I have a shed with a corrugated plastic roof. I get absurd amounts of water condensing under it, which drips onto the contents of the shed.
Is there a way (without spending a fortune) to stop this or to collect the water in some way?
Increase the slope of the roof?
water condensing under it, which drips onto the contents of the shed.
e water in some way?
Where's all the water coming from? Do you have a tumble dryer/swimming pool/steam room operating down there? If so stop.
Is there electricity available? If so you could put a dehumidifier in, if it's worth the cost to stop your stuff getting wet.
Otherwise change the shed roof to something with better thermal properties (I don't think insulating corrugated plastic is feasible).
Yes I suppose that is the only reasonable option (unless anyone has quicker ideas?). It's brick built, and I have a pile of matching bricks, so I could do that.
What slope would you reckon is needed? It would be annoying to increase it a bit then have to do it again.
Can't give you a definitive answer (looks over shoulder for expert) but I don't think it needs to be a massive slope. Any chance of jacking the roof up by putting something under each joist (piece of wood, old brick) and testing empirically?
condensing under it, which drips onto the contents of the shed.
water in some way?
Scottish weather. I very rarely see the humidity meter go below 75%!
I thought about a dehumidifier (it wouldn't be much hassle to run electricity to the shed as it's close to a building which has it already). But I assumed it would cost a lot to run. Aswell as the expense of buying one. It's just a shed for garden equipment such as lawnmower, hedgetrimmer, and a mountain bike (which is an aluminium frame so I don't mind that being wet).
I didn't really want to spend a lot of dosh on it.
I think I'll make sure the shed is sealed up to avoid more damp air getting in, then try tilting the roof.
Yes, I'll give that a go thanks.
Transparent or opaque sheeting fastened to the underside of the rafters?
The water should drop onto it, and then run down to the edges, where you can deal with it easily by some form of gutter arrangement.
Of course, this won't deal with the cause of the condensation, just the symptom.
As long as the condensation formed on the inside of the original layer, and not the new one...
My garage roof is made of box profile steel and in the centre there's one s= heet of see-through plastic to make a skylight. The metal sheet has a linin= g of OSB board but of course the window bit is not lined with OSB and that = produces lots of condensation just like you describe.
I don't think changing the roof slope would be practical - you'd still get = as much condensation - but it might all run down to one end.=20
Could you line the ceiling with some sort of boarding? That would stop it.
A subject close to my own heart as well ! Scotland too ..
I have a largely sandstone outbuilding with a clear plastic corrugated roof, that suffers lots of condensation.
About 18 months ago, I (in my wisdom at that time), I lined the roof with 6mm ply, the idea being I created a "cushion" so that the water couldn't condense on the cold plastic, instead I had "warm" plywood.
It's not really helped ! The ply is rotting and going black. Well, it was anyway .. Left a half door open for months and months and the roof seems to be clearing a bit, but am not sure if it's the open door, or the large bucket of road salt that has helped !!
Anyway, have now closed the door and removed the bucket of road salt, and instead stationed 3 diy dehumidifiers around the shed, which are basically road salt in a muslin square or tea towel hanging over a bucket, the salt draws in the water, then drips it into the bucket.
So, over the next few months I'll see if the underside of the roof stays drier or not. I can still see water condensing on the cold walls.
I have a theory that one wall in particular is sat in water and the water is drawn into the shed that way. The whole outbuilding, which is pretty big, is on an incline and I've convinced myself that the wall at the bottom of the incline is the one causing trouble. The parts of the building higher up the slight incline are definitely drier.
Am currently lining one wall with shelving which as part of the prep, I've put polystyrene in and will board over with 6mm ply. Of course, this means more water will condense onto the other bare walls !
Anyway ... line the roof, don't bother ! Of course though, there's not as many drips of water into the shed as the poor old ply lining gets most of it.
I think the diy dehumidifier is worth a shot. I also intend to scatter around the shed some tins (with holes) with wood charcoal in them to act as dehumidifiers as well.
sheet of see-through plastic to make a skylight. The metal sheet has a lin= ing of OSB board but of course the window bit is not lined with OSB and tha= t produces lots of condensation just like you describe.
t as much condensation - but it might all run down to one end.
I have a similar problem in similar Scottish conditions, and do have to just live with it. In my case there really is nothing I can do as it's clear plastic and is the only daylight source for the lean-too section of the garage and contains my lathe, and is in near enough daily use. Certainly the angle of my roof is pretty low to the extend that in the recent winters I have to go and remove the snow from it.
But the condensation is not significant - if it was the lathe would suffer and it is quite OK under an old groundsheet, so I do wonder quite why you are getting so much moisture - I guess there may be no damp proofing on the floor. If in fact your shed roof does not require to give light then lining it would solve the problem.
Rob
Agreed. I do like saving time and effort. Got some sheeting on ebay for 2 quid!
The road salt idea is brilliant! I will do that if the sheeting isn't enough. Much better than paying for a dehumidifier and some electrocity.
Albeit not a steep enough roof to allow the water to run down I suggest that if you cannot make it steeper to dry thoroughly, spray with silicone spray to provide a less water adhesive surface and allow the water to run more easily to the edge to a collection gutter.
Apart from that install double wall polycarbonate sheeting such as eBay item
320705397522 underneath to give better insulation and therefore less condensation.
Silicone spray sounds like a good idea, I'll get some of that.
As the shed isn't heated, how does insulation help? Or is it in the evening when the outside cools and the inside does not that condensation occurs?
Also looks expensive!
rote:
ening when the outside cools and the inside does not that condensation occu= rs?
The condensation is on your side, if it doesnt happen your stored goods will probably mould or rot. Just direct the condensate better.
NT
sheet of see-through plastic to make a skylight. The metal sheet has a lining of OSB board but of course the window bit is not lined with OSB and that produces lots of condensation just like you describe.
much condensation - but it might all run down to one end.
If you don't mind what it looks like you could try lining it with horticultural grade bubble wrap available in large sheets. That should provide sufficient insulation and decrease contact with cold outer skin.
Insulation and/or stopping saturated air reaching the cold surface and possibly with active ventilation when the relative humidity is low. Maybe an application at last for a solar powered fan ;-)
The bubble wrap works well in my cold frame. It's gaffer taped to the pvc panels. Bone dry in there
You don't say whether it is clear or solid opaque plastic, so this may or may not not be suitable. I had the same problem with a corrugated steel roof on an outbuilding. I found that pushing 2" thick expanded polystyrene sheet (something I had lying around - thinner may work as well) up between the rafters and making sure it was well sealed around the edges cured the problem.
Colin Bignell
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