On 14 Dec, 16:44, Steve Bilton wrote:
I went up into the loft yesterday to search out the Christmas Decs,
and discovered that the roofing felt on the underside of the roofing
tiles has condensation on it - to the extent that there is a line of
drips along the loft floor boards where the condensation has dripped.

The loft is well insulated with about 8" of rockwool, except where the
loft boards are, where there is about 4" underneath the boards. The
soffits were replaced last year with ventilated soffits and I can see
light at the edges of the roof when in the loft with the lights off,
and the air bricks in the gable walls are clear - free from
blockage/obstruction.

What do I need to do to stop the condensation? The only source of warm
air I can think of is from the loft hatch which has draught excluder
around it as it can't be insulated due to the loft ladder.

Do I need to improve the air flow? If so, how? or are there other
things that I need to do?


Weirdest thing ... same thing happened to me ! However I'm a little
puzzled because a couple of years ago I put about 20 3" vents in the
eaves to counter the damp after we had new insulation fitted. This has
worked for the past two years.

My query is because the damp is localised to one part of the roof (of
course the one where the decs were stored !). We live in an "L" shaped
bungalow, so there are 4 roof sides. It's just the one which was damp.
It's the one above the bathroom, if that's significant.

For a short term fix, I intend to put a small fan up in the affected
corner, and try and circulate some air out of the loft. Can anyone
suggest why this is happening ?