UK Extension Hotspots

Where in the UK can home extensions add most home value?

  • Home extensions can add up to 15% in your overall home value*


#1 London - W

  • £27,950

    Av. cost of extension
  • £280,238

    Av. increase in home value
  • 1002%

    Av. increase in home value

#2 London - SW

  • £27,004

    Av. cost of extension
  • £247,027

    Av. increase in home value
  • 915%

    Av. increase in home value

#3 London - NW

  • £29,240

    Av. cost of extension
  • £225,695

    Av. increase in home value
  • 772%

    Av. increase in home value

"We deliver for professional tradespeople nationwide who work on extensions day in, day out. We're all about supporting trades, which is why we’re building a service to quickly deliver tools and parts to tradespeople"

Graham Smith, Strategic Account Director, Gophr

Moving house is often a stressful experience, be it organising the removal team or trying to amend utility contracts. However, a new concern has made moving house more challenging than ever before: affording the new mortgage in the first place.

Recession aside, not since the 1860’s has house-buying been further away from average earners. High interest rates, extremely poor mortgage acceptance rates, and the average home value reaching £281,000, means that those looking to take the next steps on the property ladder are stuck in their current homes.

Homeowners have caught on to this struggle, and are commissioning tradespeople up and down the UK to extend their current homes, instead of going through the hassle of moving.

Once planning permission is approved, a team of professionals can build your extension in as little as 12 weeks! Here at Gophr, we help trade merchants deliver a huge range of tools and supplies to builders around the UK. And in the last two years, we’ve seen that demand  sky rocket.

So, where in the UK would a homeowner most benefit from building an extension? To find out, we scraped Government postcode data for England and Wales, and ran it through a leading housing organisation’s home extension calculator, establishing which UK postcode would see the best return on investment for building a medium-sized home extension.


Top 10 Results


Rank Postcode Medium extension House value inc Return on investment for
building home extension
#1 W £27,950 £280,238 1002.64%
#2 SW £27,004 £247,027 914.78%
#3 NW £29,240 £225,695 771.87%
#4 N £28,433 £194,510 684.10%
#5 AL £24,108 £150,022 622.29%
#6 HA £25,746 £155,015 602.09%
#7 UB £23,177 £138,677 598.34%
#8 SE £27,413 £157,534 574.67%
#9 E £27,570 £155,743 564.90%
#10 SM £26,445 £140,075 529.68%


Full data is available here. Please link to Gophr if this press release is used.


Remarkably, those living in the ‘W’ postcode (West London) can see huge gains from building a medium extension to their properties. On average, a medium extension costs £27,950 to build in London, however by completion the overall property value increases by an average of £280,238. This demonstrates a huge 1002.6% return on investment. This is closely followed by the ‘SW’ postcode (South West London), wherein an extension would yield a 914.7% return on investment.

London postcodes represent 9 of the top 10 in this list, highlighting the clear financial gains by extending in London. Just St Albans (‘AL’, 5th place) exists outside of the wider London area in this list, proffering a 622.2% return-on-investment for extending a home. Statista’s UK housing data shows that London house prices far eclipse the standard English housing price (£535k to the UK’s £281k), so the results may come as little surprise.


Top 10 Results (excluding London postcodes)


Rank Postcode Medium extension House value inc Return on investment for
building home extension
#1 AL £24,108 £150,022 622.29%
#2 SL £26,798 £138,930 518.43%
#3 WD £28,273 £144,386 510.69%
#4 SG £23,492 £112,710 479.78%
#5 HP £27,950 £126,533 452.71%
#6 RH £25,800 £115,385 447.23%
#7 DA £26,278 £117,447 446.94%
#8 CM £25,316 £109,730 433.44%
#9 RG £26,633 £112,664 423.02%
#10 OX £26,617 £106,388 399.70%


The Hertfordshire town of St Albans (‘AL’ postcode) comes in first place on our list of the best UK postcodes for extending the home. Investing just over £24,000 in a medium-sized extension will result in a house value increase of £150k, representing a return on investment of 622.2%. This is the strongest result outside of London’s boroughs.

In a close second is the ‘SL’ postcode representing Slough. The average extension in this region costs £26,798 to build, yet the average home value increases by £138,930, showing an ROI yield of 518.4%.

Third, and the closest area geographically to London in this list, is the ‘WD’ postcode for Watford. The average extension there costs the most in our top 10, at £28,273, however a house price value increase of £144,386 hugely offsets the additional costs. With a return on investment of 510.6%, it’s only marginally behind Slough in our list.

The final place in the top 10 goes to Oxford, with the ‘OX’ postcode. To extend their Oxfordshire property, homeowners can expect to pay just over £26,600. In return, their property value will increase by an average of £106,388, showing an ROI result of 399.7%.]


Bottom 5 results 


Rank Postcode Medium extension House value inc Return on investment for
building home extension
#101 DN £22,772 £41,728 183.24%
#102 DL £24,182 £41,752 172.66%
#103 DH £23,435 £40,412 172.44%
#104 TS £23,113 £38,794 167.84%
#105 FY £27,714 £41,414 149.43%


The ‘DN’ postcode, incorporating Doncaster, Scunthorpe, Grimsby and more, features as one of the lowest postcodes to see financial benefits in building a home extension. The cost of a medium extension is £22,772, one of the lowest figures seen across England and Wales. However, having an extension only boosts a home’s value by £41,728, showing an ROI of just 183.2% overall.

However, the UK postcode with the lowest ROI for extension building is ‘FY’, covering Lancashire (Blackpool, Cleveleys etc). The cost of building is surprisingly high in the region, with a medium extension costing £27,714 to build. This is comparable to Southern locations like Hemel Hempstead and Stevenage. However, unlike the Herts boroughs above, the average home value in Blackpool increases by only £41,414, similar to Doncaster. This means the ROI for building an extension in the ‘FY’ postcode is just 149.4%, the worst return in England and Wales.

The bottom 5 locations are all based in the North of England, highlighting the value disparity between there and homes in the South. The top 5 locations (all in London) for building an extension average an ROI of 799%, whereas in the North of England, that figure falls dramatically to just 169%. However, every postcode in England and Wales sees a significant increase in home value when an extension is built, showing that it’d benefit all homes.


We say:


“With the UK property market in a long-term state of turmoil, now is the perfect time to invest in your property instead of seeking to move. An extension, be it small or large, will open up space in your home for your family to grow. Plus, with Gophr’s rapid delivery service, taking on DIY elements of your extension has never been easier. Simply place an order for paint, tools, or more, and we’ll deliver straight to your door in no time at all. Let’s work together to make home extension building not just something for the super-affluent.”




  1. Gophr sought to establish which UK region would benefit the most from home improvement services, in this case building an extension.
  2. To find out, Gophr scraped the Government’s postcode data, available from the ONS.
  3. Then, Gophr utilised the Rightmove Home Extension Calculator, inputting each available postcode in to the site
    1. Due to Rightmove data limitations, Scotland was not able to be part of this study
  4. Data was secured for all three types of available home extension size (small, medium, large), as well as home value increases. This press release contains only medium size extension information, but full data is available for all sizes here
  5. Once data for home extension costs and home value increases had been scraped from Rightmove, a percentage return-on-investment was calculated for each applicable region.
  6. Data is correct as of 21st of May 2024.