DIY Doctor

Chimney breast damp

Postby 123bashforth » Sun Jun 26, 2011 7:02 pm

Hi all

We have an early Victorian house, and despite out best efforts to fix damp problems around the chimney breast, we are constantly failing!!

After a week of heavy rain, our problem is back again. In four of our rooms (two upstairs, two downstairs which contain the chimney breast) there is a faint smell of wet plaster. The chimney is no longer in use, but has air vents in all of the four rooms.

Also, we have a cupboard upstairs which backs onto the chimney - the paint here has water running down the surface.

This is what we have done so far....
1) We have have had a new roof installed
2) The chimney stack has been repointed and about 3 years ago it was sprayed with a "waterproofing" spray to protect the bricks. I suspect we need another respray! The chimney is also capped (but vented)
3) Bitumen has been painted on the chimney exposed in the loft cavity. Also when our upstairs rooms were redecorated, the relevant walls were coated in bitumen before new plasterboard was added.

I've now run out of ideas! I'm hoping that there is a not too expensive solution out there, as this is one of many damp problems we are tackling at the moment.

Thanks in advance for any help.
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Postby welsh brickie » Mon Jun 27, 2011 3:52 pm

It could be the chimney flashing not sealed properly.
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Postby stoneyboy » Mon Jun 27, 2011 9:52 pm

You really need to put 2 coats of silicone dampproofing on every year if porosity is the problem.
You've probably done the wrong thing by sealing the chimney in the loft - this will be helping damp get further down the chimney.
If the chimney is unused remove it to below roof level.
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Postby Perry525 » Tue Jun 28, 2011 7:24 pm

It is a strange idea, fitting vents in a chimney, I wonder what the idea was?

There is no logic in fitting a vent between the chimney and room as the inside of the chimney will always smell and the smell will enter the home.

Do you have a damp metre? Have you used it to check where the chimney is damp? If not check it out from top to bottom indoors and outside if you can.

You write that you have a cupboard that is running with water at times?

I would suggest that the problem may be condensation. Victorian homes were built at a time when we had open fires and many cracks in our homes, as such the home was kept dry by the fires pulling relatively dry air from outside.

The modern idea of sealing everything and draft proofing sometimes causes problems.

Does it get worse in winter and dry out in summer?

Do you turn your heating off or down, especially at night?

Keeping in mind that a chimney is merely a single brick thick, the chimney breast is very often the coldest spot in a room if you have double glazing, attracting all the water vapour in the room causing it to condense into the chimney.
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