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Damp Proofing

Damp above skirting chimney breast see below

Hi all

I have re papered my chimney breast, the wall felt sticky above skirting, like the
Wall paper paste had never dried.

I left it a week and still the same, so I hacked some of the plaster off but not to the
Brick, mortared it back up, replastered it, repapered it, and painted it.

Now I have white dust on the wallpaper the same patches I tried to fix.
There used to be a fire in which I boarded up and have since put a vent in, the chimney is still vented, as it was never capped off,

I was going to hack the patch down to brick and then bitumen bonding and multi finish?

The floor is made of concrete, its a 100 year old house.

Would this be the right course if action?

5 Answers from MyBuilder Damp Proofing Specialists

Best Answer

Hi Phil, as you can imagine it's very hard to advise the best course of action without actually seeing the problem but I'll try my best;

Firstly, before any treatments are applied you need to establish the cause of dampness, I would be checking the flashings, pointing etc around your chimney breast as it’s a common entry point for water which then runs down your brick/stonework and shows at the base of the wall, and is often mistaken for rising damp, quite often repairing the chimney stack area will solve most of your problems.

Secondly, when you remove plaster from a damp wall it should always be took back to bare brickwork and the sprayed with an 'Antisulphate' to neutralise any 'Hygroscopic Salts' that remain on the wall as these would attract moisture if left on substrate. The bare wall will still be wet for weeks/months to come so you need to render the wall with a specialist 'Rendering Plaster' with added water proofer, this needs applied at a minimum thickness of 10mm, once this has totally dried you can the skim the wall with two coats of multi finish plaster.

You must not decorate the wall until the plaster is totally dry, the use a watered down emulsion paint to cover the treated area, wallpaper should not be used for at least 12mth as the walls need to breath.

Hope this has been of some help, good luck with your project.



Answered 31st Mar 2011



Answered 31st Mar 2011

Just to add to the advice given, as you say it is a solid floor make sure your new backing render and plaster do not touch the floor as this will allow ground moisture to bridge into the new plasterwork.


Answered 12th Apr 2011

remove skirting hack of plaster up to 1meter high inject with dryzone dpc re plaster with plastering sand and cement three to one with plaster addivtive rendergurd gold re skim whit multi finish .


Answered 31st Mar 2011

You say the chimney has never been capped of, you may need to fit a rain/bird cowl, check the bottom does have good ventilation as well.
Sounds like you might have rising damp, I would suggest getting a Damp proofing firm out from this site, they will be able to assess and advise you,do the job and issue a gurantee, I would hold fire on painting bitumen on the walls, you may make the problem worse.
It needs to be inspected before advising.


Answered 31st Mar 2011

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