Shed damp/condensation

I put up a 10x7 shed last summer (https://www.onegarden.co.uk/garden-buildings/garden-sheds/wooden-sheds/shire-guernsey-shed-10x7). I've hardly been in there over the winter, but when I have I've noticed condensation on surfaces, and the windows misted up on cold days.

I've never known condensation in a wooden shed before, so I'm curious to know where it's coming from. I was worried it was coming up from the ground, but I was in there yesterday tidying up, and the floor was nice and dry, even under items that have been sitting on the floor. There is damp/mould along the bottom of the windows (presumably from the condensation running down), and in a few places where the walls meet the floor - mainly the corners and the joins between the wall panels. This suggests the rain is getting in behind the cover strips, running down the join, and soaking into the wood at the bottom. Strange though, as I ran frame sealant down these joins before nailing on the strips.

Unfortunately the roof has hardly any overhang, so it all runs down the walls, and there isn't enough to fit guttering.

The general advice for condensation/damp seems to be to install ventilation. There is a 1/3" gap along the top of the double doors, but otherwise the shed is very "air tight". I'm going to fit a 6"x3" grill in the eaves opposite the door, but wonder if that will be enough or if I need to think about adding heating?

Is there anything I can do about the damp wood already in the shed? Assuming it dries out in the summer what can I paint on it to a) kill the mould and b) protect it from getting damp again? Presumably anything I use on the inside isn't going to soak in enough to protect it from the moisture that's soaking in from the outside.

Posts

  • DovefromaboveDovefromabove Central Norfolk UKPosts: 55,133

    I'd have considered a certain amount of condensation in these weather conditions par for the course in a standard garden shed. 

    It's probably not rain getting in, but rather damp air condensing on cold surfaces e.g. window panes. 

    What is the intended purpose of the shed?  Will a modicum of condensation from time to time be a problem?

    Last edited: 20 February 2017 09:46:41

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  • Dovefromabove says:

    It's probably not rain getting in, but rather damp air condensing on cold surfaces e.g. window panes. 

    What is the intended purpose of the shed?  Will a modicum of condensation from time to time be a problem?

    See original post

    If the condensation is due to damp air making its way in from the outside, I'm curious as to why my last shed (a cheap shiplap with plenty of gaps) never had a problem. Perhaps the gaps also doubled as ventilation?

    The shed is just used for storage, but I'm concerned that the damp will start to cause problems - rusty tools, damp ruining anything made of fabric or paper, etc. Over the last few months I've been storing boxes of pet food in there, and after a couple of weeks I find that they feel quite "limp" - it's shiny cardboard which I'm guessing is attracting the condensation.

    It seems commonplace for people to use sheds for hobbies like arts and crafts, and fully furnished "man sheds"! How do they avoid such problems - is it down to insulation and heating? While I won't be going to these lengths, I'd have assumed that carpets and panelling would prevent the wood from breathing, or trap any damp that works its way in?

  • KT53KT53 Posts: 3,449

    If the only ventilation is a tiny gap above the door then I'm not surprised there is a problem with condensation.  My shed has a pitched roof and there is an air gap along both sides between the sides and the roof.  I did have trouble with rain penetrating one corner but overcame that by using the self adhesive flashing you can get on a roll.

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