Green Building Forum - Large area of soil in crawlspace

Large area of soil in crawlspace

DannySheffield — Tue, 19 Nov 2024 19:36:20 +0000

I have a 1930s semi with brick cavity walls. It has a crawlspace around a metre high. There is an area about 1x2.5 metres below the stairs that's walled off. I popped out a couple of bricks the other day to have a look and it's full of damp soil and rubble. I can see there's damp around the bottom, and it's making the external walls slightly damp. I've also had a mould test that showed elevated levels in the air over the stairs that I hadn't been able to explain.

Has anyone else come across this? And could it be serving a purpose (e.g. stabilising walls?), or is it more likely just soil and rubble that's been dumped and would be better removed?

Large area of soil in crawlspace

djh — Tue, 19 Nov 2024 20:24:31 +0000

Posted By: DannySheffieldcould it be serving a purpose (e.g. stabilising walls?)

Or supporting the floor? What's under the stairs if you look from above?

Large area of soil in crawlspace

Peter_in_Hungary — Tue, 19 Nov 2024 20:41:00 +0000

The wall will have been built for a reason - even if that reason is no longer there. If the area enclosed is 'walled in' without being either included in the sub floor ventilation or having it's own then that would explain the damp and mould. Providing better ventilation should solve the damp and mould problem in time. Removal of the wall would first require an understanding of why it is there (or was put there)

When you say "it's full of damp soil and rubble" do you mean 'full' or just a good amount in there. If it is actually full then it is probably better to remove some or all of it. If it is just a good amount then adequate ventilation in time should solve the damp and mould issue.

Large area of soil in crawlspace

DannySheffield — Wed, 20 Nov 2024 07:54:29 +0000

Posted By: djh
Posted By: DannySheffieldcould it be serving a purpose (e.g. stabilising walls?)
Or supporting the floor? What's under the stairs if you look from above?

There's a coal store directly below the stairs. I didn't want to remove too many bricks so I've not seen the full picture, but now I think about it there are two separate areas, with a wall separating them. The section under the bottom of the stairs is just full of loose material, but the section below the coal store looked like it might be more deliberate - the top layer seems to have some chunks of concrete and brick that are more deliberate, so might be supporting the base of the coal store.

Large area of soil in crawlspace

DannySheffield — Wed, 20 Nov 2024 07:58:04 +0000

Posted By: Peter_in_HungaryThe wall will have been built for a reason - even if that reason is no longer there. If the area enclosed is 'walled in' without being either included in the sub floor ventilation or having it's own then that would explain the damp and mould. Providing better ventilation should solve the damp and mould problem in time. Removal of the wall would first require an understanding of why it is there (or was put there)

When you say "it's full of damp soil and rubble" do you mean 'full' or just a good amount in there. If it is actually full then it is probably better to remove some or all of it. If it is just a good amount then adequate ventilation in time should solve the damp and mould issue.

One section (I realised it's in two separate sections - see comment above) seems to be full to the top, but might be supporting something. The other is more soil and rubble than air - maybe a 50cm air gap at the top. And that's all loose. That one it sounds like it's worth emptying and ventilating.

Large area of soil in crawlspace

djh — Wed, 20 Nov 2024 09:55:22 +0000

Posted By: DannySheffieldThere's a coal store directly below the stairs. I didn't want to remove too many bricks so I've not seen the full picture, but now I think about it there are two separate areas, with a wall separating them. The section under the bottom of the stairs is just full of loose material, but the section below the coal store looked like it might be more deliberate - the top layer seems to have some chunks of concrete and brick that are more deliberate, so might be supporting the base of the coal store.

It's unusual to have a coal store in the middle of a house, I think. They're normally on the outside, where it's convenient for the coalman to tip the coal. A photograph of the arrangement under the stairs (from in the normal areas of the house) and another of the area under the floor might help.

What is the floor of the coal store made of? And do you use the coal store for anything? Or the other space?

Large area of soil in crawlspace

Nick Parsons — Wed, 20 Nov 2024 11:22:53 +0000

If it's like some of the Sheffield houses I know there may have been a small under-stair cupbd accessed from inside and a coal-store next to it accessed from outside. The brickwork below the floor will be the footing for that.

djh: What is the floor of the coal store made of? +1

Large area of soil in crawlspace

djh — Wed, 20 Nov 2024 13:15:45 +0000

Posted By: Nick ParsonsIf it's like some of the Sheffield houses I know there may have been a small under-stair cupbd accessed from inside and a coal-store next to it accessed from outside.

Ah, thanks. I hadn't realized that the stairs might be on an outside wall, which is perfectly normal when I think about it. Could you take coal out of the store through a hatch or whatever inside the house?

I presume the stairs just pass above all this construction and form its roof, but the stairs aren't supported by the coal store walls or anything? So you could just demolish the coal store and fix up the floor and underfloor to be damp proof.

Large area of soil in crawlspace

Nick Parsons — Wed, 20 Nov 2024 14:34:08 +0000

''Could you take coal out of the store through a hatch or whatever inside the house?''

No, you had to take the coal scuttle to the store.

In the last example I saw the brick wall is built up to the string of the stair, so I assume it is providing at least some support.

Large area of soil in crawlspace

DannySheffield — Wed, 20 Nov 2024 19:55:17 +0000

Posted By: Nick ParsonsIf it's like some of the Sheffield houses I know there may have been a small under-stair cupbd accessed from inside and a coal-store next to it accessed from outside. The brickwork below the floor will be the footing for that.

djh: What is the floor of the coal store made of? +1

It is similar to that - but no under stairs cupboard from the inside - most of the area under the stairs is colas store. The floor is made of concrete - I'd forgotten as I insulated and boarded it a while ago. But that's the missing piece of the puzzle - the larger section of rubble is the footing for the crawlspace floor. Funny how simple the answer is when you get there!

Large area of soil in crawlspace

DannySheffield — Wed, 20 Nov 2024 19:59:21 +0000

You're right, the stairs just run over it. So I could just knock out the rubble including the current coal store floor which would fix the crawlspace. It's useful having the coal store for parcels, recycling etc, any ideas for a simple way to create a new, suspended floor? I'll see if it has joists in that bit, I'm guessing if it does they wouldn't be very happy by now!

Large area of soil in crawlspace

Nick Parsons — Wed, 20 Nov 2024 20:15:02 +0000

@DannySheffield, your post above has me quoted as saying something which @djh actually said. What I said was about the opposite of that: ''In the last example I saw the brick wall is built up to the string of the stair, so I assume it is providing at least some support.''. Don't take the wall out unless you are 100% happy that it gives no support to ... anything. Pictures would be great.

Large area of soil in crawlspace

DannySheffield — Thu, 21 Nov 2024 19:46:18 +0000

Posted By: Nick Parsons@DannySheffield, your post above has me quoted as saying something which @djh actually said. What I said was about the opposite of that: ''In the last example I saw the brick wall is built up to the string of the stair, so I assume it is providing at least some support.''. Don't take the wall out unless you are 100% happy that it gives no support to ... anything. Pictures would be great.

Sorry about that, I just fixed it. I'll post pictures below

Large area of soil in crawlspace

DannySheffield — Thu, 21 Nov 2024 20:24:08 +0000

Thanks for your help so far everyone. I've taken a set of photos which should help. I've colour coded them - yellow is the bit under the coal store that appears to be the coal store floor. Green is the bit under the foot of the stairs. The stairs have been modified at some point - they originally went straight down but the dog leg was added to make space for a downstairs toilet.

I can't get them small enough to upload here, so I posted them on postimg.cc here: https://postimg.cc/gallery/v4HbRB8

Large area of soil in crawlspace

Nick Parsons — Thu, 21 Nov 2024 21:14:19 +0000

Difficult to be certain from pics but from what I think I see I'd say dig out and cross-vent to the rest of the void (so air-brick in the 'internal' wall and the external (or leave the hole open (with a lintel if it requires one (IANASE!). Still not sure that the coal-store floor won't drop out if you remove its 'bottom'!

Large area of soil in crawlspace

DannySheffield — Fri, 22 Nov 2024 06:48:16 +0000

Posted By: Nick ParsonsDifficult to be certain from pics but from what I think I see I'd say dig out and cross-vent to the rest of the void (so air-brick in the 'internal' wall and the external (or leave the hole open (with a lintel if it requires one (IANASE!). Still not sure that the coal-store floor won't drop out if you remove its 'bottom'!

Thanks Nick. I'm guessing the coal store floor will drop out, but as the joists do appear to run through it, it should be simple to board. It feels worth getting them out in the open too and seeing if they're safe, as from what I can tell they've been stuck in damp material for decades. Also, I think it will be easier to dig out the material from the coal store than to bring it through the coalspace (although I might be wrong!).

Large area of soil in crawlspace

Nick Parsons — Fri, 22 Nov 2024 09:16:00 +0000

Aha! Had not picked up that the conc floor had joists running through it! Hope it goes well.

Large area of soil in crawlspace

DannySheffield — Fri, 22 Nov 2024 12:14:51 +0000

Posted By: Nick ParsonsAha! Had not picked up that the conc floor had joists running through it! Hope it goes well.

Thanks Nick, I appreciate your thoughts.

Large area of soil in crawlspace

jon — Wed, 18 Dec 2024 15:26:42 +0000

Posted By: DannySheffield
Has anyone else come across this? And could it be serving a purpose (e.g. stabilising walls?), or is it more likely just soil and rubble that's been dumped and would be better removed?

Yes. Though it may not be the same issue. When the floors were replaced, the builders decided to use one of the open cells as a refuse dump for other works, demo of a chimney breast and demo of an old toilet. Removed it all.

If you find debris that's incongruous with stabilising fill (eg toilet remains, fireplaces etc), then it's may be just a dump from a previous reno.

Large area of soil in crawlspace

DannySheffield — Mon, 13 Jan 2025 15:40:58 +0000

I'm most of the way through digging out the two areas full of soil and rubble. I'm going to clean up and put some air bricks in, then a suspended floor. In terms of the floor left after I dig it out, is there any benefit to putting down e.g. gravel or crushed stone? The rest of the crawlspace seems to be mainly just dirt, with some old concrete there, so it doesn't seem worth going further (e.g. putting a DPC in just that area).

Large area of soil in crawlspace

tony — Wed, 15 Jan 2025 06:11:48 +0000

Will you add insulation to the underside of the suspended wooden floor?

Large area of soil in crawlspace

DannySheffield — Sun, 19 Jan 2025 09:15:56 +0000

Posted By: tony
Will you add insulation to the underside of the suspended wooden floor?

I will, possibly to the underside of the stairs too, but that's a bit awkward

Large area of soil in crawlspace

Nick Parsons — Sun, 19 Jan 2025 11:48:39 +0000

For some reason I can only attach one pic at a time, so 3 posts coming up:

Large area of soil in crawlspace

Nick Parsons — Sun, 19 Jan 2025 11:50:34 +0000

No. 2:

Large area of soil in crawlspace

Nick Parsons — Sun, 19 Jan 2025 11:54:08 +0000

No. 3, after application of plasterboard directly to the PIR (no gap). Fixings are to the blue battens in pic 1 above. Remember where they are!!

Large area of soil in crawlspace

Nick Parsons — Sun, 19 Jan 2025 11:56:03 +0000

Not that awkward! Total lay-up adds 35mm gross, which with removal of old plaster is about 15mm net.

Large area of soil in crawlspace

DannySheffield — Mon, 20 Jan 2025 07:18:20 +0000

Thanks Nick. It looks like a similar space. The problem for me is the meters are in the way, and it's most of a £1,000 to move them a short distance. https://postimg.cc/G8BqWcFN

Large area of soil in crawlspace

Nick Parsons — Mon, 20 Jan 2025 13:11:46 +0000

https://postimg.cc/G8BqWcFN

Ooh yes - that's a bu**er! So close to being not a problem, yet it is!

Large area of soil in crawlspace

djh — Mon, 20 Jan 2025 13:34:34 +0000

Posted By: Nick ParsonsOoh yes - that's a bu**er! So close to being not a problem, yet it is!

Might it be possible to take the entire electrical board off the wall and slip some insulation behind it (aerogel?) and then screw the board back in place ?

Large area of soil in crawlspace

Nick Parsons — Tue, 21 Jan 2025 10:35:06 +0000

''Might it be possible to take the entire electrical board off the wall and slip some insulation behind it (aerogel?) and then screw the board back in place ?''

Hi djh, yes, but it's the whole corner of the board which is preventing the OP doing what's in my pics. However as you mention aerogel (gasp - £££££) it does occur to me that he could do what I did on all but the affected riser/tread, and 'slab' those instead with aerogel (or even 12mm PIR - hard to get as 'singles' or even even 25mm PIR cut down at the end to slip round the board, and sealed with silicone). Not perfect but a great deal better than a poke in the eye with a sharp stick.