Choosing the right person to build your loft conversion or renovate a compact mews home is a decision you will live with for decades. Unlike a new kitchen, a loft project touches the structure of your house, the roof line, your neighbours' walls and your Building Control record. Getting the appointment right is more important than shaving a few hundred pounds off the quote. Here is how to compare specialists properly, rather than simply picking the lowest number on the table.

Experience that matches your project

A specialist who has built twenty rear dormers is not automatically the right choice for a mansard in a narrow mews terrace. Ask specific, verifiable questions about the type of work you need.

• How many conversions have you completed in the last two years, and of what type — rooflights only, rear dormer, hip-to-gable, mansard?
• Have you worked on mews properties before? These bring tight access, shared carriageways, garages below, limited headroom and often a conservation area or listed status to navigate.
• Who produces the structural calculations, and who deals with Building Control and any planning application?
• Will your own team carry out the carpentry and roofing, or will sub-contractors be brought in? A consistent crew usually means better quality control.

For mews homes, ask how they plan to get materials in and waste out, where the skip will sit, and how scaffolding will be erected without blocking the lane for days on end. A specialist who has solved those problems before will answer without hesitation.

Insurance: ask for the certificates

Never take "we're fully insured" as an answer. Ask to see the certificates and check the details yourself.

• Employers' liability — legally required if they employ anyone, normally at least £5 million, often £10 million.
• Public liability — covers damage to your property or a neighbour's. Look for £2 million or more.
• Contract works or all-risks cover — protects the build itself against fire, theft and storm damage while it is in progress.
• Professional indemnity — needed if they are designing the structure as well as building it.

Check that the company name on the certificate matches the name on your quote, and note the expiry date. If the policy lapses mid-project, you want to know. Also ask, plainly: if a leak damages the neighbour's ceiling, whose insurer pays? A good answer comes quickly.

References and site visits

Ask for three recent clients whose projects resemble yours, ideally completed within the last eighteen months, and ring them. Written testimonials are easy to gather; a phone conversation is harder to stage.

• Did the team turn up when they said they would?
• How were problems handled when something went wrong?
• Was the final invoice close to the original quote?
• How quickly were snags put right after completion?

If you can, visit a completed conversion and a live site. On a finished job, look at the roof line, the plastering and how the staircase lands. On a live site, look at tidiness, dust protection and whether the team is working safely. Both tell you more than any brochure.

Written contracts and payment schedules

A written contract is not a sign of distrust; it is how professionals work. It should set out the scope, the drawings and specification, the programme, the payment schedule and how variations will be priced.

Be wary of large deposits up front. Payments tied to milestones — scaffold up, roof watertight, plaster complete — keep everyone honest. A retention of around 2.5 to 5 per cent, held for a few weeks after completion, is standard practice and gives you leverage if snags appear. Confirm in writing who arranges the party wall agreements, the scaffolding licence, the skip permits and the Building Control notices. Check the start and finish dates, the working hours, and what happens if the schedule slips.

Warranties and post-completion cover

Ask about warranties before you sign, not after the scaffolding comes down.

• Workmanship warranty — how long does it last, and what exactly does it cover? Ten years is common for structural elements; twelve months to two years is typical for general finishes.
• Insurance-backed guarantees — these protect you if the firm ceases trading, but only if the provider is genuinely reputable.
• Manufacturer warranties — roof windows, tiles, membrane and insulation all carry their own cover. Collect the documents and keep them with your deeds.
• Transferability — if you sell, will the warranty pass to the new owner? It is a small detail buyers care about.

Finally, insist on the Building Control completion certificate. Without it, you may struggle to sell or remortgage later.

Comparing quotes fairly

Quotes are only comparable if they cover the same things. One may exclude scaffolding, skip hire, structural calculations, Building Control fees or VAT, making it look cheaper than it is. Ask each specialist for a written breakdown, then compare line by line.

Pay attention to how they communicate now. A specialist who answers your questions clearly at this stage, in writing and without pressure, is far more likely to be straightforward when a problem arises mid-build. Trust your instincts, get everything confirmed in writing, and appoint the person who can show you the evidence — not just the enthusiasm.