Bungalow loft insulation - into the eaves?
Discussion
1960's bungalow with later dormer. Block construction, with a narrow cavity. Concrete roof tiles over felt.
One side of the house is just single storey, integral garage with a bedroom behind. The loft above has been insulated (rockwool) and boarded over for storage.
The bedroom was a spare, redecorated about 5 years ago. For 4 years it was used a few times a year as a guest room, with no problems.
For the past 15 months it has been let out to a friend/lodger, and darker spots that look like dampness have appeared around the top couple of feet of both exterior walls. No sign of mould, and not damp enough to trigger a prong type damp meter. Just darker grey spots on the pale grey matt emulsion.
I've been up in the loft, clearing boxes out of the way so that I can check what's going on. Felt is undamaged, timbers are dry.
Previous owner had cavity insulation done, the stuff that looks and feels like fine clumps of fibre. Feels reasonably dry.
Something that concerns me is that the rockwool extends over the cavity, out into the eaves over the soffit boards, blocking the vents. That seems wrong to me?
Pulling some of the insulation away from the eaves, I could feel draughts coming up through the vents, and see a bit of daylight.
Exactly where should the insulation end - above the inner block leaf, the outer leaf, or over the soffit boards?
My guess is that water is penetrating the outer leaf, moist air crossing the cavity and getting into the inner leaf.
Should I cut away or peel back some of the insulation? Is it a good idea to apply something like Thompson's Water Seal to the exterior render - cement and small pebbledash?
This is the only room in the house that has this problem, and the only one with boarding and insulation right out over the soffits.
One side of the house is just single storey, integral garage with a bedroom behind. The loft above has been insulated (rockwool) and boarded over for storage.
The bedroom was a spare, redecorated about 5 years ago. For 4 years it was used a few times a year as a guest room, with no problems.
For the past 15 months it has been let out to a friend/lodger, and darker spots that look like dampness have appeared around the top couple of feet of both exterior walls. No sign of mould, and not damp enough to trigger a prong type damp meter. Just darker grey spots on the pale grey matt emulsion.
I've been up in the loft, clearing boxes out of the way so that I can check what's going on. Felt is undamaged, timbers are dry.
Previous owner had cavity insulation done, the stuff that looks and feels like fine clumps of fibre. Feels reasonably dry.
Something that concerns me is that the rockwool extends over the cavity, out into the eaves over the soffit boards, blocking the vents. That seems wrong to me?
Pulling some of the insulation away from the eaves, I could feel draughts coming up through the vents, and see a bit of daylight.
Exactly where should the insulation end - above the inner block leaf, the outer leaf, or over the soffit boards?
My guess is that water is penetrating the outer leaf, moist air crossing the cavity and getting into the inner leaf.
Should I cut away or peel back some of the insulation? Is it a good idea to apply something like Thompson's Water Seal to the exterior render - cement and small pebbledash?
This is the only room in the house that has this problem, and the only one with boarding and insulation right out over the soffits.
clockworks said:
Exactly where should the insulation end - above the inner block leaf, the outer leaf, or over the soffit boards?
Ideally above the outer leaf (but above the cavity and linking down to the cavity insulation is better than nothing).There sould be a rafter ventilation tray or similar to maintain ventilation over the top of the insulation. It shouldn't fill the eaves above the soffit board.
Edited by Equus on Thursday 6th April 15:28
Gassing Station | Homes, Gardens and DIY | Top of Page | What's New | My Stuff