House Extension Costs Revealed: A Digestible Breakdown

House Extension Costs Revealed: A Digestible Breakdown

20 March 2018


House Extension Costs Revealed: A Digestible Breakdown

Extending can radically improve your home. Let’s face it, bigger, better and roomier is going to be more enjoyable for you and more attractive to potential buyers. Planning an extension is an exciting time. You’ve been filling up idea books and getting your creative hat on with mood boards and having a whale of a time.

But, when it comes to costing the project it all depends on what you’re going for, and that vagueness can leave a lot of people scratching their heads thinking have I thought of absolutely everything?

You’re in luck, we’ve done it for you. Here’s the breakdown:

What’s Your Budget?

This is perhaps the most fundamental of all questions: how much do you have to spend?

Try to be as accurate as possible, taking into account architect’s fees and planning permission fees (if applicable).

Be conservative, making sure you’re adding on VAT to architects and building quotes if they’ve quoted a net cost.

Generally, you’re looking at:

  • Planning permission - typically a council will charge around £170 for planning permission and £90 for lawful development certificates, but each council varies slightly.
  • Architects - you’re looking at a starting point of £80p/h, with surveys on top of that from around £1500.
  • Builders tend to quote per project, not per hour so this will depend entirely on the area you live in and what the work will be (more on that next!)

Remember to speak to your bank about a loan far in advance, just to make sure you’re getting a realistic idea of what they can lend you.

What’s Your Goal?

As the cost is entirely reliant on what you’re aiming for, there’s not a one-size-fits-all answer. However, there is a basic rule of thumb to give you a solid platform to kick things off.

Single-storey: In the South East, a single story extension could be anywhere between £1,200 and £2,000 per m2.

So, if you’re looking at a simple 5m x 5m extension, the cost will probably be in the region of £30,000 for the building work alone. Unsurprisingly, In London, you’re looking at anywhere from £50,000+ purely because of location.

Two-storey: Assuming both storeys are the same size, it’s a generally accepted rule to add 50% to the single-storey cost. Again, London is going to be slightly pricier as expected.

Kitchen or bathroom: It gets a bit more complex with these extensions as plumbing work will need to be accounted for in both budgeting and planning permission. The cost will depend on the specs: do you want a shower, bath, and WC? Do you want a high range kitchen?

As a base idea, you’re looking at about £5,000 starting for a basic bathroom and £10,000 starting for a low/mid range kitchen.

Attic: A popular choice, the attic conversion offers up various options. Velux, dormer, hip to gable and mansard (listed from least expensive to most expensive). The velux will start at about £20,000 and the mansard will cost anything from £50,000+.

Check out this article by Household Quotes for a full breakdown of different conversion types to see which is right for you.

The Final Touches

When it comes to the finishing, you’re going to need to hold tight and stick to that initial budget, as costs can quickly spiral out of control with fancy taps, bespoke flooring and tiling, to name a few.

Windows can be an unexpected cost at the end, so make sure you get an accurate price built into the building quote right from the start.
Just remember to do your due diligence when it comes to choosing a building company. Get recommendations, get referrals and get researching because it’s not something you want to enter on a wing and a prayer.

Happy planning!

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