ePrivacy and GPDR Cookie Consent by Cookie Consent How much does it cost to build an extension / conversion? Find out.

How much does it cost to build an extension / conversion?

Whether you're building a rear extension or converting your loft, get a breakdown of the costs you'll be facing when it comes to construction.

4 min read

When it comes to construction, no doubt you’ve got one question in mind: how much is this going to cost?

And why wouldn’t you be concerned? Whether you’re extending your home or converting an existing space, the biggest single expense is going to be the construction stage. Not only will you be paying for the materials needed for the build but you’ll also be covering the day-rates of those involved and the equipment they require. All this adds up pretty fast.

To help you budget for this all-important stage, we sat down with one of our top Connect recommended contractors, Alex from Home Republic. We asked him what figures can people expect to see and how exactly prices are determined from the builder’s end. Here’s what he had to say…

How contractors price their services

Most companies, whether big or small, will have some guidelines in place for putting together a quote.

They’ll likely be looking at three key factors: size of the project, whether they’re building or refurbishing, and the standard of work required. There are a few other key factors that’ll affect the budget but we’ll go more into these other considerations below.

Now it’s important to note here that when we talk about standard, we don’t mean a contractor will purposely do shoddy work. Rather it refers to the intricacy of the design, what speciality is required, and the quality of materials used.

Here’s the maths Alex uses when pricing for his own customers…

Basic build

£1500/m2 new build areas
£800/m2 refurbished areas

Standard, high-quality build

£1650/m2 new build areas
£875/m2 refurbished areas

Premium quality build

£1800/m2 new build areas
£950/m2 refurbished areas

Cost guide for common projects

Knowing the potential square metre costs of a build is great for nailing down the details further down the line but what about in those early stages? When you’re just starting to consider what project is right for you, it’s often easier to understand price with some more general figures.

Luckily, Alex was able to go through with us some of the most common UK projects and what price tags you might expect.

  • Rear extension: £75-90K
  • Side return £65-75K
  • Two-storey extension £130-150K
  • Wraparound extension £125-140K
  • Room in loft conversion £15 - £45K
  • Loft main dormer £65-75K
  • Hip to gable loft £65-75
  • Mansard loft conversion £65-75K
  • Garage conversion £15-25K

Please note: these prices are based on projects completed to a high-quality finish and is skewed to the higher end, due to London premiums. Those outside the south of England could see costs half of the ones listed above. Talk to our team for a price tailored to your location and scale.

What affects prices?

Looking at the estimates above, you might be a little surprised by the numbers. Maybe you’ve seen cheaper estimates elsewhere on the internet. However, there are a few key details that many forget when costing their projects…

Rear extensions: though they seem straight-forward, many rear extensions also involve redeveloping the whole ground floor, which is reflected in the price above.

Two-storey extension: just like a rear extension, a two-storey extension often involves the rest of the house needing work and, because of it’s size, this means redeveloping the whole home.

Other factors that affect your budget…

  • Location, see above.
  • Size, the more you build, the more it costs.
  • Complexity, anything outside the norm will require more time and expertise.
  • Glazing, the more glass you use will cost more in materials and from a structural perspective.
  • Team used, one-man bands will be cheaper but come with risks.

Southbrook Road 01

Easy ways to make savings…

If you’re looking to cut down on costs, the most important thing to remember is the importance of a good build. Using a quality builder ensures you not only have the best chance of realising your ideas and getting them to a high standard but also this quality will help you secure the best price, should you resell your home in the future.

All too often, homeowners choose a cheap quote over a good builder and pay the price, those ‘too good to be true quotes’ often being just that. Either those low prices come from the builder misquoting and hitting you with out of the blue extras or your builder is undercharging and making up the difference by taking on more projects than they can handle, putting you at risk of serious delays or even their company going bust.

Learn more about choosing a good builder here.

If you do want to save money, consider these alternatives…

  • Opt for recycled materials, rather than cheap alternatives.
  • Cut back on your fittings, such as budget-friendly cabinets.
  • Project manage the build yourself.
  • Look into small DIY projects, such as fitting your own carpets or tiling.
  • Avoid costly legal battles. Get your neighbour onside early on, have an architect manage your planning application, anything that will stop you being hit by red tape.

Considering your own project? Perhaps you’ve got planning but not sure where to go next? If so, don’t forget we provide free consultations, no matter what stage you’re at. This means you get the very best expert advice without the price tag. Book yours here.

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