Decking to support inflatable hot tub on top of old patio...

5 Aug 2011
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United Kingdom
I'm looking at decking over our dishevelled patio to take the inflatable hot tub the wife has purchased.

The patio is paving on a raised concrete slab. It was with the house before we bought it, so cannot comment on thickness.

Ideally, I'm planning to use WPC decking (such as this Eva-last Infinity Arched Profile).

The patio has a reasonably steep slope to it, over the width of 2.1m it drops about 10cm! Great for drainage, not for an inflatable hot tub.

My plan is to use pressure treated 47×100 (c16 (or c24 if available), if needed), supported on adjustable self-leveling pedestals (like these Jouplast Plastic Adjustable Decking Risers).

These are capable of 1-tonne vertical load apparently!

The joists need to be at 300mm centres.

The diameter of the tub is 1.8m, it holds 670 litres and up to 4 adults. Rated at 1.025 tonnes when full.

Will 47×100 be sufficient with joists only running in 1 direction (perpendicular to the decking)? Only I want to keep the decking as low as possible.

What would be the recommended spacing of the supports along the joists? Would 600mm be sufficient?
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What is the total size of the decking area you are planning on? It is one thing to have an area to support a tub but if the rest is just deck then the supports elsewhere don't need to be the same.
Just use all your off cuts to make legs to support your frame, put lots where you are going to put your hot tub. Dip your cut legs ends in some bitumen or something to protect them.
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Concentrate on the aera under the tub, as has been said. if you use lots of 4" posts in compression right under the tub, you'll be fine.

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