Ground Preparation

[DaleSchultz]

I have read many of the posts here all about ground preparation, but sadly most assume unlimited space above the tub, so I thought I would explain my plan and see if anyone has any input.

We currently have a Hydropool 7'x7' 5 seater 400 gallons on a deck at a cabin in Maine. We intend moving the hot tub below the deck so that I don't have to dig it out from under the snow every time we visit the cabin in the winter.

The area below the deck is now waterproof after I installed vinyl soffit materials on the underside if the deck last fall.

The floor under the deck is currently a layer of crushed stone on soil.

The space between the ground and the underside of the deck ranges from 86" to about 98"

The height of the hot tub needs when opening the cover is 78" and I am 6'6" tall (also 78").

There is a small PT wood retaining wall at the side of the area.

So the problems are:

I hate crushed stone, I want to walk around barefoot. I want to create a stable flat surface to walk on. I would prefer a wooden decking material.

I cannot dig down very far - I don't want to undermine the retaining wall.

I prefer decking to a concrete slab

I have seen designs of what they call floating decks - small decks that are not attached to the house. They are designed to move with the ground as it may heave in the winter. Problem is they need about 13" height as the concrete footings are rather tall.

I have also read pages on deck designs wherein the minimum joist sizes are usually 2x6 lumber.

so... in order to minimize the vertical space used, I have come up with this plan....

I intend placing concrete pavers on the crushed stone. (I have a good supply of them already)

On the pavers I am thinking of placing 4x4 pressure treated lumber.

On the 4x4s I will screw down standard 5/4" x 6' decking (composite or PT)

Now before everyone freaks out about the strength...

What I am attempting is to add a surface floor, that is horizontal and made of decking, to the ground.

Yes, the surface must be strong enough to support the full hot tub and occupants, but it is not a deck I plan to build.

I figure that the 4x4s will be resting along the concrete pavers and thus will have no span. They are there to hold the surface decking down.

If I space the 4x4s every 16 inches the surface decking will be doing their usual design duty span (actually less since the 4x4s are wider than a 2x6).

The proposed size is 11'3" by 10' with the 7'x7' tub spaced a tad more than 1' from two sides.

Questions:

• Would a concrete pavers distribute the load from a 4x4 adequately?
  
• How much tolerance in height difference could the 4x4s handle?
  
• Will it be too hard to get the pavers to within the height tolerance? (I have bought a laser level)
  
• Could I simply dispense with the pavers, and place the 4x4s directly on the crushed stone ? This would remove any problems of pavers being too high/low and allow the stone to settle such that the load is evenly distributed along the length of each 4x4, and would give me another 2" of headroom.
  

What have I not thought of ?

Thanks

Dale