My garage roof keeps dripping condensation!?

[hooblah]

Obviously I realise this is happening because the warm air is hitting the underside which is cold, but there's plenty of ventilation and it makes no difference!
The roof is made from corrugated cement boards (maybe with asbestos?).

So far I've tanked the walls with slurry to stop rising damp and fitted a 6" extractor fan in the back wall. The garage is 5mx3m so should be more than enough.

Now I'm thinking I need to put something against the underside of the roof to stop all the condensation.

Can anyone think of the cheapest solution?
I was considering putting up plastic sheeting with an air gap between. Good or bad idea?

 

[MattF]

I put wooden battens in mine, held onto the lowerside of the steel trusses at right angles to them, (I believe I used strips of metal with the wood, to clamp the metal onto the upperside of the trusses), then slung 3mm ply panels on there. Been that way for years, and there's only slight staining on some of the edges of the ply.

 

[eLuSiVeMiTe]

On a serious note. Insulation and a vapour barrier is the best option.

 

[Arc Tourist]

Consider doing a test by spraying an area with a can of automotive undercoating. Overall, it may be an economical and easy solution to have someone come in with a proper sprayer and cover the whole ceiling.

 

[Screwdriver]

I'm half way through building a lean to aka "Ye Olde Forge" as posted in that thread. Incredibly, even without walls, the warm air from just me being in and around is enough to kick off a spectacular amount of condensation, even from under the corrugated bitumen. I was expecting it from the tin part of the roof, but the bitumen??

Anyhow. Need to stop warm air from hitting cold surface so I intend to wedge some Kingspan in there and clad with thin ply before taping up the joints. If the air can't circulate against the cold surfaces, water vapour wont get wrung out of it.

 

[CompoSimmonite]

I'm half way through building a lean to aka "Ye Olde Forge" as posted in that thread. Incredibly, even without walls, the warm air from just me being in and around is enough to kick off a spectacular amount of condensation, even from under the corrugated bitumen. I was expecting it from the tin part of the roof, but the bitumen??

I get condensation on my fibreglass sheeted carport roof depsite it being open on 2.5 sides !

 

[frank horton]

Insulation, insulation.........only buy steel roofing sheet with an attached insulation barrier, it doesn't have to be thick........
if ur sheets are without, I'd skin the roof with 1/2 resin bonded ply then firm isulation, comes in sheets in several thickness's, mine looked like red solid sponge....no idea of the proper name......... then a water barrier, roofing undersheet.........
Job's done........
main reason I use plywood sheeting is that it looks good from underneath, u can walk safley on the unfinished roof, no need to worry about the insulation falling thru and accurate measuring, PLUS if a roof truss is out a little bit u can secure the metal sheeting with extra long screw's to the ply........
Frank

 

[nickk]

I had the same problem, bodged it by fitting OSB to the u/s of the purlins, so they act as a drip tray, that was way back in jan '99.

 

[addjunkie]

A multi foil insulation would also work, but its relativly expensive.....cheapest option is probably fiberglass above cheapest boards you can get.

Another option is to replace the roof with some kind of insulatd sheets

 

[hooblah]

Consider doing a test by spraying an area with a can of automotive undercoating. Overall, it may be an economical and easy solution to have someone come in with a proper sprayer and cover the whole ceiling.

A test for what? What will undercoat do?
I have a tin of underseal and a paintbrush.

Insulation, insulation.........only buy steel roofing sheet with an attached insulation barrier, it doesn't have to be thick........
if ur sheets are without, I'd skin the roof with 1/2 resin bonded ply then firm isulation, comes in sheets in several thickness's, mine looked like red solid sponge....no idea of the proper name......... then a water barrier, roofing undersheet.........
Job's done........
main reason I use plywood sheeting is that it looks good from underneath, u can walk safley on the unfinished roof, no need to worry about the insulation falling thru and accurate measuring, PLUS if a roof truss is out a little bit u can secure the metal sheeting with extra long screw's to the ply........
Frank

Sounds expensive. Not gonna happen.

I had the same problem, bodged it by fitting OSB to the u/s of the purlins, so they act as a drip tray, that was way back in jan '99.

So the wood goes soggy? So that's basically the same as me fitting plastic sheeting isn't it?

A multi foil insulation would also work, but its relativly expensive.....cheapest option is probably fiberglass above cheapest boards you can get.

Yeah I was thinking that. But my mate says there needs to be airflow between or moisture will just collect in the insulation?

 

[eLuSiVeMiTe]

Like I said. Counter batten. solid insulation (think they do 25mm) vapour barrier and boards. No point wasting money on something that won't solve it. Do it properly first time.

 

[gaz1]

you need to frame the roof lower and create a ceiling

use insulation rolls and thin plyboard as its only to hold up the insulation also using laths will support the insulation

you need a space of 1/2" away from the roof and 100mm insulation this will create a cold roof effect anything above the insulation will breath and no heat should get near it due to the insulation

we can only offer suggestions then not much more we can do other than experiment yourself and please do let us know your outcomes

also its advised to insulate your sides as well

look for insulated garages on google theres enough info on there

 

[Arc Tourist]

A test for what? What will undercoat do?
I have a tin of underseal and a paintbrush.

Sorry, I should have said test an "area" to see if it works for you. Guess I am on the wrong side of the Atlantic, but I understand undercoating to be a thick spray on rubberized material, not a liquid that is applied with a paintbrush, which obviously will not have insulating qualities.

 

[Screwdriver]

Sorry, I should have said test an "area" to see if it works for you. Guess I am on the wrong side of the Atlantic, but I understand undercoating to be a thick spray on rubberized material, not a liquid that is applied with a paintbrush, which obviously will not have insulating qualities.

If it is not insulating then the surface will become just as cold as the roof and you're back to square 1.

 

[steveo3002]

not very proffesional but my garage dripped so i cobbled up a wooden frame and fixed plastic sheeting pulled tight over it about 4" below the roof , seems to work well , it separates the hot /cold and catches any remaining drips

 

[Arc Tourist]

If it is not insulating then the surface will become just as cold as the roof and you're back to square 1.

Not sure, but it worked on my van overseas, I had a thick layer sprayed on the sheet metal ceiling and walls and condensation became a non issue.
Got to remember, I'm just a tourist in life, and can only suggest what I have experienced.

 

[jchand]

not very proffesional but my garage dripped so i cobbled up a wooden frame and fixed plastic sheeting pulled tight over it about 4" below the roof , seems to work well , it separates the hot /cold and catches any remaining drips

Done this too, worked a treat and made the place warmer, cost next to nothing.

 

[jchand]

I just made one corner lower and made a hole so i could have just one drip in the corner.

 

[nickk]

Not soggy,it’s wavy ,but guess down to gravity causing the sag,served me well,19 years old next month,I remember the news whilst installing it ,the EURO had just launched

 

[jchand]

Another thing that worked very well was simply lining under the roof material with 18mm osb. Make sure the ridges in the corrugated roof (if it is or if not leave a small gap) are vented at ends for air flow. Didnt need any insulation, cheap and easy and worked a treat even with gas heater going.