Shed / Outbuilding - what do I need so stuff won't rust or get mouldy

Mike_J_Smith · 19 Oct 2023 at 16:19

I'm planning to replace an old shed in our garden to store everything that is currently in our garage, to free up the space to use the garage as a gym.

I need to store the usual garage / shed stuff - tools, paint, gardening stuff, mower, etc and I also keep things like RC cars, electronics etc in there, so I want something that will be condensation free.

It doesnt need to be warm as such as I won't be spending any time in there, but I'm looking at insulating and having some form of heat source. I'll be able to run electrics to it.

I started looking, but there is such a vairety from cheap sheds up to garden room type structures. I need to measure up how much space I actually need, but I'm guessing around 4m x 3m.

https://www.gardenbuildingsdirect.co.uk/log-cabins/outpost-insulated/30368 This looks good but it's £7.5k before I even add ground works and electrics, and that's more than I wanted to spend. Do I need to spend that much to get what I want?

Any advice?

dlockers · 19 Oct 2023 at 16:29

Condensation free is tricky. You'll need something that's effectively up to housing spec (insulated etc). Can it all be put into sealed plastic boxes? That was my solution.

sovietspybob · 19 Oct 2023 at 16:36

if you can't seal it and keep it warm i think good airflow will help.

Best bet is to seal anything important like electronics in plastic boxes, my steel garage is good but stuff will still rust in there over winter due to the condensation so i oil up anything metal like tools and seal away anything like electronics or paper in plastic boxes.

Mike_J_Smith · 19 Oct 2023 at 16:54

That’s what I feared.

Maybe I need to have a think about what I actually need to store and where. I do have an option of storing electronics in the loft, it’s just more of faff. Although if I put in a loft ladder it will make life easier.

That in addition to cutting down on the tools and boxing them up properly as you both suggest may make it workable to just get a decent shed

Maundie · 19 Oct 2023 at 18:20

I have a metal shed and while condensation is a problem non of my tools have gone rusty or my Ryobi One stuff has packed up (they are stored in a wheelie tool chest though), my strimmer, mower and scarifier aren't and just left to the elements and have so far survived 2 winters in there without issues

mushtafa · 19 Oct 2023 at 20:54

I built my shed from scratch. Timber frame with timber cladding and a breathable membrane. Pretty much zero condensation or damp in there as it can air. No insulation - so will get cold.

Mike_J_Smith · 19 Oct 2023 at 21:10

Maundie said:
I have a metal shed and while condensation is a problem non of my tools have gone rusty or my Ryobi One stuff has packed up (they are stored in a wheelie tool chest though), my strimmer, mower and scarifier aren't and just left to the elements and have so far survived 2 winters in there without issues

that’s interesting as yes you’d expect a metal shed to condense up nicely! I guess the tool chest has done a good job. And to be fair my mower/gardening stuff is in an old rickety shed now with no real issues

Mike_J_Smith · 19 Oct 2023 at 21:12

mushtafa said:
I built my shed from scratch. Timber frame with timber cladding and a breathable membrane. Pretty much zero condensation or damp in there as it can air. No insulation - so will get cold.

That’s pretty cool. Do you have any references / guides for the build that you used? Or are you experienced / know what you’re doing?

That does sound like the kind of project I’d like to do but don’t have the DIY skills to back it up!

mushtafa · 19 Oct 2023 at 23:12

Mike_J_Smith said:
That’s pretty cool. Do you have any references / guides for the build that you used? Or are you experienced / know what you’re doing?

That does sound like the kind of project I’d like to do but don’t have the DIY skills to back it up!

I'll get some pics up tomorrow morning.
I'm a DIYer. Designed it in SketchUp, and built it with the help of a friend.

Lean · 20 Oct 2023 at 05:14

@Maundie I've used a product called GrafoTherm on a couple of uninsulated metal storage sheds. It works by trapping the condensation droplets then evaporating away.

@Mike_J_Smith Have a think about SIP panels. Very quick construction once you have your base sorted. SIp panels, box section roof, insulate, wrap it then clad it with what takes your fancy. You can get the panels in a precut kit or make your own openings and rebates.

Richie · 20 Oct 2023 at 06:34

Keter shed here... Had it for 5 years and never had a problem with condensation. They do come with excellent ventilation though:

Grills at each apex
Grills at both sides of the side window
Grills at the windows of each door.

Floor can be wet through use but, if I go back the next day, it's completely dried out due to the ventilation.

Mike_J_Smith · 20 Oct 2023 at 08:07

Lean said:
@Maundie I've used a product called GrafoTherm on a couple of uninsulated metal storage sheds. It works by trapping the condensation droplets then evaporating away.

@Mike_J_Smith Have a think about SIP panels. Very quick construction once you have your base sorted. SIp panels, box section roof, insulate, wrap it then clad it with what takes your fancy. You can get the panels in a precut kit or make your own openings and rebates.

Thanks will have a look.

If it’s insulated and made water tight; it’ll need ventilation and perhaps a bit of heat to avoid condensation?

Mike_J_Smith · 20 Oct 2023 at 08:09

Richie said:
Keter shed here... Had it for 5 years and never had a problem with condensation. They do come with excellent ventilation though:

Grills at each apex
Grills at both sides of the side window
Grills at the windows of each door.

Floor can be wet through use but, if I go back the next day, it's completely dried out due to the ventilation.

Is that metal?

I had a large plastic shed a while back and to be fair that was pretty good. But not the best looking thing!

Richie · 20 Oct 2023 at 13:14

Composite.

Keter fusion but they don't make this anymore. They have a very similar one though.

Been a great investment. Cost me £740 and I haven't had to do a thing to it in 5 years

alphaomega16 · 20 Oct 2023 at 13:30

Could you not get a small dehumidifier to run if you are going to have power in there, will aid in keeping things under control and you could put in a drainage area for pipe to go. Won't be doing a home so you should be able to pick up quite a small unit that doesn't use much leccie. Could also get a wireless hydrometer to keep an eye on things.

If you can't find a perfectly acceptable price on one that doesn't have this issue ofc.

Junglist · 20 Oct 2023 at 13:48

I know very little about this but I bought a shed earlier in the year with the intention of using it as a home cycling gym.

I did it on a budget and tried to make it as cheap as possible. I have a friend who works in the building trade so I was given the insulation for free but I basically filled all the gaps with 30mm celotex then boarded over it with 11mm OSB. Not the fanciest but it works fine for what I needed and apart from when I actually do intense exercise in there it has remained dry with no signs of damp - it was built back in January so I guess I'll see how it copes with winter but it's been perfect for me.

I actually think I could've done without the insualtion as it keeps the heat a bit too well whilst I'm exercising but I've got a few electric items in there that need protecting from mositure.

Lean · 20 Oct 2023 at 15:50

Mike_J_Smith said:
Thanks will have a look.

If it’s insulated and made water tight; it’ll need ventilation and perhaps a bit of heat to avoid condensation?

What I find if you use box section roof sheets(lots of colours, profiles and tile effects), you can leave out the eave fillers and insulate close to the depth of your supporting roof structure. Then vapour barrier and board over. You'll have your ventilation. Your house wrap is already breathable.

Junglist said:
I know very little about this but I bought a shed earlier in the year with the intention of using it as a home cycling gym.

I did it on a budget and tried to make it as cheap as possible. I have a friend who works in the building trade so I was given the insulation for free but I basically filled all the gaps with 30mm celotex then boarded over it with 11mm OSB. Not the fanciest but it works fine for what I needed and apart from when I actually do intense exercise in there it has remained dry with no signs of damp - it was built back in January so I guess I'll see how it copes with winter but it's been perfect for me.

I actually think I could've done without the insualtion as it keeps the heat a bit too well whilst I'm exercising but I've got a few electric items in there that need protecting from mositure.

I partitioned a mates double garage. Workshop/bike storage one side (sells bikes). Sauna/treadmill/roller in the other. All insulated. He uses a few fans coupled with high preformance exctraction for the sauna side.

mushtafa · 20 Oct 2023 at 20:04

My DIY odd shaped shed. No damp/mould or rust

Mike_J_Smith · 21 Oct 2023 at 06:59

alphaomega16 said:
Could you not get a small dehumidifier to run if you are going to have power in there, will aid in keeping things under control and you could put in a drainage area for pipe to go. Won't be doing a home so you should be able to pick up quite a small unit that doesn't use much leccie. Could also get a wireless hydrometer to keep an eye on things.

If you can't find a perfectly acceptable price on one that doesn't have this issue ofc.

Yeah this is probably a good option, I used to run one in the garage of our previous house as it was quite damp. I bought a cheap one and it was pretty rubbish, but I could probably get a decent one and it would work better.

I’m probably other thinking it all now as well, but I like to research and sit on it for a while before going ahead

Mike_J_Smith · 21 Oct 2023 at 07:09

Junglist said:
I know very little about this but I bought a shed earlier in the year with the intention of using it as a home cycling gym.

I did it on a budget and tried to make it as cheap as possible. I have a friend who works in the building trade so I was given the insulation for free but I basically filled all the gaps with 30mm celotex then boarded over it with 11mm OSB. Not the fanciest but it works fine for what I needed and apart from when I actually do intense exercise in there it has remained dry with no signs of damp - it was built back in January so I guess I'll see how it copes with winter but it's been perfect for me.

I actually think I could've done without the insualtion as it keeps the heat a bit too well whilst I'm exercising but I've got a few electric items in there that need protecting from mositure.

That’s cool; so just upgrading a standard shed which would keep things easier.