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Re: Basement conversion cost

by CDSW11 » Wed May 10, 2017 9:37 pm

I've always been told a basement conversion is 300-400k. And that it is 3,000 -4,000 psf, which is the same assuming 100sqf.

Re: Basement conversion cost

by JRobinson1 » Tue May 09, 2017 1:27 pm

Hi everyone,

Sorry for the salesy sounding email in advance.

If anyone is undertaking a basement dig, then make sure you speak to your existing home insurer in advance of the works. At this stage, most standard insurers will look to reduce cover significantly or come off cover entirely (exposing the property to a wide range of perils and invalidating most mortgage lenders requirements for insurance).

We can provide a comprehensive bespoke insurance solution for homeowners/landlords undertaking major works... If you would like a quote then please contact me at

Check out our website for further details: ... insurance/

Re: Basement conversion cost

by catfish72 » Tue May 02, 2017 4:21 pm

I would highly recommend APT Renovation - Design & Build if you are planning to extend basement space.

Check their website for further details: ... on-london/

Good luck with your project!

Re: Basement conversion cost

by jonathan @ hamptons » Tue May 20, 2014 9:07 am

Hi Julian,

Sorry I didn't notice your question last week. The stamp duty threshold at £2m has been a real issue for the last two years, and now the added confusion over mansion tax has added even more uncertainty at this pricing point. Although the £2m - £2.5m market is better than it has been for a while, it is still the toughest market to sell in.

As I've always said, do a basement if you want to stay in your house for a good long while and if it suits your lifestyle (ie want kids play space / utility / media room etc) but rarely do they make a return in the short term. They buy you more time in the same house, not profit!!

If you want specific advice then drop me a PM - I'd be happy to discuss properties & plans and give you an idea of before and after values.


Hamptons International
98-100 Northcote Road
020 7924 2170

Re: Basement conversion cost

by juliantenniscoach » Mon May 12, 2014 9:27 am

@ Jonathan, what's your take on the stamp duty implication if the basement tips you over the £2m value? Thanks.

Re: Basement conversion cost

by jay0307 » Mon May 12, 2014 12:12 am
Lo Basements Ltd is the best company and the cheapest in London for basements and underpinning, they saved me 25% compare to other basement companies in the area. great staff too

Re: Basement conversion cost

by bamse » Sat Feb 08, 2014 5:16 pm

supergirl wrote:I had a ball park quote about 2 years ago and a basement conversion is about £2000/2500 per sqm. obviously is can go much higher if you dig a lot (get yourself a pool ;), etc as someone said. But still, 2 years ago the cost of space in battersea was about £7000 per sqm so still worth digging!

you can save a lot of money if you dig under your garden as you dont need so much steel beams (a garden is lighter than a house obviously!). The law says you can dig under your garden for about 1/3 of its size (check the precise numbers). I have seen some fantastic works of basement with no natural lights but state of the art extraction, I have also project managed a few for some of my clients.

The thing is London and particularly Wandsworth is one of the few boroughs that charge a lot for skips, and everything that disrupt the pavements. So for instance if you were living outside of the M25 you could knock off 30-40% of your total quote.

PM if you need more info. PS: I am not selling myself, i dont work on those sort of projects but do know a lot about construction
Hi, any idea what the price difference is between digging under the garden on a semi detached house vs under the house? Thanks!

Re: Basement conversion cost

by Rabbit_and_Co » Wed Jul 10, 2013 1:58 pm

Hi nooze2010,

I've got no idea but my husband designed this basement conversion in SE London (he's an architect)

I'm sure he'd be happy to chat and give you an idea of costs (he's Christophe at Thomas & Spiers Architects).

Hope this helps.

Re: Basement conversion cost

by nappyvalley76 » Wed Jul 10, 2013 11:11 am

Nothing like a bit of blatant self promotion London Builders, sorry, I mean Kim 44. :D :D :D :D :D

Re: Basement conversion cost

by Kim 44 » Tue Jul 09, 2013 8:30 pm

Just had work on our new basement completed recently. I am an estate agent and had a mortgage surveyor value my house again. The new basement has added £500,000 to the property value. Not bad seeing we spent just over half that on getting it built. I've bought and sold a few properties over recent years and had 3 basements built before selling on. I find that loft conversions and extensions add roughly 50% on the money you spend on building them. If the loft cost £60k you'll get it back plus £30k on top in most areas in London. Basements add the most as they provide the most space and you can make them into a flat and rent it out. Homes with an already converted basement sell very quickly within London. The first conversion was a nightmare but the next 2 were better as I used London Builders, most property developers in London use them, I think they work on individual homes also. They work from outside the house, digging away under the front window and accessing from there only. When the works done they make access from the house to the basement. They use a similar style for lofts too and go in from the roof till everything's done.

Re: Basement conversion cost

by Emma » Mon Jul 08, 2013 10:00 am

We are looking to do our full footprint basement too and the quotes varied by over £100k - from under £300k to over £400k! So well worth getting a few. A lot of basement companies couldn't be bothered to prepare the quote - out of 8 companies only 4 got back to us as they all have more work than they need - hence the prices going up hugely!

Re: Basement conversion cost

by walesdavies » Mon Jul 08, 2013 9:25 am

We used Qualitas & I can't recommend them enough. They also specialise in whole house refurbs / building work so may prove to be more reasonable overall. Pm if u want any more info.

Re: Basement conversion cost

by nicolekirk » Fri Jul 05, 2013 12:04 pm

We are in the midst of a major renovation right now - Portaloo in drive and all :D

Let me know if you want to speak to someone who has transformed things for us so far!


Re: Basement conversion cost

by jonathan @ hamptons » Fri Jul 05, 2013 8:44 am

No problem, I run the Northcote Road office.

Re: Basement conversion cost

by Bluebird27 » Thu Jul 04, 2013 4:29 pm

Hi Jonathon,

Thanks for your feedback, that is super helpful! I may just take you up on your offer - which office are you in? The basement extension is really more of an investment for us. We are looking to sell in about 3 years so the main consideration in doing the basement is whether we can achieve a healthy profit margin or not- so it would be really interesting to hear your feedback on that.

Thanks again! x