I am having a 6m x 8m single storey extension built. Because this is near an adjacent slope I have decided as belt and braces to go for piles and ring beam foundation. Building Control are happy with this. The floor is to be the conventional 100mm compacted clean hardcore, blinded with sand, 75 Celotex, DPC, 10mm concrete, 6mm screed. But BC are not happy with this sitting on the ground due, they claim, to differential movement relative to the ring beam system. Anyone else encountered this?
makes perfect sense to me... surely the slab needs to be integrated into the ring beam for it to work. ie not groundbearing
ground bearing slabs are harder and harder to get bc approval for nowadays. you could get an engineer to commision a survey of ground conditions and design a spec...........not likely! the fact you are on sloping ground is iffy, but using piles is a warning sign to bc that you are on poor bearing ground. can your pile/ring beam designer not specify an integral beam and block system? or a beam bearing reinforced slab? i would of thought the beam and block is the usual, and not too pricey if you shop around (eg hanson encon).
What's the point of piling and then ignoring the piles and ring beam to hold the floor? It dosn't make sense. No wonder the BC wasn't happy. You shouldn't be happy either. Beam & block. Then 75mm Celotex, then 75mm screed. You've just got to watch the ffl to make sure it fits in with the rest of the house.
What's the point of piling and then ignoring the piles and ring beam to hold the floor? It dosn't make sense. No wonder the BC wasn't happy. You shouldn't be happy either. Because if you want to have an integral floor then you use pile and raft. You cant support a 6m x 8m floor slab on a few inches of ring beam on 3/4 of the perimeter (1/4 being the existing bumgalow). Since when has a ground gearing slab been acceptable?
A few inches? Surely you will be building a 300mm cavity wall off the ring beam? The b&b floor will sit on the new wall and also the existing.
why not do what I did. Putting footing in as normal, leave inside skin down 150 mm, shutter cavity side of internal wall and pour floor as normal but bear it onto inside skin by 100 mm. My solution because I didn't want to wait for beams to be made. Only thing is you eed rebar concrete.
why not do what I did. Putting footing in as normal, leave inside skin down 150 mm, shutter cavity side of internal wall and pour floor as normal but bear it onto inside skin by 100 mm. My solution because I didn't want to wait for beams to be made. Only thing is you eed rebar concrete. Only thing , you'll need at least £250 worth of structural engineers calcs to prove the design.
You cant support a 6m x 8m floor slab on a few inches of ring beam on 3/4 of the perimeter (1/4 being the existing bumgalow). You need only two sides (plus a middle beam) to support the floor beams. So you'd have a few inches at both ends of a 3m beam. Or maybe a 4m beam if the beams run in the other direction.
All suggestions have been good, but many would require respecifying the ring beam, and/or additional foundations and/or additional costs. Thankfully BC has agreed to allow the ground bearing slab on what is essentially a flat area alongside the slope that has been consolidated for over 35 years. Thanks for all the alternative suggestions.
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