Fixed Price vs Day Rate: Which Is Better When Hiring a Builder?
Should you pay your builder a fixed price or a day rate? We break down the pros, cons, and real-world scenarios - so you pick the right approach for your project.
You've found a builder you like. They've visited the site, talked through the job, and now comes the question: "Do you want a fixed price or day rate?"
Most homeowners freeze at this point. Fixed price feels safer - you know what you're paying. But builders sometimes prefer day rate, and some jobs genuinely suit it better. Pick the wrong one and you either overpay for certainty or lose control of an open-ended bill.
Here's how to decide.
The short answer
| Fixed price | Day rate | |
|---|---|---|
| Best for | Well-defined projects with a clear scope | Smaller jobs, repairs, or work where the scope is uncertain |
| You pay | An agreed total, regardless of how long it takes | A daily rate × however many days the work takes |
| Risk sits with | The builder (they absorb overruns) | You (you absorb overruns) |
| Typical rate | Quoted per project | £150–£250/day (UK avg), £250–£400/day (London) |
If your project has a clear scope of works and you can describe exactly what you want, go fixed price. If the work is exploratory, small-scale, or genuinely unpredictable, day rate can work - but you need to manage it.
Fixed price explained
A fixed-price quote means the builder agrees to complete a defined scope of works for a set amount. If it takes them longer than expected, that's their problem. If they finish early, they keep the difference.
When fixed price works well
- Extensions, loft conversions, new kitchens - any project over £10,000 where the scope can be clearly defined upfront
- Work with architectural drawings - if you've got plans, the builder can price accurately
- When you want certainty - you know exactly what the project will cost before it starts
When fixed price causes problems
- The scope wasn't clear enough - if the quote says "build kitchen extension" without specifying finishes, appliances, or decoration, you'll hit extras
- Variations creep in - "While we're at it, can you also..." is how fixed-price jobs go over budget. Every change is priced separately
- Rock-bottom fixed prices - a builder who quotes 30% less than everyone else on a fixed price has either missed something, plans to cut corners, or will hit you with "unforeseen" extras. Read our guide on signs your builder is overcharging - it applies to suspiciously cheap quotes too
How to make fixed price work for you
- Get the scope of works right first. The more detailed the spec, the more accurate the price. What should a builder's quote include? covers this in detail
- Agree how variations are handled - in writing, before work starts. A simple process: you request a change, builder prices it, you approve or reject before they do the work
- Tie payments to milestones - foundations complete, weathertight, first fix, second fix, final completion. Never pay ahead of the work done
- Hold back 5% until snagging is resolved
Day rate explained
Day rate means you pay the builder a fixed amount for each day they work on your project. Materials are usually charged on top - either at cost or with a markup.
Typical UK builder day rates in 2026
| Trade | UK average | London & SE |
|---|---|---|
| General builder | £150–£250 | £250–£400 |
| Bricklayer | £180–£260 | £280–£380 |
| Carpenter/joiner | £160–£240 | £250–£350 |
| Plumber | £180–£280 | £280–£400 |
| Electrician | £180–£280 | £280–£400 |
| Plasterer | £160–£240 | £250–£350 |
| Labourer | £100–£150 | £130–£200 |
These are for self-employed tradespeople. If you hire a building firm on day rate, expect 20–40% more because their overheads are higher.
When day rate works well
- Small jobs - a day or two of repair work, making good after other trades, odd jobs around the house
- Uncertain scope - you're opening up a wall and don't know what you'll find. Pricing this fixed would either be a guess or include a huge contingency
- Trusted builders - if you've worked with someone before and trust them to crack on efficiently, day rate can be cheaper because neither of you is paying for the overhead of a detailed quote
- Maintenance and ongoing work - handyman-type tasks where quoting each job individually isn't practical
When day rate goes wrong
- No incentive to finish quickly - on day rate, a 10-day job that takes 15 days earns the builder 50% more. Most builders are honest, but the incentive structure works against you
- Costs are unpredictable - you won't know the final price until the job is done
- Material markups add up - some builders charge materials at cost, others add 10–20%. Agree this upfront
- It's hard to compare quotes - if one builder says "day rate, probably 8–10 days" and another says "£4,500 fixed", you're comparing apples with oranges
How to make day rate work for you
- Set a budget cap - "I'm comfortable with up to 10 days at your rate. If it looks like going beyond that, let me know before you continue"
- Ask for a time estimate in writing - even on day rate, a good builder can estimate how long a job should take
- Keep a daily log - note what work was done each day. This isn't about distrust - it's about having a record if there's a dispute
- Buy materials yourself - for bigger jobs, buying materials directly means you know exactly what you're paying. Some builders prefer this because it removes their liability for material choices
- Review weekly - don't wait until the end to check progress against the estimate
The decision flowchart
Choose fixed price if:
- Your project costs more than £5,000
- You have drawings, plans, or a detailed specification
- You want to compare quotes from multiple builders
- Budget certainty matters more than flexibility
Choose day rate if:
- The job is under £2,000
- The scope is genuinely uncertain (opening up walls, investigative work, repairs)
- You've worked with this builder before and trust them
- The work is ongoing maintenance rather than a defined project
Consider a hybrid approach for:
- Projects where most of the work is clear but some elements are uncertain
- Example: fixed price for the extension build, day rate for any remedial work discovered when connecting to the existing house
What about "price plus" or "cost plus"?
Some builders quote on a "cost plus" basis - they charge for materials at cost, plus a percentage markup (usually 10–20%) for overheads and profit, plus labour at an agreed rate.
This sits between fixed price and day rate. You get more transparency than a lump sum but less certainty. It works well for:
- Renovation projects where the scope is mostly clear but discoveries are likely
- High-spec projects where the homeowner wants to choose specific materials during the build
- Trust-based relationships where both sides want fair pricing without the overhead of re-quoting every change
The risk: Like day rate, there's no hard ceiling on cost. Always agree a target budget with a contingency allowance (10–15%) and a process for approving anything beyond it.
Red flags - whichever approach you choose
Watch out for these regardless of pricing model:
- Large upfront payments - never pay more than 10–15% upfront, or the cost of materials for the first stage
- Vague scope on a fixed price - a "fixed price" with a vague scope isn't fixed at all. It's a starting price
- No written agreement - whether it's a formal contract or a detailed email, get the terms on paper
- Pressure to decide - "this price is only good until Friday" is a sales tactic, not a professional practice
- Day rate with no estimate - a builder who won't estimate how long a day-rate job will take is either inexperienced or avoiding accountability
For more on spotting problems in builder quotes, read our how to read a builder's quote guide.
Get an independent check
Whether you're looking at a fixed-price quote or trying to work out if a day-rate estimate is fair, MyBuildAlly can help. Upload your quote and our AI will check the pricing against regional benchmarks, flag any scope gaps, and tell you whether you're getting a fair deal - so you negotiate from a position of knowledge, not guesswork.