Home extension: DIY or call in the builders?

How much you do yourself depends on your experience, skills and confidence. 

Nick Evans is a DIY enthusiast in Pembrokeshire who – despite no formal building training – converted a garage into bedrooms by himself.

“In theory you can do all of it yourself,” Nick says. However, he adds that gas is an exception, as it’s a legal requirement to use an engineer on the Gas Safe Register, while it’s also advisable to get an electrician for electrical work.

First of all, think about what exactly you want to achieve, and draw up some plans. If you want to keep your budget down, it’s best to opt for a simple configuration, such as a rectangle with a pitched roof.

Also, try to keep the groundwork as simple as possible. If you can, avoid areas with pipes, drains and trees. Make sure your costs are inclusive of the building foundations.

You can build some extensions under permitted development rights, meaning you may not need to apply for planning permission. There are some constraints to bear in mind:

• The area of rear and side extensions must not exceed 50% of the total free area around the property.
• The exterior appearance must be sympathetic to the house and neighbourhood.
• The width of side extensions must not exceed 50% of the width of the existing house.
• The maximum length of rear extensions is 3 metres for terraced or semi-detached houses. For detached houses, it goes up to 4 metres.
• Only single-storey extensions are allowed if the distance to the boundary is less than 2 metres.
• The height of single storey extensions must be under 4 metres. Two-storey extensions must not exceed the existing house eaves.
• Balconies and terraces are not allowed within permitted development rights.

Even if you’re building within permitted development rights, you’ll still need to comply with Building Regulations. To stay on the right side of the law on both counts, you may feel more comfortable hiring an architect or architectural technician for this. Plans must be properly drawn up, and submitted to a building control body (BCB).

“Building Regulations actually make your life much easier,” says Nick. “They list everything out that you need to know. And your local building control team will be happy to help you.”

He says: “Throughout the process, take lots of photos. This provides evidence to the building control body that you’re doing things to code, which is important for things like insulation and installing a damp proof course. They will also give clear guidance as to when they’ll need to come out and inspect your work.”

Even if you’re not terribly practical, you can make a start on your project and save some money by sourcing your own materials.

“If you open an account with Jewson or a local building supplier, you’ll automatically get a discount,” says Nick. “I got 10% off my materials, but if you haggle, you could get more. You’ve got nothing to lose by saying ‘I’m going to be dropping £15,000 with you, so how much discount can I get?’

“This sidesteps any potential markup that builders might charge you,” he adds.

If you’re confident that you’ll do a good job, it’s time to brush up on DIY videos on YouTube.

“Brickwork isn’t too difficult,” says Nick. “I’ve bricked up, put in a doorway and windows, and built a stud wall.”

However, he adds “There have been mishaps, and there’s a lot to learn. Rendering is an art, for example. There are things you just won’t be able to do yourself”.

If you do hire a builder, then ensure they have the right insurance. All tradespeople working on your house should have:

• Public liability insurance
• Employer’s liability insurance
• Installer’s all-risk cover
• Professional indemnity insurance

It’s also important to inform your buildings insurance provider when you’re having work done on your property. If you don’t, you’re unlikely to be covered for any damage or loss caused as a result of the work. And as an extension is likely to add value to the property, you need to update your policy accordingly.