When you decide to extend your home, choosing a builder is the decision everything else hangs on. You want drawings that work, a price you can hold to, and a site you can live beside. Below are ten things to settle before the first wall comes down, and how NU Projects handles each one.
1. Who you speak to, and how often
Agree the name of your project manager and the day you will hear from them. Poor communication is what turns a small problem into a three week one. On our jobs the same project manager runs the work from the first meeting to the final walk round, and cost and programme are reviewed with you while the work is happening.
2. Who draws it and who builds it
Ask whether the people drawing the extension are the people who will build it. Ours are. Architectural designers, interior designers, a quantity surveyor and an MEP director sit in one studio in Fulham. The Building Regulations, the structure and the party wall position are settled on the drawing, not argued about on site.
3. The design starts with how you live
A rear extension can give you a wide kitchen or a long one, and the two suit different households. We ask where you eat, where the children do their homework and where the coats go. Then we draw. Extra bedrooms, a bigger kitchen and a room to work in all pull the plan in different directions.
4. Materials and workmanship
An extension is judged on its junctions: where the glazing meets the brick, where the floor meets the threshold. Get the materials scheduled before the price is fixed, so nothing is picked in a hurry. Our joinery, kitchens and fitted furniture are made by Cochrane Bespoke, our joinery partner.
5. Programme and sequence
Ask for a programme with dates on it, not a number of weeks. Steel has a lead time. Glazing is measured after the structure is up, so it arrives late by design. Building control inspections have hold points. A builder who can show you the sequence has thought about it.
6. How to check a builder’s record
Ask for two clients whose extensions finished in the last year, and telephone them. Ask what went wrong, because something always does, and ask how long the answer took. Ask to see the final account beside the original quote. We give ours out when we are asked.
7. Design and build under one contract
Design, planning, construction and the finishes sit in one contract here. You are not the person carrying a drawing from an architect to a builder and hearing two accounts of why it costs more. There is one number to call when something needs deciding.
8. Living in the house while it is built
Most extension clients stay put. Settle before you start where the temporary kitchen goes, which rooms are sealed off, what the working hours are and where the skip sits. We sheet the route in, clean down at the end of each day and keep the dust behind a screen.
9. What the price includes
Read the exclusions before the total. Ask whether the figure carries the structural engineer, party wall fees, building control, the kitchen, the flooring, the decoration and VAT. Ours is a priced document you can read line by line. Published rates for this kind of work are on our cost calculator.
10. Insulation, glazing and running cost
An extension is the cheapest chance you will get to improve the fabric of the house. Insulation, airtightness and the glazing specification are decided at design stage, because they are expensive to change later. Better fabric lowers what the finished house costs to heat.
If you want these answers for your own house, tell us about it on our contact page, or call the studio on 020 7731 6841.
Published 15 February 2026. Written by the NU Projects studio, edited since for house style and accuracy.