How to Choose a Loft Conversion Company: 10 Questions to Ask

Is your quote fixed price, or is it an estimate?

A fixed-price quote means the number in the contract is the number you pay. There are no surprises when steel proves harder to fit than expected, or when the party wall award runs an extra week. By contrast, an "estimate" or "quote subject to survey" is far less binding. Some companies use a deliberately low estimate to win the job, then add costs later. As a result, you should insist on a written fixed-price contract before you sign anything.

Does the price include planning permission checks and building regulations?

Yes. Both should be included in a specialist's quote as standard. These are two separate processes: planning permission governs what you can build, while building regulations govern how it must be built. A company that expects you to arrange building regulations yourself is not behaving like a specialist. The same goes for one that hands you a folder of drawings and tells you to phone the council. In practice, managing both approvals is a core part of the service you are paying for.

Is structural engineering included?

Yes — it should be. Every loft conversion needs a structural engineer to design the new floor joists, ridge beams, and any steelwork that supports the structure. So ask plainly whether structural calculations sit inside the price or get billed separately. Reputable specialists include them. If the answer is "we'll sort that out later", treat it as a warning sign. The structural design drives much of the build cost, so pricing a job without it means the quote is incomplete.

Who actually carries out the work — your own employees or subcontractors?

Subcontractors are not inherently a problem. Many excellent companies use trusted trade partners for specialist work like plumbing or wiring. What matters is accountability. You need to know who will be on site, who supervises them, and who is legally responsible if something goes wrong. However, a company that gives vague answers about site management is a concern. So is one that cannot name its regular subcontractors. Neither should be trusted with a structural alteration to your home.

Are you fully insured? (Public liability, employers' liability, professional indemnity.)

Yes — and ask to see the certificates, not just a verbal confirmation. Public liability should be a minimum of £1–2 million. Employers' liability is a legal requirement for any company with staff. Professional indemnity covers design errors, which matters because loft companies are usually responsible for the structural drawings. A legitimate firm will produce these documents without fuss. If there is any reluctance, walk away immediately.

Can I speak to three recent customers whose projects are similar to mine?

Yes, and the references should be recent — within the last 12 months — and relevant to your type of conversion. A firm that built dozens of dormers three years ago may have changed its management, workforce, or standards since. So ask for references from similar projects. For example, if you want a mansard in a conservation area, ask to speak to a homeowner who had exactly that done recently. Good companies provide these without hesitation.

Can I visit a completed project?

Yes — insist on it. Photographs only show what a company wants you to see. Visiting a finished conversion in person tells you far more. You can walk up the staircase, check the finish on the dormer window reveals, and see how the insulation boarding meets the eaves. Top specialists arrange these visits routinely, with the agreement of past customers. If a company cannot manage a single site visit, ask yourself why.

How long have you been specialising in loft conversions?

There is a real difference between a general builder that "also does loft conversions" and a company that does them exclusively. Specialisation matters enormously for the structural and planning decisions a conversion involves. This is doubly true in London, where party wall duties, permitted development limits, and conservation area rules pile on complexity. So ask directly what share of their annual workload is loft conversions. Then ask how long the key project managers and site supervisors have done this work.

What warranty do you provide on the structure?

A 10-year structural warranty is the standard from reputable loft companies. Ask what it covers: does it include the roof structure, the new floor, and the dormer? Then ask the crucial question. Is it backed by a third-party insurance provider, or is it just the company's own promise? A warranty is only as good as the firm behind it. Crucially, a third-party-backed warranty still protects you even if that firm ceases trading.

What does the price exclude — specifically?

Even with a fixed-price contract, some items sit legitimately outside the scope of works. Common exclusions include interior decorating and painting, fitted wardrobes and furniture, and the party wall surveyor's fee if neighbours appoint their own. Certain planning application costs and statutory utility diversions often fall outside too. So ask for a written scope of works that lists everything in and everything out. If a company resists providing this, it is usually because they intend to add costs later.