Second floor walls

[bobbobberson]

Hi,

We have an 1800's listed farm house. Last year, we had the exterior re-rendered in the appropriate lime render. The worst room of the second floor is my childs bedroom, this is on the side of the house so has 3 external walls
One wall in particular has always been quite damp (wall in green) - I assumed this would improve with the external render, however I am guessing that the wall is still deeply damp so could do with stripping away and re-finishing in a lime base coat with a finishing lime skim

The other walls have very loose finish in places, so I have begun to remove the really loose bits to see what is underneath. At first glance I assumed gypsum basecoat with a gypsum finish, however doing the vinegar test just now the basecoat seemed to fizz a lot whilst the top coat produced a few bubbles. Could it be that the base coat here is lime, and the top coat is gypsum? The basecoat seems to have hair in it, which is a good indication of lime I guess?

I want to give repairing and finishing a go, and have been reading up on lime. My first thought was to remove everything, and look to re-plaster using appropriate lime, however I am unsure now as if it has a good base of lime it might be worth patch repairing with lime again and then putting the appropriate lime skim over that?

I am keen to not just band aid stuff, I want to ensure that we get the benefit of our external render being the proper breathable type now which is better for the fabric of the building, but I also need to temper this with not going too crazy on the interior walls and effectively looking for problems

Thanks!

 

[Kearn]

Stop removing any of that. You’ve an earth / daub base coat with a chalk rich lime top coat. Albeit a very thick one… very likely original to the build of your house. Also appears that there is a lively green distemper which is happily allowing moisture to escape from the wall.

Those finishes aren’t causing you issues. They will show up issues from within though as they let the moisture escape from the wall. That’s their job.

You need to find the cause of the damp.

The top of your wall looks darker than the rest, so I’d start sketching up high - gutters/valleys/weathered side/eaves leak/pipes…

Way more context required here in terms of externals pics, type of elevation, house construction, when the damp presents itself…

Equally, when was the external finished removed and redone in lime? What lime was used? How long was the wall left exposed before the lime render went on? How thick is your wall and what’s it made of?

A damp wall will take forever to dry out, people assume taking off the wrong stuff and popping lime back in solves the issue straightaway. However all the stored moisture in the wall fabric needs to escape, this takes time and shows itself on the surfaces as it goes. Often as salts. Rule of thumb is a month per inch of thickness.

Ideally you leave the bare wall as long as possible as it will shift stored moisture faster this way. It will still dry when lime rendered, just slower and visibly. Also, correct lime (not NHL) will take much longer to go off on a wet substrate.

Patience may be your plan here, sounds like you’ve down the right thing externally and internally is fine. Extra ventilation and gentle heat wouldn’t go a miss though…

 

[bobbobberson]

Stop removing any of that. You’ve an earth / daub base coat with a chalk rich lime top coat. Albeit a very thick one… very likely original to the build of your house. Also appears that there is a lively green distemper which is happily allowing moisture to escape from the wall.

Those finishes aren’t causing you issues. They will show up issues from within though as they let the moisture escape from the wall. That’s their job.

You need to find the cause of the damp.

The top of your wall looks darker than the rest, so I’d start sketching up high - gutters/valleys/weathered side/eaves leak/pipes…

Way more context required here in terms of externals pics, type of elevation, house construction, when the damp presents itself…

Equally, when was the external finished removed and redone in lime? What lime was used? How long was the wall left exposed before the lime render went on? How thick is your wall and what’s it made of?

A damp wall will take forever to dry out, people assume taking off the wrong stuff and popping lime back in solves the issue straightaway. However all the stored moisture in the wall fabric needs to escape, this takes time and shows itself on the surfaces as it goes. Often as salts. Rule of thumb is a month per inch of thickness.

Ideally you leave the bare wall as long as possible as it will shift stored moisture faster this way. It will still dry when lime rendered, just slower and visibly. Also, correct lime (not NHL) will take much longer to go off on a wet substrate.

Patience may be your plan here, sounds like you’ve down the right thing externally and internally is fine. Extra ventilation and gentle heat wouldn’t go a miss though…

As the old saying goes, dont go looking for issues... so that being said, alot of what you see did actually fall off/was loose enough to move - so I haven't removed anything that was solid! There is a lot there which has seemed to have blown though.

The probable cause for the damp on the worst wall (green) was the chimney stack on the floor above. We got the breast re-flashed this year, and it seems to be holding up. So it may be alot of the moisture was down to that.

External was base coated and rendered in PRB Belle Epoque. The walls were left bare for a good few weeks whilst the delivery came and the renderers were off on another job. The walls are stone and are around 400-450mm thick

Interesting points about the walls constantly moving the moisture, I assumed that it was wet plaster showing the moisture and getting saturated.

May I ask what you would recommend I do with the patches of blown lime which have come away? Also, if the green wall is not blown and is simply just emitting the moisture, would the best course to be to just leave well alone and paint over (we hate the green, not our choice!) with the knowledge that it will keep showing moisture? I dont have an issue with that, however we have had some white mould growth on this wall, which was before we repaired the flashing, so it might no longer be an issue after painting.

Thanks for your reply!

 

[Kearn]

Think you know where your source was then, clearly up high.

A few weeks is negligible for a wall that thick! There’s a ton of wetness in the stone needing to get out, slowly. Give it warmth but more importantly, ventilation via airflow. And give it patience. Could be 18mths of drying time here. You can’t make it dry overnight.

An interesting choice, to import render from France? It’s basically NHL3.5 plus some stuff, nothing too nasty from a quick scan… but it will allow moisture out more slowly than a proper lime. Which means your internal walls will work harder as they appear still properly coated.

The green wall needs to be coated with a limewash or genuine distemper, otherwise that wetness will be trapped in. Mould is interesting, may indicate the green isn’t what I assume, or that the conditions are right and you need more ventilation.
Speak with Rose of Jericho or Ingilby. LimeWash is the preference as it’s pure, make it yourself for pennies with putty plus water and pigment if you wish. Or purchase and pay to ship water for the sake of consistency colour.

Distemper gives a broader range of bolder colours, as there’s a binder to hold the pigment. Still good, just not as good.

blown plaster isn’t always bad, we have some hollow patches on walls, I’ve left them. Ceilings, different matter!

You’ve a very thick chalk lime there, which is odd - the trick to reattach is stainless steel screws and stainless penny washers, with some localised touching up. However, you need to screw into something which is trickier via daub and into stone.

 

[aockenden]

Wow definitely looks like legit stuff on that wall. Lots of clay and lime and hair in there! I agree with Kearn that it looks like whatever moisture source exists is above the room. There appears to be a tide-mark with the TOP half looking darker and wetter and the bottom half looking dry. Assuming this is not an optical illusion with the picture, this is quite telling. Under normal circumstances, if a wall gets soaked (or even after plastering), it almost always dries from the top down, meaning the first part of the wall to get lighter in color is the TOP, so the exact reverse of your situation with this wall. Got any pics of the outside of the house on the opposite side of this green wall? Also, what side of the house is this green wall on (north, south, east or west)?