We have on order a 27 foot round steel above ground pool. We've dug out our area using a tractor to make it more or less level, and I'm working now on hand levelling the rest. Ground is undisturbed, with some clay (I can squish the dirt in my hand like playdoh). We live in Canada, with a lot of frost heave and full, full freezes in the winter. Our pool instructions call for trenching and laying 2inches thick of "rock dust" or mortar in a circle around the pool, 24inches wide, and the footings and rails will sit on top of this. Pavers are optional in the instructions, due to frost heave, and I feel we'll be best off just putting the uprights/footings right on this compacted rock-whatever trench (open to corrections )
After calling around to the landscaping companies around here, all are suggesting a 25mm washed rock to use, as it will compact nice and firm, and allow for water to drain through the rocks to help us with drainage and frost heave.
So, here's what we are thinking....and where I need help with my layers:
1) Lay down a 2inch thick base of the washed rock over the full area (not just in a trench). So now we have a giant circle of rock. Of course will compact it down, level it, compact again, etc etc so it is firm.
2) Install the pool walls and uprights on this base.
3) Inside the pool, my understanding now is that I need to install my foam cove AND THEN put in material for my liner base, like foam or sand or foam and sand (Logic tells me I should do the base and THEN the cove.....but I'm reading otherwise?)
4) This base inside the pool.....we are going to get 1inch of the extruded polystyrene (can't afford the 2inches ), and then we need something for between the washed rock and the foam.....we can a) use the appropriate sand or b) use more of the washed rock. If we go with sand, and underneath the sand as our main base is this washed rock, will the sand not just wash out into the cracks of the gravel? If so, should my layers be: washed rock, a liner or tarp, 1inch of sand, 1 inch of foam, then the pool liner?
Does this all sound like the appropriate pool sandwich, so to speak? Or would you just trench out the 24by2inches for the washed rock, and then put your inside base right on top of the soil?