4×3m Garden Room
The Perfect Home Office
Overview
The 4×3m garden room is the UK's most popular size — big enough for a comfortable home office or hobby room, small enough to fit most gardens without planning permission.
What it's great for
Furniture & layout
Fits a large desk, office chair, filing cabinet, small sofa or daybed, and still has room to move around. Great for L-shaped desk setups.
Planning permission
At 4×3m and a typical ridge height of 2.9m, this build falls comfortably within Permitted Development rights for most UK properties, provided it's not within 2m of a boundary.
Build timeline
3–4 weekends for the structure, 1–2 weekends for interior fit-out. Total: 5–6 weekends.
Key materials
- ✓~60 linear metres of 4×2 CLS timber for the frame
- ✓12m² of EPDM roofing membrane
- ✓14 sheets of 18mm OSB for decking/sheathing
- ✓12m² of PIR insulation board (100mm walls, 150mm roof)
- ✓25 linear metres of cladding boards
For exact quantities and a full materials list, see the Build Pack.
Estimated DIY cost
Standard spec, with electrics — materials only
Your DIY Cost Estimate
Materials only — does not include your time
Professional cost is an estimate based on typical UK contractor rates (approx. 2.75× materials). Actual quotes will vary.
Try the full calculator to adjust spec and extras.
Free build checklist
Get our material checklist and build timeline free.
Other size guides
Ready to build your garden room?
Get the complete DIY build pack — full plans, materials list, and step-by-step guides for £49.