Garden room costs in Devon — the real numbers

One of the more common phone calls we take goes something like this: 'I've had three quotes for a 4 m × 3 m garden room. They range from £12,000 to £34,000. What's going on?' The answer is always the same — the buildings look similar from a spec sheet but are structurally, thermally and finish-wise almost different products. Here are the numbers, what's actually included, and where the cheap end of the range cuts corners.

Three real footprints, three real prices

• — 013.6 × 2.8 m single-user office. From £15,500 including install, VAT, foundations, glazing, insulation, electrics, EPDM roof and 10-year structural warranty. Devon-installed within our standard 6-8 week lead time.
• — 024.2 × 3.2 m proper studio with meeting armchair and generous storage. From £18,500 on the same all-in basis. This is our most-built footprint across Devon.
• — 035.0 × 4.0 m substantial studio or golf simulator room. From £24,000 all-in. Suitable for a substantial home office, a full gym setup, or the base spec for a home golf simulator.

Above these base prices the meaningful cost variables are: cladding upgrades (charred cedar and thermo-ash both add £900-1,600), glazing upgrades (triple-glazed sliding doors ~ £1,200 over standard), interior specification (natural clay-plaster interior +£2,400 over painted birch-ply), lighting spec, and travel surcharge for plots more than 60 miles from our Paignton studio.

What our quote always includes

• — 01Ground-screw foundations. Not concrete slab. Half a day on site, no excavation, no soakaway redesign. £400-700 cheaper on a larger footprint than a concrete raft priced honestly.
• — 02142 mm SIP wall construction (0.20 W/m²K). Not stud-wall. This is the biggest single spec difference between our builds and the low end of the market.
• — 03172 mm SIP roof (0.16 W/m²K). Better insulated than most new-build houses.
• — 04Painted birch-ply lined interior. Not plasterboard-and-paint. Sits properly at every seam.
• — 05Aluminium doors and windows, anthracite frames as standard. Not white uPVC.
• — 06EPDM rubber roof, 25-year manufacturer warranty.
• — 07Full electrical spec (13 A ring, 4-6 sockets, LED lighting, external light, spec'd for heat pump or infrared heating).
• — 08Painted or laminate flooring.
• — 09Delivery, install, waste removal and 10-year structural warranty.

Where the cheap end of the Devon market cuts corners

A £12,000 garden room isn't the same building as a £16,000 one. Here's where the £4,000 delta usually comes from, from the quotes we've seen:

• — 01Stud-wall construction (90 mm) instead of SIP (142 mm). Real-world running-cost difference: £8-12/month more to heat.
• — 02White uPVC doors and windows instead of aluminium.
• — 03Painted plasterboard interior instead of birch ply.
• — 04Fibreglass roof instead of EPDM.
• — 05Concrete slab foundation quoted without honest excavation costs (which appear on invoice day).
• — 06'From' pricing that excludes install, delivery, foundations and VAT.

“The £12,000 quote and the £16,000 quote are for different products, not different prices. We'd rather send an honest £18,500 all-in than a £15,500 headline number with £3,500 of extras that turn up later.”

— Arden & Oak — the pricing brief

Where Devon adds cost

Most of Devon sits inside our standard delivery zone from Paignton — no travel surcharge for the South Hams, Teignbridge, Torbay, Exeter or the mid-Devon belt. Further out (North Devon, deep Cornwall, upper Somerset) a modest travel surcharge applies, which we publish transparently at the quotation stage.

AONB and conservation-area planning conversations don't cost more — we handle the paperwork within the standard quotation. Pre-application enquiries (£100-300 depending on council) are billed at cost if a plot needs one.

For town-specific pricing conversations see our dedicated pages for Kingsbridge, Totnes, Dartmouth and the wider South Devon hub. Or use the configurator to price a specific spec against your plot.