Fifteen Grand for a Shed: Inside the Garden Room Trade Cashing In on Working From Home

A Market Built in the Side Garden

Drive down almost any residential street in Surrey, Cheshire or the commuter belt outside Edinburgh and you will spot one: the composite-clad garden room, pitched roof, bi-fold doors, a heat pump humming beside it. What began as a pandemic stopgap has hardened into a genuine trade. Industry estimates put the UK garden building market at well over £400 million annually, and the contractors serving it are rarely the national housebuilders. They are sole traders, two-man bands and small groundworks firms who found that a £15,000 garden office could carry the margin of a far larger job — without the planning battles, the party wall notices or the eighteen-month payment terms.

For many builders, the appeal is obvious. A garden room is a self-contained package: no messing with the client's kitchen while they live in it, no sequencing around school runs and Christmas. Pour a pad, frame it up, clad it, wire it, done. Several firms we spoke to report completing two or three installations a month with a crew of three, quoting between £1,400 and £2,200 per square metre depending on specification. Compare that with the per-metre rates on extensions — often undercut by the very same firms — and the economics explain the boom.

The Permitted Development Grey Zone

The regulatory picture is where things get murky. Most garden rooms fall under permitted development rights, provided they sit within stated height limits, cover no more than a proportion of the garden, and are not used as self-contained living accommodation. That last point is doing a great deal of quiet work. A growing number of installations — garden annexes with shower rooms and kitchenettes — edge close to, or across, the line where an annexe becomes an extension in the eyes of a planning officer.

Contractors are navigating this with varying degrees of diligence. Some firms we spoke to obtain lawful development certificates as a matter of routine, protecting both themselves and the client. Others rely on a sales script: 'no planning needed' as a closing line, with the fine print left for the homeowner to discover when they come to sell. Conveyancers are increasingly flagging garden rooms without certification, and a handful of lenders have begun asking questions about annexes used as bedrooms. The trade has no formal accreditation body to standardise practice — a gap that several established contractors believe will eventually be filled, probably after a high-profile enforcement case.

Building Regs by Another Name

Building regulations present a subtler problem. A structure under 30 square metres with no sleeping accommodation sits outside full Building Regulations approval in most cases — but that does not mean it is exempt from the rules on electrical safety, structural integrity and, increasingly, fire performance. Part P compliance for the supply, fire spread between the room and the boundary, and the adequacy of foundations on clay soils are all areas where the market's fastest operators cut corners.

Two Winters In

The real test arrives around month eighteen. Cheap composite cladding that looked immaculate at handover begins to warp where fixings were spaced too widely. Roof membranes installed without adequate ventilation traps condensation against the inner lining. Pads poured shallow into shrinkable clay heave in a dry summer and drop in a wet one, racking door frames out of square. One Midlands contractor who moved into garden rooms after two decades of extensions described the pattern bluntly: 'We're getting the callback calls now — not from our own clients, but from people whose installer has vanished.'

That last point matters. The low barrier to entry that makes the market attractive also means it is crowded with firms who arrived on a wave of demand and will leave on the next trough. Homeowners paying £15,000 are frequently buying from a business with two years of trading history and no long-term service network behind it.

Where the Trade Goes Next

The established contractors we spoke to see two paths. The first is consolidation: positioning garden rooms as a proper construction product, with engineered foundations, certification, insurance-backed warranties and pricing to match. The second is a race to the bottom, where £9,000 installations with five-year lifespans poison the market's reputation for everyone.

For builders already in the trade, the advice from those further down the road is consistent: treat a garden room as a small building, not a product delivery. Get the ground conditions assessed, certificate the electrics, put the boundary fire strategy in writing, and price the job as though you will still be maintaining it in year ten — because if you intend to stay in this market, you will be.