DIY Quote Checking vs Getting Professional Help - A Practical Guide
You can check a builder's quote yourself with the right knowledge. Here's a practical guide to DIY quote checking - and when to get professional help instead.
You've got a quote from a builder. Maybe two or three. Now you need to work out whether the price is fair, the scope is complete, and the terms are reasonable.
You can absolutely do this yourself. But doing it properly takes time, attention to detail, and enough knowledge to spot what's missing - not just what's there.
This guide walks through exactly how to DIY your quote check, what you'll catch, what you'll probably miss, and when it makes sense to get someone else involved.
The DIY approach: step by step
If you're going to check a quote yourself, here's the process. Work through it in order - each step builds on the last.
Step 1: Check the scope of works
Read every line of the scope. Not a skim - a proper read. Compare it against what you actually discussed with the builder during the site visit.
If something you talked about isn't written down, it's not included. Verbal promises mean nothing once the work starts. "We'll sort the garden out after" doesn't count unless it's on paper.
Look for vague descriptions like "works as discussed" or "finish to a good standard." These leave room for argument later. You want specifics: what work, what materials, what finish.
Step 2: Verify materials are specified
A good quote names the materials. Not necessarily the exact brand and model for everything, but enough that you know what you're getting.
"Supply and fit kitchen" tells you nothing. "Supply and fit Howdens Greenwich range in Cashmere, laminate worktop, stainless steel sink" tells you everything. The first could be a £3,000 kitchen or a £15,000 one.
Check that key items - windows, doors, boilers, bathroom suites, flooring - are specified clearly enough that you could price them yourself.
Step 3: Compare prices against benchmarks
Use a cost estimator to get rough benchmark prices for your project type, size, and region. This gives you a ballpark. If the benchmark says £45,000–£55,000 and your quote says £72,000, that gap needs explaining.
Check materials you can price yourself. Windows, bathroom suites, kitchen units, and boilers all have searchable retail prices. A 10–15% markup over retail is normal for a builder. A 50% markup is not.
Step 4: Check payment terms
Standard terms are staged payments tied to milestones. Foundations complete - pay 15%. Shell up - pay 25%. Roof on - pay 20%. And so on.
Watch out for:
- Large deposits - anything over 15% upfront is unusual
- Calendar-based payments - "£5,000 on the first of each month" isn't tied to progress
- No retention - hold back 5–10% until snagging is complete
Step 5: Check exclusions
Every good quote has an exclusions section. Read it carefully.
Common items that catch people out: building control fees, party wall agreements, scaffolding, skip hire, drainage connections, decoration, and garden reinstatement. If these aren't listed as included or excluded, ask.
Our guide on what a builder's quote should include lists every item you should expect to see.
Step 6: Verify builder credentials
Check Companies House if they're a limited company. Ask for a copy of their public liability insurance certificate - not just a claim they've got it. Look up Gas Safe, NICEIC, or FENSA registration if the work involves gas, electrics, or windows.
None of this checks the quote directly, but a builder without proper credentials is more likely to produce a problematic quote.
What DIY checking catches
If you follow the steps above carefully, you'll catch most of the common problems.
Obvious scope gaps - no mention of building regulations, scaffolding, or skip hire. These are the items that turn a "complete" quote into an open-ended bill.
Price outliers - a bathroom suite quoted at £4,500 when the models listed cost £1,800 retail. A day rate of £450 when the regional average is £280.
Vague scope - "works as discussed" instead of a written description. "Decoration to living areas" without specifying primer or full paint finish.
Suspicious payment terms - 50% deposit, payments not tied to milestones, no retention for snagging.
Missing credentials - no insurance documents, no trade body membership, no company registration.
These are the things you can spot with a checklist, some internet research, and a bit of patience.
What DIY checking misses
This is the harder part to accept. There are real, expensive problems that most homeowners simply can't spot - not because they're careless, but because they don't have the trade knowledge.
Subtle scope gaps that need trade expertise. A bathroom refurb quote that doesn't mention tanking (waterproofing behind tiles) might look complete to you. A plumber would spot it instantly. When the tiles start coming off the wall eighteen months later because moisture got behind them, you'll wish someone had flagged it.
Specification quality. The quote says "combi boiler, 28kW." Is that good enough for your house? Does it have enough hot water capacity for two bathrooms? Is the brand reliable? Unless you know boilers, you can't assess this.
Regional pricing nuance. A kitchen extension at £2,400 per square metre sounds fine for Birmingham. For central London, it's suspiciously cheap. For rural Wales, it's expensive. Context matters, and free benchmark tools aren't always granular enough.
Building regulations requirements you didn't know existed. Your loft conversion quote mentions insulation and plasterboard. But does it mention fire door upgrades, escape windows to regulation size, smoke detection to the current standard, and the staircase headroom calculation? These are legal requirements, not extras. If they're missing from the quote, they'll appear as costly surprises.
Specification clashes. Two items in the quote that contradict each other - underfloor heating specified alongside carpet, or a flat roof with insufficient drainage fall. These require experience to spot.
The DIY checklist: 10 things to check
Before you call anyone for help, run through this list. You'll catch the majority of problems.
- Does the scope match what you discussed? Line by line, not roughly
- Are materials specified? Brand, model, or at minimum quality grade
- Is there a price breakdown? By trade or phase, not just a single lump sum
- Are exclusions listed? What's NOT included matters as much as what is
- Are payment terms staged? Tied to milestones, with retention at the end
- Is the deposit reasonable? 10–15% is standard. Over 20% is a concern
- Is there a validity period? The price should hold for at least 30 days
- Does the price seem right? Compare against online benchmarks for your area
- Are credentials verifiable? Insurance, trade body membership, company registration
- Does the builder communicate well? Responsive, clear, willing to answer questions
If the quote passes all ten, you're in a strong position. If it fails on three or more, get a second opinion.
For a deeper walkthrough of each section, see our guide on how to read a builder's quote.
When to get professional help
DIY checking has limits. Here's when it makes sense to bring someone else in.
The project is over £50,000. At this scale, the cost of missing something is significant. A scope gap worth 5% of a £80,000 project is £4,000. Professional checking pays for itself many times over.
The work involves trades you don't understand. Structural engineering, drainage design, specialist roofing - if you can't assess the specification, you can't assess the price. You need someone who can.
Quotes differ significantly in scope. If three builders have quoted different amounts but each quote includes different items, you need someone to normalise them. Working out which quote actually covers the same work is harder than it looks.
Something feels wrong but you can't pinpoint it. Your gut is surprisingly good at detecting problems. If the quote doesn't sit right but you can't explain why, a professional pair of eyes will either find the issue or put your mind at rest.
You're about to make a decision you can't easily reverse. Signing a contract for a £60,000 extension is a big commitment. Spending £10 on a quick AI analysis - or £500 on a QS review - before you sign is cheap insurance.
Types of professional help
Not all help costs the same or does the same thing.
AI quote-checking tools (£10 per project) - upload your quote and get it analysed against benchmark data in minutes. Good for spotting pricing anomalies, scope gaps, and vague descriptions. Won't visit your site or provide a professional opinion. Tools like MyBuildAlly fall into this category; one-off payment, no subscription. Check current pricing and see a sample report to understand what you get.
Quantity surveyor (£500–£1,500) - a thorough, line-by-line review by a qualified professional. Their opinion carries professional weight. Best for large or complex projects.
Building surveyor (£300–£600) - a site-specific assessment of your property, not just your quote. Useful for older buildings or projects where the site itself creates risk.
Architect (varies) - if you already have an architect, they should be reviewing quotes as part of their service.
It's not either/or
Here's the thing most people get wrong: DIY checking and professional help aren't competing approaches. They work best together.
Do the DIY check first. Run through the ten-point checklist. Catch the obvious stuff. Then, if you've got questions or concerns, bring in help for the specific issues you can't resolve yourself.
You don't need a quantity surveyor to tell you the deposit is too high. But you might need one to tell you whether the structural steel specification is adequate for a double-storey extension.
Start with what you can do for free. Escalate when you need to.