Hot tub on sloping patio help

[Jimmylondon07]

Hi All

Looking for some advice if possible please. I have a hot tub being delivered at the end of July and I am putting it on a patio which slopes away from the house for drainage purposes. It drops around 3 inches over the 8ft length of the tub so it's a pretty severe slope.

I am looking at creating a level surface for it and as I couldn’t find a tradesman to take on the job, have built a rather simple frame knocked together with 95x145mm pressure treated timber with two 100mm screws and an angle bracket in each corner to provide the strength. I also have a gravel grid ready to install once it’s level which is designed to bear most of the weight of the tub (they can support something like 420 tonnes per square metre so the manual says).

Firstly I need to level it within the frame though, and I am not sure what material would be best to do it with. I had considered lining it with rubber playground style tiles to protect the flags as much as possible in case I ever get rid of the tub, and then levelling it with compacted MOT type 1, followed by the gravel grid filled with pea gravel. However I am wondering if that might be overkill and whether compacted building sand might work with the grid placed on top of that?

The hot tub weighs around 1600kg fully filled so it’s a heavy old thing, here is the frame so far:

https://imgur.com/3F7KgxX

Any suggestions would be most welcome as I am a little bit stuck and would hate to get this wrong.

Thanks

Jimmy

 

[Ian H]

Could you use 8ft furrings, 75mm to nothing instead of the frame?

Basically a big wedge.

 

[conny]

Could you use 8ft furrings, 75mm to nothing instead of the frame?

Basically a big wedge.

Think you may need to use 100-125 tapering down to 50 so you could put a fourth brace across the thin end.
Without this brace the other side may begin to push apart when people step in and out of the pool. The 50mm ends would give a decent fixing area for the brackets/screws.

 

[Jimmylondon07]

Thanks both for the responses. As I have already bought the gravel grid and assembled the frame I feel obliged to continue on with what I have...hindsight is a wonderful thing as the firrings look a much better idea!

In the installation instructions for the gravel grid it recommends a subbase of 150mm of hardcore, then a layer of landscaping fabric followed by a layer of sand, with the gravel grid going on top of that and finally it’s filled with gravel to provide the strength.

As I already have the hardcore base under the patio and the patio is solid I was kinda hoping a layer of compacted sand would do the same thing, but obviously there will be more sand at one end than the other to account for the slope in my case. Is another layer of compacted MOT type 1 overkill considering the patio surface is already hard?

 

[Ian H]

You might break your slabs while compacting it.

 

[Jimmylondon07]

Yeah that was my concern with the Mot type 1. I thought about either laying some thick vinyl flooring offcuts over the slabs first to try and absorb some of the downward impact, and/or using a tamper to compact it as much as I could manually. Think that's probably a waste of time with type 1 but might get away with it if it's just sand.

Buying a hot tub seemed like a good idea at the time lol.

 

[scbk]

Is there no way the hot tub could go down on the grass somewhere, then put a few slabs up to it? Maybe post a few more photos of the rest of the garden

 

[conny]

Is it an inflatable one or a solid body type?
If it's inflatable you have to drain them over winter as they can be damaged if the temperature drops below 4ºC

 

[Jimmylondon07]

It's a solid body type conny so it'll be up all year round, think I'll use it much more in the winter than the summer actually!

scbk I do have plenty of grass immediately in front of the patio but the garden slopes away from the house quite severely so I'd have to dig down quite far to level that and also remove all the trees and bushes that are in the way at the moment. I also have ace views from the patio that I don't have from the grass, so it would be a shame to lose those. They were part of the reason I bought the tub!

Thanks

Jimmy

 

[conny]

Nothing beats sitting in a hot tub at night with your loved one and a few glasses of wine and gentle snow falling

(Yep, I'm a soppy romantic when I'm with my wife.)

 

[Jimmylondon07]

Not so bothered about the mrs being in there with me in all honesty conny

Won't be any romance either way if I cannot sort this base out though, just a big repair bill lol.

 

[mattylad]

How about lining the base with marine ply before adding anything else, that way it should protect the paving?

 

[Jimmylondon07]

That is a good shout Matty, thanks for that. I also just found something called a cement multiboard which might work, it is water/damp proof, easy to cut and looks like it can take quite a bit of compression as it’s used for flooring applications as well.

• High thermal insulation capacity
• High compression ratio. (minimum 40 tonnes per sqm)
• Easy to cut with sharp knife / fine tooth saw
• Resistant to tile cement, building cement and most other building compounds
• Water and damp proof
• 100mm thick

If I line the slabs with that do folks think it could tolerate a layer of MOT Type 1 hit with a wacker plate without damaging the slabs underneath?