Condensation On Rafters

[hamd01]

Im currently working on converting an old bran we have into a usable space. I was up a ladder yesterday and spotted some damp on one of the rafters. Its an old barn with a pitched roof, and the darm spots were quite obvious. Ive circled in the photo where I noticed the wood was damp.

The roof was done before we moved in, and is less than 2 years old. Ive inspecte the outside closely, and had a builder friend look.....cant see any problems....no loose tiles, and it looks a nice job.

My builder friend has suggested that its likely to be condensation. Ive never spotted it before, but have recently done the wall insulation, and floor insulation, so perhaps theres more moisture going up in the air than ever before. His suggestion was to check the ceiling insulation, make sure its thick enough, and then install a membrain over the top of the insulation, to prevent moisutre getting up there.

The previous owner boarded the ceiling (badly), so im going to have to take the boarding down, and see what the state of the insulation is, then either replace it with thicker, or just put a membrain over. In my head, Im thinking that the moisture has to go somwhere, so would instead just accumulate on the membrain?

 

[datarebal]

Vcl should be warm side of insulation .
How about a picture of the outside

 

[catlad]

Its a cock up so take it all down.

 

[JohnD]

It must be winter again.

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

 

[hamd01]

Vcl should be warm side of insulation .
How about a picture of the outside

Here is the outside. I've taken the boards back and what's underneath is 100 mm of Kingspan, then the breathable felt, then the tiles. There was no vapor barrier between the insulation and the plasterboard.

What I'm thinking is going to be the perfect solution is take the insulation down, install some spacers under the felt to create some air flow, then put the insulation back then a vapor barrier, then replace the board.

Today it's absolutely tipping it down and I've just gone out there and everything is bone dry.... Which I think adds weight to the theory that it is condensation buildup.

 

[Harry Bloomfield]

Today it's absolutely tipping it down and I've just gone out there and everything is bone dry.... Which I think adds weight to the theory that it is condensation buildup.

You say you are converting that barn - Is there much wet work, being done inside? That could be the cause of the condensation..

 

[hamd01]

You say you are converting that barn - Is there much wet work, being done inside? That could be the cause of the condensation..

Yeah the inside now has a bathroom and a boiler with rads....I spent a full day working in there on Thursday which is the first and only time I've seen the dampness.... Perhaps a combination of me being in there all day working and having the boileron for the longest it's ever been on.