Middle Foundation for 7m wide 2 room extension

[JP_]

I'll be getting a structural engineer / techie drawer to do this, but just trying to work out approx costs of building before ordering the drawings.

I will be building about 8m wide, which will be partitioned to create a thin kitchen (about 3m) and a living room (about 4m). The extension will be somewhere around 6-8m deep.

Would it be better (and maybe cheaper?) to have a foundation for the partition wall, rather than span concrete beams across the 7.5mish gap? Having the foundation will allow a block wall too (although, maybe can do on suspended block and beam floor anyway?) which will be handy for hanging kitchen cabinets and TVs on each side.

The big question is, is it needed? If I had a well insulated stud wall, then maybe no foundation needed, but I was wondering if the the larger beams needed would actually be more expensive than digging and filling another foundation trench.

 

[freddiemercurystwin]

Why aren't you doing a ground bearing slab?

 

[noseall]

Yes a middle wall will be essential for non-trampolining floor beams, takes away the need for a crane and will go on to support the roof.
As per Freddie - why bonkers floor beams and not a slab?

 

[JP_]

TBH, I thought I'd have to have them! Can I put down a slab even though the existing sub-floor has air bricks - its a 1930s bungalow with suspended timber floor. I had an extension done on my last house, and was told (by architect) that it needed suspended block and beam to carry on the air flow.

If slab is easier, more stable and cheaper, then I'd certainly go for that!

 

[JP_]

Just read

https://www.planningportal.co.uk/info/200130/common_projects/17/extensions/4
and
https://www.homebuilding.co.uk/comparing-floor-structure-costs/

So, just need ducting, and save about £1500?

 

[freddiemercurystwin]

https://www.diynot.com/diy/threads/garage-floor-building-control.171482/

 

[JP_]

MInd you, can you have air bricks running the other way? It's a long bungalow, going front to back. The survey suggested more air bricks (something about distance apart). Surely, if air bricks were on the sides, they wouldn't also need to be on the front and back? The air won't care will it?

 

[freddiemercurystwin]

told (by architect) that it needed suspended block and beam to carry on the air flow.

Just tell your stupid architect to expand his mind a little and show him the photos in this thread.

 

[JP_]

I won't be using the same one again this time!

 

[JP_]

update....

 

[noseall]

My criticism is; why have you built the remaining 300mm, up to ground level, in block and not (engineering) brick?

Full marks for tamped sub-slab though.