How to Get the Cheapest Extension Quote (Without Cutting Corners)

There's a cheap way to pay less for an extension and an expensive way to pay less. The cheap way is competition and clear information. The expensive way is cutting the things that come back to bite you. This guide is about the first one.

Why two quotes can be £15,000 apart

Builders price the same job differently for reasons that have nothing to do with quality: how busy they are, how much risk they read into your drawings, which suppliers they use, whether they actually want the work this month. A builder with a full order book quotes high because they don't mind losing it. A good builder with a gap quotes keen. You can't tell them apart without asking several.

Five steps to the lowest honest price

1. Get at least 3–4 quotes for the identical spec. This is the single biggest lever. One quote is a number; four quotes is a market.
2. Give everyone the same, detailed brief. Vague briefs get padded quotes — builders add a cushion for the unknown. The clearer your drawings and requirements, the tighter the pricing. See how to describe a job accurately.
3. Compare line by line, not just the bottom number. A cheap total can hide excluded VAT, "provisional sums", or a kitchen left out. See what line items are telling you.
4. Supply your own fittings where it helps. Buying the kitchen, tiles or doors yourself can remove a builder's margin — just agree who guarantees what.
5. Be flexible on timing. A builder who can slot you into a quiet month will often sharpen the price. See why timing changes the price.

The false economies that cost more

• Cash, no paperwork. The "discount" disappears the moment anything goes wrong and you have no contract and no insurance claim. Here's why.
• Skipping the structural engineer or Building Regs. Unsigned-off work can't be sold and may have to be redone.
• Cheapest possible foundations or roof. The parts you can't see are the parts you can't cheaply fix later.
• Taking the lowest quote blind. The lowest number sometimes means something was missed — and the "extras" arrive mid-build. The hidden cost of the cheapest quote.

Let builders compete for your job

The hard part of getting four quotes used to be chasing four builders who may or may not call back. That's exactly what BidsAndMore is for: you describe the job once, and vetted local builders come to you with their prices. You compare them in one place and choose — the competition does the price-negotiation for you.

FAQ

How many quotes should I get for an extension?

At least three, ideally four. Enough to see the spread and spot the outlier that's either too good to be true or quietly over-priced.

Should I always take the cheapest quote?

No — take the cheapest credible, like-for-like quote. If one is far below the others, find out what's different before you sign, not after.

Related: Why multiple quotes save money · How to compare bids without just picking the cheapest