Rising damp from chimney?

Submitted by NightElf193 t3_123rc7x in DIY

So we've had a damp problem and we're told it's because of the unused chimney (central chimney), so we had it blocked off, airbricks put at the top and in the loft. This was about 4-6 weeks ago, we've had the dehumidifier running alot but it doesn't seem to have dried out (we are coming out of winter which I imagine doesnt help). We decided to get a damp professional in and he says there is still damp and believes its rising damp and we need a vent low in the chimney and some sofit vents and DPC injected in the walls too.

Anyone with experience able to say if we just need to allow things to dry out longer?

Our main worry is that we have a young child and there has been some white, fury looking stuff lurking in the kitchen cupboard that backs onto the chimney. We spray white vinegar often but I'm in a huge panic about possible health concerns. Am I over thinking this?

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Sluisifer t1_jdw5a28 wrote

No one can tell you what is happening without inspecting the property. Is there are reason you doubt the professional? Seek a second opinion if so, a professional opinion not reddit.

The mold is a concern, but the white fluffy stuff is mostly allergy issues that develop over time. If no one has respiratory symptoms it's not any acute threat.

But in general, moisture/vapor problems are quite serious and absolutely need to be addressed. It's worth taking the effort to really identify the issue and fix them properly. It might take a lot of effort finding an appropriate inspector and contractor.

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Trigs12 t1_jdx025z wrote

If you've stayed there for a while and its only just started 4-6 weeks ago, i would think its likely something has happened to cause the damp.

Potential roof/flashing leak letting water into the chimney, leaky gutter/downpipe etc.

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NightElf193 OP t1_jdxf7jh wrote

I believe it was there when we moved in early 2020. There was always a strange smell in the kitchen cupboards next to the wall where the chimney is and I just assumed the previous owners kept herbs, onions or something in there. There was never anything visible or obvious until we noticed white mold forming on a pan we never used in the cupboard. Assumed we didn't dry it properly, washed it, put it away and noticed the same thing some time after (few months ago). That prompted me to do some investigating. I pulled back some wallpaper in the living room where the chimney breast is and the paste was sticky so I knew something was going on. There was no mold that I could see in the living room, no dampness of the wallpaper, only the sticky paste and dark plaster behind it.

This all led to the chimney work 6 weeks ago. I don't know how long it should take to dry out, or if there is more going on. All I do know is that I'm worried all the time about my little boy.

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Trigs12 t1_je1i1dy wrote

Too many variables/possibles to really say over the internet. It might never dry out if the issue causing the damp isnt sorted, or you might be able to dry it out in good weather, but the next wet weather you get dampness again.

Could be high ground levels outside,causing damp to travel across especially if solid walls. If the specialist has recommended injected dpcs, high ground levels are the first thing id be checking.

But really, the specialist you've had out should be able to identify anything like that, and if you have any doubt, it may be worth a second opinion.

The injected damp course is something that splits opinions greatly. Some people say its great/bad. Others say rising damp is a myth entirely.

But at the end of the day, there is likely a reason for the damp in the first place, and that should be identified first, if the chimney fix hasnt been sucessfull.

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NightElf193 OP t1_je1qr2z wrote

We had another guy out today and he said similar, but believes the damp course is worn out and needs replacing. Upstairs and top half of the downstairs walls are bone dry so I guess rising damp is the answer.

When you say high ground levels, I may be sounding dumb here...but we live on a hill, is that what you were referring to?

Interestingly too, our garden is slightly uphill so rain rolls down towards the house, not sure if that could be a problem but I'd hope what that was taken into consideration when the house was built...it is a 1960s ex council house (I'm in England), I believe they were built well 🤞🏻

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Trigs12 t1_je1v0sm wrote

That should have been taken into consideration, when built. But thats what i mean about high ground levels.

Over the years, people tend to add new layers of gravel/soil etc on top of the old stuff, and now the ground levels are higher than what they should be against the building.

The dpc is generally 150mm above external ground levels. External ground level, depending on floor makeup, being 150mm at least below your finished floor height.

Assuming its cavity walls due to council house,cavity going down 225mm from your dpc (depending on floor makeup), the cavity should stop anything crossing over , but again, sometimes (usually when initially built) the cavity gets filled slightly with mortar/rubbish from the brickwork above being built, and you dont have a cavity, you have a damp bridge letting water soak across.

Combine that with your garden running water towards the house, and its a potential problem. Ground might not be high though, and just the dpc work alone, possible also some drainage along the house at the bottom of the slope might fix it.

I dont know enough about the old damp courses to comment on it being worn out. I think plastic dpc started to get used in the 1970's, so its possible yours is slate or some other material.

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