On site · High risk
How do you handle changes once work has started?
Nothing gets built until the change is priced and agreed in writing.
- When it lands
- The first time anyone says 'while we're here'.
- What it costs to get wrong
- Unpriced variations are the number one source of end-of-project disputes and unexpected final bills.
Nothing on a building site is free, and nothing agreed verbally stays the size it was when you agreed to it. The variations rule is simple: priced and agreed in writing before it is built.
Agree the rule before anything changes
Say it once, at the start, in the friendliest possible terms: any change, however small, gets a written price before work proceeds. Builders who work properly welcome this, because it protects them from disputes about what was agreed too.
How £31,000 accumulates
Across a five-month build, a homeowner agreed to changes in passing on site — a wider opening here, better glazing there, move that door. The final account carried £31,000 of variations. Not one of them was individually shocking. None had been priced when agreed.
By the time they appeared as a total, the work was built and the argument was unwinnable.
Keep one log, running total visible
A single list: date, what changed, who asked for it, the agreed price, and the running total against your contingency. Update it the day something changes, and share it with the builder so both of you are looking at the same number.
The value of the running total is that it makes the fifteenth change a conscious decision rather than a reflex.
Time as well as money
Every variation should state its effect on the programme. A change that adds £900 and two weeks can cost far more than £900 if you are paying rent while you wait.
Why this one matters
On site, decisions get made fast and verbally. Writing them down takes two minutes and removes the entire category of 'I thought that was included' from your project.
Do this week
- Send the variations rule to your builder in writing.
- Start the log — even if it is currently empty.
- Set the contingency figure the running total is measured against.
The realistic choices
Written variation order every time
Email is fine. Description, price, time effect, agreed by both.
Running change log
One shared document, reviewed and signed off weekly.
What good looks like
- Every change has a price and a time impact before the work happens
- A running total of variations you can see at any moment
Questions worth asking
- What does this change do to the completion date?
- Is this a change, or was it always in the scope?
From real projects
£31,000 of verbal yeses
Across a five-month build, a homeowner agreed to changes in passing conversation on site — a wider opening here, better glazing there. The final account carried £31,000 of variations with no prices agreed at the time. Most of it was payable.
The lesson: 'Can we just…' costs money. Every one of them gets a number before it gets built.
Putting it into practice
What this decision should leave behind
The steps to work through, the paperwork worth keeping and the questions to send your builder today.
- · Agree the rule before anything changes
- · Keep a single variations log
- · Track the running total against contingency
- · Template: Variation instruction form
- · Paperwork: Variations log
- · Paperwork: Written quotes for each variation
Next decision
When do you lock your finishes and fittings?