Hot tub, insulated base

[JohnMo]

Need some help

My next job is a hot tub, will be a round wooden one, heated by a heat pump. Looking to build an insulated base for it to sit on. Weight approx 2.4Te, diameter approx 1700mm.

 

My initial thoughts were, dig down, DPM, PIR insulation 100-150mm thick covered in slabs (have loads to use up). But base will be square, hot tub round, heat will just move sideways out of the base and make the insulation useless. So not sure that works.

 

Anyone any ideas?

[crispy_wafer]

Random thought, Sink into the ground a little so you can build an insulated upstand?

[saveasteading]

You'll lose so much heat out of the side and top that it isn't a great concern.

But I agree with @crispy_wafer, and you could score the boards to threepenny-bit principle  to nearly a circle.

Have you checked the insulation strength? If it squashes it becomes useless.

[Russell griffiths]

Why not build it just like an insulated house slab. 
I would use xps not pir, rough the surface up, flexible outdoor tile adhesives and tile the bit you can see. 

[JohnMo]

Thanks all

So looks like XPS300 should be ok,compressive strength wise. 

 

But I may need to to cover it with something to load spread to stop any point loads. So maybe slabs?

[SteamyTea]

1 hour ago, JohnMo said:

My next job is a hot tub

Worked in the health and leisure industry and we called them bacterial breeders.

[JohnMo]

14 minutes ago, SteamyTea said:

Worked in the health and leisure industry and we called them bacterial breeders.

Going to add an automatic sanitizer to add chlorine (?) as needed, plus sand filter.

 

[Nickfromwales]

Make the hot tub a-la ICF? 

[Nickfromwales]

4 hours ago, SteamyTea said:

Worked in the health and leisure industry and we called them bacterial breeders.

Or around here…”sex pond”. 

[ProDave]

3 hours ago, Nickfromwales said:

Or around here…”sex pond”. 

Cuddle Puddle