If you are weighing up an extension, the honest answer is that costs vary widely depending on size, specification and your site. As a joinery and building firm working across Kilwinning and North Ayrshire, we see the same questions from homeowners every week, so here is a straightforward guide to what you can realistically expect to pay in Scotland right now.
Most single storey extensions in Scotland currently come in somewhere between £1,800 and £2,800 per square metre for the build itself. A modest 20 square metre kitchen extension therefore tends to land in the £36,000 to £56,000 bracket before fees and fittings, while a larger 35 square metre build can pass £70,000 once you add a decent kitchen.
Two storey extensions are better value per square metre because the roof and foundations are shared across both floors. Expect roughly £1,600 to £2,400 per square metre, so a 50 square metre two storey addition might cost £80,000 to £120,000 depending on finish. These are guide figures, not quotes; ground conditions, access and specification all shift the number, which is why a proper site visit matters before anyone gives you a firm price.
A build quote normally covers foundations, walls, roof, windows and doors, first and second fix joinery, plastering, and basic electrics and plumbing. Where budgets go wrong is the items that sit outside the headline figure, so it pays to ask any builder exactly what their price includes before you compare quotes.
Unlike England, almost every extension in Scotland needs a building warrant from your local council before work starts. In North Ayrshire that means submitting drawings and structural calculations to the council's building standards team and waiting for approval, which can take six to twelve weeks depending on workload.
Planning permission is a separate matter. Many single storey rear extensions fall under permitted development and do not need a planning application, but the warrant is still required. A good builder or designer will tell you early which consents apply to your project, and the timescales are worth building into your plans so you are not paying for scaffolding while paperwork sits in a queue.
Two extensions of identical size can differ in cost by twenty or thirty per cent. Drainage runs, moving a boiler, steel beams for open plan layouts, and poor ground needing deeper foundations all add cost that is invisible until someone investigates properly. On older Ayrshire properties, tying new work into stone walls takes more care and labour than joining onto modern brick.
Specification is the other big lever. Timber windows, bifold doors, underfloor heating and high end kitchens can add £10,000 or more compared with sensible mid range choices. If budget is tight, spend on the structure and insulation, which are difficult to upgrade later, and keep finishes simple, as they are easy to improve in future years.
Ask for itemised written quotes from two or three local firms rather than a single figure on a text message. An itemised quote lets you see what is included, compare like with like, and spot anything missing. Be wary of a price far below the others, as it usually means something has been left out.
A staged payment schedule tied to completed work is normal and protects both sides. You should never be asked for a large sum up front beyond a reasonable deposit for materials. Local references matter too; a firm that has worked in your area for years has reputation to protect and knows the local council's building standards process well.
Not always. Many single storey rear extensions fall within permitted development rights, but you will almost certainly need a building warrant from the council regardless. Your designer or builder can confirm what applies to your property before you spend anything significant.
A straightforward single storey extension typically takes ten to fourteen weeks on site, with two storey projects running four to six months. Add two to three months beforehand for design, the building warrant and any planning consent.
Once you factor in Land and Buildings Transaction Tax, legal fees and removal costs, extending often works out better value if you like your location and the house suits extension. It depends on how much extra space you need and what your street's ceiling price will support.
Tell us about the build or the joinery and we will come out and give you a free quote.
Tell us about your project and we will get you a free quote.