Concrete slab on sloping ground

[Ljc1980]

Hi guys

I'm planning a self build side extension and assumed Id need a suspended timber floor as the site ground level drops 3-4 feet from one end to the other. As well as the fact the house currently has this type of floor as it's built on the slope.

However I'm thinking it may be possible to build up the cavity wall to floor level and infill with hardcore prior to laying a slab instead.

A few questions about doing this

Would this create too much pressure on the side of existing house with 3-4 feet of compressed fill against the current wall, bearing in mind this is currently above ground level?

Could this cause damp by breaching the existing dpc of existing external wall?

Would I need to put vents through the slab as there are vent bricks for the current floor that would be covered?

Any help or advice would be great!

 

[Ljc1980]

This pic shows sort of what I'd be trying to do.

Untitled

• Ljc1980
• 23 Oct 2014
• 1

 

[oldbutnotdead]

Can't see why you'd want to go to the expense and trouble of filling that fairly large hole with hardcore and concrete.
Asymmetric load on existing wall- yes 4' of crushed hardcore is going to put a fair old load on it but if it has been built properly that's not a show stopper

Bridging DPC- if DPC in the existing wall is near ground level then you have potential issues there. Even if the DPC is higher you'll increase the amount of water in the existing wall by piling harcdore next to it.

Existing vents in existing suspended floor- yes you'd have to duct them otherwise your existing floor might start giving you problems.

Just put a suspended timber floor in. If joist span is excessive (thus pushing the cost up) then build a dwarf wall half way across so you can use sensible section joists. 100mm Celotex between them, nice bit of redwood T & G on top and off you go.