Specifications

An adequate footing is poured, usually at the same time as the footing for the house walls.

A 4 x 4 foot elevated block foundation is accompanied by a smaller 24 inch by 16 inch rectangle also in block.
In the second course of the foundation is an 8 x 8 inch cast iron door which allows the removal of ash.

The block are layed in type s mortar.
It will take several years before the ash drop becomes full

The foundation slab is framed by two inch boards which when removed will leave a 2 inch clearance between the foundation slab and the structure of the floor.
The opening in the middle of the foundation is covered by a sheet of Duroc, Cement board. The cantilevered portion of non combustible flooring (Right) is framed with plywood.
More rebar are to be added.
The core holes in the corners and all the core holes of the block supporting the chimney will be filled with concrete, and armed with a single bar. The other core holes are blocked with broken bricks.
The polystyrene form in the middle of the sheet of Durock is to form the hole that will allow the ashes to fall through the grate in the fire box floor and into the foundation.
The piece of polystyrene to the right is to form a primary air channel. This channel runs from between the core and facing (beneath the fire box) into the void of one of the blocks on the last row of block in the foundation. This allows primary air to be introduced from the basement or outside, and introduced directly into the fire box.

The slab poured and finished.

De-formed the slab is now ready to be worked upon. Once the polystyrene form has been removed a hole is easily cut through the Durock into the void of the foundation.