We have built a flat roof extension to our bungalow and now have condensation dripping through the ceiling.
The construction is,
3 layers polyester based roofing felt on 19mm ply. 25mm s.w. cross firrings to give a 1:40 fall on 50 x 200mm sw joists@400mm cts.
80mm celotex insulation between the joists and a further 50mm under the joists. Batterned to take 12mm plaster board and ceiling dry lined.
The condensation first appeared through the ceiling after the ceiling was dry lined. The condensation was forming between the ply roof and the insulation. We placed a dehumidifier in the roof which the reduced the condensation but was obviously not a cure.
The soffit was not vented on the flat roof as we had used breathable felt. However, the condensation did disappear after we vented the soffit with a 70mm soffit vents every 1m. We thought we had found our cure.
After heating the rooms, the condensation has returned and in places increased.
Does anyone have any idea how we can solve this problem without major reconstruction of the roof?
The gap between the ply and the insulation is approx. 150mm.
The construction is,
3 layers polyester based roofing felt on 19mm ply. 25mm s.w. cross firrings to give a 1:40 fall on 50 x 200mm sw joists@400mm cts.
80mm celotex insulation between the joists and a further 50mm under the joists. Batterned to take 12mm plaster board and ceiling dry lined.
The condensation first appeared through the ceiling after the ceiling was dry lined. The condensation was forming between the ply roof and the insulation. We placed a dehumidifier in the roof which the reduced the condensation but was obviously not a cure.
The soffit was not vented on the flat roof as we had used breathable felt. However, the condensation did disappear after we vented the soffit with a 70mm soffit vents every 1m. We thought we had found our cure.
After heating the rooms, the condensation has returned and in places increased.
Does anyone have any idea how we can solve this problem without major reconstruction of the roof?
The gap between the ply and the insulation is approx. 150mm.