Plastic and metal sheds have gained great popularity over recent years, they are easily assembled, extremely durable and low maintenance - offering good looks and a long life.

But, if any dampness is present in the foundation base, metal or single walled vinyl clad structures will suffer from condensation similar to any enclosed, unheated space.

This is because the interior of a shed is warmer than outside and the problem starts with moisture present in the foundations. or which may have ingressed from outside. This warm moisture will rise and form condensation when reaching the colder roof and wall panels. Droplets of water are formed, these fall onto the floor and the condensation process begins once more.

Preventing Condensation

As many of these sheds do not include a floor as standard, you must take great care in assembling them properly. Making sure that the roof and wall panels overlap accurately is vital, and you should also check that every screw or plug washer is in place. There should be zero ingress of water from any fixing.

Also, ensure you do not store damp items in the shed as this will add moisture. Instead, let wet gardening and leisure items dry out fully before storing.

Tarpaulin covering a base area

It's a fact that condensation inside a shed is a difficult thing to prevent. However, building the base correctly is essential with a damp proof membrane covering the entire base area.

Instructions on how to construct a base can be found in How To Build A Concrete Shed Base.

After building the base, make sure the concrete is completely cured before proceeding, this can take over a week or longer in damp weather, and, after the shed is secured to the base, seal the inside with silicone along the base rails to prevent water seeping into the interior.

Shed construction diagram

Solving The Problem

If the base is in place or condensation is already present, here are two suggestions to cure the problem:

The first method is designed to remove moisture from the atmosphere. Remove the shed from its base and build a timber floor on raised bearers, a few inches larger than the base. Using screws, fix the floor in place and apply a silicone seal inside the base rails. Air should now be able to flow under the floor and keep the base dry. You must also ensure that water cannot collect under the floor.

A second method insulates the shed and prevents moisture from condensing. Use meths to clean the underside of the roof panels, ensuring they are completely dry. Glue polystyrene panels to the underside of the roof using 3M Spray 77 Adhesive which is formulated to bond polystyrene to metal and is not affected by cold or heat. Coat both tiles and the roof panel, and the bond should be secure after 1-2 minutes on a warm and dry day.

Metal and plastic sheds have many advantages over traditional materials and, with proper preparation and careful construction, there is no reason why condensation should become a problem that prevents you from buying such fantastic products.