The Dreaded Damp - Episode 01

[AndyC]

Hi All, I love to get your insight on a few things, regarding my ongoing battle with damp...

Situation:
We have 2 internal walls with damp, in our ground level dining room. Both walls are solid brick with no insulation, lime plaster internally (mostly...), and painted brick externally, with a chemical injection damp proof course, applied to the bricks (!), not the mortar.
To date we've fixed our roof, replacing all guttering to ensure rainwater is draining away correctly - I'm pretty confident this part of the equation is now resolved.
We've removed the wallpaper internally to reveal a series of bodge-job fixes over who-knows how many years, including patches of modern non permeable plaster, rubbery type sealants (internally), blocks of wood & breeze block fragments in plaster... its a bit of a Frankenstein!
I have a plasterer ready to start that will remove all the blown plaster and other obstacles, taking back to brick where necessary, and redoing in lime.
However, I've just noticed following some recent rain, the exposed lime plaster is showing a lot of damp in the areas that had damp (previously covered in modern plaster) - which I would expect to be drying out nicely now that everything is 'open'.
I'm now having a poke around outside at the external paint, which I'd noted was all bubbling and very old - but the mortar was OK. After removing some of the paint today I've discovered some bizarre wooden inserts in the mortar which look like they've been there for a very long time. Worth nothing that these are only in the 2 walls with issues. Given that they've been painted over, I'm thinking they might be acting like sponges, holding onto and channelling the moisture inwards.
I've looked into removing the external paint entirely by DOFF, but with quotes coming in at £20k+, theres simply no budget for it.
I did have a damp specialist have a look while the paper was still on the walls, and he thought that due to the shape of the damp looking like a temperature gradient it was being caused by a cold corners condensation / dew point etc., and not rising damp.
I intend to lift the floor adding underfloor insulation, and add a radiator to that side of the room to address the dew point issue.


Questions:
1. Has anyone seen these kind of wooden inserts being used in external brickwork before? Should I be removing and repointing? Or are they needed?
2. If I remove the bulk of the old external paint, is there a suitable masonry paint out there that allows everything to breathe?
3. Any other ideas on what might be contributing to the issues here?

Pics attached of internal corner, adjacent external wall with paint scraped off, and wooden inserts in mortar.

Many thanks!

 

[malcolm]

Masonry paint is impermeable and also cracks at mortar joints so a load of water coming in and no way for it to get out. I had damp in an upstairs bedroom because of masonry paint. My DOFF was £5k but that was 10 years ago so would be double now and I already had the scaffolding.

A low budget approach might be to rake out the mortar joints where the paint might be causing damp, repoint with lime, then paint over everything with Pozilime (a lime wash that will stick to masonry paint). The bricks themselves don't breathe too much - it's all in the mortar.

The wood inserts are what people used before rawl plugs were invented. Someone wanted to nail something to the wall in the past and bunged a bit of wood in to take the nail.

 

[AndyC]

Masonry paint is impermeable and also cracks at mortar joints so a load of water coming in and no way for it to get out. I had damp in an upstairs bedroom because of masonry paint. My DOFF was £5k but that was 10 years ago so would be double now and I already had the scaffolding.

A low budget approach might be to rake out the mortar joints where the paint might be causing damp, repoint with lime, then paint over everything with Pozilime (a lime wash that will stick to masonry paint). The bricks themselves don't breathe too much - it's all in the mortar.

The wood inserts are what people used before rawl plugs were invented. Someone wanted to nail something to the wall in the past and bunged a bit of wood in to take the nail.

Thanks Malcolm, thats all very helpful.

£5k for your DOFF work seems like a bargain these days! I'm now toying with the idea of buying the equipment (around 4K), and doing it myself. Did your bricks come up well or did you have to repoint everything?

Plan B is to scrape off the excess and give this supposed 'breathable' masonry paint a try, although I have my doubts: https://northernpaintsandcoatings.co.uk/lp/breathable-exterior-masonry-paint/
I'll also research the lime wash you suggested - thanks!

Very interesting about the wood inserts - looking at their positioning, its right where an entrance to a huge orangery used to connect to the house, (sadly gone now, and road in its place - pics below in case you're interested). But all starting to make sense - thanks for the insight.

-Andy.

 

[jamest]

Interestingly enough, I have a problem with polymer masonry paint on my house and had arrived at much the same solution as Malcolm suggested - strip paint off the mortar and leave the bricks except where flaking, re-point in lime as needed and then paint with a breathable paint. I too had converged on Ingilby paints pozilime exterior limewash or Earles masonry paint, as both will go over existing painted finishes. I have tried Ingilby pozilime before on a different project and it does stick to modern paint fairly well. The Earles stuff has (according to the manufacturer), very good breathability - they quote an SD value of 0.01, which is similar to limewash. If they were lying, it would be easy to call them out!

 

[AndyC]

Interestingly enough, I have a problem with polymer masonry paint on my house and had arrived at much the same solution as Malcolm suggested - strip paint off the mortar and leave the bricks except where flaking, re-point in lime as needed and then paint with a breathable paint. I too had converged on Ingilby paints pozilime exterior limewash or Earles masonry paint, as both will go over existing painted finishes. I have tried Ingilby pozilime before on a different project and it does stick to modern paint fairly well. The Earles stuff has (according to the manufacturer), very good breathability - they quote an SD value of 0.01, which is similar to limewash. If they were lying, it would be easy to call them out!

Thats good to know, thanks James.

 

[malcolm]

£5k for your DOFF work seems like a bargain these days! I'm now toying with the idea of buying the equipment (around 4K), and doing it myself. Did your bricks come up well or did you have to repoint everything?

My experience is here: https://www.periodproperty.co.uk/forum/threads/paint-stripping-brickwork.14124/#post-206882 and also what happens without a hot water pressure washer earlier in the thread.

Bricks were fine. Some of the pointing was fine but a lot of it was really soft and when the soft stuff was brushed away there was a 20mm recess that needed repointing. I think the walls with the soft pointing had been painted for a longer time than the walls where the pointing survived. Lime doesn't like to be soaking wet for 50 years or more.

That's quite an orangery!