How to Tackle Condensation in Your Garden Shed

What’s with the condensation issue in steel sheds while timber ones remain unscathed? Ever wonder how to solve this dilemma in your metal garden shed? Well, look no further because you’re in the right place!

Our guide will assist you, but keep in mind that insulation alone won’t provide a complete solution. Keep reading to discover the solutions and bid farewell to condensation once and for all.

(Disclaimer: This post is intended as general advice. Garden Buildings Direct cannot be held responsible for any actions that may void a building’s warranty).

Condensation Explained

Metal condensation

(Image Credit: Public Domain Pictures)

Condensation is where water settles on a cold surface when humid air comes into contact with it. They come in the form of droplets.

This occurs after evaporation in the water cycle (where the liquid turns into vapour). And we’ve probably all seen this happen with a cup of hot coffee on a cold morning.

When next to a window (and outside is colder), steam from a hot coffee condenses on a window as droplets. And your shed is no different. Check out the video below for an explainer regarding condensation:

What Causes Condensation?

Steel condensation

(Image Credit: Flickr)

Condensation in your shed is caused when the outside is cold, and the inside is warm. As the temperature outside gets colder, so does the fabric of your shed (metal, in this case).

This is because metal sheds are usually made from thin, heat-conductive sheets. When it’s cold enough, it reaches a ‘dew point’. This is the temperature at which air must be cooled for water to turn from vapour into liquid (dew).

Cold metal in contact with warm air means that droplets form as condensation on the inside of the shed’s roof. It usually happens on the roof because hot air rises, making it the moistest area.

Warm air rising can form condensation on:

  • ceiling/roof
  • walls
  • windows

This is usually because it has nowhere else to go. The problem is this condensation can then drip back down into your shed. This, in turn, can damage the contents of your shed.

So let’s learn how to stop condensation in your metal shed or plastic shed before it even happens.

How to Stop Condensation: Inside 

Condensation drops

(Image Credit: Wallpaper Flare)

There’s no reason to shy away from metal garden sheds just because of concerns over condensation. And to prove it to you, we’re going to show you how to beat it once and for all. Just follow these steps to save a cheap bike shed or storage shed.

To stop condensation in your metal shed, you need to:

  1. Keep the interior dry
  2. Provide adequate ventilation
  3. Combat moisture when building
  4. Properly insulate your shed
  5. Use a dehumidifier

And to do this, you could follow these steps: 

  1. Lay a flooring moisture barrier when pouring a concrete floor
  2. (Optional) Install a timber sub-floor for insulation and ventilation
  3. Use anti-condensation roofing and cladding sheets
  4. Bolt shed to base and caulk base with silicone
  5. Spray insulation foam 
  6. (Optional) Fix polystyrene tiles to the roof
  7. Use a dehumidifier
Does my shed need a vapour barrier Garden Buildings Direct infographic with three tiles for different sheds and climates with icons and arrows regarding air flow, insulation, and vapour barriers
Use this infographic to decide if your wooden shed needs a vapour barrier.

Got it? Great. Now let’s have a look in detail at just how those steps will help keep your metal garden shed moisture-free.

Anti-condensation roofing sheets

If you’ve got a metal shed, condensation on the roof can be a real killer. What you need to do is find a way to absorb moisture and keep water away from your roof. This will help you prevent rust and damage to your metal shed. 

A good place to start is by constructing a roof with anti-condensation roofing sheets. These work by absorbing and retaining any moisture until it’s hot enough to evaporate. Plus, metal roof sheets form natural gullies to get rid of run-off water.

But you might still want to protect the underside of your shed’s metal roof. And we can’t blame you. To do that, we suggest using a spray cavity filler. A closed-cell polyurethane spray foam will help prevent condensation from forming.

You can also apply polystyrene tiles to help insulate your roof. To prepare to treat the underside of your metal roof:

  • Clean roof panels from the interior with methylated spirits
  • Dry them sufficiently
  • Using a spray glue (for polystyrene-metal bonding), fix tiles to the underside of your roof

Top tip: Make sure to buy a spray that isn’t affected by hot or cold. And try to work on a warm day.

Now, while this might not cure your little metal shed or condensation, it will help to insulate it. This can help ensure that there’s no contact between warm air and the metal surface of your shed.

This is especially useful as most metal garden sheds can’t be fully insulated. This is because they’re usually constructed with a rail system. So insulation batts tend not to stay in place.

But we’re not done there! Another area to work on would be your:



(Image Credit: Flickr)

Having good airflow through your metal garden shed will ensure that areas can’t get damp. It’ll also help regulate the temperature difference between your shed and outdoors.

You can always improve ventilation by opening windows or skylights if you have them. This can also help to reduce condensation between double-glazing. But this is a time-consuming and short-term approach.

You might be better off installing wall vents in your metal shed’s eaves. Or, you could even install a whirligig or an electric fan if you’re hooked up to utilities. 

To help with this, you could use a moisture trap or dehumidifier in your outdoor garden building. This will help to remove water from the air in your shed so there will be less chance of it forming as condensation.


Another tip for condensation in a metal shed is to create a tight seal. Ventilation can help with airflow at the top of your shed. Then caulking can deal with moisture at the base.

After bolting your metal shed to a concrete slab or base, make sure to caulk the inside around the base. Use silicone or a mastic sealant around the inner rails. This can ensure that groundwater doesn’t seep into your shed. From there, you’ll be ready to combat condensation on the outside of your shed.

From there, you’ll be ready to combat condensation on the outside of your shed.

How to Stop Condensation: Outside

Dripping condensation

(Image Credit: Flickr)

Trust us; we’ve seen it all over the years, from people swearing off metal sheds altogether to trying to tell us to wrap them in plastic!

One of the quick fixes we hear a lot is using paint to stop condensation in metal sheds. Not any old paint, mind. And while insulation paint is thick and will offer some protection, it’s rarely the answer.

Sure, use it in combination with the other points in this guide. But if that’s your last-ditch attempt, it’s probably too late for your shed. Instead, we like to combat condensation in metal sheds before it even happens. And you know us, we’re all about that base.

Condensation in concrete slabs

Most metal sheds will usually be installed on a concrete slab. That’s because it’s easy to bolt them down and provide stability.

The problem with this, though, is that concrete is also very porous. This means it holds moisture and can lead to dampness and condensation in your metal shed. 

But there are a couple of ways that you can save even a cheap metal shed from this fate.

  • Use a damp-proof moisture membrane when laying the foundation
  • Allow the foundation to cure for 3-7 days after concreting (longer if still damp)
  • Ensure your concrete base is only a few inches larger than your base rail

If you follow these steps, you can stop drying water creating a condensation cycle in your new metal shed. Some metal sheds also come with bungs if you’re not bolting it down. So make sure to insert these as per the instructions.

If you are bolting your shed to a (dry!) concrete base, make sure the bolts go in straight. If they’re not straight, they won’t create a level seal and can let water in. If in doubt, you can always caulk around the bolt heads too.

Location, location, location  

Make sure to place your shed somewhere higher than the surrounding ground. This will allow water to run away from your garden shed and keep your foundation dry. Once you’ve sorted the base, it’s time to think about the roof again.

The lower your metal shed’s roof pitch and the deeper the corrugations in your roof sheets, the bigger the problem. This can lead to water that doesn’t drain properly, pooling, condensation or ‘shed sweating’.

So make sure that you choose appropriate roof cladding. But also, situate your metal storage shed away from heavily planted areas. Shrubs and trees can block airflow to your vents. 

They can also cause condensation from dripping overhanging branches. And their roots will hold water around your base.

Should I Still Buy a Shed? 

The short answer is – well, yeah! While we’ve focused on metal sheds today, condensation is an issue that buildings made from other materials can also suffer from, wooden sheds being one of them.

Don’t let this guide fool you – we’re here to help solve problems and buying a metal shed solves more than it creates. They’re practical and durable. Plus, they’re lightweight and come at an attractive price point.

Just make sure you follow the steps laid out in this guide. Then you can combat condensation before it even occurs.

Let’s recap:

  • Choose appropriate roof cladding
  • Seal and insulate your shed
  • Build on an appropriate, dry base
  • Install ventilation or aerate 
  • Use a dehumidifier
  • Check tools and contents regularly for damp
  • (Optional) Fix polystyrene tiles to the roof

Then you should have no problems at all.

And if you do opt for a metal shed, you’ll overcome a lot of the maintenance problems associated with timber sheds. It’s horses for courses, though. The only reason you tend not to get condensation in timber sheds is that there are natural gaps in the joins.

So if you want an air-tight metal shed that’s durable and easy to build – make sure to seal the base and bolts! And speaking of bolts, you don’t want to miss these shed security tips

Shop Metal Sheds


The best stage at which to combat condensation is before you even build your shed. If pouring a concrete base, make sure it isn’t much wider than your shed base. Otherwise, it’ll draw excess moisture. Also, allow the concrete to set and dry sufficiently. 


Otherwise, you can use a ventilated and insulated wooden base. We also suggest adding vents to your eaves. You can even use anti-condensation roof sheets, caulking, and insulation spray. These will all help regulate temperature and keep a tight seal. Then finish off with a humidifier.

Double-glazing will help to regulate indoor vs outdoor temperature. Then, installing air vents or opening windows can help to stop moisture from forming.

Yes, unlike timber sheds. But it’s nothing to be afraid of. The positives of metal sheds (price point and durability) far outweigh a bit of condensation!


Read back over our helpful guide to stopping condensation for more info.

If you’re working in your metal shed or using it as a storage shed, chances are it’ll be warmer than outside. But this doesn’t have to be a problem. What you want to do is regulate temperature rather than simply make your shed cool.


To do this, install ventilation and use a dehumidifier at the very least.

A lot of guides will tell you to use insulation paint. But for stopping condensation, this won’t solve your problems. Plus, a shed’s rail frames make it hard (or impossible!) to install wall and roof insulation batts. 


Instead, we suggest using an insulation spray on the underside of your roof. If bolting your rail base down, make sure to caulk on the inside and around bolt holes. Then you can also affix polystyrene tiles to the underside of your roof.

Timber acts as insulation so it doesn't get as cold as quickly as thin conductive metal. Timber also has gaps between joins. These allow hot air to escape and regulate temperature.