Shed building (or upgrading) is one of those projects where which timber you choose really does mean the difference between “like new in ten years” and “soggy, sagging mess by next winter”. There are three areas in which the best timber for sheds applies; the frame, floor and roof. These are driven by different requirements, so it is worth selecting the materials warranted for each job.
Framing for a shed
Most sheds use structural softwood for the frame (studs, rails and roof joists), as it is affordable, workable timber that provides adequate strength for typical garden buildings. Where possible you should use graded timber, usually sold as C16 or C24. For most sheet materials there are two standard grades of timber. C16 is the most common and suitable for the majority of D.I.Y. sheds; C24 is stronger, straighter (more costly) and useful for longer spans or where a heavier roof covering is to be used.
Pressure-treated timber is the best choice if parts of your frame are likely to get wet (just a few inches into ground). Treatment will prevent your cladding rotting and most ground contact so should reduce the likelihood of insect attack, however it does not make timber waterproof.
Flooring for a shed – water resistance and rigidity
Floors in sheds cop a hard time of it too: human foot traffic, tools stored inside or floors where lawnmowers are stored leak damp upwards. Tongue-and-groove (T&G) floorboards or exterior-grade plywood are probably the best options. For Timber Merchants Winchester, visit https://www.timbco.co.uk/timber-merchants-winchester
T&G planks provide an interlocking surface which will minimise any variance and spaces.
Exterior plywood, see types often labelled WBP/exterior provides good stiffness and spreads loads well.
If you are storing heavy items, avoid typical indoor plywood or thin sheets also as they have the tendency to bend and delaminate over time. No matter what you opt for, the flooring system beneath it (bearers and joist) will need to be treated as such that they aren’t touching the ground by placing on a proper base.
Choose Roof Sheets: Light, Stable and Weather-Treated
Shed roofs are where your deck is the ceiling, similar to a flat roof but with just enough pitch that it sheds water efficiently and you can apply any covering material like felt or shingles if need be.
The most common options are:
OSB3: A popular shed-roof board. It is strong, economical and can be used in humid locations if covered correctly.
Premium-grade exterior plywood: a little pricier, but moisture-resistant and strong.
Roofs: They’ll get ruined fast if moisture gets in… but don’t put up MDF (or interior-grade boards) as they swell quickly.
The takeaway
If you want a shed that will last, specify graded softwood for the frame; T&G boards or exterior plywood for the floor and OSB3 (or more expensive) quality exterior plywood on the roof. Combine these materials with the right treatment, airflow and a flat solid base and you will have dry shed that remains in shape for many years to come.