Damp/condensation proofing of garden sheds

[Re6/6]

Any advice please on the damp proofing/condensation reduction in a new wooden garden shed for the storage of model railway track and baseboards? I was thinking along the lines of lining the inside with 'Celotex' insulation or a similar type and some sort of lining material. I'm also thinking about a polythene damp-proof membrane (advisable and/or necessary?) then the insulation, maybe rockwool type could be used and then foil-backed plasterboard.

 

I'm not up to date with the latest thinking, so any advice/experiences would be very helpful.

 

Anybody with experience of non-electrical de-humidifiers please?

 

Many thanks

 

John

[petethemole]

Others are no doubt better informed as to various methods, but in my experience, with using sheds for storage (of things I would rather have in the house) it's wise to check the fit of the door. you could spend loads on materials and still find that cold, wet air gets in through the gaps round an ill-fitting door. Believe me, I know

[Pannier Tank]

Any advice please on the damp proofing/condensation reduction in a new wooden garden shed for the storage of model railway track and baseboards? I was thinking along the lines of lining the inside with 'Celotex' insulation or a similar type and some sort of lining material. I'm also thinking about a polythene damp-proof membrane (advisable and/or necessary?) then the insulation, maybe rockwool type could be used and then foil-backed plasterboard.

 

John

 

Rather than use a polythene damp proof membrane I would suggest you take a look at a Breathable Membrane.

 

[The Stationmaster]

John,

I used a polythene membrane (all sorts of old bits of polythene sheeting overlapped and taped together) against the outer skin and then the insulation was mainly anything I could get hold of for little or, preferably, nothing varying from a load of cardboard ex computer boxes from work, offcuts of polystyrene foam (keep well away from electric cables), polystyrene granules out of packaging, fibreglass wool floor insulation and even some screwed up newspaper. The flooring was the basic shed material covered with smooth roofing felt topped with exterior grade plywood. And what I also incorporated was a high level air inlet leading to a just above floor level outlet so air was kept circulating (the fan installation I planned wasn't finished before we moved - that was to use a 12volt heater fan recovered from a scrapped Citroen). In addition the shed had a clear space area under all of the floor with a sort of low headroom cellar arrangement under one end so there was plenty of air circulating there too.

 

I never had any trouble at all with damp either rising or atmospheric and the sections of the portable layout lived there quite happily for a couple of years before we moved plus there was stuff like a control panel, switches and other electrics also in the shed without problems but no rolling stock on a long term basis.

 

I'm not sure how effective the vapour barrier was but nothing ever suffered from damp or mildew. Where I am now I have a much, much, better quality garden shed building but it is uninsulated and although there are no obvious signs of damp some tools show signs of very light surface corrosion although that might be nothing to do with the shed and simply down to the state they were in when they went into it. 'The room' (half a garage) where the portable layout and various other stuff is now stored has brick outer walls without a vapour barrier but is very highly insulated using Kingspan (similar to Celotex I believe) and thus far nothing shows any signs of problems with moisture but as yet it hasn't had to endure layout building/operating and we humans could create a whole new lot of problems once more time is spent in 'the room'.

[Guest Max Stafford]

When i built my workshop with the help of Tony Graham three years ago, I basically put a polythene damp proof layer on the floor before plying with 9mm marine. I did the same on the walls with polystyrene type insulation in the gaps before covering with the poly and ply. Power was fed into the shed via a buried cable and I use an oil-filled radiator in winter to keep the internal temperature at a reasonable level. The shed is mounted on sleepers and ballast, maintaining a constant airflow underneath. In retrospect, I would put an insulating layer beneath the ply also and perhaps insulate the inside of the roof too but to date, the structure has been solid and I have experienced no problems with condensation, dampness or any other environmental difficulties.

 

Dave.

[Re6/6]

Thanks all for the advice. I neglected to mention that the proposed shed would be in a location where there wouldn't be any electric power supply available, hence my paranoia about the damp! This is only a proposal ATM. The main thing that would seem to be very important from all of the above is that it would have to be well ventilated. The layout to be stored (it would only be for storage and space within for people would not be necessary) is on plain boards with no 'scenics' etc and is very well sealed with epoxy resin, so hopefully damp absorbtion/warping and all those sort of issues shouldn't be any problem, so basically what I'm asking is probably unusual (in relation to the hobby's normal requirements) as generally a power supply would be available, but not in this case unfortunately!

 

Thanks

 

John

[The Stationmaster]

John,

My shed had a power supply but things were only turned on when I was working there and the rest of the time it was left with everything 'off' and no problems.

[petethemole]

John, I appreciate you don't have power at the shed, but for the possible benefit of others, I'll mention that my storage shed now hsa power and there's a freezer in it. This puts out a low level of warm air, which seems to counteract the moisture that gets in round the door (it's warped).

[RBAGE]

To resurrect an old thread, I wonder whether anyone can advise on my problem with condensation in a wooden shed.

 

I've had my original shed for almost 20 years. Built on a concrete base with damp course. 25mm ply walls and roof. Insulated with 2" expanded polystyrene throughout, I've had no problems with condensation, except around the windows, which is what you might expect with single glazing.

 

I've recently extended the shed. I've insulated the roof with 2" expanded polystyrene and a sheet of the aluminised bubble wrap type of insulation just to try and keep it toasty.

 

All was fine until this recent bout of hot humid weather when the condensation started. Not dripping from the roof but running if you tapped the plywood covering for the ceiling.

 

I've taken down the ceiling and when I removed the bubble wrap stuff it was like Niagara falls. Fortunately, I've taken action before I started the layout.

 

I am now told that if you put polythene sheet in the roof, condensation will collect on it.

 

I now intend to put as much ventilation in to the shed as I can reasonably as a precaution but wondered whether removing the "bubble wrap" resolve the situation or should I remove all insulation so that the temperature inside the shed can follow the outside temperature as quickly as possible. Hopefully avoiding the temperature differential that encourages condensation to form.

 

Any advice?

 

Bob

[JZ]

FWIW, my shed has been up for seven years now and not had any condensation issues. Wall are insulated with fibreglass matting, roof with the bubble wrap type stuff, with a 2 inch air space, floor uses the same with 4'x2' flooring boards on top(all over the original shed floor). One very important thing, which some forget, is guttering. Most rain falls on the roof surprisingly and you don't want it running off and being blown onto the sides. I keep a 1kw radiator on over the winter and boost heat with a halogen heater when working out there. Half an hour with that and the shed will keep it's heat for a good couple of hours when working in it. For the summer I have an aircon unit. Another important thing is to treat the outside at least every two years, whatever it says on the can. Also check whether what may look like condensation in the roof is actually a leak. Always use heavy roofing felt rather than the lightweight stuff you usually get. Nail and use bitumen adhesive.

 

Edit to add that the shed is 20'x10'.

[Andy Hayter]

Polyethylene sheet or bubblepak are excellent materials for keeping damp out.  They are (as you now know) excellent at keepig it in.

 

What you need is to ensure that there are some gaps to allow moisture out (preferably near the apex since you can use the natural air flows to create air circulation).  You might also benefit from a small air vent near the apex on the end wall. 

 

Alternatively rip it all out and put in a breathable membrane then insulation and if you use bubblepak as part of the insulation make sure there are holes to allow air movement.

 

Ideally ensure there is an air gap between the walls and any insulation material you put in.

 

Ripping it all out and doing nothing will just ensure that the shed is permanently damp.

[brianusa]

We have the basic metal garden shed to keep the ride on mower and other odds and sods in.  Not the best situation but over here is a product called Damp Rid.  A powder in a special container that absorbs moisture which drips  into a container beneath.  Don't know if its available back home but there's probably some kind of substitute available.  Works quite well and certainly better than nothing.

 

Brian

[Campaman]

My 16 x 8 ft shed is sat on timbers on a concrete base with a damp membrane in it, I do not have any insulation apart from the floor is carpet tiled and do not suffer from any damp or condensation.

 

It may be the design of the shed or the quality of it, its a Chalet/Summer room style, walls are 1/2" tongue and groove with 3/4" floor and roof boards.

 

My old shed was a cheaper one that I fully insulated and lined, it sat on decking, I had so many problems with damp and condensation I had to scrap it.