Climate Zone 5A in the Midwest, 1999 home.

A raised deck of unknown installation date was removed. The deck was 20′ long and there is a cantilever \___/ shaped windows and french door near the middle.

There are two courses of exposed CMU foundation (visible above grade) before the sill/siding starts.

No ledger was used. The deck was connected directly to the bottom exposed edge of the cantilever (not underneath and to the foundation). The bottom 1.5 pieces of siding are rotten on the cantilever and house.

A semi-raised patio will be constructed in its place, and the siding repairs made before completion. The patio next to the house will go against the foundation and will not touch the siding.

My question is regarding the cantilever area. Being a semi-raised patio, a retaining wall is being constructed. Since sufficient compaction cannot be done under the cantilever (only ~2′ of exposed height), the wall will follow the bay’s dimensions. A single stair will be needed in front of the french door, which is planned to be .5″ in front of the siding to allow drying. 

The height of the patio being below the siding placed against the house means the directly area under the bay will have this same height as well.

Since there is a gap, what, if anything, should be done in the void underneath the bay/cantilever area?

We have trees with many leaves, and the previous deck was difficult to keep the area between the deck and the house clear of debris. While the area is covered by a soffit overhang, snow would still cover the deck during winters.

The contractors are currently suggesting that it could be mostly filled with non-compacted crush, and the gap being small would not lead to significant debris build up or significant water entry.

On the sides of the bay, under the windows and not the door where there will be a step, I think the siding repair could include flashing that covers the gap and rests on the pavers themselves.
An image would be like hardie siding install page 25, image 4.36, from this guide: https://www.jameshardiepros.com/getattachment/d24d99fd-89c1-4fca-9756-d0aa0c33c4d9/intro-tools-hz10-us-en.pdf

The compaction and retaining wall blocks are currently being built. Didn’t know what the exact plan was going to be until the deck was demolished. Any advice would be appreciated. The project is ultimately to resolve grading and drainage issues, so I would hate to leave a void without proper draining under the bay that would cause me issues (or worse tear out the patio).

-Joe