loft condensation

[martin1976]

i noticed just before xmas there was condensation in my loft.

it seems to be mainly above the bathroom. the house was built in 73 i think, and has approx 8 inches of loft insulation.

the condensation is on the felt under the tiles, and on the wooden beams.

ive put batten peices in between the felting above the bathroom to space it out, which seems to have helped with the airflow.

i purchased some 70mm vents and a hole cutter, and today put a vent in the soffit. i was going to install a load more, but i dont think this will have any effect, as due to the angle of the roof you cant get right over to the edge, but what i thought was the inside of the fasciaboard seems to be brick/concrete that supports the beams?? i got my girlfriend to shine a torch into the hole, and i cant see the light from in the loft?

is it worth me installing more vents, or is there any other simple way of venting it up there??

would it help if i use an acrylic paint on the bathroom ceiling?

 

[PrenticeBoyofDerry]

You need to vent out both sides of the eaves not just down one side.
Fit a few in, is the insulation as away from the eaves leaving a gap for air circulation, is your house open to the elements, not in a sheltered area.
Have you installed a vapour check barrier or foil backed plasterboards.

 

[martin1976]

hi, thanks for the quick reply!

ive not installed a vapour barrier, and i dont think the ceiling is vapour backed plasterboard. i dont really want to take the ceiling down or the insulation up, which is why i thought the acrylic eggshell paint stuff might help?

might try spacing some battens in the felt on the other side of the roof then if u think that might help?

its dried out a lot since xmas, but its still looks damp on the wood towards the edges.

any help and advice is greatly appreciated.

 

[martin1976]

do u think the acrylic paint would act as a vapour barrier as I'm sure there isn't a barrier on the ceiling?

 

[JohnD]

no

//www.diynot.com/forums/viewtopic.php?t=160032

 

[martin1976]

I think the shower is the culprit. have u ever seen a roof where it is angled so the soffits are not accessable from inside? I've read a lot saying soffit vents will clear the problem but i don't think it will help in this case?

 

[PrenticeBoyofDerry]

It's ventilation you need if you can install more soffit vents, I would go for it.
You could also consider venting the gable end or venting the roof with tile vents.

 

[misterhelpful]

I live in a terraced house with no overhanging eaves and had a serious condensation problem in my loft the previous Christmas - water dripping from felt and soaking wet rafters.

Soffit vents were not an option so had 4 tile vents fitted and that stopped the condensation. There was a little this winter when there was 10" snow on the roof for 2 weeks, but as soon as it melted the vents did their job and it dried out in no time.

 

[ajrobb]

downlights?

Two coats of acrylic paint should give a pretty good vapour barrier as long as you don't have any downlights.

With your battens for airflow under the insulation, you have effectively lost the insulation.

Some extractor fans are installed wrong and exhaust into the loft.

 

[martin1976]

I have no downlighters..

the bartender aren't under the insulation, they are between the felt overlaps under the tiles to let air flow through.

think I might look into the acrylic paint, and open our the felt joins each side.

its dry up there now so it was probably just because of the extreme cold. better ventilation can't hurt though!

would this be a problem if its only wet for a couple of months a year? it wasn't dropping off, just surface moisture?

 

[martin1976]

sorry bartender = battens..

on a mobile device and predictive text thought I meant something else, lol.

 

[PrenticeBoyofDerry]

If your timbers are getting damp due to condensation or (well anything really) They could go rotten and fail.

 

[martin1976]

ive been back up there today, and felt the timbers. they are actually dry, although darker to look at, i assume they have been wet at some point, leaving them marked?

ive opened up ap many of the overlaps in the bitumen felt under the tiles as i can, it now seems a lot more "airy" in there. the cobwebs at the top in the centre are moving because of the breeze.

also, where i said i cant get to the soffits, because of the concrete beams running across, there seems to be a gap in this in the centre of the house -about 8 inches. i think it is possibly a lintle laid each end of the top inside wall? the roof beams seem to be sunk into it. this is definately the inside wall as i can see the power cable for the shower dissappearing into the bottom of it.

maybe a few more soffit vents will create some ventilation through the centre gaps in this? i dont know why the council would have built it like this but i assume the whole estate is the same..