If you’ve started researching house extension costs online, you’ve probably already encountered a frustrating range of figures. One site tells you £1,500 per square metre. Another says £3,000. An Instagram post from someone who “just finished their extension” quotes something else entirely.

The truth is that all of those figures can be correct - and none of them is particularly useful on its own. The cost of a house extension depends on so many variables that headline numbers without context are almost meaningless. This guide is an attempt to give you something more honest: a realistic picture of what drives costs, what you should actually budget for, and how to think about your project before you’ve spoken to anyone.

Are you dreaming of a contemporary grand design but worried you won’t get planning permission? Many people think that bold, modern architecture is a risk when it comes to gaining approval – but don’t give up on your dream house too early. Not everything has to be ‘in-keeping’ to satisfy the planners. With the right strategy, a well-designed contemporary home can succeed even on difficult sites. This guide walks you through every stage of the process.