Floor level on extension build

[jack24]

Hi,

Wondering if someone could help with this question. I am at the stage of getting builders sorted for building a single story extension. The plans specify the floor as being built up to the floor level in the house by screed on concrete slab on a bed of hardcore (radon barrier and DPC in there somewhere too). There is quite a drop from the backdoor to the ground at the rear of the house and one builder has suggested going for floorboards instead which (I assume) means less work for him and less cost (ie he doesnt fill with concrete but I assume he still needs the hardcore?). The property is about 35 yrs old and has floorboards downstairs ie not concrete floors. Is this simply a way for the builder to do less work (and hopefully charge less money) or is it a valid way to construct an extension in this day and age. I assume there would still be a need for a radon barrier? Would there be an insulation issue (one of the other builders has specced poylstyrene floor insulation on top of the concrete screed? We are planning to have wooden floors (prob on top of the boards/concrete which should make things warmer. Any advice would be appreciated, I'm lost trying to interpret vague builders ,

Thanks

Jack

 

[David E]

I can't see why a beam & block floor could not be used with 50mm Kingspan/Celotex (or what ever thickness BC require) and a floating chipboard floor laid on top.

Follow link for description. http://www.bison.co.uk/default.aspx?id=43

 

[Johnboy54]

You still need the 4" of concrete even if you go for a wooden floor. BC says it stops the weeds. Not sure why the builder is saying polystyrene on top of the concrete - it goes below. You still need insulation between the joists if you go for wooden. Cost-wise, I'd go for concrete.
Your plans should stipulate what's needed?
If you're changing from one floor to another - which you can - BC will clarify what they want in that floor.

 

[chappers]

not strictly true, polystyrene goes over the slab if you are laying underfloor heating in your screed.