To tar a shed, use wood tar on the external timber cladding, corners, exposed lower boards, and vulnerable end grain, while avoiding unsuitable interior surfaces and non-compatible modern coatings.
A shed can be tarred when the aim is a dark traditional timber finish rather than a painted garden-building look. Tar works best on bare timber, rough sawn boards, or a previous compatible tar finish. It is less suitable over glossy paint, plasticised coatings, damp algae, or manufactured panels that are not designed to absorb a surface treatment.
Start with the weather-facing walls and work in manageable areas. Brush the tar with the line of the boards and keep it from pooling in grooves, laps, and bottom edges. The lowest boards, exposed corners, door frames, window surrounds, and cut ends usually need more attention than the middle of a dry wall because they take more rain and splashback.
A shed treatment is not the same as pouring roofing tar over a roof. Roof coverings need products made for roofing systems, while craft and heritage wood tar belongs mainly on timber surfaces. Allow for smell, drying time, and possible marking before storing delicate items against newly treated walls.