The seven cost blocks in an extension quote and where homeowners are most often caught out.
Extension pricing looks opaque because so much of it is decided before anything visible happens — ground conditions, drainage, structure and services.
This guide separates the blocks so you can read a quote properly and see which savings are real and which just defer cost to a later invoice.
Every serious extension quote can be split this way:
Two extension quotes often differ because one is a shell price and the other is a finished-room price. Neither is wrong, but they are not comparable.
Ask each contractor to mark every block above as included, excluded or provisional. A provisional sum is not a price.
Keeping the footprint simple, avoiding drainage runs, keeping bathrooms and kitchens near existing services, and choosing standard glazing sizes all reduce cost without compromising the space.
Whether you want the whole build or just the glazing package, we'll give you a straight assessment.
Some extensions fall under permitted development and some do not — it depends on size, height, boundary distances and your property's status. Always confirm with your local authority.
Far longer than a glazing project — it is a multi-stage build with inspections. We give a stage programme at quotation rather than a single headline figure.
Yes. We're often brought in for the windows, bifolds and rooflights on someone else's build.