Modular extension cost in Scotland

What the figures cover

The ranges are for a finished, heated, decorated room joined to the house: foundations on ordinary ground, the structure, roof, windows and doors, electrics, plastering and flooring, and a day of crane hire where one is needed. They assume a flat or gently sloping garden and a lorry that can get within reach.

The low end is a plain rectangle with standard glazing. The high end has wide sliding doors, roof lights and better cladding. Glass is the fastest way to move from one end to the other.

The three ways of building

Finished modules (£2,100 to £3,300 per m²) leave the factory as complete sections of room, often with the wiring and plaster done, and are lifted onto the foundations by crane. They are the quickest on site and the most demanding to deliver.

Timber-frame panels (£1,400 to £2,400 per m²) arrive flat and are stood up in a few days, then finished inside like any other build. Timber frame is the ordinary way of building houses in Scotland, so there is no shortage of people who know it.

SIPs panels (£1,300 to £2,400 per m²) sandwich rigid insulation between two boards. They give thin, very well insulated walls, which helps where the permitted depth is tight and every centimetre of floor counts.

Costs particular to Scotland

Three items sit outside the build price and work differently here.

The building warrant fee is fixed nationally by the value of the work, under fee regulations revised from 1 April 2026. Work worth up to £5,000 pays £215. A job valued between £50,001 and £60,000 pays £1,035, and one between £90,001 and £100,000 pays £1,375. Apply late, after work has started, and the fee doubles.

The value is the council's, not your builder's price. Councils use a cost-of-works table to put a figure on the job; Dundee City Council's, from January 2026, counts a single-storey extension at £1,400 per m². That is a fee yardstick, well below what the room will cost you to build. A structural engineer who is an approved certifier of design adds a fee of their own but usually speeds the council's checks.

A planning fee applies only if the extension falls outside permitted development. In a conservation area it always does. The householder fee is set nationally by the Scottish Government; check the current figure when you apply.

There is no Party Wall Act in Scotland and so no party wall surveyor to pay. If the extension touches a mutual wall or shared ground, the cost is a solicitor's time reading the title deeds.

Delivery beyond the central belt

Most of the factories that make extensions are in the central belt or in England. A site in Stirling or Fife adds little. One in Wester Ross, Orkney or the Western Isles adds haulage, ferry fares for vehicles, and nights away for the fitting crew.

Mobile cranes are hired by the day, commonly £400 to £1,500 depending on size; a contract lift for one day, supervisor and slinger included, is about £1,400. A crane that travels half a day each way is paid for the journey. Once a load is wider than 2.9 m it is classed as abnormal and needs notice to the police before it moves, which rules out wide modules on many single-track roads. That is why remote and island jobs are nearly always panels.

Keeping the price down

Keep the shape a rectangle and the width within one lorry load. Put the money into the opening between house and extension, which is the part you will notice every day. Have the kitchen or the decorating priced separately if you want to compare builders fairly. And get the warrant granted before the factory starts, because changes made after manufacture are the most expensive kind.