Extension Quote Example: What Should a Builder's Quote Include?

The short answer

A builder's quote for an extension should let you check the price rather than take it on trust. That means measured lines with a quantity, a unit and a rate, grouped into sections that add up to the tender sum, with the VAT position stated — and then, in writing: what is included, what is excluded and why, what has been assumed, the payment stages, how long the price holds, and how changes will be valued.

If a quote does not have those things, it is an estimate wearing a quote's clothes. For the difference between the two and the levels of detail that produce a reliable number, see How Much Will My Extension Cost?.

---

What a real priced quote looks like

Our estimating platform QuoteWise publishes a worked extension quote example built from a real, anonymised single-storey rear extension in Surrey. It is worth looking at rather than reading about, because the shape is the point: work grouped into plain-English sections, each line carrying a quantity, a unit and a rate, and section subtotals that add up to the tender sum.

The shape of a single line is what to look at. A quote that gives you one word and one number — "foundations", then a lump sum — tells you nothing you can check. One measured line in the published specimen reads:

Excavate trench foundations — 34.128 m³

The adjacent workbook columns show the labour rate per cubic metre and calculate the line total. Written that way, you can check whether the measured volume matches your drawings and whether the rate is in line with what other builders quoted for the same work. That is the difference between comparing quotes and guessing between them — and it is why we have linked the real document rather than described it.

If you are at the comparing-builders stage, the same site offers a free builder's quote template in Excel and Word so every builder prices the same scope, and a bill of quantities example for larger projects. Both are free, with no sign-up.

---

The nine things to look for

1. Both parties, and the property

Your name, the builder's company name and number, and the address the works relate to. A quote that does not name the parties is not doing contractual work.

2. A reference and a date

So that when the scope changes — and it usually does — there is no argument about which version you both agreed.

3. A description of the works

One or two paragraphs in plain English, before any numbers. You should be able to read that alone and recognise your own project.

4. Measured, sectioned lines

Every line with a quantity, a unit and a rate, grouped so the sections subtotal to the tender sum. This is the part that makes the rest checkable.

5. The tender sum, with VAT stated

One headline figure, and the VAT position explicit. If a builder is not VAT registered, that should be stated rather than left for you to assume.

6. What is included

Labour, plant, materials, supervision, waste removal, the final clean. The things most homeowners assume are in unless told otherwise — so they should be written down.

7. What is excluded, and why

Planning and Building Regulations fees, party wall awards, structural engineer's fees, asbestos, unforeseen ground conditions. Each should read as "no allowance" with a reason. A £0 line reads as included at no cost, which is the opposite of what the builder meant.

8. What has been assumed

Foundation depth, ground conditions, access for deliveries and plant, that existing drainage and electrics are sound, who supplies the kitchen. Assumptions are what let a quote go out before every question is answered — they are a sign of a careful builder, not a cagey one, as long as they are visible.

9. Payment stages, validity and variations

When money is due and against what, how long the price holds, and how an instructed change will be valued. Agree variations in writing before the work happens, not at the final account.

---

Provisional sums: the line that catches people out

A provisional sum is an allowance for work the builder knows is coming but cannot yet measure — a drainage connection whose route is unknown, a steel beam the engineer has not yet sized, a kitchen you have not chosen.

Used properly it is honest: shown as its own visible line, labelled provisional, with a note of what it covers and what it assumes, and adjusted against the actual measured work once it is known. Used badly it is where budget shock comes from — a provisional sum buried inside a rate looks like a fixed price and behaves like an open one.

The question to ask is simple: which of these lines are provisional, and what happens to my total when they are settled?

---

Red flags

• One lump sum, no breakdown. Nothing to compare, nothing to check, nothing to price a change against.
• Exclusions written as £0. A zero reads as included at no cost.
• Provisional sums with no explanation — or none at all on a job with obvious unknowns.
• No VAT position, no validity period, no variations clause.
• A total well below the others with no stated reason. The cheapest quote is often the one with the most work missing from it.

---

Getting to a quote you can actually compare

Most of the trouble with builder quotes starts earlier than the quote. Three builders given a planning drawing and a phone call will price three different jobs, and no amount of reading their quotes carefully will fix that — the specification is what makes the numbers comparable in the first place.

That is the order our Seven Step Process and home extension service are built around: design, approvals, full specification, then quotes. Pricing locally? See our guidance for house extensions in Oxted and renovation work around Godstone.

If you already have drawings, our quick estimate request can give you a budget picture before you commit to the next stage — or book a free consultation and we will tell you what your quote is missing.