Damp on chimney

[Jameswolf]

Hi all

I have a 1930's house with a disused chimney on the outside of the house. The 1st floor bedroom plaster in line with the chimney is damp and discoloured. To the side of the chimney is a window and the woodwork in one corner has also become damp and lifted the upvc frame on the inside. The 2 issues are possibly unconnected? But they are within 50cm of each other. I would like thoughts on how to remedy the problem.

Some more info...
The chimney breast becomes white in high temperatures. Assuming it was a ventilation I added more ventilation in October last year with 2 ventilated flues (some ventilation already existed at top of chimney). I have also added some lead work where the chimney steps down to become wider - i though the gutter was dripping onto the brick work and seeping in. The crown of the chimney does not pretrude much beyond the width of the brickwork. When it rains the water drips onto the brickwork and looks to get very wet - possibly the issue?

Dampness also got into the woodwork to the window at the side of the chimney and caused the mdf to balloon and lift the upvc internal frame. I have since chiseled out the expanded wood to see if I can identify where the problem is. Maybe it just needs sealing outside and is unrelated to the damp?

I am at a bit of a loss as to what to do next. I thought it was a ventilation issue but not sure now. There is no dampness downstairs so if not ventilation then it is penetrating.

 

[^woody^]

I'll avoid the diagnosis and skip to the chase - removal to roof level is the only viable option.

Then replace frost damaged bricks below eaves level and coat the area with a quality silane water repellent.

 

[Jameswolf]

Thank you for taking the time to reply. Which bricks do you think are frost damaged? The bricks that are white on the first pic, the photo was taken in summer. I believe this is a humidity issue.

What do you think about rendering the existing bricks rather than remove and replace? Or would this lock in the moisture that exists?

 

[^woody^]

All the bright orange bricks are frost damaged.

Rendering a chimney is just masking a problem. But the render adds risk - ongoing maintenance and a massive risk of it being defective very early on and you won't know, meanwhile water gets in and accelerates structural decay of the brickwork. It's rarely advisable to retro-render a stack.

 

[Jameswolf]

OK done some research and can see what you mean about frost damage. You say remove bricks to roof level. You can see from the first pic that part of the adjoins most of the inside wall of the chimney - so you think keep that in tact and rebuild the other 3 sides from the eaves would be OK?

Also I know the previous owners took some height from this stack 20 years ago. How about adding an oversailing course? I think the size of the slab on top of the chimney is helping as it is barely the width of the stack and the water is falling straight onto the stack as can see from the 2nd photo.

 

[^woody^]

The drip is not going to help.

Sorry I did not see that wall on the back of the stack. What is it?

 

[noseall]

Sorry I did not see that wall on the back of the stack. What is it?

Looks like they couldn't be arsed forming a lead back gutter, so roofed it instead, lol.

Perhaps an anti-wobble stiffener.

 

[Jameswolf]

I took some closer photos. Not sure what the purpose is…

What are your thoughts on keeping the side that adjoins this section intact?