Charity Citizens Advice helped people with 40,000 issues last year relating to work carried out on their properties.

Two thirds of the reports were about substandard services, such as jobs being completed late or due to poor workmanship.

With the summer and bank holidays a popular time to carry out maintenance and improvement, Citizens Advice has revealed the five most common building jobs which caused problems:

• Roofing – 4,971 cases: one person contacted Citizens Advice when a builder failed to complete the work to their roof which led to thousands of pounds worth of water damage.
• Fitted kitchens – 4,766 cases: a homeowner needed advice after a contractor disappeared without finishing the installation of their kitchen, leaving them with no doors on their cupboards.
• Fitted windows and doors – 3,879 cases: Citizens Advice helped one person who had their windows boarded up for 11 weeks after hiring a builder to fit an extension.
• Plumbers – 3,210 cases: problems include someone who had waste water pouring down their walls due to an incorrectly installed pipe. Many homeowners may also need sewer line repair services when signs of a sewage backup or sewer damage become apparent.
• Driveways, patios and decking – 3,116:  one person contacted the charity when their patio started to sink a year after installation, blocking a drain.

The charity said many people come to it to find out how to resolve their home improvement problems, as well as their rights around refunds and compensation.

Gillian Guy, chief executive of Citizens Advice, said: “Thousands of people are turning to us for help after bad building work leaves them with a home improvements nightmare.

“People trying to improve their homes are finding them in a worse state than before they started. Dealing with botched jobs and unfinished work means many are left out of pocket and face huge disruptions to their lives.

“When you’re looking to get building work done it’s important to get things in writing such as quotes and contracts so you can refer back to them if things go wrong. Keep copies of receipts so you can prove what you paid for a job.”

Anyone with an issue can call Citizens Advice consumer service on 03454 04 05 06.

What to do when hiring a trader

Here are the charity’s tips on how to find a reliable trader:

• Get references or recommendations: you can either get recommendations from people you know, or use a website that rates traders. If you can’t get a recommendation, you should ask the person you hire for examples of work they have carried out in the past.
• Trade body member: find out if they are a member of a trade body. Trade bodies have codes of practice and can help resolve problems if things go wrong.
• Get a written quote: Don’t get an estimate. Be clear about what the quote covers. A quote is legally binding and the builder can’t change it without a good reason. An estimate is just a guess at how much the work will cost, and so it could change. You can compare quotes from a number of contractors to make sure you’re getting a fair price.
• Get a written contract: this should cover timing, payments, who will pay for materials and subcontractors, and what exactly is being done. If you can, you should pay in stages rather than upfront.
• Keep copies: get copies of receipts and your written contract as evidence, as well as photos of any problems which arise.

What to do when things go wrong

Citizens Advice suggests taking the following steps:

• Ask the builders to fix the work if it is not up to scratch or is unfinished.
• Ask for some money back. Suggest a figure and explain why it is reasonable – for example, you may have to pay to have the work fixed.
• Complain in writing to the trader or their company, and check to see if they are a member of a trade association to see if they can help.
• Look for an approved alternative dispute resolution (ADR) scheme – this is an independent third party who can help you to reach a resolution. The trader should provide you with the name of a certified scheme.
• If they still refuse to comply, you can consider taking them to county court but be aware you will need to pay fees.