How much design detail do you need before asking builders to quote?
You need enough design detail for each builder to price the same scope of work. If the drawings, finishes, structure and specification are vague, the quotes will usually contain assumptions, exclusions and hidden differences.
Early concept drawings are useful for planning and design decisions, but they are rarely enough for accurate builder pricing. Builders need to understand what is being built, how it is likely to be constructed and what level of finish is expected.
A stronger tender pack reduces the risk of comparing one detailed quote with another quote full of missing items. It also gives you a clearer basis for conversations about programme, cost, buildability and value engineering.
For residential projects, Barnes Design normally recommends developing the drawings and key specifications before asking builders to quote. This does not remove every unknown, but it does give the project a much better starting point.
Practical checklist
✅ Existing and proposed plans, elevations and sections.
✅ Structural approach and any engineer input required.
✅ Window, door, rooflight and glazing sizes.
✅ Kitchen, bathroom, utility and services assumptions.
✅ Finishes, fixtures and key material choices.
✅ A clear scope of works or tender notes.
✅ Any planning conditions that affect the build.
Next step
If you already have planning drawings, Barnes Design can help develop them into a more useful package before you speak to builders.
Ready to talk through your project?
Tell us a little about your property, plans or early ideas and we can help you understand the best next step.
Areas we work across in South London
Barnes Design is based in South West London and works with homeowners, developers and business owners across nearby South London areas. For house extensions, side return extensions and rear extensions, we regularly support clients in and around Wandsworth, Balham, Clapham, Tooting, Wimbledon, Battersea, Streatham, Putney, Fulham, Kingston upon Thames and the surrounding boroughs.
