Most people start planning an extension with one question: what will this actually cost? The honest answer depends on size, spec and what is under the ground, but you can get a realistic figure before anyone sets foot on site. Here is how the numbers usually break down for homes in and around Kilwinning.
For a standard single storey extension built in block and render or brick with a pitched or flat roof, most local projects work out at somewhere around £2,000 to £3,000 per square metre for a finished shell with basic internal fit out. A higher spec with bifold doors, roof lanterns and underfloor heating can push that well beyond £3,000.
In practice, that means a small rear sun room or utility of around 12 to 15 square metres often lands in the £30,000 to £50,000 bracket, while a 20 to 25 square metre kitchen and family room extension is more commonly £50,000 to £85,000 once the kitchen itself is included. These are guide figures, not quotes. Every house is different, and a builder who prices without visiting is guessing.
Before any digging starts, you will need drawings and, in almost every case, a building warrant from North Ayrshire Council. Warrant fees are scaled to the value of the work, so on a typical extension expect to pay several hundred pounds. If your extension falls outside permitted development, a householder planning application adds a further fee, currently around £600.
Plan for professional fees too. An architectural technician or architect will typically charge £1,500 to £4,000 for warrant drawings, and a structural engineer is often needed for steel beams where you are knocking through an external wall, usually £500 to £1,500.
Ground conditions matter more here than many people expect. Parts of North Ayrshire have a history of coal mining, and a mining report or deeper foundations can add cost if your plot is affected. Soft or made up ground on some newer estates can also mean extra depth on foundations, which is one of the few costs that is genuinely hard to predict until the ground is opened.
The west coast weather is another factor. Driving rain and wind make good detailing on roofs, flashings and render essential, and it is worth paying for quality materials rather than saving a few hundred pounds now and dealing with damp later. Access also counts: a semi in Pennyburn with a clear side path is far easier to build on than a mid terrace where every barrow of material has to come through the house.
The biggest overspends usually come from changing the design partway through or leaving key choices like doors, flooring and kitchen units undecided until the build is underway. Firm decisions early mean a firm price.
Always set aside a contingency of 10 to 15 percent for things nobody can see in advance, such as old drains in the way or rotten timbers where the new roof meets the old. Ask any builder to itemise their quote so you can compare like for like, and check whether VAT is included, as that alone can make a 20 percent difference between two quotes that look similar.
Many modest rear extensions fall under permitted development, but limits on depth, height and how much of the garden is covered all apply. You will almost always still need a building warrant, so check with North Ayrshire Council or your designer before committing.
Once the warrant is approved, most single storey extensions take around 8 to 14 weeks on site, depending on size, weather and how quickly finishes like kitchens are delivered. Getting drawings and a warrant in place can take a few months before that, so start early.
For many local families, extending works out cheaper once you factor in solicitor fees, Land and Buildings Transaction Tax and removal costs. It also lets you stay in a street and school catchment you already like, though it only makes sense if the extension adds value in line with what you spend.
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.