What Should Be Included in a Builder's Quotation for a Major Renovation or Extension?

A price on one line is not something you can interrogate, compare, or hold anyone to. It tells you nothing about what has been allowed for, what has been assumed, and what has been quietly left out — and every one of those becomes a conversation later, at a point where you have no leverage because the walls are already down.

The purpose of a detailed quotation is not paperwork. It is that both sides are describing the same job in the same words before any money changes hands.

Everything below is reasonable to expect on a major renovation or extension. If any of it is missing, ask — and treat reluctance to answer as information in itself.

The basics

• The full registered company name, company number, registered address and VAT number. If there is no VAT number on a quotation running into six figures, ask why.
• The address of the works and a clear description of the scope.
• The drawings and specification it is priced against, by number and revision. A quotation that does not name the drawings is priced against nothing in particular.
• A validity period. Material prices move, and an open-ended quotation is a hostage to that.
• Proof of insurance — public liability, employers liability and, if design is included, professional indemnity. Ask for the certificates. Any contractor should expect to be asked.

The money

• An itemised breakdown by trade or work section, not one number. You should be able to see what the groundworks, the structure, the roof, the joinery and the finishes each carry.
• VAT shown separately, with the rate stated. On a listed dwelling that rate is 20% — zero-rating for approved alterations was abolished in 2012.
• Provisional sums clearly marked as provisional, with what each covers and what would change it. A provisional sum is an allowance for work not yet fully defined; it is not a fixed price, and it will be adjusted.
• Prime cost sums for items you have not yet chosen — sanitaryware, tiles, ironmongery, kitchen. These are allowances for supply, and picking something dearer costs more. Ask what standard the allowance actually buys.
• Preliminaries — scaffolding, welfare, skips, plant hire, site protection, temporary works, the site manager's time. These are real costs on every job. A quotation with no prelims line has either hidden them in the rates or forgotten them.
• Contingency, if one is included, stated as such — and if one is not, say so, because the risk has not gone away just because the number has.

Exclusions and assumptions

This is the section that decides whether the price survives contact with the job, and it is the section most often absent. What has been assumed about the ground, the drainage, the existing structure and access? What is specifically not included?

• Foundation depth and ground conditions — particularly on Essex clay, and particularly near mature trees. If a depth has been assumed, it should say so, and it should say what happens if it is wrong.
• Asbestos removal, almost always excluded until a survey says otherwise.
• Structural surprises in an existing building — rot, failed lintels, previous alterations done badly.
• Statutory fees, planning fees and Building Control charges.
• Professional fees — architect, structural engineer, party wall surveyor, heritage consultant.
• Utility diversions and new or upgraded supplies, which are slow and frequently expensive.
• Landscaping and making good externally, which is regularly assumed to be included and regularly is not.
• Decoration — often excluded, and worth a large number on a whole-house project.

Programme and payment

• A start date, a duration and a programme, however outline.
• Payment tied to defined stages of work agreed before starting, not to arbitrary dates and not in advance of the work being done.
• How variations are handled — priced and agreed in writing before the work is carried out, not presented as a surprise on the final invoice.
• Retention, if any, and when it is released.
• What happens at completion — a snagging walk-round, a defects period, and what is covered by it.

Three builders pricing from three different sets of assumptions will produce three numbers that cannot be compared, and the lowest is usually the one that has assumed the most.

1. Give every builder the same drawings and the same written specification. Without that you are not getting comparable prices, you are getting three different jobs.
2. Line the breakdowns up side by side by work section. The gaps tell you where the difference actually is.
3. Read all three exclusion lists together. An item excluded by one and included by another explains far more of the difference than the headline figure does.
4. Ask each builder the same three questions about the riskiest parts of the job — foundations, the existing structure, and drainage — and compare the answers rather than the prices.
5. Ask what is assumed about foundation depth, and what happens if the ground says otherwise.

• What form of contract are we using? On a project of any size there should be a written contract, not just an accepted quotation. The JCT Home Owner and Minor Works forms exist for exactly this.
• Who is on site day to day, and who do I speak to when something needs deciding?
• Which parts are subcontracted, and are those firms insured?
• How will I be told about a delay or a cost increase, and when?
• What is your defects period, and what does it cover?
• Can I see two or three recent projects like mine, and speak to those clients?
• Are you VAT registered, and is VAT included in the figures I am looking at?

Every quotation we issue is itemised, priced against an agreed design with the specification attached, and says what is included, what is excluded, what is provisional and what would change a provisional figure. Payments are tied to defined stages agreed before we start. Variations are priced and agreed before the work is done.

We do not issue single-figure prices, and we would encourage you to be wary of anyone who does — including us, if we ever did. The full set of commitments is on our Standards page, written down specifically so you can check whether we have kept to them.