Putting in an airbrick

[Martin Pentreath]

Hi,

Any comment on this? While fiddling about under the floorboards of my living room I realised that the airbrick actually vents behind the skirting board. The house was built around 1880 and the airbrick looks original to me, and the level of the floors and skirting hasn't changed.

Conclusions: the victorians were an incompetent bunch of cowboys in need of a building control department and I need a new airbrick.

This chimes in with the fact that the compartment under the floor, which is about 18 inches deep and has a bare earth base, smells a bit damp. I guess it hasn't been properly ventilated for the last 130 years. Luckily there doesn't seem to be any sign of rot anywhere, I guess if it was going to rot it would have done so while George V was still on the throne.

The brickwork is held together by mortar which seems to consist of nothing more than talcum powder (unscented) and the outside at that level has a rendered plinth. So I guess if I choose a suitably located brick from inside, drill through at the four corners to the outside and guided by the four holes use a bolster to break though from the outside inwards I should be able to put an airbrick in. Somthing like this I guess?

I make good around it with sand and cement?

Does the plastic airbrick actually perform any useful function, or could I just leave the hole in the wall covered on the outside of the building by one of these:

[Cicero]

Should I make good around it with sand and cement?

================================== It would be worth a quick check to see where the other airbricks are located before you do anything. They're usually positioned to vent the underfloor area by cross ventilation. I don't think a single air brick would produce the necessary cross ventilation. The one you've found might be just an erratic.

I would be inclined to use a proper clay airbrick (or several) if you find that you do need replacements. They look better and more authentic on older buildings. As far as the white vent is concerned, I think it might not be strong enough for outside wear and tear and would look bad in any case . Cic.

[TMC]

Should I make good around it with sand and cement?

> Cheers!

if it has not broken after 130 years don't fix it now

The mortar is probably sand and lime

Others with more experience may disagree but I am not a fan of knocking such walls about unless I have to

Anyway isn't the wall 2 bricks thick

If you really want to go ahead I think maybe a core drill to put in a circular hole would create much less collateral damage

Tony

[Martin Pentreath]

Hi Tony and Cic, thanks for the replies.

Agreed that a clay airbrick would look better, would Travers Perkins have something suitable?

As for cross ventilation, the room in question is the rear room on the ground floor of the typical victorian terrace layout, with the airbrick in the wall onto the back garden. The adjoining front room has a similar airbrick venting out to the front, and under the floor there are some gaps in the wall between the two rooms to allow some air flow from front to back. There is also some ventilation under the boards via the adjoining cellar and its coal hole grate. I haven't checked out the front airbrick yet, but even if it's doing its job the current one at the back seems to be obstructed by the skirting, and there is definitely a damp and musty smell under the floor of that room which there isn't under the better-ventilated front room.

I did toy with the idea of using a core cutter, but something tells me circular airbricks are not available?

Cheers!

Martin

[Dave Plowman (News)]

Not unusual if the skirting board is spaced off the wall. Air will find its way round. The rear addition on my Victorian house is like that - the suspended floor is nearly at ground level so you couldn't have the ventilator below it. The main part of the house is a step up and the ventilators are below floor level.

[Cicero]

================================== There's no problem getting clay air bricks. I'm pretty sure Wickes stock them and any decent builders' merchant will have them. I think you're better off staying with the authentic thing rather than trying to cut a circular hole which could cause damage if the mortar is as soft as you suggest.

It does look as if your builder put that airbrick in the wrong place but you're probably too late to sue him, so I would suggest putting in a new one to correspond with the others.

Cic.

[mail]

guess?

Should I make good around it with sand and cement?

these:

> Cheers!

Dear Martin Firstly, use the existing airbrick if it is feasible. All that is needed is for you to "ease" it off and then lower the inside of the tunnel leading to the skirting board by taking out bricks. This can be done with a masonry saw, or as suggested using a core drill or indeed a series of say 1" holes with a long drill bit angled down at 45 to 60 degrees so the hole comes out into the subfloor void. I would not be entirely suprised if some was not already there but filled up with rubble. If the brick has had it, you should use a sub-floor air VENT (a brick is 80% brick :20% air and a vent vice versa) There are lots of architecturally nice reproduction vents in cast aluminium or iron available if you look

As stated by others you need to plan your vent system with cross vents

There is a BS that covers this - from memory (unreliable) it is

3000mm2 per metre run of external wall which equates to a 9 x 3 " air vent every 1.5 m of wall run. This seems a bit excessive to me and I normally specify a 9 x 6" vent at sensible sorts of centres say 1 to 4 m depending on the site

Check that the sub floor walls are not solid but honeycombed or if solid are "holed" in appropriate centres

Consider the merit of putting polythene on the oversite if it is damp and weighing down with sand

Chris

[TMC]

The odd times that I have done this I have used a terracotta plastic vent on the outside with a length of flexible pipe through the wall probably you would not need the pipe is the wall is like 9" solid rather than cavity

Tony

[George]

Don't knock the Vics for putting up houses,no doubt that air brick has been put there in the last 30 years?

I dont think the Vics used air bricks 130 years ago? what they did do was put a board with 3 or 4 holes in it and sited this board below the threshhold of the front door.

Gimme a Victorian house anyday.

[Martin Pentreath]

From the point of view of room sizes, cellars, ceiling heights, nice windows, fireplaces and general "character" I totally agree with you. However, from the point of view of build quality this place was built by the 1880s equivalent of cowboy Barratt subbies without the benefit of a building control officer to keep them within sight of the straight and narrow. I know when the neighbours' cat has had a tin of sardines because I can hear it purring. Having said that, I'd rather have the character and something which despite its faults has survived two world wars (not to mention one world cup) than modern-day ticky- tacky.

[Dave Plowman (News)]

Yes - and cast iron grills elsewhere. The size of two bricks. You can still get them in most decent yards.

[Dave Plowman (News)]

I'm surprised - most have a 9" solid brick wall between them and it would have to be a pretty loud purr. Main problem with Victorian houses is the lack of heat insulation. They must have been a hardy lot. Or coal was cheap.