Compare Extension Quotes: How Many Should I Get in 2026?
Three matched written quotes is the UK sweet spot. Two is not enough to spot outliers, four or more adds little value once you have already seen the range and burns builder goodwill. The trick is making the three quotes comparable — send the same one-page scope and reject any quote that is more than 25% below the others as scope-missing, not a bargain.
Why three quotes is the sweet spot
One quote leaves you blind to the going rate. Two creates a binary you cannot interpret — are they both high, both low, or simply spread? Three gives you a triangle: an outlier, a middle and a benchmark. Four or more risks burning builder goodwill (busy good builders will not quote against five competitors) and slows decisions by weeks. For most UK extensions in 2026, three written quotes is the right number.
Why a matched scope matters more than the number of quotes
Three quotes against three different scopes is worse than one quote against a tight scope. Before you invite quotes, write a one-page brief covering: total m² and footprint, single or double storey, structural opening size, foundation depth, roof type, glazing spec, flooring spec, kitchen/bathroom inclusion, finish quality, and any client-supplied items.
What "variation" should you expect?
For UK extensions in 2026 expect a spread of 10–20% between three reasonable quotes. A spread above 25% almost always means one quote has excluded something (groundworks, structural calcs, finishes). Investigate before celebrating the bargain.
What to do with the three quotes once you have them
1. Identify the outlier
If one quote is more than 25% below or above the others, ask the builder to walk you through the exclusions before discounting it.
2. Compare on scope, not price
Pin the quotes side by side and tick off each line of your scope. Missing lines are red flags.
3. Reference-check the leader
Ask for two recent extension references and arrange to visit one finished job.
4. Confirm payment schedule
Stage payments tied to milestones — never a large upfront deposit.
FAQs
Related guides
Get 3 Free Quotes — Vetted UK Extension Builders
BestBuilders matches you with up to 3 vetted UK extension builders. Compare quotes — no cost, no obligation.