Damp patch mystery on ceiling

[vinn]

If the fascia was not replaced and any other rot in the eaves vicinity was not treated then its possible that you might still have continuing fungal problems.

No, your 50mm headlap will have to remain, it should just about do unless water is obviously entering through the short lap.

How water enters & distributes itself in a roof can be tricky to spot and locate - it could be very mild seepage is getting in making identification even harder.

Ref. the support tray and the above details: only by your roofer (or yourself?) going up to the eaves and lifting tile courses, and exposing the fascia & then taking photos can you, the householder, have any idea of whats going on up there.
The support trays should have been installed all along the eaves not just in the photo area.
Best practice and common sense say the tray goes below the felt.

You want to get into the loft and have a clear view of the shallow triangle where the rafters and joists meet the wall plate - pull all insulation away & use a corded inspection lamp.

Your gutter looks to have only been cleaned in that one section.

 

[vinn]

Hygroscopic salts will show differently to what we see in the photo.
They are most typical around chimney breasts on upper floors.
However moisture contaminated by very wet brickwork (no soot needed) can contain them.
Humidifiers will work for a time but dont solve damp or condensation problems.

OP, hygroscopic salts, humidifiers & cutting out plasterboard are useful ways to deal with things sometimes but you need to find the cause or you could be posting on here for the next few years.

 

[dancubas]

Hygroscopic salts will show differently to what we see in the photo.
They are most typical around chimney breasts on upper floors.
However moisture contaminated by very wet brickwork (no soot needed) can contain them.
Humidifiers will work for a time but dont solve damp or condensation problems.

OP, hygroscopic salts, humidifiers & cutting out plasterboard are useful ways to deal with things sometimes but you need to find the cause or you could be posting on here for the next few years.

Thanks for your detailed replies. I agree re. finding the root cause and cleaning gutters, I will actually get these cleaned asap, I know this has to be done regularly regardless of the situation. There were problems with wet brickwork here in the past but those seem to be fixed, this patch is on the ceiling and is not directly connected to any brickwork. The centre of the patch is about a foot away from the brickwork. There is no dampness in the roof at all, I have checked it myself and a builder also had a close look at it a couple of days ago, so the moisture on my ceiling must have come from water which was (is?) somewhere in the ceiling joists. It's possible there was a big leak there before we bought the house, which got fixed, but perhaps water seeped down and has been sitting there for a while.

I have drawn a line around the patch to see if it spreads any further, I will keep a close eye on it.

 

[theprinceofdarkness]

Point not made :- If you had some sort of leak above your ceiling the bottom of the joists should have water marks on them, some sort of dark line or even a tide mark. Lift the loft insulation , perhaps with a spirit level to have a guess at which way water would go. Get a powerful torch and a mirror. if you can't see any water marks then the ceiling is cursed. Find the water marks and you may be surprised where the drip is/was. The exposed bit is not smart but not that bad, so There might be a drip from a ridge tile or some other feature.
Frank