new grp roof, but the osb wet all the time

[chrispollin]

hi guys, im new here - and on with lots of wee projects around the house

just recently had a new garage built. and we opted for a grp roof to go on it.

now ive a concern with the new roof as the last two mornings after fitting, ALL the osb boards are wet all over.

a bit of history on the build, we had the osb boards fitted, then our builder covered it all in visqueen plastic to protect it which it did, we then had some bad weather but the roof was dry.

the roofer then came out ripped the plastic off and fitted the upstand and drip board parts aroud the edge of the garage, he never refitted the plastic properly and some water penetrated through to the osb.

on the day the roof was laid, the boards were dried off with a large blow torch and the roof laid. the roofer tells me all went well, we had rain later that day.

can anyone offer any suggestions? im assuming if it was leaking, it couldnt possibly be every single area?

is it condensation?

is it residual moisture from the osb?

keen to try and track down the root cause here guys, so any help would be much appreciated.

regards

chris

 

[catlad]

If the boards are only wet after rain then I would say the roof has not bonded properly, grp is a fair weather installation only.

 

[cotswoldbuilders]

Glass fibre doesnt take to well to damp boards, the roofer may have only dried of the top of boards.
I would only have been happy laying the resin etc on a perfectly dry roof.
You might have some future delamination, there could be some pin prick holes which will be hard to find.
The boards shouldnt be wet every time it rains.

 

[chrispollin]

hi guys,

its a bit of an odd one - well the underside of the boards were dry after they laid the grp -

this morning wet again, opened the door and within about 2 hours, they were al dry again. we had a heavy rain shower (been working in garage all day) and the boards are still dry. ?

i removed a small bit of wood from the underside of the osb and it was bone dry. this all seems to be surface layer?

surely it would have gotten wet again after that heavy rain fall we had.

condensation??? how to prove it though?

 

[JohnD]

leave the doors open so there is a good current of air, to prevent condensation.

Does the garage floor have a dpm?

 

[chrispollin]

hi,

yes theres a dpm on the floor

 

[cotswoldbuilders]

Do you park your car in there, if so do the boards look damp afterwards, ie a hot engine may cause condensation on a cold roof.
You might need to increase ventilation.

 

[chrispollin]

hey, not yet, its pretty empty at the mo