Underfloor insulation next to walls

Hi all

Similar to a recent post about underfloor insulation I am taking advantage of the B&Q £3 per roll offer and have insulated the under floor of our new extension with rockwool style insulation suspended on chicken wire to maintain an air gap under the floor. I have covered this will foil insulation as we are installing UFH so this will hopefully reflect heat back into the room.

The question I have is what should I do around the edge? Can I insulate right up to the external walls or will this create a bridge for damp?


The red arrow shows the gap next to the new cavity wall, the green arrow points to the gap next to the original wall with no cavity.

see http://www.matthouldsworth.com for some more images of the underfloor insulation.

Any advice would be great.

Thanks

Matt Houldsworth

Is this on the ground floor? Where is the damp course in the walls? If it’s above the level of the insulation you need to either stop it short or put a membrane around the edge to prevent any chance of damp migration.

Thanks Richard

Yes this is ground floor, if I put some 9 inch DPC between the wall and the insulation that should work?

A liquid membrane, something like Syntheprufe; http://www.ruberoid.co.uk/pages/rub...product_page/default.aspx?CatID=57&ProdID=161 or similar may be better, easier than trying to fix a plastic membrane to the wall & there will be no chance of moisture wicking up between it & the wall. Once dry, blind it with sand to prevent the insulation sticking to it like the preverbal to a blanket.