BUILD COST CLINIC
If you’re planning on having an extension, start by reading quantity surveyor Tim Phillips’ ultimate cost guide
With ever-increasing interest rates slowing down the housing market, many homeowners are staying put and choosing to extend their homes rather than move. When working at recent Homebuilding & Renovating Shows in the ‘Ask the Expert’ centre, I’ve had more people asking “How much would an extension cost?” than any other topic.
A quantity surveyor is the best person to speak to for Early Cost Advice (ECA) and also for preparing a Bill of Quantities/ Schedule of Work for tender purposes. In this feature, we’ll look at some typical costs and the factors that influence them. I’ll also highlight some ‘hidden’ costs that are often overlooked at the budgeting stage and highlight potential savings. Ultimately, what you can build will come down to planning permission and/or Permitted Development rights, but this article aims to give an overview of costs for different styles and materials.
The cost of a householder planning application will vary according to where you are in the UK, but as a guide the cost is currently £206 in England. You may not need to pay for planning permission if your extension is small enough to meet the definition of ‘Permitted Development’ but always check the position with your local authority prior to any work. If you are able to use Permitted Development rights, it is still advisable to apply for a Lawful Development Certificate, as this proves the extension is legal. These will cost 50% of the relevant planning application fee for the extension, so £103 in England. The certificate doesn’t expire and it is a cost worth incurring as it can provide instant reassurance for a future buyer. Permitted Development rights also allow for larger rear extensions to be built without planning permission, but you will still need to obtain prior approval from your local authority at a cost of around £100.
Predictably, as with every extension project, costs can vary hugely and will generally be dictated by the size, location, design and quality of your chosen finish. With that in mind, it’s worth considering this aspect early on in the planning process.
WHAT ARE THE BASIC COSTS?
It would be sensible to budget for costs between £1,500 – £2,250/ m² of new internal space, therefore a 30m² single-storey extension could range from £45,500 – £67,500. This is obviously a wide range but it highlights the number of variables involved in this type of project. Looking at it posi
