Damp on external wall old property

mutty_hc

Pics:

https://ibb.co/gyg2d16
https://ibb.co/5cTnYRF
https://ibb.co/9v1YGcz
https://ibb.co/7vLW886
https://ibb.co/kyVwcZ2

Hi all,

Having some damp issues on an external wall.

Wall is approx 200 years old
DPC was fitted, but one of those injected ones 25 years ago - so probably not any good
Exterior has a coating on it, but has no cracks or holes that I can see.
Interior wall has thick wallpaper/ polystyrene coating on it, so considering whether to leave this on or not currently.

Basically issue is - two small areas are getting damp patches on them, one around the left hand base of a fireplace, and one on the right hand side around an electrical socket.

They do not grow in size and get damper when we have heating on/ to a degree when it rains (but cannot correlate this yet).

Any ideas on what I should do to remedy it?

Thanks.

FreeBear

mutty_hc wrote: »

Exterior has a coating on it, but has no cracks or holes that I can see.
Interior wall has thick wallpaper/ polystyrene coating on it, so considering whether to leave this on or not currently.

[damp] around an electrical socket.

It looks like moisture is trapped in the wall by the polystyrene paper and is finding its way out around the socket. Long term solution is to strip off the wallpaper, and fingers crossed, it is unadulterated lime plaster underneath. If it is, all well and good - Repaper with a good quality paper (not vinyl) or paint with a breathable paint (lime wash or clay).

Externally, you need to find out what was used to paint the walls - You'll probably find it is some unsuitable modern stuff like Sandtex. Stripping it off is going to be messy and expensive (blasting with a suitable medium may be the only option).

Having said that, if there is signs of an injected (and useless) DPC, a previous owner may well have gone the whole hog and had waterproof render slapped on the internal wall - That is just going to cause more grief and expense to remedy.

Discountdave

I recently renovated a property with a lot of damp. Initially I discussed this with various 'experts' in sorting out damp and was continuously advised to hire them for an expensive course of damp proof injection. However, after reading about many problems with this I started looking into it further and it was evident that the house never had a DPM and by potentially meddling with the current damp issue in this way, it was more likely to divert the damp somewhere else in the house as opposed to fix the actual root of the problem.

After researching further, I found that by replacing the floor with Limecrete (which is breathable so requires a permeable surface laid on top), I was able to stop the damp altogether without adding in a DPM and potentially making it worse. I bought the limecrete from Mike Wye Associates. It was a hell of a job, I have to be honest, but has worked a treat and the house is now bone dry.

This was several walls on the ground floor, so i'm certainly not suggesting you need to re-lay all the floor area of the house for two small areas of damp, but it may well be the current DPM being applied 25 years ago to the house (that was perhaps never designed originally to have a DPM) and possibly a weak point is causing this area to be the outlet for the moisture build up.

mutty_hc

Thanks both for the replies.

Couple of queries pertaining to the advice,

I believe the wall was replastered beneath this wallpaper - it looks like typical brown colour plaster (will take a few pictures and post them) - how would I determine if this was the correct type?

I am going to double check what was done 25 years ago, it was definitely some work on 'rising damp' - which when googled seems to be a total waste of time/ money.

Externally the house is covered in a waterproof coating (fitted by previous owner), so our hope was we could breath the house internally (which I am figuring this particular wall cannot do?)

What would the best way forward be in the interim? Strip the wallpaper back to the plaster?

ANDY597

Personally, id strip off the wallpaper and see if you can further identify where it's spreading from.

Chimney leaks are common, so could well be water impregnation further up the chimney and this is its final resting point.

Your outside pictures don't seem to have any obvious cracks or faults.

stuart45

mutty_hc wrote: »

Thanks both for the replies.

Couple of queries pertaining to the advice,

I believe the wall was replastered beneath this wallpaper - it looks like typical brown colour plaster (will take a few pictures and post them) - how would I determine if this was the correct type?

If the wall had an injected DPC, the odds are that it had 2 coats of 3/1 sand/OPC cement with an added waterproofer. Although this can hold back the damp for a number of years, when slight cracks form in it the damp can find it's way through to the surface.

FreeBear

mutty_hc wrote: »

I believe the wall was replastered beneath this wallpaper - it looks like typical brown colour plaster (will take a few pictures and post them) - how would I determine if this was the correct type?

Externally the house is covered in a waterproof coating (fitted by previous owner), so our hope was we could breath the house internally (which I am figuring this particular wall cannot do?)

Brown with a slightly pink hue will be your standard Gypsum plaster. Probably Thistle Multifinish. Used on a damp wall, it will change colour depending on how much moisture it absorbs/releases each day. Over time, it will turn to mush and crumble - Not what you really want on a wall.

Lime plaster will generally be a white or light grey. The base coats may contain animal hair or straw along with grains of sand of varying sizes. Traditional building materials invariably came from local sources, so some areas will use lime plaster that is predominately chalk whilst other areas use sand or even clay.

Colour is your main guide for identifying what type of plaster you have - Another test is to take a small sample, add some vinegar. If it fizzes, it should be lime.

mutty_hc

Hi all,

Some further images from the room, pulled some paper back and revealed the following:

https://ibb.co/8rDz3RC
https://ibb.co/3T662Px
https://ibb.co/bgLvgxb
https://ibb.co/Lz4SFRR

The larger revealed patch is to the left of the fireplace (note this is an installed one with an electric fire which we do not use, externally there is not a chimney)

The smaller patch is to the far right of the same wall, I revealed this as I noticed small patches of possible damp forming here, but it felt dry unlike the other two areas.

The plaster seems to have been coated in some kind of paint, not sure what - I am in touch with previous owner so will find out. The paste used was yellow hence colour differences/ some yellow patches.

Walls feel cold but not wet

Plaster looks like gypsum

I'm trying to work out whether this is condensation or something else currently, what definitely occurs is when house is aired these patches dry out considerably and when windows are not open they get damper.

Patches are only forming around plug sockets (therefore these are in the wall) and the small area at the base (which I can see isn't fulled sealed as it connects to the skirting board)

I am trying to think of what could remedy this in the short-term (airbricks/ vents?) with a view that we can begin to overhaul larger issues in the longer-term (e.g. replaster with lime etc.)

Also - if the plug has damp forming around it should I stop using the plug itself? - I am assuming yes.

Thanks

FreeBear

mutty_hc wrote: »

Plaster looks like gypsum

Patches are only forming around plug sockets (therefore these are in the wall) and the small area at the base (which I can see isn't fulled sealed as it connects to the skirting board)

If the wall had waterproof render/plaster slapped on. it is quite possible that the back boxes the sockets sit in didn't get bedded in to the same "waterproof" mix - This would give an easy path for any moisture in the walls to exit in to fresh air. The polystyrene coating certainly hasn't helped. With the gypsum plaster that is evident, I suspect that the house had the full DPC & tanking (snake oil) treatment that so many of these damp "experts" peddle.

Short term, strip off the polystyrene (it isn't thick enough to provide any real thermal insulation), and run a dehumidifier in that room. With the heating on over winter, and fingers crossed, the damp may recede a little. Next spring, you can look at your budget, and decide on what option is the most cost effective.

mutty_hc

FreeBear - thank you for your advice, will strip wall on Friday and post some more images back.

What are my options longer term in sorting this out as I'd like to start looking into it now to prep myself.

Thanks

FreeBear

mutty_hc wrote: »

What are my options longer term in sorting this out as I'd like to start looking into it now to prep myself.

Option 1) Patch up, redecorate, and then sell hoping the buyer doesn't realise what is in store.


Option 2) Strip off all waterproof render/plaster internally and externally. Remove the paint on the exterior walls (you'd need a specialist shot blasting company that uses a mild abrasive - Dry ice perhaps). Rake out any mortar joints that have cement in them. Then repoint, render, & plaster with a suitable lime mortar/plaster. When stripping the walls inside back to brick, you might want to consider internal wall insulation - Several options open to you for that.


Do uou have concrete floors or original suspended timber flooring ?