Repairing damp internal wall advice

[mrkrunkles]

Hello all, I bought and moved into my first home, a mid-terrace solid wall pre-1900 property, 3 or so years ago and have always have some degree of damp issues, especially in the open-plan living room. After researching the recommended maintenance of such a property I've come across the advice that I should treat gypsum like the devil, and remove all the plastering on the exterior facing walls that we did when we moved in, and replace with lime.

I hacked away some of the plaster and in my frustration at trying to get to the bottom of my long-running damp issues dug down to the brick to see exactly what I'm working with, it seems like a coconut/ horse hair base coat with a lime skim.

Can anyone confirm that the top layer looks like lime? And is it possible that I could hack off the gypsum, buy some lime filler to fill in some cracks and paint over with proper breathable paint to get some degree of decent finish? Or does it look like the plaster and substrate are beyond a small fill job at this point?

To add onto the problems, the exterior of the house is rendered in what seems to be a hard cement render, is it possible that making the interior of the property more breathable would alleviate my damp problems or is it all futile if the outer jacket is cement coated?

Thanks

 

[Willsa]

The plaster looks just like mine - that's definitely lime.

I can seemingly notice damp patches on the paint finish. Where is this wall located, what's on the other side of the walls, where is the water coming from?

If you take a photo by stepping away to get all the damp in and trace over the outer lines of the patch in editing, then it will be easier to identify what is going on there.

Difficult to advise at the moment.
Don't patch before the wall is dry, that's a definite.

 

[mrkrunkles]

The problem walls are the external walls, both front and back of the downstairs, this particular patch has been the worst as it suffered from heavy efflorescence when I had the new plaster on it, but both front and back walls are showing signs of damp gradually darkening the paint in the middle of the walls, along with damp at the bottom too. I'm inclined to believe that much of this is condensation.

When we moved in the house was plastered in gypsum and it had blown quite badly in multiple areas, along with having signs of some damp. We took down the old blown plaster and replastered then painted in Dulux, not knowing anything about maintaining an old house as this was our first and the estate agents only gave us the number of a damp guy who was useless (we only found that out after he'd had some money off us for doing some ineffective damp treatment)

Anyway I'm thinking of now removing all the new plaster again on the external walls and either trying to repair the lime
plaster that is already there and painting in earthborne or a similar paint, which I may be able to do myself, or having to get a plasterer to skim coat with lime. Any advice from anyone who has experience patching old lime plaster walls would be appreciated.

 

[Willsa]

I see a tide mark above the skirting... What material is the floor? What is behind the skirting - plaster to the ground, air bricks, pipes, damp, water droplets?

What about the ground levels outside that wall - a decent amount lower than the floor inside? Is it concrete or earth outside?
Anny downpipes/ drains there?

There are more questions, but this will make a start! Need to understand what the water source is!

 

[Willsa]

Patch repair with Gypsum and Dulux would not cause the damp this pronounced - could only exacerbate a tad.

I had a bone-dry Victorian terrace in an elevated, South facing position in a chalky ground area.
Got painted in Valspar, skimmed in Gypsum where needed, one room plasterboarded and... Still dry as sand.

The terrace I'm in now... Wet soil that used to be a river estuary, low position, west- east facing, badly maintained, wet, rotting and eaten by woodworm. Can't just "throw around" Dulux here, have to get dry!

 

[malcolm]

Solid walls were designed to dry to the outside through lime mortar. My place had damp all over the place (even upstairs) because the bricks had been painted in plastic masonry paint. An ancient timber frame had been cement rendered for nearly 100 years and the dust that remained was soaking wet. Soaking wet walls are bad for insulation too.

Removing the cement render would probably do the trick without messing around with the interior. My interior walls are mostly gypsum skim over lime from 1920 and don't cause problems. I've been lucky they had lining paper so emulsion paint hadn't been applied directly to the plaster. I'll lining paper again over the bare plaster.

Making the interior breathable when the exterior isn't breathable can help as it steepens the moisture content gradient from outside to inside. If the outside is always going to be soaking wet then it will help if the interior can dry quickly as it means the wall just beneath the surface also dries. With waterproof coatings the wall just beneath the coating would be soaking wet. But the problem here is probably going to be exterior concrete render painted with plastic paint because (in the absense of gutter leaks) you wouldn't normally get damp halfway up a wall. For the damp at the bottom it's worth checking exterior ground levels are a few inches lower than inside, but again it will probably be the render.