When choosing a builder, always ask for references and check these to ensure that they are genuine. Ideally, you should be able to visit recently completed work and talk to the owners.
It is advisable to obtain at least three written quotes from different builders, but do not necessarily choose the cheapest. Make sure that all quotes reflect the same work specification in terms of materials, site clearance, time scale etc, and that wherever possible these are fixed quotes rather than estimates.
Before making a final decision, ensure that you have asked your builder the following questions:
What types of project have they worked on before?
How long have they been in business?
Do they have premises you can visit?
Do they have membership of a Professional Body/Trade Association? If so, ring the organisation to check that the builder is really a member and ask about the kind of assurances that offers you e.g. protection if anything goes wrong.
Is their work guaranteed?
Is this guarantee insurance-backed so that you are still covered if the builder goes out of business?
What is the expected timeframe for the work and what are you entitled to if this deadline is not met?
What is included in the price?
Will they agree to independent conciliation in case of any dispute?
Once you have chosen your builder you may wish to formally agree the arrangements and terms you have discussed using a simple contract which can offer peace of mind and some legal protection.