Foundation advise

[Baxter Burgundy]

I'm after some advise on where to go after my digging a foundation hasn't gone quite as I had initially planned.

I'm building a foundation for a hot tub, my plan was to dig a hole, fill with hardcore and compact that down, top with sand, cover with a damp proof membrane and then use those plastic grid type foundations filled with 10 mm pea gravel as the top layer which the hot tub would sit on.

I'm pretty sure I've over engineered it in terms of the depth I dug the hole, I took it down about 65 cm. I have filled it with hardcore and compacted it down, but I underestimated how much I would have to put in the hole and am now a bit short. It is currently about 20 - 25 cm from being flush with the ground. Also it could be a bit flatter.

I am reluctant to buy more hardcore if I can avoid it because I'll then have to go to the expense of hiring out the compacter out again. So my question is will filling the remainder with extra pea gravel and then put the plastic foundations at the top be acceptable or will the pea gravel sink over time? Also does it matter that the hardcore is not perfectly flat, I would have thought it would be OK as long as the pea gravel at the top is flat?

 

[cAtLeYx]

wow - looking at the amount of stone you have removed Id of said the original ground would of been sufficient. Type 1 stone should be used as it is made up of graded aggregate thus allowing good compaction with no voids. (you could use 6F2 to fill the majority & then finish with Type 1). Id put a tantalised timber framework in at 400mm centres and overlay with with decking marine ply etc. This of course could be fabricated to suit the hot-tub dimensions and then back fill the remainder with pea gravel etc.

Hope this helps.