New roof fitted and now condensation

I got my roof replaced in April this year, stripped back to bare trusses, sheeted with OSB new felt, tile batton and tiles .

Was very happy with job, have been up in the loft in heavy rain etc no leaks, workmanship was good etc.

Was up in the loft tonight and the inner surface of the OSB was damp, when i ran my hand over it my hand was wet. the temp outside is -1 C at the moment.

I never had a problem with condensation before the roof was replaced and wondering why should i have a problem now.

I have a cold roof space, well insulated between floor joists and floored with caber flooring .

any advice would be greatfully received

Ross

ventilate it

Should it have had a layer of plastic sheeting fitted to act as a vapour layer?

What is the easiest/ best way to ventilate the loft space ?

i noticed that my UPVC soffits dont have vents is this something that can be fitted now when they are in position, what other ways is there?

these fitted to your soffit http://www.screwfix.com/search.do?f...P&gclid=CIPC0tyj554CFU0B4wodtGTfIQ&source=aw.

and these http://www.harcon.co.uk/slatetileridge/index.aspx fitted to the roof.

both a simple job.

when your roof was re-tiled the contractor should have fitted continuous vents http://www.fascias.com/en-gb/dept_269.html and vented ridge.

The reason you had no problems prior is that the roof space was so well ventilated and was possibly the bane of your life!

Basically - you no longer have sufficient ventilation and you may have been better off to have omitted the OSB board.

You have 2 options - 1 live with the situation; or 2 insulate the roof, what you will be trying to do is stop the warmer moisture laden air inside the house coming into contact with the cold surface of the OSB. Without getting to involved this solution will require insulation between the rafters say minimum 50mm PIR (has excellent vapour resistance) you will need to maintain a minimum 25mm gap between the underside of the OSB and the insulation material, then fit a vapour proof membrane (to keep the majority of the warm moisture laden air on the warm side of the construction, then either finish off with a layer of plasterboard over the rafters or add a thermaline insulation board such as british gypsum thermaline super depending on how thermally efficient you wish to make the roof. Then and this is a BIG then - you will need to ventilate the gap between the insulation and the OSB hence the minimum 25mm gap but ideally 50mm! Which is where the eaves and ridge ventilation comes into play.
This option would allow the space to be utilised for storage or as a work space depending on the available area.

A further option would be to insulate between ceiling joists, however, this option is not guaranteed to get rid of the condensation problem.

Regards