Builder Quote Red Flags: 9 Warning Signs to Watch For Before You Sign

You've got three quotes for your extension, renovation, or building work. They all look different — different prices, different formats, different levels of detail. How do you know which one to trust?

The truth is, the cheapest quote isn't always the best value, and the most expensive doesn't guarantee the best work. What matters most is what's in the quote — and what's suspiciously missing.

Here are the red flags every homeowner should watch for before signing on the dotted line.

Red Flag 1: No Breakdown of Costs

A legitimate quote should itemise the work clearly. You should be able to see separate costs for:

• Labour — How many days/weeks, how many workers
• Materials — What's being used, quantities, and specification
• VAT — Clearly stated and calculated
• Preliminaries — Skip hire, scaffolding, site setup
• Contingency — A sensible allowance (usually 10-15%) for unexpected issues

Why it matters: A single lump sum with no breakdown makes it impossible to compare quotes fairly. It also makes it easier for a builder to claim "extras" later because nothing was specified upfront.

What a good quote looks like: Individual line items for each element of the build, with unit costs where appropriate. You should be able to see exactly what you're paying for.

Red Flag 2: Verbal Quotes Only

If a builder gives you a price over the phone or in person but won't put it in writing, walk away. A verbal quote is worthless if there's a dispute later.

What you should expect: A detailed written document — either a formal quote or a fixed-price proposal — sent by email or post. It should include the builder's full business details, the scope of work, the price, and the estimated timeline.

Red Flag 3: Huge Upfront Deposit

A reasonable deposit is 10-15% of the total project cost, payable when contracts are signed. This helps the builder order materials and secure your slot in their schedule.

Red flag levels:

• ✅ 10-15% deposit — Normal and reasonable
• ⚠️ 25-30% deposit — High but sometimes justified for bespoke materials
• 🚩 50%+ deposit — Major red flag. No legitimate builder needs half the money before lifting a tool
• 🚩 Full payment upfront — Never, under any circumstances

Best practice: Agree a payment schedule tied to project milestones. For example: 10% on signing, 25% on completion of foundations, 25% on reaching roof level, 25% on second fix, and 15% on final completion and snagging.

Red Flag 4: The Quote Is Dramatically Lower Than Others

If you get three quotes and one is 30-40% cheaper than the others, that's not a bargain — it's a warning sign.

Why builders underquote:

• They plan to add costs later through "variations" and "extras"
• They'll cut corners on materials (cheaper alternatives, thinner timber, lower-grade insulation)
• They'll use unqualified or inexperienced labour
• They've underestimated the job and will either ask for more money or disappear when it gets complicated

What to do: Ask the cheapest builder to explain specifically where the savings come from. If they can't, or if the answer is vague ("we're just more efficient"), be very cautious.

Red Flag 5: No Mention of Building Regulations or Planning

Any significant building work in the UK needs to comply with Building Regulations. Many projects also need planning permission or must fall within Permitted Development rights.

A professional quote should reference:

• Whether Building Control approval is needed and who handles the application
• Whether planning permission is required
• Party wall agreements (if working near shared boundaries)
• Structural engineer involvement (if removing load-bearing walls or altering the structure)

Red flag: A builder who says "don't worry about building regs" or "we'll sort that later" is putting you at serious legal and financial risk. Non-compliant work can't be sold and may need to be demolished.

Red Flag 6: No Timeline or Completion Date

A proper quote should include:

• Estimated start date
• Estimated completion date
• Key milestones (foundations, first fix, second fix, etc.)
• What could cause delays and how they'll be handled

Red flag: "We'll start when we can" or "it takes as long as it takes." A professional builder knows how to plan a job and commit to a timeline. Flexibility is fine, but vagueness is not.

Red Flag 7: No Mention of Insurance or Warranties

A professional builder should reference:

• Their public liability insurance (you should already have verified this)
• Warranty on workmanship — Typically 1-2 years minimum, sometimes longer
• Manufacturer warranties on materials (windows, boilers, roofing, etc.)
• Who is responsible for contract works insurance during the build

Red flag: No mention of what happens if something goes wrong after the work is completed. You need to know who's responsible and for how long.

Red Flag 8: Pressure to Sign Immediately

Classic high-pressure tactics include:

• "This price is only good for 48 hours"
• "I've got another client interested so I need to know today"
• "If you sign now I'll knock 10% off"
• "Materials are going up next week so you need to commit"

Reality check: Good builders are busy, but they don't need to pressure you. A fair quote should be valid for at least 30 days. Material price increases do happen, but a trustworthy builder will explain this calmly, not use it as a pressure tactic.

Red Flag 9: Can't or Won't Provide References

Every established builder should have a portfolio of completed work and a list of happy customers willing to vouch for them.

Red flag responses:

• "I don't have any references" — Why not?
• "I can show you photos" — Photos can be anyone's work. You need contactable references.
• "Data protection means I can't share customer details" — Nonsense. Previous customers can choose to be a reference.

What to do: Ask for at least 3 references from projects completed in the last 12 months. Call them. Ask specifically: Was the work completed on time? Were there unexpected costs? Was the builder easy to communicate with? Would you hire them again?

How to Compare Quotes Properly

Once you have 2-3 quotes, compare them using this framework:

Factor	Quote A	Quote B	Quote C
Total price (inc VAT)
Itemised breakdown?
Materials specified?
Timeline included?
Payment schedule?
Building regs mentioned?
Insurance referenced?
Warranty offered?
References provided?

The quote that ticks the most boxes is usually the one to trust — even if it's not the cheapest.

How Chat to Your Builder Can Help

Comparing builder quotes is confusing, especially if it's your first time. Before you sign anything, make sure you've also checked your builder is legitimate. Our expert builders review quotes every day and can tell you:

• Whether the price is reasonable for your area and project type — see our 2025 extension cost guide for benchmarks
• What's missing from the quote that should be there
• Which items look overpriced or suspiciously cheap
• Whether the specification is adequate or if corners are being cut

Whether you're getting quotes in London, Manchester, Leeds, or Edinburgh, a 30-minute quote review consultation costs just 59 and could save you thousands. If you're a first-time buyer, this is especially important. Book your consultation today.

For a full step-by-step walkthrough of everything a quote should cover, see our complete guide to checking a builder's quote.