Cowboy builders are legendary. We have all heard stories of extensions left half built, and the three-day job that took six months to complete.

The problem is so big that the Office of Fair Trading gets more than 100,000 complaints every year about building work. In fact, so many of us are afraid of poor workmanship or being ripped off, that a shocking £4bn worth of necessary repairs are left undone.

So if you need a job done that is beyond your own DIY capabilities and you know you have to employ a builder, how can you be sure that the job is done properly and meets your expectations?

For larger jobs, such as loft conversions and extensions, consider taking on a chartered surveyor or architect. He or she will not only deal with design, planning permission and the building regulations but will help you find the right contractor and oversee the work to ensure it is completed satisfactorily.

However, if the job is so small that you don't feel you need professional advice, here are some simple guidelines to help you find a competent builder who will do a good job at a competitive price.

Do shop around for the right builder and get at least two, preferably three quotes. If possible go on personal recommendation - but always check the quality of past work before making a decision. Alternatively, contact reputable local firms and ask them to supply you with references. Always follow these up. Ask if you can go and take a look at their work. Don't forget to ask:

• was the work completed on time?
  
• were there any unexpected costs?
  
• were the builders punctual and tidy?
  

All these things add up to a job well done.

Do ask questions. Find out the following:

• Does the builder have the right experience?
  
• Will he agree to staged payments for work satisfactorily completed, with the final payment paid after the work is properly finished?
  
• Will he itemise the invoice so you can see exactly what you are paying for?
  
• Will he accept a penalty clause for failure to complete the work on time?
  
• Will he agree to independent arbitration should there be dispute?

Get the answers to these questions in writing
Do use a builder who is a member of a trade association, such as the Federation of Master Builders or the Construction Employers Federation. Relevant organisations are listed in the back of the Yellow Pages. They can provide you with a list of members in your area. If a builder says he is a member of a trade association, don't just take his word for it. Check his credentials by contacting the organisation concerned. They will be happy to let you know if someone is one of their members.

Do get written specifications and quotes so you can see in advance exactly what is to be done, how it will be carried out and what you are paying for. Compare the paperwork you are given by different companies so you can ensure you are being quoted 'like for like'.

Do use a written contract and agree a completion date. The JCT Building Contract for Home Owners/Occupiers and Contract for Home Repairs and Maintenance is suitable for small building projects. Copies can be bought from RICS Books for less than £10.00.
The Federation of Master Builders also provides a contract for use by its members which sets out the agreed work in easy-to-understand terms.

Dont't automatically accept the cheapest quote. Good builders are hard to find and are in constant demand. Consequently they may charge more than the competition. However, if you have checked the company's credentials, have taken up references and are satisfied that the work will be carried out to a high standard, your peace of mind is worth paying for. Don't settle for second best - if you have to pay to put right shoddy workmanship, it can cost you more in the long term.

Dont't pay cash on the promise of a 'cheap' deal, and never pay for work in advance. If there is a problem, you are unlikely to get your money back. A deposit to cover the cost of materials can be negotiated if you are comfortable with this arrangement. Also, beware anyone who offers to do a job VAT-free; either the builder in question does less than £55,000 worth of business a year or you could be dealing with a rogue trader.

Dont't do business with anyone who knocks on your door and tells you they are working in your area and has noticed that your roof, driveway or guttering needs urgent attention. They are unlikely to be legitimate.

Finally, look out for the Quality Mark. This nationwide, government-backed scheme aims to provide householders with a reliable source of professional tradesmen to carry out work on their homes. It is in the form of a register of not only builders but also other traders who can carry out domestic maintenance, repair and improvement work. All builders and traders are independently assessed for technical competence, must meet health & safety standards, are fully insured and financially sound and guarantee their work for six years.

For details of chartered surveyors in your area contact the RICS Contact Centre on +44 (0)870 3331600