Once the walls are formed a floor frame is made up of 100mm by 50mm solid wooden joists spaced at a maximum of 600mm. This frame slots down into the walls to make the whole structure very rigid. A layer of 15mm thick clean plywood is laid across the floor joists and fixed to them. As with the walls all edges are rounded and smoothed and the whole floor is varnished underneath so that the ceiling is smooth to the touch.
On top the whole area is covered in snug fitting, 14mm thick soft foam tiles. These interlock tightly together and not only make the top floor comfortable to sit or kneel on but help to reduce the impact of bumps and knocks.