How do I remedy this wall?

[bobski1]

We have a vestibule which looks as though it was added on by previous owner. It suffers badly from condensation and as a result mould spots. I took the tiles off & stripped back everything back to the plaster too see if there was anything obvious. I give it a kick of white and noticed these areas coming through where the plaster or filler is crumbling away. The outside is rendered and there's a water but on the other side of the wall and the downpipe for the drain.

I'm wonder what the cause of these issues is and how best to remedy them, do I take it back to brick apply some kind of sealant & replaster? Or do I need to go further and perhaps replace the tender & DPC, assuming it's there somewhere

[Little Lofty]

Looks to be only single skin? Pretty tricky to keep it 100% dry if it is.

[Kwackersaki]

We have exactly the same issue. Similar flaking paint and efflorescence not helped by a leak in the roof that’s soon to be fixed.

There are special condensation resistant paints and we’ve put in a window trickle vent but when you open the main inner door and heat escapes, the outer wall/door is soaked!

Not really sure if there is any solution other than heat it or knock it down!

Edited by Kwackersaki on Tuesday 12th March 07:29

[Lotobear]

Treated battens on DPC strips and thermal board to finish. And a cill board to cap it off below the window

[Kwackersaki]

Lotobear said:

Treated battens on DPC strips and thermal board to finish. And a cill board to cap it off below the window

Thanks. Will prefer to go that route rather than demolish.

[Little Lofty]

Build a small stud wall in front of the outer wall and insulate it.

[Lotobear]

Little Lofty said:

Build a small stud wall in front of the outer wall and insulate it.

..pretty much what I'm suggesting above. 25mm x 50mm slate battens and 50mm thermaline board over the top - 75mm o/a thickness and minimal thermal bridges.

[Tim Cognito]

We had similar on the last house, tap the render outside it might be blown but as said very difficult with single skin. We have a single skin porch in this house and at some point I want to build a stud wall to make it somewhat above outside temperature.

Don't waste your time with alkaline primers, or anything else meant to block efflorescence, it will always come back.

In the end we put some of that lined thermal wallpaper over it and sold the house a year later.

[bobski1]

Little Lofty said:

Looks to be only single skin? Pretty tricky to keep it 100% dry if it is.

Yes you are correct it is a single skin wall, as it's the doorway there is always moisture coming in, generally we leave the door open so it is just one big hallway as I found with the middle door closed it is worse and the mould builds up faster.

Ideally I didn't want to have to build out the area too far as there isn't much pace especially with a pushchair to get through the door very shortly.

I don't have massive amount of time so I was thinking something simple like chip away the plaster and cover with something simple like a PVC sheet like they have in commercial settings, easy to wipe and keep clean.

If I do go stud route:
1- do I still need to take off the plaster or leave it as it is?
2-DPC between the battens and where it touches the wall only?
3-If I screw the battens doesn't the moisture travel through the screw or am I over thinking it?
4-I am going to remove the tiles and add some self levelling first so can build off that before laying down the cohair I have to cover the area.

There is also a spot over the door which has mould spots so I think I need to dig this out too and replace or at least place on some DPC before reapplying plaster?

Thanks for all the help

[Lotobear]

bobski1 said:

Little Lofty said:

Looks to be only single skin? Pretty tricky to keep it 100% dry if it is.

Yes you are correct it is a single skin wall, as it's the doorway there is always moisture coming in, generally we leave the door open so it is just one big hallway as I found with the middle door closed it is worse and the mould builds up faster.

Ideally I didn't want to have to build out the area too far as there isn't much pace especially with a pushchair to get through the door very shortly.

I don't have massive amount of time so I was thinking something simple like chip away the plaster and cover with something simple like a PVC sheet like they have in commercial settings, easy to wipe and keep clean.

If I do go stud route:
1- do I still need to take off the plaster or leave it as it is?
2-DPC between the battens and where it touches the wall only?
3-If I screw the battens doesn't the moisture travel through the screw or am I over thinking it?
4-I am going to remove the tiles and add some self levelling first so can build off that before laying down the cohair I have to cover the area.

There is also a spot over the door which has mould spots so I think I need to dig this out too and replace or at least place on some DPC before reapplying plaster?

Thanks for all the help

Though the wall is only single the central issue is almost certainly condensation in your cold unheated space (mould is, with a few exceptions, nearly always associated with condensation as it needs pure condensate to support it). The thermal board will raise the surface wall temperature and eliminate the condensation and if there is any slight penetrating moisture it will be 'covered up' and the battens are protected by the dpc strips and their treatment. If you are really concerned about the batten fixings use membrane plugs to fix the battens. Use DPC under the battens only - a full sheet membane is not necessary and may in fact create an interstitial condensation risk. you are forming a 'dry lining'.

The plaster can be left - no benefit in its removal, it stiffens the wall

[bobski1]

Any particular thermal board you would recommend? The area isn't that large and storage is an issue for large sheets/offcuts.

Does thermal board require any special fixings or any of the right length will do?

DPC: https://www.screwfix.com/p/capital-valley-plastics...

Battens: https://www.travisperkins.co.uk/roofing-batten/tre...

Cill board I think I have an offcut from when I replaced the one in the bathroom so can trim that down to fit over the structure.

also is it work DPC the edge of the thermal board when it meets the outside wall on the left hand side or leave a gap and fill with mould resistant silicone of some type? The RHS is no issue as that little section has no issues.

[bobski1]

Any recommendation on the thermal board? Got next week to execute so trying to order bits in this week