Cost and planning advice
Plan your extension with clearer numbers.
Understand the decisions that affect construction costs, permission requirements and everyday design. Then estimate your own project budget.
Calculate my extension price →Rear extension costsCosts by size, plus the extras that affect real budgets.
Side return extension costsWhat makes a narrow side return more complex to build.
Rear extension ideasPractical layouts, light and design decisions to explore.
Extension planning permissionPermitted development, prior approval and the important exceptions.
Building regulationsHow structural safety, insulation and inspection fit together.
These guides provide general UK cost context. Planning and building control guides explain England's rules; requirements differ elsewhere in the UK. Check your own proposal with the relevant professionals and authorities.