Tendering and contracts
How to tender building work
Short answer
Send every contractor the same pack: the drawings, a specification or schedule of works, the building contract you intend to use with its particulars filled in, the dates you need, and the pre-construction information that CDM 2015 requires. Citizens Advice suggests getting written quotes from at least three traders.
When the prices come back, put them on the same footing before you compare them: check the arithmetic, confirm everyone has priced the same scope, set aside the provisional sums you gave them, and have each contractor price or withdraw anything they have excluded or qualified. The lowest total is not always the lowest price for the same work.
What goes in the tender pack
A tender only works if every contractor prices the same thing on the same terms. The pack should contain:
- Drawings, at a scale that shows what is to be built.
- A specification, a schedule of works, or both. The specification sets the standard; the schedule lists the work item by item. See schedules of works.
- The contract and its particulars. Name the form (see which building contract) and fill in the variables before tender. For JCT's Minor Works Building Contract 2024 those include the commencement and completion dates, the liquidated damages rate, the rectification period, the interim valuation dates, the percentages certified before and after practical completion, and the insurance option. Every one of them affects the price.
- The dates. When you want work to start, and when it must finish.
- Pre-construction information under CDM 2015.
- How to return the price, by when, and in what form.
A client must provide pre-construction information as soon as is practicable to every designer and contractor appointed, or being considered for appointment, to the project.
On a home, regulation 7(1) moves this duty off you and onto the contractor (or the principal contractor, where there is more than one), or onto the principal designer if it agrees in writing. The tenderers still need the information, because hazards such as asbestos, a shared drain or a live-in household change what the work costs. ClearCDM sets out what CDM means for domestic projects.
JCT publishes model forms for inviting and submitting tenders in its Tendering Practice Note 2024, which is £35 plus VAT through JCT On Demand on JCT's 2026 price list. JCT's notice launching its 2021 Home Owner contracts also points to a sample enquiry letter for sending to potential contractors.
How many contractors to invite
Citizens Advice recommends written quotes from at least three traders before you decide, and warns against relying on a verbal quote. Three returned prices let you see whether one is out of line.
Inviting many more has a cost. Every contractor spends unpaid time pricing a tender, and the longer the list, the smaller each one's chance of winning. Asking first whether a contractor wants to price, and when they could start, avoids tenders that come back late or not at all. JCT's Tendering Practice Note treats this as a preliminary enquiry, with its own model letter and questionnaire.
The tender period
No law sets a tender period for private work. Give contractors long enough to get prices from their own sub-contractors and suppliers, set one return date and time for everyone, and keep to it. If a question from one contractor changes what is being priced, send the question and the answer to all of them, so that the prices stay comparable.
Comparing the returns
Putting tenders on the same footing is often called levelling. Work through each return in the same order:
| Check | What you are looking for |
|---|---|
| Arithmetic | Totals that do not match the items. JCT's Tendering Practice Note has a section on examining priced documents for errors. |
| Scope | Items left out or marked as excluded. Citizens Advice warns that a price well below the others may not be for exactly the same work. |
| Provisional sums | These are sums you set for work that cannot yet be fully described. Every contractor should carry the same figure, so compare the prices without them. |
| Preliminaries | The contractor's costs of running the site: management, site set-up, security, safety and protection. A low figure here can mean something is missing. |
| Programme | How long each contractor says it needs, against the dates you gave. |
| Qualifications | Conditions the contractor has attached to its price. |
A worked example
Three contractors return prices for the same extension. The figures are illustrative.
| Contractor A | Contractor B | Contractor C | |
|---|---|---|---|
| Tender total | £168,000 | £176,500 | £181,000 |
| Kitchen fitting excluded | Yes | No | No |
| Contractor A's price for the kitchen fitting, asked for after tender | £9,500 | ||
| Level total | £177,500 | £176,500 | £181,000 |
Contractor A looked cheapest by £8,500. Once the excluded work is priced, B is lower.
Questions and qualifications
A qualification changes what you would be buying. "Price excludes any work below ground" or "subject to steel prices at the date of order" moves risk back to you. Ask each contractor to withdraw its qualifications or to price them, in writing, before you choose. JCT's Tendering Practice Note covers post-tender discussions, and the principle is simple: whatever you agree with the chosen contractor after tender should be recorded in the documents the contract is signed on.
Citizens Advice also draws the distinction that matters here. A quote is a fixed price; an estimate is a rough guess that can rise.
What this means for you
A tender is a test of the information you send out. If the pack is complete and the contract particulars are filled in, the prices will be close to what you pay. If it is thin, the differences between the returns are mostly differences in what each contractor assumed.
Parallel Architecture prepares tender packs, runs the tender and compares the returns line by line: see tender and contract administration.
Sources
- Construction (Design and Management) Regulations 2015, regulations 4 and 7 legislation.gov.uk
- Citizens Advice: before you get work done on your home (England) citizensadvice.org.uk
- JCT, Tendering Practice Note 2024, contents jctltd.co.uk
- JCT, Price List 2026 (issue 03) jctltd.co.uk
- JCT, MW 2024 User Checklist jctltd.co.uk
- RICS, NRM 2: Detailed measurement for building works, 2nd edition (October 2021, reissued October 2022), section 2.5 rics.org
- JCT Home Owner Contracts 2021 launch corporate.jctltd.co.uk