the external air brick a little than did up the whole floor
You mean the floor venting has been extended under the new concrete oversite.

It will probably be below the external brick vent so it will have a telescopic fitting through the cavity wall.

I doubt whether much air flows through vents extended that way, but any air pressure caused by wind from a different side of the house will be able to form air flow through the duct and out.

If you are worried just add another air vent elsewhere.
Thanks for the replies!

The concern I have is not with the copper pipes but rather now I have the 2 original air bricks at the front of the living room and only 1 at the rear of the room (via the pipe under the solid cement floor).

So I guess my real question is will only having 1 exhaust pose a big risk or do you think it will be ok?

@Notch7 I thought about adding another air vent but I don't think that's possible as the extension runs the entire length of the living room back wall, also it's a mid terrace so venting sideways isn't possible.
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Perhaps you could check the moisture levels of the joists with a meter???

Or do some sort of basic air test on the flow, like blocking with clingfilm and blowing air through. It might well be fine after all.

Btw you can't vent under joist air into a living space because of radon gas build up.
If everything looks sound, and you have no damp, I don't see the problem. Lift some boards and check it again in a year or two

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