Foundations needed for an internal load bearing wall

[Grannyjan]

We are converting part of a single storey stone built barn into living accommodation and we have removed a wooden partition between an old garage and a cow shed. This has left a gap between two concrete slab floors, only one of which is going to be part of the domestic accommodation. We therefore have to build a block wall, where the gap is. The wall will be to the height of the existing walls and will support a wooden floor, to provide a storage area in the roof of the non-domestic part. The barn is built without foundations but on an area of rock. Excavation the gap I have found a cobbled floor on top of large lumps of local stone, closely packed but I have not yet reached bedrock.

How deep should I go with my excavation? Can I put a concrete foundation on top of the layer of stones? How deep must the concrete be?

[stoneyboy]

Grannyjan,
Try driving a metal spike at various places into the gap. If it won't go in far you're probably OK laying concrete direct on this surface. The foundations should be at least 125mm deep.
end

[Carl Beau]

We are converting part of a single storey stone built barn into living accommodation and we have removed a wooden partition between an old garage and a cow shed. This has left a gap between two concrete slab floors, only one of which is going to be part of the domestic accommodation. We therefore have to build a block wall, where the gap is. The wall will be to the height of the existing walls and will support a wooden floor, to provide a storage area in the roof of the non-domestic part. The barn is built without foundations but on an area of rock. Excavation the gap I have found a cobbled floor on top of large lumps of local stone, closely packed but I have not yet reached bedrock.

How deep should I go with my excavation? Can I put a concrete foundation on top of the layer of stones? How deep must the concrete be?

Hi.
This wall will become a supporting wall if it is going to hold flooring to another floor level. So your foundation has to be a min of 600mm deep by 450mm wide