Day rate or fixed price?
Split your work by predictability. Day rate (£240–£400 nationally) suits repairs, ground/prep work and renovations where the scope can shift — you hit a steel lintel and the plan changes. Fixed price suits extensions, loft conversions and anything well-scoped, because the customer is protected and you keep the upside if you work efficiently. London runs 15–25% above the national figure; the North sits below it — see the live number on the builder benchmark page.
Pricing an extension
An extension is your highest-value work. Roughly: labour 40–50% of cost, materials 30–40%, subcontractors 10–15%, your profit and overhead 10–15%. Build the price up from real costs rather than a gut number — the job-cost calculator is built for exactly this.
A single-storey rear extension (≈4m × 3.5m): your labour ~16 days at £320 (£5,120), brickwork sub £3,200, carpentry £2,800, windows/doors £1,200, electrics £750, plumbing £400, materials £2,100, waste £400 — about £16,000 cost. Quote ~£20,500 for the works (a ~28% markup) plus £1,200 for building-control liaison and the structural engineer, then VAT if registered. That banks roughly £5k gross for four to five weeks of work and coordination.
Charge for building control
Every extension over 15m² or affecting structure needs building-control sign-off. The homeowner pays the authority fee, but the time is yours: engineer drawings, the application, three or four inspections you wait around for, and any remedial detail. Quote your liaison time explicitly (£300–£500) rather than letting it quietly eat your margin.
Managing subbies without bleeding margin
Get a firm quote from your electrician or plumber (not "around £600"), add 10–15% to your customer price, and pay them promptly — good subs remember reliability. Don't invoice sub costs at zero margin: coordinating a £15,000 job for 2% of it isn't worth your time.
Common mistakes
- Pricing extensions like repairs — £300/day across a £25k build loses money. Fixed price with profit built in.
- Not locking material prices — quote in January, install in May, and 8% inflation is out of your pocket. Lock supplier quotes or add an escalation clause.
- Absorbing scope creep — "while you're here…" is a new quote, not a freebie.
Send every quote as a clean document with the quote builder, and track the payments in Get Paid.