Damp understairs cupboard

[jayc89]

We have an approx 3 x 1m understairs cupboard. The floor tiles are laid direct to soil so are always damp. The walls look like they were at one time covered in some sort of tanking that's just flaking away now (beneath a sort of pebble dash coating it's incredibly chalky).

 

To the left is our kitchen, the right is the staircase and hallway, directly in front is a brick wall and beyond that a ventilated void beneath a beam and block floor.

 

I've thought about cutting a couple of bricks out of that wall and fitting air bricks to allow for some circulation which should help (keeping the cupboard door open has reduced the humid feeling down there) but it's not really an ideal solution as we're just encouraging a draft. Whilst we'll never achieve modern airtightness standards, I would like to avoid making it any worse.

 

Ideally I'd dig out the existing tiles and relay the floor, incorporating some sort of DPM. The main concern is, with the property being 150 years old, we don't have a DPC for that to lap over so by doing so will I just move the moisture elsewhere? Given it's next to our staircase I don't particularly want to encourage the moisture up towards that.

Any ideas/suggestions would be greatly appreciated.

 

[tonyshouse]

Limecrete floor, limewash or lime render the walls, linseed oil the floor limewash with egg whites in it for the walls. Damp should move down not up unless the water table is very high. 

[Faz]

Not a bad solution or you could have a go with Sika tanking render / slurry.

 

If the rest of the house is on beams can you drop the level in the cupboard below the beam level - not a great thought having damp around timber beams although they seem to have got used to it if the house is 100+ years old!

[Ajn]

1 hour ago, tonyshouse said:

Limecrete floor, limewash or lime render the walls, linseed oil the floor limewash with egg whites in it for the walls. Damp should move down not up unless the water table is very high. 

is it not too late given all the gypsum product that appears in the picture?

Edited March 22, 2022 by Ajn

[jayc89]

Limecrete's a good call. I suspect 80mm of the finer grained foam glass would be suitable for such a small area, finished with 50mm of lime screed? I'd want to try limit the build up and/or how much I have to excavate as it'll be a faff getting material in/out of there.

1 hour ago, Ajn said:

is it not too late given all the gypsum product that appears in the picture?

If I was to go the lime route, I'd expect to knock all the old render off first. I did this in the section beyond the wall in this pic, so I know it's stuck on pretty well

[Iceverge]

I suspect that that moisture is being pushed up due to the fact it's below external ground level ( correct me if I'm wrong but I seem to remember steps below your stairs leading down? )

 

Either way I would do absolutly nothing to trap moisture there for the time being, including laying any kind of floor on top. Water has a way of appearing one way or the other. At the moment I think it may be acting as a drying sump for the soil beneath your house. 

[jayc89]

9 hours ago, Iceverge said:

I suspect that that moisture is being pushed up due to the fact it's below external ground level ( correct me if I'm wrong but I seem to remember steps below your stairs leading down? )

 

Either way I would do absolutly nothing to trap moisture there for the time being, including laying any kind of floor on top. Water has a way of appearing one way or the other. At the moment I think it may be acting as a drying sump for the soil beneath your house. 

 

That's right, where the wall steps out is ground level. It's probably 0.5m below ground level at its lowest. Other than in the hight of summer the floor's never dry there. 

Would you avoid even breathable floors inc. Limecrete? If so, why?

Edited March 23, 2022 by jayc89

[Iceverge]

Any increase to the floor's permeability will push more moisture up through the structure. Limecrete is more vapour open than Concrete but nowhere as near as much as soil. It is not a solve all solution. I certainly I wouldn't put it over damp soil and expect the permeability change not to cause any issues elsewhere. Instead of a damp floor, you'll get damp walls. 

 

A table from the below shows my thinking .

 

 

https://purehost.bath.ac.uk/ws/portalfiles/portal/203983214/Phillips_et_al_2019.pdf 

 

 

I think a french drain dug around the perimeter of the house well below the level of the floor in the cupboard and always drained to a lower plain would solve the issue. Alternatively just put 100mm of gravel in the floor or make some kind of slatted base to keep your goods dry and leave the floor alone.  You'll still need to remove the moisture through heat and ventilation. 

 

 

The elephant in the room here is of course the house design being tweaked and bent around a vintage staircase and now a damp 3m2 cupboard. I would fill in the cupboard, and knock the stairs, add some EPS and limecrete over. Expecting a sunken room, often below the (localised) water table in an old house made from nice permeable materials to ever be dry is optimistic at best. 

 

 

 

 

 

 

[jayc89]

The house has certainly been tweaked although the cellar was always damp, which was a driving force in decided to block and beam over it.

 

There’s certainly heat in the area, the cupboard you can see to the right houses are UFH manifold. It’s ventilation that’s currently lacking. Even with the cupboard door constantly open, it helps a bit, but it’s no where near drying it out fully. 
 

A French drain has been a consideration for a while now, although this section of the house is pretty much dead central so I’m not sure how useful a French drain around the perimeter would be for this situation.

[Iceverge]

Only two choices where the damp is coming from, 

 

Condensation from when moist internal air meets a cold surface or

 

Water infiltration.  If there's heat in there already I'd wager it's the latter. Have you thought about making a model ?

 

Fill a large dish full of your local soil, compact it, dig a "cellar" in the middle and pour some water around the edges to see if it replicates the behaviour of your real house, with the slow influx of damp. 

Edited March 24, 2022 by Iceverge

[jayc89]

Just to close the loop here - I spoke with Ty-Mawr about my damp cupboard. They recommend limecrete with a foam glass/Glapor sub-base as apparently that will prevent any moisture wicking up without introducing the side effects associated with a physical DPM.

[jayc89]

Render's finally off. It looks like there was some additive to the stuff applied to the lower half as it was a pig to get off, whereas the top half came off in large chunks. I'd have preferred to get more off, but it was taking chunks of the brick off too. Short of sand blasting, I'm not sure what else I can do with it?

The floor has also been dug up. Turns out it was clay slabs laid on about 300mm of sand and rubble. The sand was sopping wet so there's no wonder the slabs and bottom of the walls were damp.

 

I presume this was all dumped under there when they finished building the house back in the day as we're actually in a clay area (which also explains why they sand has never dried out!)

 

Materials for the new floor and to render the walls will be ordered tomorrow. I've decided on a glasscrete floor, apparently the foam glass is non capillary so should stop the "rising" damp, and lime on the walls - Harling coat, scratch coat and float coat all mixed with pozzolan. I probably won't apply a finish coat given it's only a cupboard plus I've never plastered before in my life so thought the cupboard was a good starting place, at least it's then hidden if it looks a dog's dinner. 

 

[markc]

Strange to have steps to nowhere, are there more steps going down to a filled in cellar?

[ProDave]

"Coal Hole"  Is that a bricked up window the the side where coal used to be tipped in?

[jayc89]

The other side of the brick wall is what was once a cellar. It was a bit of an odd one, as it's not fully below ground floor level so the space above it, to the 1st floor was wasted. It's since been block + beamed over to make new ground floor room.

[jayc89]

Hardcore (foam glass) when in yesterday, wrapped in geotextile. The following morning the cupboard already felt less humid. 

 

 

 

A 2:1 Sand/NHL5 mix followed. It's looking much tidier now! It's my first time screeding using sand/lime (or cement) so it would good practice for when I need to tackle a larger room!

 

 

Hoping to get to re-plastering the walls mid-August. First will be a harl coat of Reabilita Cal CS followed my a couple of coats of NHL 3.5. 

[Roger440]

On 24/07/2022 at 14:35, jayc89 said:

Render's finally off. It looks like there was some additive to the stuff applied to the lower half as it was a pig to get off, whereas the top half came off in large chunks. I'd have preferred to get more off, but it was taking chunks of the brick off too. Short of sand blasting, I'm not sure what else I can do with it?
 

 Use a needle scaler. What i did to clean the bricks back to actual brick. Sure, it degrades the faces, but so does chipping off the plaster if its stuck and the bricks are soft. Good base for lime plaster though.

[Adsibob]

On 22/03/2022 at 15:49, jayc89 said:

I've thought about cutting a couple of bricks out of that wall and fitting air bricks to allow for some circulation which should help (keeping the cupboard door open has reduced the humid feeling down there) but it's not really an ideal solution as we're just encouraging a draft. Whilst we'll never achieve modern airtightness standards, I would like to avoid making it any worse.

You shouldn’tairtight a damp house. Unless you have MVHR drying the place already