Wet Loft

[Vass]

Hopefully someone can point me in the direction I need to proceed as this is one area I haven't a clue.

We noticed water dribbling down approx 6 to 8 inches drop right across the top edge of the wall over the window of a North facing bedroom, akin to condensation on the walls you sometimes see in the bathroom after a hot shower. (the house is central heated and windows are often left open for fresh air.) We are getting signs of mould now in the bedroom where this dampness is apparent

I went up into the loft to check the edges of the roof space to see if any insulation had covered the gaps left to allow the roof to breath (if that's what they do)

This all seems fine, but the black inner lining under the tiles of the whole roof is wet. but only on the north side. And I mean really wet.

What's happening? is the wet in the roof getting to the bedroom? is that possible?

who do I get in to fix it? Any help much appreciated please.

Many thanks

[Vass]

Sorry, for clarity

"We noticed water dribbling down approx 6 to 8 inches drop right across the top edge of the wall over the window of a North facing bedroom,"

this is inside, on the bedroom wall

thanks

[Paul - xxx]

I'd first try to find out a source for the water. Check guttering, roof tiles, ridge tiles etc etc.

If there's a lot of moss on some tiles, say, then they could be providing a reservoir of water that can then flow up (capillary action) the inside of the tiles .. One roof at our school was like that and when the wind blew from a certain direction and it rained we had real trouble!

If you get into the roof space you should be more easily able to see any holes, particularly near the ridge line.

[Andrew Gabriel]

Sounds like condensation. Check for sources of moisture, such as:

Gaps for air to pass into the loft from the house, e.g. large holes around pipes/cables, poorly fitting loft hatch, recessed lights.

Uncovered water tanks, particularly an expansion tank which can be warm. Also check it's not pumping over.

A roof leak. Probably not an obvious one or you would have seen it, but check for wet gable walls, chimneys, etc.

Also important is ventilation, but it doesn't help much at this time of year, where your roof is likely colder than the air temperature for much of the time. Loft insulation makes this worse.

I would lay something under it like a large sheet of paper or hardboard for a day to see if it is dripping. Condensation under the sarking is not uncommon, but if there's enough for it to be dripping off, that needs investigating. Don't leave the paper or hardboard there for more than a few days as the top of the loft insulation must not have any moisture barrier on it.

Also, what sort of sarking is it? The newer ones have different surface each side, and the inside surface is slightly textured to prevent any condensation running and forming drops, but that won't work if it was put on the wrong side down.

I would start by diagnosing the problem. Most of the people you get in will be unable to do that, but you will get plenty of help here.

[Another John]

Is it dripping off the roof trusses at some single point(s), penetrating the insulation, pooling on the plasterboard of the ceiling, then running down the edge?

I once had a bathroom light fitting half-full of water; this was rain penetrating the tiles, running down the roofing felt, dripping off the truss at a certain point, penetrating the insulation (only one small area appeared wet, but of course it was soaked through), pooling on the plaster board, and then finding its path of least resistance into the light fitting.

Of course all of that is diagnosis, and you're looking for a fix ...

John

[Harry Bloomfield]

If moss is the cause, you can prevent the moss growing by running some bare copper wire along highest part, so the copper sulphate can be washed all over the roof. Copper sulphate kills the moss off and prevents its return.

[Dave Liquorice]

That gets my vote for all over wetness on the cold side of the roof. Had it here the other month but that was after several rooms had been skim plastered on walls and ceilings and one wall approx 20' high and

20' wide had a layer of browning and skim. The loft hatch was also absent...

Mr Gabriel has given the common sources of warm damp air from the house getting into the cold loft.

[Vass]

thanks for this the 2 tanks in the loft are empty (asbestos), new Combi boiler now in the garage all pipes removed and holes filled. The hatch is a terrible fit with no insulation on it (just a 1/4 ply) easily 5mm gap on all sides Even with new CH, upstairs is harder to heat than downstairs. Can this really be that much of the cause?

The roof is the original 1961, thick hard material thats torn in a couple of places one can get rainwater in if wind blows in the right direction

I'l have another dig around the eves this weekend.

Thanks

[Terry Casey]

We had something similar happen here. It turned out to be the old galvanised iron water tank which had corroded along the water line. It happened after the loft insulation was topped up and the tank obviously got disturbed in the process, which simply hastened its demise.

The leak didn't become visible until some time after the work was done so it must have been quite a small one.

[Dave Liquorice]

Quite possibly depending on your living habits, drying washing indoors, use or otherwise of extractors in bathroom(s) and kitchen(s) etc. You also mention new CH, was the house centrally heated before? If not the structure, although not showing signs of damp, will be drying out.

Draft proof and insulate that loft hatch for starters.