Remember this applies to all traders, including builders, plumbers, decorators and electricians.
It includes materials, too. They should be of satisfactory quality, as described and fit for purpose.
Whatever your situation is, if you can communicate with the trader or company, then do so.
When you communicate with them, explain the problem, how they can resolve it, and give them a realistic timescale within which to do it.
Peter Litchman, Which? Legal Solicitor says: 'It’s essential before you do anything to check if you need planning permission or building regulations approval for the work you want done.
'And always get a written contract from your chosen contractor, setting out what you have agreed.
'It should include things like the start and end dates, late completion penalties or discounts, how and when payments are to be made, tidying at the end of each day and resolution of disputes. Try and pay for at least some of the work by credit card to get extra financial protection and pay as little as you can up front.
'For bigger and more expensive work you can agree to make payments in stages as the work progresses.
'If things do go wrong and you have followed the above steps, problems will be easier to fix.'
If you talk to the trader or installer face-to-face or on the phone, get it in writing as well.
But don’t talk about a dispute via text or WhatsApp - use email so you have an official record of the dispute.
Agree a date by which they need to complete the work.
If they don't turn up for that, contact them again to agree a final date by which all the work needs to be done.
Make it clear that if they fail to meet that deadline, you'll ask someone else to do it and you'll be claiming back the costs from them.
Remember that when a trader only guarantees their work for a set period of time, that guarantee does not affect your legal right to have the work done with reasonable care and skill.
A trader cannot claim that you can't get a repair on work after your guarantee period is over, if you've discovered that the work was not done to a reasonable standard.
If you can, when you're requesting that a trader fixes their work, include estimates from other traders for the job.
This gives the trader a clear indication of how much you will claim from them if they don't put the problem right.
If they're not cooperative, warn the trader that you'll take them to court if necessary.
You should also find out whether the trader or company has an official complaints procedure you should follow.
Look at your home insurance policy to see whether it covers you for legal expenses for issues with traders or builders.
Look carefully at what is included and also what is excluded.
Major renovations can be more complex, especially if architects, project managers and subcontractors are all working a project together.
If you're complaining about work during a major renovation, you should make your complaint to the main contractor.
In some situations, withholding money might help with negotiations – but we wouldn’t recommend it.
Not only could it have the opposite effect and put you in a deadlock situation, it could also put you in breach of your contract.
This could enable a trader to take legal action against you and would put you in a weaker position if you wanted to go to court.
If you used the trader or company’s finance option, withholding money could also affect your credit score.
If resolving things amicably hasn't worked, ask for the trader or company's complaints procedure.
If they don't have one, find out whether they are a member of a trade association, as there may be a dispute resolution scheme that you can use.
To use any resolution scheme, you’ll need to show that you’ve tried to resolve the issue with the trader first.
Traders and businesses aren’t required to be part of an ADR scheme, or even to use one for the purposes of your disagreement.
But traders and businesses are legally obliged to point you in the direction of an accredited scheme, and specify whether or not they're willing to use one.
There are different types of ADR:
The Consumer Ombudsman deals with complaints about home maintenance and improvement, but you can also visit the Ombudsman Association to find another home-improvement related one.
If a trader or company isn't willing to use an ADR scheme, there are a few other ways in which you can try to recover any money you have lost.
If the job cost more than £100 and less than £30,000, your credit card company is jointly liable if something goes wrong.
It isn’t a legal obligation, so banks have to agree liability, but it's worth looking into. There is a 120-day time limit from noticing the issue to making a claim.
If you made a payment using PayPal or a finance agreement, you might be able to complain and get your money back through the Financial Ombudsman Service.
If you're concerned that the trader might not be acting lawfully, you could report the issue to your local Trading Standards.
Some local Trading Standards offices also offer conciliation services.
While a few local Trading Standards allow you to report issues directly, for most you'll usually have to report your concerns through Citizens Advice.
National Trading Standards collates data from local branches across the UK and works with the police and Action Fraud to help spot and deal with emerging threats.
Reporting a dispute doesn't automatically guarantee a follow up. Trader disputes are looked at in among other crimes, so depending on its severity and available resources, your dispute may just be logged for reference.
If none of this works, it may be time to seek a resolution through legal action.
The Ministry of Justice Practice Direction on Pre-action Conduct sets out the steps the involved parties must take before going to court.
Think about the evidence you will need to prove your claim if you go to court. This may include photographs of the poor workmanship.
You may need to get an independent report on the work. Try to reach an agreement with the builder as to who should provide this report.
Wherever possible, this should be someone you both agree has the expertise to assess the issues and advise on what steps are necessary to put them right.
If a new trader has completed the work, write to the original trader claiming back the money you've had to spend and detailing exactly what work was done.
If they don't pay up, you'll have to start court proceedings to claim the money back.
The small claims court is a quick and simple way of using the courts to settle disputes - you don’t need a solicitor, and the hearing itself is fairly informal. But it should only be used as a last resort.
If you do decide to go to small claims court, you’ll be asked if you want to use the Small Claims Mediation Service first.
This is free and will be provided by the court. If it doesn’t work, the case will be put forward for a hearing in court.
You can use Which? Trusted Traders to find a vetted, checked and assessed tradesman near you. All of our traders have been vetted by ex Trading Standard professionals to ensure you hire a reliable tradesperson.