The mistake everyone makes when doing an extension – and it could cost you thousands

You’ve been saving for years and planned every last detail of the extension you’ve been dreaming of, from the hardwood flooring to the exact shade of paint. Now it’s time to call a builder and get going, right? Wrong. If there is one mistake I see time and again when it comes to building an extension, it is a lack of preparation and patience. I understand why; you’re excited to get started. But skipping some of the basic building blocks for your build could cost you thousands in the long run. Shorts The best builders will start talking to their clients a year before any work even happens. They will work with you, as well as with a designer or architect, a surveyor, and the local council, to make sure everything is nailed down before they start. This is important. Be very wary of any builder who can start next week – even if that’s what you’d love to happen in an ideal world. My favourite builders are always booked up 18 months in advance. Ask your builder to recommend a designer; after all, they’re going to be working together on the project. They should listen to you and to each other to work out the best plan, which will make the most of your space. Get a ground survey of your property. This will flag any potential problems, from hidden drains, unstable soil or old pipes that could add obstacles – and costs – to your build. Some will involve a test hole being dug to see what’s below the surface. This will cost anywhere from about £500 to £2,000. Don’t scrimp. I’m always baffled by people who skip the ground survey because it’s too expensive, but are more than willing to spend £4,000 on a new coffee machine for the new kitchen they’re planning. Spend the money on the survey and get a cheaper coffee machine, it’s important to know everything upfront. I’ve seen people face added costs of £8,000 or more because it turned out there was an old stream running beneath their home. People ignore trees, thinking there’s nothing to worry about if it’s a few metres away – but not the roots, it’s about how much moisture the tree takes from the ground and what that does to the soil. I’ve seen instances where a drain was crushed because someone built a two-storey extension over the top and didn’t think about reinforcing it. It can lead to flooding and black mould. Some people end up having to take up the entire floor and the kitchen island, and start again. These are expensive mistakes. All of these problems can be avoided if you just take your time. With any other expensive purchase – like a car, for example – you would do your research, read reviews, do the background checks, not rush the decision, and make sure to get the best deal. But all of that seems to go out of the window when it comes to an extension. You might be trying to get the best price, but ask yourself why one builder is so much cheaper than the others. Building work is expensive at the moment. Material costs have gone up about 70 per cent in the past five years. So don’t listen to your parents when they say: “How much? Our extension cost us £15,000 back in the day!” If you find a good builder, who has been recommended to you by someone you trust and you’ve seen their work, then that’s gold dust and they’re worth paying for. A good builder will want to do things properly and do all of that proper preparation work ahead of time. And if you know what you’re dealing with, it should all go smoothly and there shouldn’t be any nasty surprises or additional costs, which is better for both of you. My biggest tip of all is to start speaking to a builder when you’ve saved three-quarters of the money you think you’ll need for the extension. That way there’s no rush and by the time you’ve finished saving, the prep work has been done and the builder is ready to start. An extension is expensive and complex but, done properly, it can truly enhance your life and your home. Stop worrying about the £4,000 coffee machine, the white marble worktops and the cigar humidor, and make sure you get the basics right.