Guide · 6 min read

Variation management for UK builders.

How to stop extra work going unpriced, unsigned and unbilled, from the first request on site to the final payment.

What counts as a variation

A variation is any change to the agreed scope, price or programme of a building job. Extra work, omitted work, a different specification and a change of timing can all be variations. When a client asks you to move a socket or change the tiles, they are asking for a variation, even if it sounds small.

Why extra work gets lost

  • The instruction is verbal, so nobody writes it down.
  • The work starts before anyone agrees a price.
  • The extra is priced at the end, when the client has already moved on.
  • The programme changes, but orders and subcontractors do not.

A process that works on site

  1. Log it on the day. A photo, a short note, who asked for it and the time.
  2. Price it before the work starts. Use your own rate cards for labour, plant, materials and subcontractors.
  3. Get written agreement. The client should see what changes, what it costs and how it affects the programme. Record the date and their signature.
  4. Update the programme and orders. Tell the site team, subcontractors and suppliers from the signed scope.
  5. Bill it in the next payment. Anything signed but not yet billed should stay visible until it is on an invoice or application.
  6. Track it until it is paid. Keep one record per job, showing signed, billed and collected amounts.

What a variation record should contain

  • A description of the change and the reason for it
  • Who requested it
  • A price breakdown the client can read
  • The effect on the programme
  • The date, the client's signature and a reference linked to the job

Check your contract

Most building contracts have a variations clause. It sets out how instructions are given, how they are priced and how quickly they must be notified. Read the clause in your own contract, and have a construction solicitor review your templates once.

This page is general information, not legal advice.

How to measure the gap

Take three finished jobs. List every extra you can find in messages, site diaries and emails. Check each one against your invoices. The difference is your unbilled work. Our variation audit does this for you and shows the gap in pounds.

Book a variation audit How to price a variation

Related guides

  • Pricing a variationHow to price extra work for a UK building job: rate cards, the programme effect, overheads and a worked example.
  • What is a variationWhat counts as a variation in a UK building contract, the common types, what usually isn't one, and why the paperwork matters.
  • Extra work on siteA six-step checklist for UK builders when a client asks for extra work on site: pause, price, get it signed, then start.
  • Variation or change orderVariation or change order: what the terms mean in UK building contracts, what matters more than the name, and how to record every change.
  • Avoiding unpaid extrasFive habits that stop unpaid extras on a building job: site logs, photos, same-day pricing, written confirmation and billing in every application.