Underfloor insulation next to walls

[digitalquill]

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?

Untitled

• digitalquill
• 25 Jan 2011
• 1

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

 

[Richard C]

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.

 

[digitalquill]

Thanks Richard

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

 

[Richard C]

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.