Don’t get caught out: what to look for in a builder’s quote
Founder, Planning to Build
So you’ve got some quotes and you’re getting ready to hire a builder for your extension. Before you commit to anything, take a good, hard look at those documents - they’ll be one of the most important parts of your entire building project. Getting this stage right could be the difference between a stressful experience and a successful one.
A well-prepared quote should be clear, detailed, and leave no room for surprises. But all too often, quotes are vague, full of jargon, or missing key information — and that can lead to misunderstandings, hidden costs, and disputes down the line.
In this post, we’ll walk you through exactly what to check in a builder’s quote, so you can move forward with confidence, protect your budget, and make sure you’re getting the right work at the right price.
Key details every builder’s quote should include
This section breaks down the essential information every quote should include. Think of it as a checklist to help you review what you’ve been given, ask the right questions, and make sure nothing important has been left out. If something’s missing, now’s the time to catch it, not halfway through the build.
Let's go into the details:
Costs
It goes without saying that the cost breakdown is the most crucial part of any builder’s quote. It should be clear and transparent, with the total price for the project explicitly stated. This figure should cover all aspects of the work, from labour to materials, so there are no surprises once the project is underway. Ambiguity around pricing can quickly lead to disputes, so make sure everything is accounted for upfront.
Getting a detailed quote is essential — but having a realistic ballpark figure before you even speak to a builder gives you a major advantage
It helps you set expectations, spot inflated prices, and feel more confident in conversations. That’s why we created our Extension Estimation Calculator — a free tool that gives you a quick, tailored cost estimate based on your project details.
👉 Try our calculator now to get a clearer idea of what your extension might cost, before the quotes start rolling in.
In addition to the total price, you must also check whether VAT is included or excluded, as this can significantly impact the total cost of your project. Some builders may list their quote excluding VAT, while others may include it in the price.
Builders who are VAT-registered will charge VAT on top of their quoted price, typically at the current rate (currently 20% in the UK). This means that if the builder is VAT-registered, the total price you’ll pay will include VAT as an additional charge. Be sure to check whether VAT is included or excluded in the quoted price to avoid any unexpected costs when it’s time to pay.
We have paid most of the original quote. Call from QS 'I've made a cock up and need to recover some additional costs I hadn't spotted including some VAT I've had to pay using some of the cash you'd paid.' This is to the tune of £20k which he's agreed to waive his overhead of £6k on.— Reddit user on r/LegalAdviceUK
Payment terms & deposit
Clear payment terms are essential to ensure both you and the builder are on the same page throughout the project. A reputable builder will outline a payment schedule that includes a deposit to secure the work and then breaks down any subsequent payments into stage payments based on key milestones or completed work. This approach ensures that you are only paying for work that has been finished to your satisfaction.
The final balance should be due upon completion or after the final inspection, depending on the agreement. It’s important to understand the timing of these payments — whether they’ll be due at specific intervals or once certain tasks are completed — and what is expected in exchange for each payment. Always ensure the terms are in writing, and make sure you’re comfortable with the timing and amounts before signing anything.
🚨 Watch out for changing payment terms
If your builder starts changing the payment terms after the initial agreement, it could be a red flag. Sudden requests for higher deposits, unexpected stage payments, or changes in the final balance could indicate cash flow issues or a lack of transparency.
Always stick to the payment schedule outlined in the quote and make sure any modifications are agreed upon in writing. If a builder tries to adjust payment terms without a valid reason, it’s worth pausing to assess whether this is a sign of potential problems down the road.
It's very common (and generally expected) to pay a deposit to a builder before work begins. The deposit serves a few important purposes:
- Secures your place in their schedule
- Covers initial material purchases or setup costs
- Demonstrates your commitment to the project
A typical deposit is usually around 10–20% of the total project cost. Anything significantly higher than that, especially early on, can be a red flag. It’s wise to ask for a clear breakdown of what the deposit will be used for and ensure it’s documented in the quote or contract.
Scope of work
One of the most important things a builder’s quote should include is a clear scope of work. This is the section that outlines exactly what the builder is planning to do. It should give you a solid understanding of what’s included in the price and, just as importantly, what isn’t. While some builders may give a high-level overview, it’s worth asking for more detail if the quote is vague or overly general.
Ideally, the scope should list the rooms or areas that will be affected, as well as the key tasks involved such as demolition, brickwork, roofing, electrics, and plumbing. Even if the builder doesn’t go into full technical detail, there should be enough information to show they’ve properly understood the project and are quoting for all the right elements. If it’s too light on specifics, follow up and ask for a breakdown. This is your opportunity to check they’ve included everything you expect before work begins.
Timelines
A good quote shouldn’t just tell you what the builder will do, it should also give you a sense of when they’ll do it. Clear timelines help you plan your life around the build, avoid delays, and hold the builder accountable.
At a minimum, the quote or contract should include:
- A provisional start date
- An estimated duration of the project
- Any key milestones or phases, such as groundwork, roofing, or first fix electrics
- Information on what might cause delays (e.g. weather, supply issues)
Insurances
A reputable builder should have a few key types of insurance in place to protect you, themselves, and the project. Here are the main ones to look out for:
- Public Liability Insurance: This covers injury or damage to third parties such as if a passerby is hurt or a neighbour’s property is damaged due to the building work. It’s essential, and any professional builder should have it. You can ask to see a valid certificate.
- Employer’s Liability Insurance: If the builder has employees or sub-contractors working under their direction, they are legally required to have this. It covers injury or illness to workers on-site. Lack of this insurance could be a red flag, especially for larger jobs.
- Professional Indemnity Insurance: If the builder is offering design services as well as construction (e.g. structural changes or layouts), this insurance protects you if there are errors in the design that lead to problems later.
- Contract works insurance (also called contractors’ all-risk insurance): A type of insurance that covers building work while it's in progress. It protects against damage to the new structure or materials before the project is finished.
A professional builder should have no issue providing copies of their insurance certificates. Don’t rely on verbal assurances - ask to see documentation for each relevant policy (especially public liability and employer’s liability). Check the expiry date and make sure the policy will still be valid for the duration of your project.
Warranties & resolving defects
A professional builder should stand by their work and that means offering a clear warranty or written guarantee once the job is finished. At a minimum, this should cover defects in workmanship or materials for a reasonable period (typically 6–12 months), though some builders offer longer guarantees depending on the nature of the work. Make sure the quote or contract outlines:
- What is covered under the warranty
- How long the cover lasts
- What to do if you notice a problem
- Whether the builder will return to fix snagging issues or minor faults after completion
In addition to the builder’s own workmanship warranty, certain materials or installations — like windows, doors, roofing systems, boilers and damp-proofing — often come with manufacturer or installer-backed warranties. These can range from 5 to 20 years or more, depending on the product and supplier.
Spotting gaps on what is not included
It’s easy to focus on what a builder says is included in a quote, but just as important is what’s left out. Hidden costs often come from assumptions: things like skip hire, decorating, kitchen fitting, or even clearing the site at the end might not be listed unless you specifically ask. If it’s not in writing, you can’t assume it’s covered.
This is where getting multiple quotes (ideally three) really pays off. Comparing them side by side helps you spot what one builder includes that another doesn’t. One quote might mention waste removal, while another leaves it out entirely. Some might include electrical and plumbing work, others might expect you to arrange those trades separately. These gaps matter, and identifying them early can save you from expensive surprises and awkward conversations down the line.
A practical example...
Imagine you’re getting quotes for an extension to your home. You receive three quotes from different builders. The first quote is £25,000 but doesn’t clearly break down costs. It simply lists "general labour and materials" with no specific details. The second quote is £27,000, but it includes a full breakdown of materials, labour costs, and a timeline for completion. The third quote is £29,000, but it also includes the option for high-end materials like custom windows and flooring, which is clearly listed as an upgrade.
If you don’t carefully evaluate the details in these quotes, you might end up selecting the lowest bid (£25,000) without realising that the cost doesn’t include certain essential elements, like specific materials or enough time for completion, leading to unexpected price hikes later in the project. On the other hand, the higher bids might include options that match your vision but could seem unaffordable if not broken down properly.
This is why it’s essential to go beyond just comparing numbers. Look at what’s included in each quote, and ensure everything you expect from the project is covered. It’s also worth asking each builder to clarify their costs if anything seems vague.
What to do if important details are missing from the quote
Not all builder quotes are created equal, and it’s common to find quotes that leave out key information. But that doesn’t mean you should ignore it or assume it’s covered. Here’s what to do if you spot gaps:
Ask for Clarification
If something’s missing—like VAT, a timeline, or what materials are included — go back to the builder and ask. A professional builder should be willing to clarify or revise their quote to make things more transparent. Questions to ask: “Can you confirm if VAT is included?” “Can you provide a breakdown of materials?” “Is the start date and estimated timeline fixed?”
Get it in writing
Verbal assurances aren’t enough. If the builder says something is covered but it’s not written down, ask them to update the quote or add a note in writing. This protects both you and the builder later on.
Don’t be afraid to push back
A quote is a proposal, not a final contract. If you’re uncomfortable or uncertain, don’t be afraid to go back with questions or ask for revisions. A good builder will respect that you want clarity.
Walk away if needed
If a builder won’t provide clear answers, dodges your questions, or is reluctant to put things in writing — it might be a warning sign. Trust your gut. It’s better to delay the project than end up tied to a contractor who isn’t transparent.
Choosing the right builder and understanding their quote in detail can make the difference between a smooth, well-run project and one full of costly surprises. By knowing what to look for — and what questions to ask — you put yourself in control.
Use this guide as a checklist, compare multiple quotes, and don’t be afraid to follow up on anything that’s unclear. A well-prepared quote sets the tone for the entire job — and getting it right at the start is one of the smartest steps you can take when planning your extension.
Love visual guides? Download a high-res version of our 6 Key Points Every Builder's Quote Sould Include infographic.
