Start With Insurance and Credentials

Before you talk about slates, skips or staircases, ask for the paperwork. A reputable builder will expect the question and will have the documents to hand. Anyone who gets defensive at this stage is telling you something useful.

• Public liability insurance. Ask to see the current certificate and check the level of cover. Two million pounds is a common minimum, but a large extension or a renovation near a boundary may justify more.
• Employers' liability insurance. This is a legal requirement for anyone who employs staff, including apprentices and labourers. If your builder works alone, ask whether they ever bring in subcontractors, and if so, whether those people are covered too.
• Company details. A company registration number, a VAT number if they are registered, and a trading address you can verify. A mobile number and a first name is not enough.
• Scheme membership and qualifications. Gas and electrical work must be carried out by suitably registered people. For work on listed buildings or in conservation areas, ask about previous experience of that specific type of property.

It also pays to ask how long they have been trading and whether they have worked in your area before. Local knowledge of narrow lanes, parking restrictions and how the local authority operates is worth a great deal.

Get the Quote in Writing

There is a real difference between a quote and an estimate, and it matters. A quote is a fixed price for a defined scope of work. An estimate is a best guess. Ask which one you are being given, and get it in writing by email so there is a clear record.

A useful written quote should set out the materials and labour separately, state whether VAT is included, and list what is not covered. Common exclusions include scaffolding, skip hire, waste removal, building control fees, decorating and making good. Ask about each one directly rather than assuming.

Check how long the quote remains valid, particularly if material prices are volatile, and confirm who is responsible for ordering and paying for materials. If you are buying the tiles or the kitchen yourself, agree delivery dates and who will be on site to receive them.

Agree Timescales and the Working Day

Ask for a start date and an estimated completion date, and get both in writing. Then go a little further and agree the practical details of the working day: what time they will arrive, what time they will finish, which days they will be on site, and who will actually be doing the work.

Welsh weather deserves a mention here. Wind-driven rain off the coast, sudden gusts in the hills and short winter days can all slow progress. A sensible builder builds a little float into the schedule. Ask how delays will be communicated and how they will affect the completion date.

Sort out the site logistics early. Where will materials be stored? Where will the skip go, and do you need a permit from the council for it? Is there parking for a van or a delivery lorry? Will the water and power be turned off at any point, and for how long? If you are living in the property, agree where the toilet facilities are and how dust will be contained.

Check References From Recent Jobs

Ask for three references from jobs finished in the last twelve months, ideally similar in size and type to yours. Recent references are far more telling than work completed five years ago. If possible, ask to visit a completed job or a current site, with the owner's permission.

When you speak to those customers, ask specific questions:

• Did the builder turn up when they said they would, and did they finish on time?
• Was the final bill close to the original quote?
• How were problems or disagreements handled?
• Was the site left tidy at the end of each day?
• Would you use them again, and have you recommended them to anyone else?

Online reviews are worth reading, but give more weight to detailed, local ones than to a handful of vague five-star comments. Ask which local authority building control team they usually work with, as they will often have a working relationship there.

Plan for Changes and Extra Costs

Almost every building job changes once work begins. A joist turns out to be rotten, you decide to move a socket, the plaster behind the tiles is beyond saving. What matters is agreeing in advance how those changes will be handled.

Ask for any variation to be confirmed in writing, with the cost and the effect on the timetable, before the work is carried out. Agree a day rate for additional labour and how materials for extras will be priced, whether at cost plus an agreed percentage or at a fixed figure. Set aside a contingency of around ten to fifteen per cent of the total budget for the unexpected.

Payment should be staged and linked to milestones, such as the completion of the footings or the roof going on. Never pay the full amount upfront, and keep a small retention until snagging is finished. Always get a receipt, and be wary of anyone who asks for large sums in cash.

Local Knowledge That Makes a Difference

Wales has its own set of practical considerations. Work in a conservation area, on a listed building, or within a national park such as Eryri may need consents beyond ordinary planning permission, and the process can take time. A builder who has navigated that before will save you weeks.

Ask how materials will reach the site if you live up a steep lane or at the end of a single-track road. Ask how they will protect your home from damp and salt-laden coastal air. And if you are in an area where Welsh is the first language, it is entirely reasonable to ask for a written quote or a summary in English if you need one, or to ask whether correspondence can be in Welsh.

Good builders in popular parts of Wales are often booked months ahead, so start your conversations early. Be cautious of anyone who can start a large job next week without a convincing explanation. Take your time, ask the awkward questions, and put the answers in writing. It is the simplest way to protect your home, your budget and your peace of mind.