Key Takeaway
The number one thing that goes wrong on extension projects isn't the design — it's the contractor. Here's what vetting actually means, what your building contract should include, and why Hampshire Build built a vetted panel.
If you're planning a home extension in Hampshire, you'll spend a lot of time thinking about design. Room layouts, roof styles, glazing options, bi-fold versus slide-and-turn doors. All of that matters — but none of it is the biggest risk on your project.
The biggest risk is the contractor.
Time and again, the extensions that go badly — the ones that run over budget, drag on for months beyond the agreed completion date, or leave homeowners with snagging lists longer than their specification — come down to one thing: the wrong builder was chosen.
What Goes Wrong When Contractors Aren't Vetted
The problems are usually predictable in hindsight. A contractor who quoted low to win the job, then raised prices once work began. A team who disappeared for two weeks mid-build with no explanation. A builder who presented glossy photos of other people's work as their own portfolio. Poor communication, poor finishing, poor accountability.
The frustrating thing is that most of these problems are avoidable — with the right process upfront.
What Vetting Actually Means
Vetting a contractor is not about checking they're on a trade register or that they have public liability insurance, though both matter. Real vetting means speaking directly to previous clients — not the references the contractor gives you, which are obviously curated to impress.
It means asking specific questions: Did the project run to programme? Did the final cost match the quote? How did the contractor respond when problems arose? Would you use them again?
It also means price-testing. A single quote from a contractor tells you almost nothing. You have no way of knowing whether you're being overcharged, whether the contractor has priced the job correctly, or whether the quote leaves room for the specification you actually want. Competitive tendering — sending the same specification to multiple contractors and comparing detailed, like-for-like proposals — is the only reliable way to understand market pricing for your specific project.
Finally, it means track record. Has this contractor built extensions like yours before? Do they understand the requirements of a building regulations-compliant extension — structural steel sizing, insulation standards, air tightness? Have they worked alongside planning and building control processes, or will they be learning on your job?
What a Building Contract Should Include
Even when you find a contractor you trust, the contract matters. A good building contract for a residential extension should set out the scope of works in precise detail, agree a programme with key milestones, and specify payment terms that protect you as the client.
The critical point on payments: they should always be in arrears. You should never be paying for work before it's been completed and inspected. Milestone-based payments — where each stage of construction is signed off before the next payment is released — mean you're never financially overexposed. If the contractor stops work, you haven't paid for work that hasn't happened.
Be wary of any contractor who asks for large upfront payments, or whose contract is vague about what each payment covers. A clear, detailed schedule of works, tied to a clear payment schedule, is non-negotiable.
Why Hampshire Build Built a Vetted Contractor Panel
As extension designers, we work with homeowners from the first sketch through to a build-ready set of drawings. Over time, we saw the same pattern repeatedly: clients with excellent designs going to market without any support on the contractor side, and sometimes ending up with the wrong team on site.
Hampshire Build's vetted contractor panel exists to solve that problem. Every contractor on the panel has been reference-checked through real previous clients, price-tested through competitive tendering on live projects, and approved by us before being introduced to any client.
When a Premium Package or Premium Plus Package client is ready to go to tender, we prepare a detailed schedule of works from the drawings and specification, and we send it to suitable contractors from our panel. Clients receive detailed, comparable proposals — not vague estimates — and we help them evaluate the submissions objectively.
All builds that proceed through our panel are governed by a Hampshire Build building contract with milestone-based payments in arrears. Clients are financially protected throughout construction.
How to Access the Panel
The vetted contractor panel — including full contractor details, reference reports, and the competitive tender process — is available exclusively through our Premium Package (£2,950+VAT) and Premium Plus Package (£4,950+VAT) packages.
If you're thinking about an extension in Hampshire and want the peace of mind that comes with a vetted contractor, the starting point is a complimentary 30-minute design call with Mark. You can book directly at hampshirebuild.co.uk/contractor-panel, or view all packages here.
Getting the design right matters. But getting the contractor right matters just as much — and the two things work best when they're handled together, from the start.
