condensation on garage roof

[knockavacca]

i have a corrugated garage roof, how can i treat it to stop condensation its realy bad this wether thanks

[buildersmate]

Warm air contains mosture (water vapour). This rises and when it hits a cold surface (corrugated roof - same temperature as the outside air just above it) the water vapour condenses. That's why it's worse in cold weather. Try thinking about where the source of the warm moist air is coming from (the house when the door's open? - if it's attached?) The only other way is to insulate the roof space just under the roof line, putting vapour barrier (polythene sheeting) adjacent to the insulation on the warm side. Probably not worth the effort and energy to do this though.

[knockavacca]

thanks for your reply, appreciated mike

[KARL]

Putting a continuous vapour proof layer underneath the roof sheeting with only a slight gap would possibly cure this. You could use simple, supported polythene sheeting but twin-wall polycarbon sheeting (which is more rigid and possibly easier to support) would be better and last longer. Neither is very expensive.

[knockavacca]

thanks karl cheers