Damp proofing your shed

A damp shed, workshop or garden building is not a good place to be. The damp can cause mold, mildew or fungus to grow and moisture can cause warping or cracking of the structure.

Moisture can get to your building from many directions, from below it can seep up through the concrete in the form of rising damp. From above rain and snow can get through leaks and faults in the roof. And from the sides from driving rain, dripping or splashing. A shed can also be affected by humidity caused by the weather or people so the moisture might be generated on the inside.

Photo by Andy from Workshopshed


There are several features you can include in your shed design that will help. Firstly looking at the concrete slab base, concrete is not typically waterproof so an underslab vapor barrier can stop rising damp. Ensure that the sheets are overlapped and glued together. You can also add underfloor insulation at the same time. Alternatively, a liquid slip-resistant concrete sealer can be applied on the top to both seals and protect the floor.

For green building projects or if you are unable to install a concrete slab you can elevate your base so that air can flow below. Traditional wooden shakes are one way to produce a waterproof roof or modern materials such as mineral impregnated felt sheet or a butyl rubber membrane can be used.

Glad to see a few people are interested in the shingle making project. Here is the first video in a series. This one explains the material and what I am aiming to do with the logs. A bit of time spent videoing today – but still made progress with the logs. 2 logs converted from round logs to finished shingles today.

Posted by John Coupe on Wednesday, 16 May 2018

When designing the roof, include overhangs to allow the water to run off rather than down the side of the building. Guttering can also take the water away. Drainage around the shed is also recommended so you don’t get flooded by ground water.

Vapor barriers can also be designed into walls. Note that these are installed on the warm side of any insulation to avoid condensation. Use tape to seal the joints. It is best to follow the manufactures installation guides when installing a barrier system as those can provide tips for fitting around doors, windows and joints.


When building your shed look for high-quality building materials. Just because materials are salvaged or reclaimed does not mean you need to have holes in your roof. Equally new wood can be of variable quality. So choose enough for waste when planning your build.

Overlap planks and joints to stop water ingress or leaks. A flexible sealant is also best as wooden buildings will move and change shape through the seasons.

For a small build, a DIY approach is good, but for larger building projects you can get a total moisture control package from industry experts such as W.R Meadows which would ensure for a quality construction project.

About the Author

Emily Roberts is a keen writer with a passion for everything DIY, interior and home design related.

One thought on “Damp proofing your shed

  1. Insulation Direct says:

    Thanks for sharing the valuable information. Underfloor insulation can also help regulate the shed temperature and protect from damp.

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