Hi
So for some time our loft has had quite a bit of what I assumed was condensation - water where the rafters meet the felt. Quite a lot of it.
We've never had a "leak" as such or noticed any water getting onto our upstairs ceiling.. until now.
A small damp patch has appeared and I can see where some water has got through the foot thick insulation and pooled on the loft side of the plasterboard.
My question is, is this likely to all be condensation or something else such as water running down in-between the felt? Obviously I need to get someone to take a look but I'd like a vague idea of what might be happening if possible!
The loft is well ventilated with airbricks both ends and has a shed load of insulation since the free insulation initiative a few years back.. many thanks in advance for any thoughts.
https://ibb.co/cwhpqqx
https://ibb.co/5hCZxYW
https://ibb.co/Ld7SzFK
(you can kind of see in the middle picture where the water has dripped onto the rockwool)
Looks like condensation to me. With all that insulation the roof void and the sarking felt will get very cold. Presumably there is no vapour barrier at ceiling level?
We had new roof three years ago - the underlay was properly crumbly and if you went up during rain it was running in at points and showed up as really wet patches on the sarking..
For 4 years prior to this, it looked just like yours with condensation on the underside of the felt.
Presumably there is no vapour barrier at ceiling level?
Nope, just rockwool, very old horrible fibreglass insulation and then the ceiling boards.
I'm wondering now whether it has been more noticeable since we had the free extra insulation thrown up there.
(and the damp rafters against the felt are pretty widespread across the roof tbh)
Condensation would tend to be over the felt, looks like it's tracking down from above I. Some way. It may have also tracked sideways then hit the rafter then down.
If you follow the wet patch up the rafter does it stop or go all the way to the ridge? what's the roof? Slate, clay, concrete tiles? If you use some binoculars can you make out any damage? If the effected side hit by the prevailing wind? Or have you noticed the damp worse when the wind is from a particular direction?
and the damp rafters against the felt are pretty widespread across the roof tbh
Didn't see this comment.
Looks like condensation to me. With all that insulation the roof void and the sarking felt will get very cold. Presumably there is no vapour barrier at ceiling level?
Well it's one or the other. Not all three. Which problem are you suggesting he has. Vapour coming through the roof , condensation forming where warm air meets cold surface or a cold roof space making water appear ?
What's the outside covering of the roof ? Concrete by chance ? That looks very wet (and looks to have been so for a while)for condensation
We just had a new roof so would be disappointed if this happened so soon. Are there any loose tiles on the windward side, did the roofer point in the pulleys. I just checked ours and the leadwork, pointing is intact. From past experience the leak can be a fair way from where you are looking.
You could lay down a few sheets of newspaper to see where the drips are coming from, look up and follow the joists.
I've just had my roof felt replaced because I had what looked like this exact problem.
The old felt had started letting water seep though, wetting the rafter as in your pictures. If I poked at the felt it had gone brittle and crumbled to the touch.
The felt in your pictures look exactly the same type as my old felt!
Wish my house leaked so little 🙂
Need to get someone to go up on the roof to check the covering whether that be slates or tiles. Also, check any flashings.
I’ve just had my roof felt replaced because I had what looked like this exact problem.
The old felt had started letting water seep though
its not the felts job to stop water, if water is getting onto the felt there is a problem with the slate/tiles above.
last house i rented which was a crap timber framed one, suffered really badly with condensation and would drip badly all over the whole loft space but all the moisture was on the felt.
i would get the roof checked first
Obvious question but does it do it when it's not raining?
Ensure there is a clear gap between the insulation and the felt down to the soffits.
You can get plastic spacers that hold open the joins in the felt to help ventilation (when we had an insulation top up grant, they fitted them at the same time).
Draught seal your loft hatch (and any other openings such as down lighters, fire safe of course). Remember the more you open the loft hatch to check the condensation, the more warm moist air rushes into the loft where it will want to condense and make it worse.
Edit: if you have a cold water tank is it sealed, and the same for a central heating header tank. And, check the heating is not faulty and heating up the header tank causing it to evaporate)..I can't remember the fault condition but I imagine you'd know if this was happening as there would be other issues
We had the same in ours when we moved in, fitted a load of lap vents and it's been fine since. A lack of ventilation was our problem, prevailing wind blows at the gable end and we are sheltered by a larger house next door.
They're a cheap, simple fix.
Are both end walls wet to touch as well?
Worth checking if the insulation is blocking airflow around the eaves. This can lead to condensation and is an easy fix.
My condensation looked exactly like that after I upgraded the insulation.
I sealed the loft hatch properly, installed soffit insulation baffles and put in lap vents and it went away.
You dont have to buy lap vents, I just used chunks of spare expanded polystyrene packaging.
I had a similar problem that started when I replaced my (rotten) eaves with new shiny upvc ones. The gap seal was simply too good, there was no air flow and the loft created its own microclimate and started raining on me.
I added some soffit vents - problem solved.
My roof is 40 years old btw, with concrete tiles
While it’s possible that the damp you are seeing is caused by a leak it is more likely to be condensation if it’s widespread over the roof. If it is leaks then it is coming from porous tiles or poorly fitted ridge tiles.
The condensation will be caused by the combination of factors that someone earlier raised. You most likely don’t have a vapour barrier in the ceiling as the majority of properties don’t, even new builds, the extra insulation lowers the temperature in the loft and condensation then occurs on the cold surface. Interestingly you said your loft is well ventilated with air bricks on the gables, if this is all the ventilation you have then it’s certainly not well ventilated and that’s possibly an issue. You should have vents at low level along your fascia with an equivalent area of a 10mm gap continually, I’d usually recommend more than this as it tends to be restricted by gutters or blocked by pvc fascia. Not knowing your house it’s hard to say but the easier fix is a number of vent tiles as low as practical on the roof both front and back. A good air flow keeps the loft dry and healthy.
