Is this a water stain?

FreshlyCutFlowers

The house tends to average around 60 % humidity these days which seems correct given outside temperatures of 13, outside humidity of 85% and indoor temperatures of 18 - 19. 
This one room at the end however is always higher than other rooms, often going to 80 if we sit in it to eat dinner and generally resting at 70% - 75%.

When using dehumidifier the humidity goes down to 60 - 65 if I let it run but it immediately shoots back up.. I thought maybe it's just because the room has more external walls than any other room so condensation naturally moves there but then I noticed this slightly visible patch on the wall and wonder if it's a water stain?

Is this just a poor paint job or water damage?

It's very hard to see the stain, and front on its next to impossible. I've added an edited image with increased contrast to clearly show the shape.
On the roof this wall is underneath the join of the two walls, but the roof looks fine I thought.. What can you experienced people see? 

stuart45

Are the walls cavity or solid?

grumbler

What's the roof slope?

It looks almost flat in the photo.

donemedosh

The roof looks fine to me as flashing & tiles all look good.If the roof is leaking then the staining is usually brown in colour. If you have high humidty & these walls are cold it is a good bet it is condensation. If it is blackish colour then this is mold forming (clean with HG mold cleaner).Increase the room venterlation What sort of temp does the room have.Hope this helps

stuart45

Parapet walls can be a problem if the details aren't right. The pointing on the coping stones needs to be good and a supported DPC under them.
Also there should be a tray if it's a cavity wall.

FreshlyCutFlowers

grumbler said:

What's the roof slope?

It looks almost flat in the photo.

It's fairly flat but not entirely. 

donemedosh said:

The roof looks fine to me as flashing & tiles all look good.If the roof is leaking then the staining is usually brown in colour. If you have high humidty & these walls are cold it is a good bet it is condensation. If it is blackish colour then this is mold forming (clean with HG mold cleaner).Increase the room venterlation What sort of temp does the room have.Hope this helps

I had as much as 80% humidity and 7-8 degrees in October when the cold kicked in.. Could this be from then maybe..

I believe this extension build is poorly insulated and potentially the reason why I can't keep humidity down even with dehumidifier.. Not sure what I can do, it gets expensive to keep the heat running constantly but I also can't lower humidity..! 

stuart45 said:

Are the walls cavity or solid?

I believe solid. The wallpapered wall is an external wall whereas the affected one is internal. The other side is tiled however (bathroom) and shows no sign of problems. 

Spies

If you can't lower humidity that suggests to me there is indeed a leak. 

FreshlyCutFlowers

Spies said:

If you can't lower humidity that suggests to me there is indeed a leak. 

That's what I was thinking but I can't figure it out.. The room is also quite a drafty so could be that outside humidity just rushes in but even then I thought the higher temperature I set would mean a lower humidity.. 

Many things in the room is leaking, maybe it all adds up to the thiamine issue? 
The upc garden doors have some gaps in them which I can't get tighter.. 
The kitchen (neighbour room, no door between) has a drafty trickle vent even when it's closed but I suspect that's normal..? 
Some air come in via a the kitchen extractor fan when not in use

I was thinking of getting some curtains for the doors but with the high humidity even that seems like it can create more damp patches. 

grumbler

FreshlyCutFlowers said:

grumbler said:

What's the roof slope?

It looks almost flat in the photo.

It's fairly flat but not entirely. 

I think it must be at least 12.5° for these tiles. That's the minimum slope achievable for a tiled roof (with best interlocking tiles).

Spies

If higher temperature in the room isn't lowering the relative humidity, then  what's actually happening is that extra energy is causing additional moisture to evaporate. 

If it was simply a draughty room, you'd stuglle to bring up the temperature but the humidity wouldn't be sky high. 

FreshlyCutFlowers

Spies said:

If higher temperature in the room isn't lowering the relative humidity, then  what's actually happening is that extra energy is causing additional moisture to evaporate. 

If it was simply a draughty room, you'd stuglle to bring up the temperature but the humidity wouldn't be sky high. 

Interesting.. The outside humidity however has been 90%..i thought that could lead to constant trickle of humidity exchange between inside and and outside