Calculating the cost of your extension.
Extensions can vary greatly in shape, size and therefore budget. Whether you are planning a simple pitched roof extension or a larger project, costs can start to add up very quickly.
It's not just the size of your extension. Where you live can also dictate price. In some areas the qualified tradespeople you need could cost less than £100 a day or more than twice this. Knowing the day rate of local tradespeople can be useful research prior to securing extension quotes.
Below are different ways to create costings for your conversion based on the permitted development of 3 to 4 metres in the UK. In England until 30th May 2016 if you secure approval from your Local Authority you may be extend your home by twice this length.
Estimates by size
Most builders can give you an idea of what your extension will cost per square foot or metre. For example, a basic single storey extension would typically cost around £1,000 per square metre but it could be up to £1,600 or more for a premium two storey extension.
So a 3 x 5 metre extension would cost £15,000 and up to £50,000 for a two storey, more premium extension. These costs are just to create a room, they would not typically include the cost of a kitchen or bathroom.
This average cost should cover design through to decorating of standard rooms, but it is worth having a 10-15% contingency to cover unexpected costs.