Hi Everybody, I have a detached sectional concrete garage with a metal roof, I am wanting to make it in to a games room for my kids but there is a terrible problem with condensation on the roof dripping onto everything. At the moment I have put a pool table in there and put some visquin over it attatched to the rafters to stop dripping on the table whilst they are playing put would like a more permanent solution. I have read just about every forum and website going for the last week (kingspan, expanding foam, salt, even cat litter?) and my head is literally spinning . Most comments talk about plenty of through ventilation but there already is. Thing is I'm not an expert at DIY and havent got alot of money to spend on it due to xmas so lamens terms would help. Many thanks in advance

Use cheap 100mm loft insulation (usually on 3 for the price of 1 at wickes or B&Q) between the rafters, then screw 12.5 mm plasterboard to the underside of the rafters to hold it in. This is fine provided the rafters are at 60cm centres or less.

Hi, thanks for the reply. I was thinking of doing this as was the cheapest option but was told by a builder friend that the insulation would act like a sponge and absorb all the water and would not stop the condensation. The rafters are approx 56cm apart and around 100mm deep. Thanks

There is a risk of that happening, but the water needs to get in for it to become a problem. If it cannot get onto the underside of the metal to condense, then it isn't a problem. Done properly, this will work. Done badly it will do as he says.

Ok, probably not for me then as couldnt guarantee that I would do it properly or not cover area fully....confused.com

Was thinking of using kingspan when finances are a little better, not an option at moment as its a big garage (around 20ftx10ft) and would cost too much. Is that the better option and just cope for the moment through the winter?

http://www.idealworld.tv/Roofix_-_5_Lit ... GB/$s=roof

Would this do the trick on inside of corrugated roof

No it wont do the trick, thats roof repair paint.
Unless the roof sheets are plastic coated your wasting your time.
If you went for insulation, it would have to be solid in between, all joints taped and visqueen fixed, then solid boarding, and this would do only temporary.
If your going to use it more than a garage you need a proper roof on, ie extra timbers to take 18mm ply or osb board with either 3 layer torch on, glass fibre or best option epdm.
You might want to google Warm roof construction.

Thanks for your advice, dont mean to sound ungrateful but my only option is a re roof? Wouldnt kingspan do the trick or polystyrene sheets. Sorry i'm grasping at straws here but no way can afford a new roof, if so the visqueen sheeting will have to stay put.

the problem is that the roof is getting cold and the warm air is condensing when it hits the roof, hot air rises hits the cold roof and forms water droplets....

I would put battens up and put insulation up leaving an air gap between the insulation and the corrugated metal roof (this air gap will be cold)

then i would put a vapour barrier on the warm air side of the insulation and then plasterboard or put up osb or ply... (personally I put ply up in my workshop so i could screw stuff directly into the walls)

what kind of ventilation is there?

_________________
- Dave
http://www.pamperhouse.net
http://www.invertedcircle.co.uk

Not very savvy so bear with me, there is around a 1 inch gap between the top of the garage door and garage when closed, also at each end of the garage where the underneath of the corrugated roof sits on the beams there are the gaps where it rises and falls..if that makes sence

If there is a gap between the insulation and the roof there is a significant risk that warm moist air will still find a way through and then condense into your insulation, this will become sodden and eventually drip onto whatever is holding it in place.

Spray foam professionally applied is a long term solution as it will bond to the internal cold surface and eliminate it altogether, this is probably more than you want to do with an old garage to be fair.

What root is saying is correct you need to install a cold zone if you are going down the more conventional insulation route, in essence you need to keep the warm air well away from the cold metal, again this might be more work than you want.