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Carpets, Lino & Flooring

New concrete sub-floor has a gap with the wall. Fill in or not?

Anonymous user 28/02/2024 - 4.00 PM

We removed our wooden sub-floor and replaced with a concrete slab, that has a DPM about 1-2 inches below the concrete. The concrete was laid after the skirting was installed (replacement was decided later). There is a draught coming through the gap - air is coming in from the airbrick. I'm not sure if we should fill in the gap between the wall and the concrete as I don't know if the gap is supposed to be there. I've read conflicting information about damp/concrete expansion which makes me reluctant to fill in the gap. However, the floor gets quite cold in winter so ideally I'd like to address that. The walls are solid afaik. We would also like to level the floor so also worried that if the levelling compound is laid down, it would run-off the sides. I've no idea what to do about concrete so I'm kind of stuck.

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2 Answers

Anonymous user

Fill the gap with expansion foam which comes on a roll. It’s available from most builders merchants.

Answered11 May 2021

PB Improvements

Rating: 5 out of 5

Southampton

Fill the gap with expanding foam from a can. Trim off excess when dry. Levelling compound can't, then run down the gap. Don't worry about concrete expansion as it shrinks while drying. If levelling PRIME the concrete first. Don't use too much water if using water based leveling compound. Its usually 4.5 to 5 litres for 25kg bag.

Answered19 May 2021