1. Get the structural design right first

A £600 structural engineer review at design stage can shave £4–8k off steel costs by sizing the beam properly. Most overpriced quotes assume worst-case steel.

2. Buy the kitchen, doors and tiles yourself

Builders mark up materials 15–25%. Buy bi-folds, kitchens, bathroom suites and tiles directly — pay the builder a clear fitting cost. Saves £3–10k on a typical extension.

3. Avoid winter starts

Concrete pours, screeds and renders all suffer below 5°C and need protection or delay. A January start often becomes a March build, with you paying winter rates.

4. Fix the spec before quoting

Vague spec = padded quote. The more clearly your scope is defined (door make, tile size, socket count, paint colour) the tighter the price comes back.

5. Compare against Bangor benchmarks before signing

BuildPriceIQ shows you what a Bangor builder typically charges for the same scope. Three of four quotes usually cluster within 6–8% of that figure — the outlier is the one to negotiate or drop.