What timber size for a shed?
For a garden shed, 45 × 95 mm studs at 60 cm centres are usually enough; 45 × 145 mm if you insulate. Rafters and joists depend on the span, snow and roofing: the tool picks the smallest size that passes in bending and deflection.
How is the number of timber lengths worked out?
Every part (stud, plate, lintel, rafter, joist…) is listed with its length, then parts are packed into the lengths sold in store to keep waste low. The cutting plan shows what to cut from each length.
Is the structural check reliable?
It is a simplified preliminary design following Eurocode 5 (C24 timber, snow by region and altitude). It helps choose sizes but does not replace a professional design, especially in mountain or windy areas or for a habitable building.
How to use it
- Start from an example (shed, gable cabin, insulated garden office, open log store, log cabin, cabin on piles on sloping ground, hip-roof pavilion), then adjust the outside dimensions and wall height.
- Choose the roof: lean-to, gable (with ties or on a ridge beam), hip or flat, the pitch, overhangs and roofing (steel sheets, corrugated sheets, shingles, EPDM, tiles, polycarbonate).
- Describe the walls: timber frame, posts and rails or stacked logs, the sides left open, then doors and windows with their position. Lintels, king and jack studs and cripples are added automatically.
- Choose the foundations: concrete pads, ground screws or piles with a timber floor (different heights at front and back for sloping ground), a concrete slab, or an existing base.
- Set cladding, insulation and climate (snow region and altitude), and the timber lengths sold near you.
- Read the results: materials list by trade, cutting list part by part, cutting plan length by length, dimensioned plans (walls and openings, foundations, floor, roof framing), wall elevations with stud centres, 3D view (with top, front and side views) and preliminary sizing. Enter your prices for a budget, then print or export the list.
Example: 3 × 2.4 m lean-to shed
- 2.10 m walls framed in 45 × 95 at 60 cm centres, an 80 cm door at the front and a 60 × 60 window on the side, 9 mm OSB bracing.
- Lean-to roof at 12°, 30 cm front overhang and 20 cm elsewhere, steel sheets. With a ground snow load of 0.45 kN/m², roof snow is about 0.36 kN/m²: 45 × 95 rafters at 60 cm centres work for a 2.30 m span.
- On 6 concrete pads, two doubled bearers carry joists at 40 cm centres and a 22 mm OSB floor.
- The list gives the number of lengths of each size to buy, the panels, cladding boards, made-to-length steel sheets, screws and anchors.
Good practice
- Keep timber off the ground: bearers on pads or post bases, damp-proof course under sole plates, cladding at least 15–20 cm above the ground. Foundation timber is use class 4, sheltered framing class 2, cladding class 3.
- Brace the frame: without panels or diagonals, a frame racks into a parallelogram at the first gust.
- Ventilate the cladding: a 2 cm air gap behind the boards and a breather membrane make them last much longer.
- Anchor the shed: a light shed can be lifted by wind; fix plates and bearers to the foundations.
For the floor finish inside, plan it with the tile and flooring layout planner. Planning rules vary by country: check them before building.
Guide written and checked by the Otoolia team · updated 13 November 2026.