Photo: Anna Shvets

Why is my plastic shed roof wet inside?

Condensation is what happens when water vapour reaches a temperature low enough to turn back into a liquid. This is called the dew point and typically happens in the colder months when warm moisture in your shed rises to meet with the cold metal or plastic roof.

roofingmegastore.co.uk - 6 Proven Ways to Stop Shed Roof Condensation | Roofing Megastore

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Rot and mould have been common problems for typical wooden sheds for decades. So much so that now many opt for plastic or metal instead. Whilst lesser in appearance, they more than make up for it with limited maintenance requirements, increased durability and in some cases greater life expectancies, with some guaranteed for 25 years. Though despite all of this, water still finds a way to make our lives difficult, with metal and plastic roofs at risk of suffering from condensation which can damage not only the structure of the shed itself, but everything contained within. You may have started to notice this in your own shed, but not to worry, below we’ve listed just some of the solutions you can employ to keep it safe and dry.

Why Does My Shed Roof Have Condensation?

Let’s start with a bit of science. Condensation is what happens when water vapour reaches a temperature low enough to turn back into a liquid. This is called the dew point and typically happens in the colder months when warm moisture in your shed rises to meet with the cold metal or plastic roof. Typically, this moisture will come about from a combination of a damp base and a lack of ventilation, and it doesn’t take much for it to become a problem. Once the droplets start to form, a cycle begins with water falling onto your floor only to be heated to vapour which will rise for the process to start again. Breaking this cycle is key to stopping condensation.

How Can You Stop Shed Roof Condensation?

As mentioned, condensation can only come about when there is moisture to be heated into vapour and when that vapour has nowhere else to go but up to your roof. Every solution you employ should serve to mitigate these two factors. To stop moisture from forming and improve airflow.

Membranes, Floors & Cladding

When originally installed it’s likely that your shed, especially if it is made of metal, was done so over the top of a concrete base. This is done to ensure a level ground on which to build and for added stability. However, concrete is also a porous material. It holds in moisture very well, and so can actually be a root cause for the condensation cycle you may find yourself stuck in. A simple first step is to protect your shed from this moisture. If you haven’t started installing just yet, it would be well worth getting yourself a damp-proof moisture membrane to install when laying your foundation. These plastic sheets can be inserted into the base around 2 inches higher than the surrounding area and serve to prevent water, both in the soil and concrete, from ingressing further into your shed. No water means no moisture which means a significantly reduced risk of condensation. For a fresh install, you’ll also want to wait 3-7 days for the concrete to dry before continuing your build. Similarly, and perhaps more ideal if you’ve already installed your shed, you could fit a fully functional floor alongside some wall cladding. There are many options available for easy to install, interlocking foam floors which also boasts great water resistance. As for cladding, it works on a shed much in the same way as a home - offering some added insulation to help regulate the internal temperature.

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Caulk the Base

If you’ve already bolted your shed onto its base, another solution is to caulk the inside using a silicone or mastic sealant. Piping this around the inner rails will help prevent water from getting in, though bear in mind an exposed concrete floor can still get damp and absorb moisture from the surrounding soil.

Raise the Shed Off the Ground

If your shed doesn’t have a concrete base, or if none of the above solutions work for you, you may want to consider raising the shed off the ground entirely using a timber frame. This will not only provide a difficult to bridge gap for the moisture on the ground but will also allow air to flow under the building to help keep it dry. When doing this make sure that the frame is a few inches bigger than the base, and that it has been fully secured with screws and a suitable silicone seal inside the base rail. This will provide added protection against harsh weather and help prevent water from pooling. Note: When building, take care to ensure there are no obvious entry points for water to collect underneath the floor.

Move Your Shed

The last solution when it comes to protecting your floor is a simple one. Water will always drain downhill, so it is easy to avoid the bulk of it just by moving your shed to a higher position. Plants, trees, and other shrubbery can also hold water, not to mention block any vents that you may have fitted so it is also worth avoiding these as well.

Improve Ventilation

Speaking of vents, after you’ve sorted the floor of your shed, they will be next on your to-do list. A good flow of air helps prevent condensation several ways. It limits stagnant, cool air from changing back into a liquid, reduces humidity and will also dry any moisture that does form far more quickly than it would naturally. Opening a door or window may do the trick on a smaller shed, but for more substantial builds, vents in your eaves are the way to go. You may even want to consider a whirligig or an electric fan alongside these for sheds larger than 12 x 6. These also come with the added benefit of subjecting your interior surfaces to hot air, raising their temperature away from the dew point.

Anti-Condensation Roof Sheets & Paints

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With steps taken to limit moisture from getting in below and to improve airflow, the last thing to look at is the roof itself. Namely, building it (or replacing it) with Anti-Condensation Roof Sheets. As the name suggests these are specially designed to absorb and retain moisture so that it can be evaporated when the temperature rises, as opposed to forming droplets. These are not the only anti-condensation products on the market however, you’ll also find numerous paints and spray foams all designed to protect the underside of your shed roof in the same way. An alternative here is also to simply insulate your roof so that it stays warm enough to never reach the dew point, although this may be a slightly more expensive option. Note: Anti-condensation sheets should be used alongside appropriate ventilation. If your ventilation is not sufficient or the pitch of your roof is too low (lower than 10-degrees) then the sheets may end up holding too much water and drip. We recommend referring to the manufacturers' specs before choosing to install any specific sheeting, sprays, or paints.

In Summary

You can stop condensation from forming on your roof by both preventing moisture from getting into your shed and controlling the temperate so that any that cool air cannot turn back into its liquid form. If your shed is not raised, make sure it is sealed and water-resistant, install vents to improve the airflow and invest in anti-condensation sheets and sprays.

Any Questions?

If you have any other questions about shed roof condensation or are currently looking to start up your next project and need a helping hand, our award-winning team is here for you. Simply call us on 01295 565 565 or chat to us online.

roofingmegastore.co.uk - 6 Proven Ways to Stop Shed Roof Condensation | Roofing Megastore

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