Slight condensation issue

[Tudor]

Hi folks

My loft originally had 100mm of insulation between the 4" x 2" joists. I needed to board out the centre of the loft, a space of 3.5m x 4.0m I added some 2" x 2" joists on top of the existing ones, in line not cross batten, and added a further 100mm of insulation. I then laid a job lot of conti board as I had a load going spare. I have today checked under the boards and found that they are all damp with condensation. Two questions,

Is it because I have used conti board?
Should there be a space between the insulation and the board to allow air circulation?

Thanks.

Dan.

 

[masona]

Is it because I have used conti board?

Could be because the conti board is a cold surface.

Should there be a space between the insulation and the board to allow air circulation?

Would've be easier to cross batten to allow cross air flow

 

[Tudor]

Thanks masona.

I have taken up some of the conti board and put down a couple of sheets of ply to see if that works. If so, then I will pop out and get some 2 x 4 sheets of loft board and do it again and bin the conti board.

 

[JohnD]

You need to have airflow under the boards to carry away the moist air.

Changing the type of board will not stop the condensation.

You should also look at sources of damp and condensation to reduce the causes (see Wiki/Building/Condensation