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Damp/sluggy gap behind skirting board - should I fill before fitting IWI?

Postby lucyhellyeah » Mon Mar 01, 2021 9:23 am

Hi everyone,

I'm shortly going to be fitting wood fibre insulation boards to my downstairs bedroom. The render stops 100mm above the bottom of the masonry, and there's also a poured concrete floor was finishes a few mm before the wall. I'm concerned about damp (as it's a cold, north facing wall and the pavement is only slightly lower than the floor level), and I also want to avoid repeating what happens at the moment, which is that slugs regularly find their way around the skirting into the room!

Question is: should I:
- Use a sand:cement:SBR mix to cover the exposed masonry down to floor level, or...
- Leave the gap and use caulking &silicone to make a tight seal around the skirting
- something else?

NB: the drilled holes in the masonry are, I presume, the injected damp course that was done about 5 years ago.

Thanks so much in advance for your advice!
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Postby stoneyboy » Tue Mar 02, 2021 10:44 pm

Hi lucyhellyeah
Your problem with the wall condition behind the skirting will be very difficult to solve.
If the path outside is yours you need a 10cm wide open channel along the wall about 15cm deep. This will help the wall dry out and stop mud being carried inwards.
However the wall is treated at low level it will be a compromise unless extensive remedial work is carried out. You could fill the area with a strong sand cement mix with a waterproof additive included in the mix. This may encourage damp to rise up the wall.
Regards S
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