My house is built on piles, due to its location on a flood plain. The piles are H-shaped and support two timber framed floors above; I think on a 'ring beam' type construction.

The entrance to the building is via a hall/utility room built at ground level on a slab foundation. This lies directly in the middle of the building, which leaves two large areas unused under the main building.

I would like to make the most of this space by building blockwork walls in between the piles. To do this, I would need to dig trench foundations between the piles to support the walls. Would this be a viable construction method and comply with current Building Regulations? Or would I have to lay a slab foundation for the whole area tying in with the ground floor slab foundation?