Airbrick replacement

20 Nov 2021
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United Kingdom
Hi, just signed up and wondering if anyone here can help with this one…

We live in a 1920s solid-walled house (red brick, cement rendered) that has a tendency towards dampness in the basement. Generally it’s all in check but we do get the odd issue here or there.

When we moved in we had gas heating installed and the meter box is located externally on a bay wall, unfortunately we had to have one of the airbricks removed and the hole filled as they won’t mount the meter otherwise.

Gradually we’ve noticed damp starting internally on this wall that we are pretty sure wasn’t there before. I was suspicious it’s something to do with filling the vent as something could be bridging the DPC. I had a hunt around in the basement and noticed that the hole hasn’t been fully-filled, instead only the front portion has been filled a little and rendered over.

Outside with the damp meter and the wall is good, apart from the filled in section that’s going off the scale (30%+) So I’m thinking this is the problem, I just don’t know how to solve it. As this portion of wall is now thinner, no doubt it is colder than the other walls so will be getting condensation internally. If I fill the hole completely, I will end up bridging the DPC, so that won’t fix it either. I can’t move the meter as any other location would have the same problems on the front of this house. I can’t put in a new air brick either.

I’ve covered the outside area with some waterproof tape and DPM as a temporary ‘wonder if this will fix it’, but it’s not a permanent solution even if it does work.

Any suggestions appreciated as I’m pretty much out of ideas.
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Can you take a picture of the inside where they haven't filled in fully and one from outside showing where the air brick was?
If they have installed the meter over the original air brick you may be able to install a new one a few bricks further along.
The gas meter can’t be installed within 1m of an air brick, there’s another air brick already on the front face of the bay. I also had a couple of extra vents installed a couple of years back, further back in the area to eliminate a ‘dead’ spot and get a decent through draft.

So I’m not overly bothered at losing the vent, I just can’t work out what the right way is to fill the hole effectively in a way that won’t bridge the damp proof course or result in a cold spot for condensation to settle on.

Here’s a few pics to help explain…. The taped over section below the gas meter is where the air brick used to be..

C1ED16AD-1B3C-4AD0-8A4B-F8B25451D0AC.jpeg FD5FC777-4966-4515-BEDD-68BC8BF34832.jpeg C12810AF-E839-4EF3-897F-70A700F0033E.jpeg 051E30CF-0C66-4FF7-97EA-CCA207ED146C.jpeg 45F279AF-8475-4748-9944-D0C1E3697EDD.jpeg
You should remove that render below the DPC - I'm surprised you haven't got extensive damp.
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You should remove that render below the DPC - I'm surprised you haven't got extensive damp.

i have read this. A lot. However, every single house around here is built in the same way. They are all solid walls with render to the ground. The ground around the house is sloped away from the walls and water doesn’t pool against them. I suppose that must’ve been the design in the 1920s.

However, we are going to be getting the side gable wall rendered in the new year and we’ll be taking a look at getting a bellcast bead pit along the DPC level. Was thinking of a French drain as well, but got to see how the money goes!
Just because all the other houses are rendered in the same way doesn't make it right. It needs to come off to above the dpc and it may be it was covering the damp previously but was disguised by the painted render. may be it was covering the damp previously but was disguised by the painted render.

I am not sure what you mean? This bit hasn't changed, the house has been painted render for many years. The only bit that has changed in the past couple of years is the removal of the air brick with the fitting of the gas and I'm wondering how I can block this off without bridging the DPC or leaving extra-cold surfaces for moisture to condense on internally?

But regarding your main point - if I have the render taken off below the DPC and a bead fitted all around the property, what do I replace the render with down there? A bunch of damaged red bricks (from removing the render) can't just be left exposed. So am I best using a sand & cement render with waterproofer down there, and perhaps when I get full walls re-rendered, use something more breathable for above the DPC line?
I didn't realise the bricks below were damaged. I don't know about the waterproof cement to be honest, I'm a diy'er. You could possibly blank off the internal hole with a piece of marine plywood(?).
They're not damaged. Not at the moment. But I don't know of any way of removing render that's well adhered to bricks without damaging the face of them? Fair enough if the render was boast and falling off, but it's not.

Also, if the brickwork were left exposed, would this not just be inviting more water in to the basement area (below the DPC)?

Any thoughts on whether removing this lower render and fitting a bead could be done without re-rendering the wall at the same time? This place is a fair size and we're looking approx. £4-5k for each wall, so it's going to be a slow process. In the past year we've had it re-roofed as it seemed to be the sensible thing to do before rendering to prevent any possible damp penetration from above. In the next year we'll probably get 1 or 2 walls rendered if we are lucky, but if it was possible to get the render hacked off and a bead fitted without quite so much expense, I'd be all over that one! :)
Just posted after you, i dont have much time now but will come back later.

Can you show on a pic where your DPC is and where your FFL is?

You have historic damp injection holes and Pic 3 shows v. damp bed and bricks
and a joist with rot
- the left side of the bay shows a step-up that might be bridging any DPC?
As above, below the DPC remove all thick paint and render back to brick and end rendering with a Bellcast just above the DPC.
so you've had and still have damp problems.
Why not examine the skirting boards and walls in the bay interior and along the front of the house?

Regs gas meter distance from a air brick is 180mm - which you dont quite make. Brick up the opening after removing the tape stuff.
How many air bricks do you have in total on the front elevation?

Maybe show your basement damp issues later unless they are directly connected with what youve shown so far?
:) Yes, this is a house with a few problems to get sorted :) we knew most of it when buying but as always, solutions can be slow to come by... some of it has been relatively easy (for example, a lot of damp issues have been down to very poorly fitted double-glazing units that I've re-sealed) but some is more challenging.

It's had a few goes in the past at fixing damp issues with an injection course (including some completely pointless vertical injections and others well over floor level). and an electro-osmosis belt stuck around it. Sometime back in the 70s a small extension was put on that totally blocked up all the air-flow. The old coal-hole door was removed and no additional vents were put in. So it got damp down there. Unsurprisingly this resulted in some rot and lots of the floor timbers have been removed and replaced - the black on the timbers is some kinda creosote treatment to prevent further problems. Most joist ends have been DPC-wrapped as well, as you can see, a few haven't.

The DPC is bitumen, and the electro-osmosis belt has been attached at DPC level so it is quite hard to see as the belt is cemented in - I assume the cement bridging the DPC here is a fully-waterproof cement, but who knows. Looks like the belt was supplied by Rentokill once upon a time. In the pictures, it's at the level of the mortar joint at the top of the air-vent. It's also not connected to anything, and reading up on them it would seem they're pretty much snake-oil anyway so that hasn't bothered me (yet!)

Part of the problem down there is also ground-water based - although we are on a relatively high-up plot, and the land slopes to the rear of the house, if there is a LARGE amount of rain, we can get a small puddle in the middle of the basement - I will emphasise this is VERY rare. I have seen it once since we moved in 3 years ago. Generally, the soil is moist down there, but I've increased airflow with additional under-floor vents in a couple of dead-areas and it is certainly drier now than it used to be. We also had all the wood re-treated for potential woodworm, just to be on the safe side really.

I'd just like to get these issues sorted out - it sounds to me like the render below DPC would be a great thing to do, just not sure the house will look right with bare brick below the render - where the ground runs away, this could be as much as a meter of bare brick.

In NI the gas supplier insists on a full 100cm between the gas meter and any air brick, they even moaned about the one that has been left open and carefully measured it with a tape... in total, there's 4 air bricks on the front (double-fronted) there's a further 3 on one side and 4 on the other, all clear and unobstructed, and all (just) above concrete path level. Yes, the raised step is the front door step and runs across from one bay to the other. There's no blocked up vent hole internally, so it's an always-been-there part of the house.

Skirting board will probably need replaced - we aren't quite ready to rip up that living room yet... still in a state-of-flux up the stairs with one bedroom and an en-suite left to do up there before we can start ripping out the downstairs living rooms, but I'd lay money on it being pretty tatty behind it.

Phew. Did I get every point there? :D :)

Honestly, it's a pain in the ass, but hopefully we'll get there in the end. All comments gratefully received, but bear in mind I have the budget of a human being, so realistic solutions appreciated more! :)
Just another couple of pictures for context - The blue line on the first image is the approximate FFL.

The 2nd image shows the whole front, with door step and air vents. I'm looking at that thinking it's interesting that the lower render (below the DPC) looks to have been patched in - it could just be from destruction when the injection DPC was put in, or it could be something completely different.

Still escapes me why I've had multiple builders over, all looking at the outside of the house for one reason or another, and nobody has said I need to take off that lower render. Even the 3 who've quoted me for rendering work seemingly haven't noticed this 'slight' flaw...

I haven't yet managed to find anybody locally who seems to know what they're talking about when it comes to analysing damp problems. The 'specialists' are all too keen on getting a survey fee so they can recommend DPC injection for home buyers mortgages and the straight-out builders aren't interested in solving problems as I guess there's not much money in it for them.

IMG_5611.jpgIMG_5614 2.jpg
the main issue is you have written a huge amount but it's not clear what your question is, even after re-reading it! Ask a clear question and I'm sure help will be forthcoming.
Sorry for the confusion, the last posts I wrote were a reply to @tell80, that's why it ended up quite long. I thought it was wise to explain the entire picture instead of selected bits and pieces.

The questions have expanded as the thread went on, the outstanding ones being ...

Firstly how to fill the ex-air-brick hole in a way that won't bridge the DPC (I'm not sure a bit of marine ply would be a fitting alternative to the render that seems to be currently causing a problem) - or maybe people don't even feel that's an issue worth addressing here?

Secondly when I get the below-DPC render hacked off, what way should I re-cover it? A waterproofer with sand & cement? Or should the brickwork be left exposed, in which case wouldn't that be inviting more water in to the basement area (below the DPC)?

And lastly there was, Any thoughts on whether removing this lower render and fitting a bead could be done without re-rendering the entire wall at the same time? (Rendering each wall is approx £5k so I can't get them all done at the minute)

I'm just grateful of any advice - I don't know if it's just where I am (near Belfast, NI) but I'm finding it very hard to find anyone locally who really knows what they're talking about with damp. Builders here seem unwilling to investigate (even at a price, I'm not looking for freebies), and 'damp experts' are just expert at charging for a survey for homebuyers before telling you to inject a DPC. If anyone's in the area and has any recommendations?

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