So 

say I was going to build a two story home  10m x 7m as a guide . 
what is the likely ( ball park figure ) extra cost in effectively have the ground floor as a basement and only one floor above ground? 
forget all the complex what if’s , such as ground type . Is there such a thing as it’s likely to be … x amount more expensive 🤷🏻‍♂️

x2 times more than GF. But sooo many factors.

How much have you got?

Because it will take it all and then some!

I’m going to be a bit more positive here and say yes it’s going to be more expensive but not necessarily prohibitively so, but with the caveat that site location and ground conditions are the over riding factors. Much easier to basement into a hillside than boxed in on all sides, big hole with battered sides is much easier and cheaper than sheet piling, big Big much away unless you can loose it on site, plus many more factors like drainage, access etc.

£100K - there's some numbers here on BH somewhere - err, search for 'basement'. I can't remember whether that's the incremental cost or the whole caboodle.

 

>>> such as ground type

 

Actually, that could make a big difference - if you're on soft clay and going to have to dig deep foundations anyway, then the incremental cost for the basement will be less. If you're on hard rock...you get the idea.

 

p.s. I see I have 1.2 £K/m^2 as a rough number from one of the threads here.

Edited January 3, 20242 yr by Alan Ambrose

Nah - listen to your uncle Pocster .

 

You get a man with a digger to dig the hole . You do the slab , retaining walls , waterproofing ( whatever method ) piece of piss .

Double the cost of the whole building.  Treble the cost of any one storey.

 

Plus I, as a contractor, would add risk money. Anything that could be a problem is multiplied.

 

That also assumes a clever and practical design. 

 

I was looking into a hole while on holiday (as I do).

This was a deep excavation for  a basement. But a it was in a dry area of Spain, with no water table concerns, and self supporting sides, they just dug a hole and used clay block-work for the walls, and the usual concrete frame holding it all up. That will still cost more than an upper floor, but not much.

 

In central London, dig a basement. Perhaps central Edinburgh where it isn't rock. Elsewhere, no.

 

I've done one. Not good value but the client owned the site and wanted more space. Plant and kitchens went in there. It was a pain throughout, especially as it, being watertight, held the rain in.

 

 

If you have decent ground conditions and you want it to be fully habitable space you could budget costs of 1.5 x the going rate per m2.  The finished value is likely to be about 75% of the above ground value per m2.

Ah from here in 2015 prices, there's a few other scraps of information if you search. Allow inflation and +-50% for ground conditions?:

 

 

 

my 120m2 basement cost £100k in 2015 so no more expensive,

 

 

But there would be no windows, and various other simplifications. 

If it's a garage or plant room, of course it is plainer.

 

The muckaway cost itself could be very high ( location) , but is possibly shown elsewhere  as site prep.

120m2 x 3m x 1.3 bulking.  say 500m3 or 25 lorries to load, transport and tip. 

Ok thanks for all the differing views ( I thought as much ) 

I currently have planing for a 1.5 story hip roof  home in Devon on a tight plot . Planners are not giving an inch on dimensions of the home or roof design ( tried to go a tad higher with a mono pitch roof and they are having non of it . ) even tried a couple of “ bolt on “single story pods ( util and down stair loo and office combo) but flat no! 
so thought ok leave all the above ground as is and do a basement or even half a basement for a little more space currently foot print of living space ground floor is 55.6m2 

this is the dilemma 🤔😁

20 minutes ago, Nic said:

Planners are not giving an inch on dimensions of the home or roof design

Nor did mine (and that was Torridge in Devon) going to appeal I got exactly what I wanted and it was not as difficult as I thought, I did my own 🤷‍♂️

32 minutes ago, joe90 said:

Nor did mine (and that was Torridge in Devon) going to appeal I got exactly what I wanted and it was not as difficult as I thought, I did my own 🤷‍♂️

Please PM with the details if that’s ok that would be great 👍🏼