Prefab extensions in Scotland

Building warrants

In England you can start an extension and have it inspected as you go. In Scotland you cannot. You apply to the council, as verifier, for a building warrant, with drawings and a specification showing the work meets the Scottish building standards. Starting before it is granted is an offence.

For a prefab build, the panel maker's drawings, structural calculations and insulation figures go in with the application. If a certified structural engineer signs the design under the approved certifier scheme, the council does not recheck the structure, which can shorten the wait.

The warrant fee rises with the value of the work. When the job is finished, a completion certificate goes to the council, which must accept it before the extension is occupied. Keep both documents with the title deeds.

Permitted development in Scotland

A single-storey ground-floor extension falls under class 1A. Among the conditions: it must not be on a front elevation or one facing a road, it can be no higher than 4 m, and where any part comes within 1 m of a boundary it may reach no more than 3 m behind a terraced house or 4 m behind any other kind. The footprint of the extended house cannot be more than double the original, and there is a cap on how much of the garden can end up built on (Circular 1/2024).

Anything taller than a single storey comes under class 1B. Every part must be at least 10 m from the boundary, so in practice most two-storey extensions in Scotland need a planning application. Conservation areas and flats are excluded from both classes.

If you are unsure, the council can issue a certificate of lawfulness. The Scottish Government's guide to adding an extension explains the process.

Why panels suit Scottish sites

Timber frame is the default here, so finding a firm to erect panels is rarely a problem, even well outside the central belt. Closed panels also shorten the time a half-built room stands open to the weather, which counts for a lot on the west coast.

Finished modules are harder away from the cities. A crane may have to travel a long way, single-track roads limit the load, and a ferry crossing adds cost and a booking to keep. Panels travel flat on an ordinary lorry.

Ask how the cladding and its fixings have been chosen for your exposure. A detail that lasts in Perth may not last in Stornoway.

Neighbours and boundaries

Scotland has no equivalent of the Party Wall etc. Act 1996, which stops at the border. Here, rights over a mutual wall or a shared boundary come from your title deeds and the common law. Check the deeds before designing foundations close to the line, and speak to the neighbour early. The council may also notify neighbours of a planning application.