Unidentified leak

[KDragon]

I've had my loft insulated and boarded recently to turn into a loft room. It's only been 5 months and I now have this brown sticky substance coming out but only in one place. I've cut a hole in the new boarding to see what's going on but it feels quite dry. We have a newish roof without any visible signs of a problem and there are windows already fitted in the loft.
I was literally about to put down the carpet and get this room finished when this happened. So disheartened Does it all need ripping out and doing again?

 

[freddiemercurystwin]

Been up in the loft to have a look?

 

[Harry Bloomfield]

Any smells of rotting flesh?

 

[JohnD]

Is this the sloping loft ceiling on the roof? Roof leak.

Is this the ceiling of the room below? Probably a plumbing leak. Colour suggests the central heating F&E tank.

 

[KDragon]

This is the sloped roof of the loft. The roof is not even 10years old and was absolutely fine before boarding. There are no pipes up there or bodies

 

[JohnD]

Dead animal or bird seems likely then.

 

[KDragon]

The roof was totally bear. We've had it insulated and boarded on the inside and now this is coming through. No animals in the loft

 

[RandomGrinch]

This is the sloped roof of the loft. The roof is not even 10years old and was absolutely fine before boarding. There are no pipes up there or bodies

It looks like there is rockwool above the boarding. Has this been rammed tight against the breathable membrane?
Is there any vapour barrier above the boarding?

 

[JohnD]

The roof was totally bear. We've had it insulated and boarded on the inside and now this is coming through. No animals in the loft

They sometimes try to nest under the tiles. Cut a hole somewhat above the stain. It will be easier to make good afterwards if it is a neat square. It can be as big as you need to see what's going on.

Strangely, the stain suggests the timber is horizontal, not sloping.

 

[KDragon]

Not entirely sure as we paid to have it done. From what I can see it looks like the is the roof, membrane, rock wall then board. Not much of a gap I'm sure there's meant to be though. This is why I'm looking for advice as I'm sure it's been done wrong

 

[RandomGrinch]

Not entirely sure as we paid to have it done. From what I can see it looks like the is the roof, membrane, rock wall then board. Not much of a gap I'm sure there's meant to be though. This is why I'm looking for advice as I'm sure it's been done wrong

Irrespective of what actually caused the 'leak', it seems as if your boarding/insulation has been installed incorrectly.

I'm guessing that building control haven't been involved and this is an uninhabitable 'loft storage room'?

If this was to be a habitable loft room, BC would have stipulated minimum standards for insulation - something like: a 25mm min gap to roof membrane, with ventilated soffits and ridge allowing cross ventilation, PIR insulation between the rafters, another layer of PIR attached perpendicularly, a vapour barrier and plasterboard.
This would have cost a fair amount.

As it is, with a 'loft storage room', you get what you pay for.
But if you insulate, you must leave a ventilation gap to the roof membrane (min 25mm), you should still allow cross ventilation above the insulation, and you should ideally have a vapour barrier above the plasterboard to help avoid interstitial condensation forming.

 

[KDragon]

That's exactly what I thought thank you. It will be a loft storage/occasional room so still want it done properly. Wish I'd done it myself as then I would have at least done it right. Just trying to save time, and now it looks like it will need ripping out.
Unless anyone has any sensible suggestions to help airflow between the boarding and roof, vents?

 

[RandomGrinch]

It will be a loft storage/occasional room so still want it done properly.

The problem with BC, there is no grey area, you either have a habitable space, or an non-habitable space.
If you want a proper loft room, that brings with it a raft of BC measures mostly regarding safe fire egress. You are more or less getting a full loft conversion at that point.

If you stick to a non-habitable 'loft storage room', you are less restricted, but questions may be asked later - i.e. by your insurance company if something were to go wrong, or come time to sell.

Some loft conversion guidance is attached, the section on ventilation may give you an idea of what should be done, for a full conversion.

And as you say, let's see if anyone else has some suggestions