How to Stop Condensation in a Metal Shed

Metal sheds are practical and durable solutions for storing things in your backyard. They are also cheap and fairly easy to assemble, but they come with one fairly major caveat: condensation. This leaves many metal shed owners wondering how to stop condensation in metal sheds.

The best way to stop condensation in a metal shed is to apply closed-cell polyurethane spray foam. The spray foam will fill every cavity and gap on your metal shed walls, ceiling, and under your floor. Once sealed, moist air will not be able to contact shed surfaces, allowing it to escape instead of condensing on walls and ceilings. Couple the spray foam with a dehumidifier, and you will solve your condensation problem.

Condensation forms and results in some serious interior moisture. Whether it’s your walls or your metal roof sweating, the moisture can saturate any items you’ve stored in your shed. In this article, we’ll take a look at how to stop condensation in a metal shed so you can store your stuff without worrying about it getting water damage.

How to stop condensation in metal shed

How Does Condensation Happen in a Metal Shed?

At night, when the outside air cools off, the interior of the shed is still warm. The warm, moist air rises in the shed and comes in contact with the cooling roof surface. Warm air contacting cool surfaces will result in condensation on the underside of the shed roof.

Since warm air rises and is full of moisture, the question then becomes, how does all that warm, moist air get into my shed in the first place? If you have a concrete pad for a shed base, or just a gravel or dirt floor, then you have your answer.

Moisture rises out of concrete and other uninsulated surfaces. Without a vapor barrier between those surfaces and the shed interior, you are going to have consistent moisture in your shed.

If you are wondering how moisture rises, just know that water vapor is lighter than the gases it takes the place of, which leads to rising moist air. Thus, if you go into your metal shed early on a summer morning, you will have condensation.

How to Stop Condensation in a Metal Shed

Some research will tell you that there are many ways to fix metal shed condensation, from wrapping your shed in plastic to applying special paint on the exterior surfaces. We are going to take a look at a simple, cheap, and effective solution that will stop your shed from sweating.

Below we’ll go over the ways on how to accomplish both simply and cheaply.

1. Prevent Moisture in Shed

Moisture can infiltrate your shed in a variety of ways, so you’ve got to be diligent about where you place your shed to keep your shed waterproof. Placing your shed in an area that is higher than the surrounding ground, where water will run away from your shed, is the first step in ensuring you have a metal shed foundation that is not prone to holding water.

If the high ground isn’t an option, you can always use a weeping tile, a trench, and gravel to divert water away from your shed base. Also, make sure there are no shrubs or trees adjacent to your shed. These have roots that hold water and will keep moisture near the base of your shed.

In addition to placing your metal shed foundation on higher ground, you’ll want to include a vapor barrier in your shed foundation. Whether you have concrete or gravel, you’ll want to put a vapor barrier between the earth and gravel or concrete. Why? You want to prevent moisture from seeping up through your shed floor into the shed interior.

If you opt to pour a concrete floor, make sure you ventilate like crazy until it cures. New concrete has a huge moisture content, so you’ll want to ensure you have an exhaust fan and venting to the outside afterward. Ensure your foundation isn’t wider than the actual base dimensions of your metal shed. If it extends too far away from the shed, it will conduct moisture toward your shed and under it.

An airtight seal is another way to keep the interior of your metal shed dry. Caulking around the base and other rails where air seepage can occur will mitigate air intrusion.

If all these options don’t seem to help stop your condensation issue, then perhaps you are storing moist materials in your shed. Snowblowers or lawn tractors will acquire tons of moisture during use – wash or brush them down afterward before storing them. Firewood that hasn’t dried out also has tons of moisture – build a proper woodshed with ventilation instead of using an enclosed metal shed for firewood storage.

2. Ensure Proper Ventilation

You need ventilation in your shed – period. However, too much ventilation will draw in moisture, while not enough won’t allow enough moisture to be expelled. Ensure you have the right amount of ventilation per square footage of your shed.

There are tons of options for ventilation, but they can be grouped into passive, semi-mechanical, and mechanical. Most have some type of passive gable venting or soffit venting under the eaves. However, this isn’t always effective. Installing a semi-mechanical turbine on your shed roof will draw out more of the moist air.

Adding a mechanical option, such as a wall or roof exhaust fan – both can run off extension cords – will be more effective at removing moist air. Just make sure you’ve weatherproofed the interior of your shed first, so you don’t have to run the exhaust fan all day and night.

3. Add Insulation

The best way to control condensation in your shed, after you’ve followed the above steps, is to insulate your entire shed. Applying closed-cell polyurethane spray foam will cure your condensation problem in your metal shed.

Using a spray foam kit from your local home reno store, you can cover the entire interior surface in spray foam to ensure there is no air or moisture seepage into your shed. This is the most effective way as insulation batts and foam boards will still have gaps once installed, which caulk or fix-a-crack will not always fix.

The foam will ensure there is no contact between the warm, moist air in your shed and the roof or wall metal surfaces. This will allow your shed ventilation to do its job and expel that air to maintain a dry, cool environment. During the day the insulation will ensure your metal shed interior is thermally protected.

Since metal sheds are typically constructed with metal rail systems, there is not a stable enough interior framing system to fit foam boards or fiberglass/mineral wool batts. This makes spray foam ideal for a metal shed interiors. You can simply spray right over the metal rails without having to create an interior frame to fit insulation.

If you have a wood base for your metal shed, think about insulating beneath the wood floor. A wood floor is extremely porous, and if you have poor drainage around your shed, moisture will come up through the cracks and cause tons of condensation in your shed. Lifting your base and applying spray foam underneath will stop moisture from getting into the shed via the metal shed base.

While spray foam is not the cheapest option, it is still a cost-effective option when doing a shed. The small surface areas of metal sheds mean that once complete, you’ll never need to do any more condensation-proofing to your metal shed again.

4. Use a Dehumidifier

metal roof condensationA dehumidifier takes moist air in a space and a fan draws it in over a refrigerated coil. The air is then expelled back through the dehumidifier devoid of moisture. This will dry the interior of your metal shed space and keep warm moist air from rising and condensing on the ceiling.

Dehumidifiers these days are still not cheap, but new models with energy star certification work efficiently. Many have outlets that allow you to attach a garden hose so you don’t have to periodically empty the reservoir, making continuous operation simple.

On its own, a dehumidifier will not reduce condensation in your metal shed. It should be coupled with insulation and other waterproofing measures to work effectively.

An insulated metal shed will result in a greater temperature differential between exterior and interior, resulting in a reduced ability for the interior air to hold moisture. Use a dehumidifier to reduce the chance of excess moisture building on interior shed surfaces.

Paint to Stop Condensation on Metal Roof?

Anti-condensation paint is a popular option amongst those who want to get rid of the “damp” feeling

in their basements. It is important to note that this paint will not stop significant condensation problems.

Anti-condensation paint is an elastomeric coating. The term “elastomeric” basically means a naturally occurring compound with elastic properties. So, although the anti-condensation is termed “paint”, it is closer to an elastic membrane you might use with foundation or house wrap.

At nearly ten times the thickness of regular house paint, anti-condensation paint does have insulating qualities. Most of these types of paints require a minimum of two coatings, giving you a minimum thickness of what would be equal to 20 coats of paint.

So, will it work? Yes and no. For mild condensation issues, then it will likely work. A mild condensation problem would be rubbing your finger against your metal shed ceiling in the morning and seeing a slight damp streak.

Anti-condensation paint will not help metal sheds that drip condensation. For these sheds, you’ll need to take care of the actual moisture source before using anti-condensation paint.


The best way to stop condensation in your shed is to properly situate your shed before you install it. Coupled with providing a vapor barrier beneath your shed foundation and installing adequate drainage, you should be able to avoid condensation before it starts.

If you’ve already installed your shed, then seal it up and insulate. We suggested spray foam as the best way to protect your metal shed from condensation. If you are on a budget, then foam boards or batts can work too. Just make sure you seal all the gaps between the batts or foam boards.

Lastly, be careful relying on products that tout themselves as fixing your condensation problems for good. You’ll need to rely on proper insulation, ventilation, and remove moisture sources from your metal shed interior to kick your condensation problems for good.

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