position of air bricks

[untitled]

Hello All,

Can anyone advise on the quantity and position of air bricks? I have three of them to the side and rear of my property as shown in the photo. They are positioned on top of the slate DPC but are not below the floor. In fact they are in the middle of floor height behind the wooden skirting.

Should I remove these and place them under the DPC and if so, is there any advice on minimum spacing or quantity?

Thank you. If anyone can help with my damp issue posts as well that would be really appreciated...

 

[Feltwell]

Those bricks are suffering a bit aren't they?

Your air bricks may be at a certain height but could be ducted behind to ventilate under the floor. Have you got any loose floorboards so you can see underneath? I made a hidden hatch under one of my sofas in the lounge in the end. If you look underneath you'd probably see a bit of light coming through if they are ducted, if not then poke a bit of old stiff electrical cable down them and see how far you can get it to go and if you can see it under your floor. It would be very odd if the original builder went to the trouble of putting airbricks in that didn't allow air under the floor! However, who knows what subsequent owners have done, sometimes in misguided attempts to stop draughts, or if those airbricks are in fact original.

That air brick looks like it could do with a quick clean to get it back to full efficiency, but even then it's not the best for airflow by the look of it. I usually see airbricks below DPC, but I don't see any reason why they couldn't go above.

As to is you've got enough airbricks - can't say without seeing the house and layout, but even then it's only an opinion. Have you got signs of damp caused by poor sub-floor ventilation, such as rotten joists or boards? You want a cross-flow of air ideally. Sometimes the problem can be because sleeper walls or internal walls under the floor are blocking the airflow, resolving this can be as simple as knocking a few single bricks out. You can also ventilate into a cellar if you have one - the more airflow the better.

 

[untitled]

Hi Feltwell,

Thank you for your reply. Indeed, those brick have seen better days. The reason for this and my subsequent question regarding air bricks has come about because I've remove a DPC bridging plinth render on the exterior of my property. See http://www.periodproperty.co.uk/forum/viewtopic.php?f=1&t=14854&p=204809#p204809 for the thread. Removing this plinth has severely compounded my damp problems and now the internal walls literally drip with moisture. Penners has given some advice on this.

In terms of the air bricks I am investigating this as if I am to reinstate the plinth, repoint or change the original work I should also look at the air bricks. Curiously this one, and the others in fact, look like they have been installed removing the slate DPC. The wall directly above this air brick is always damp and the fact that the DPC seems to be missing made me wonder if this was the cause.

I'll lift some floorboards and have a look as you suggest. If it has been installed incorrectly do you know if I can put it lower and reinstate some slate for DPC above it?

I'll work on the premise that the more airflow the better and see. Yes the room has always had some damp (slugs etc). After we removed the carpet and have had the floor clear for 4 years it got better.. "till I removed that external DPC bridging plinth that is!

Thank you very much.

Will report back.

 

[Feltwell]

I see what you mean about the air brick interrupting the slate DPC, I didn't spot that. That isn't right at all, and suggests the air bricks were added later. Air bricks being below DPC is fine - they're like that here, with no problem.

A slate DPC if installed correctly won't fail, so if you removed those air bricks and repair with some new DPC, lapped a reasonable way onto the old slate one either side, you should make a good repair.

I haven't seen your other posts but I presume you've checked all the usual damp sources - guttering and downpipes are ok, ground levels outside lower than inside by a reasonable amount, room is adequately heated and ventilated, no excessive sources of moisture internally such as condensing tumble dryers, portable gas heaters etc.

 

[untitled]

Good to get this confirmed. I'll move them below as you suggest. Thanks

 

[Keithj]

A random thought for a Wednesday afternoon...

Is that an "aftermarket" airbrick for a fireplace in the room?
In our last (modern) house we wanted a fireplace (gas, coal effect, but better than nothing) so had one installed with a flue on the outside. The installer insisted that we needed an air brick "to meet regs" to let air in for the fire. He would have cut a hole like that in the wall beside the fireplace if we'd let him.