Damp - condensation from lintel?

[Loofah]

I have two damp patches that have appeared on one of my ceilings either side of a window. It's a bungalow that we have extended and this is in the new bit so only a couple of years old; one damp area appeared last year and I thought I'd just done a bad painting job but that has not gotten worse and a new patch appeared.
So far I have checked the tiles which seem fine, the flashing or membrane that runs to the gutters (fine), and been into the loft recesses and removed all the fibreglass insulation and cannot see any evidence of moisture.
I'm clearly missing something so I'm hoping someone knowledgeable on construction can suggest some other things to check out, perhaps there is a bridging issue where there should be a disconnect, or a moisture barrier hasn't been fitted.
The lintels over the windows are all steel and this is the only room that has the problem.

Older damp area-

New damp-

Taken from plans- (we haven't done the loft conversion yet so the celotex is not fitted and the image may be superfluous)

Many thanks

 

[JohnD]

Looks to me like the damp is coming from the roof, for example if there is condensation in the loft running down the roof felt, or possibly a spilling gutter.

Look in the loft with a torch and photograph what you see.

The pattern of damp does not correspond with the lintel. Is there a dormer above? Photograph the outside wall including the roof and gutter.

Does this room get condensation on the window glass on cold mornings?

How do you dry wet washing?

 

[Loofah]

OK, full disclaimer I have got this wrong. While some windows had steel beams above, this one does not, it has a lintel and I've managed to dig out a pic from the build -

The 'new' damp area looks to be exactly where the concrete pad is supporting that steel beam.

@JohnD Thanks for the response. I've been into the loft and lifted out the insulation and there is nothing at all that looks damp or damaged. It absolutely could be condensation running along the top of the felt and then into the ceiling somehow, I'll have to lift some tiles to have a peek.

Occasionally get a small amount of condensation just at the bottom of the window (vented); clothes dried other side of house and this is the only room affected

 

[JohnD]

Occasionally get a small amount of condensation just at the bottom of the window (vented); clothes dried other side of house and this is the only room affected

The window condensation might be a result of damp from the source above.

 

[George_engineer]

If the contiguous insulation couldn't be installed around the beam so there's a cold bridge. Warm damp air from inside gets up and condenses on the steel.

Not really sure there's an easy answer. Can you get to the steel and retrofit insulation?

 

[JohnD]

Are there holes in the ceilings, for example for downlighters?

 

[Loofah]

If the contiguous insulation couldn't be installed around the beam so there's a cold bridge. Warm damp air from inside gets up and condenses on the steel.

Not really sure there's an easy answer. Can you get to the steel and retrofit insulation?

The fibreglass insulation laid in the loft did stretch across into the soffit space but was all dry. Do you mean inside of the beam rather than over the top?

Are there holes in the ceilings, for example for downlighters?

Yep. Easy to access from above. I'm relatively sure this is not the window condensation causing the issue, if it was then wouldn't it affect the areas closest the window first?

 

[JohnD]

Holes in ceilings allow warm, humid air from the house to rise into the cold loft, where it can cause condensation.

You may notice it if you go up there with a torch on a cold night.

(They also allow fires to rise into the roof area, but this happens less often.)

 

[Loofah]

Holes in ceilings allow warm, humid air from the house to rise into the cold loft, where it can cause condensation.

You may notice it if you go up there with a torch on a cold night.

(They also allow fires to rise into the roof area, but this happens less often.)

There would be noticeable water damage of some description though wouldn't there? Even if just discoloration. I didn't notice any when I looked but I'll have to go see if I can access the end of that steel anyway so I'll have another look

 

[JohnD]

Loft condensation on cold nights forms mostly on the underfelt.

It often freezes or forms as frost, and melts off after sunrise, dripping onto ceilings

See also

CONDENSATION IN LOFT (ANSWERS)

This seems to be the time of year for condensation in lofts, so instead of replying to lots of queries I though I would write this "one-size-fits-all" post. Please also see //www.diynot.com/wiki/Building%3ACondensation-in-Houses Condensation in lofts occurs when the amount of water...

www.diynot.com

 

[Loofah]

Appreciate the link but this is so localised and there's no evidence to suggest seepage such as condensation. It's a very dry loft space and the room below is not showing any signs of excessive condensation of used for drying etc.
I've just checked the soffit vents and they're in place and not blocked so my next check is to lift tiles and start poking about there. It will also show the other side of the felt to me so I can be sure of the condensate or not situation.
Damp is such a pain in proverbial!

 

[George_engineer]

The fibreglass insulation laid in the loft did stretch across into the soffit space but was all dry. Do you mean inside of the beam rather than over the top?

It's hard to tell from the photos but comparing the photo to the drawing I'd have thought the top of the beam isn't well covered. Doesn't matter so much for timber because it's pretty insulating itself, but steel conducts heat away easily.

 

[Loofah]

It's hard to tell from the photos but comparing the photo to the drawing I'd have thought the top of the beam isn't well covered. Doesn't matter so much for timber because it's pretty insulating itself, but steel conducts heat away easily.

Thanks. I'll go back to the loft and see how well wrapped I left it!

 

[jeds]

Mould is a result of surface condensation, in this case I would say due to cold bridging. Check insulation around the area of the mould and look at where a cold bridge might be coming from. Make sure there are no gaps in the insulation and increase or extend the insulation around the area. As advised above, particularly around any beams, padstones, etc.

 

[Loofah]

Small update. I've been back in the loft and pulled out the insulation again; it didn't feel like there was a huge amount in the far corners (toward the eaves and soffits) of the steel and there was no wood blocking filling either. I don;t know why the wood blocking is placed inside the steel but it's found elsewhere so I assume it has some purpose?
Still can't see any pooling damp but reasonably content it's a cold bridge that I should add more insulation to. The pic shows the steel and the gaps where there should be a block of wood.
I'm assuming the best idea for now is to add some wood (?) and pack additional insulation in?

The other damp patch is a similar story although no steels involved. I think it's just a cold bit of the roof and not enough fibreglass has been put in; no sign of pooling water or ingress