How to build a raised Platform for a sauna?

[ST79]

Hi, 

Considering an outdoor sauna for the backyard.

It needs to be on a raised platform (decking recommended) but with the cost of hardwood currently I wanted to see if there were other options.  

The platform will be on a slight slope, and with the platform raised around 250mm off the ground at the lowest point, and maybe 300/350 at the highest.

Hoping to frame this in treated pine and use villa board or similar to sheet it?  Do need to avoid any water pooling underneath though to avoid damp etc. 

Or would it be better to just do TP decking to allow water through? 

Drainage in the soil below is good.  

What size posts/bearers and footing depth is required to support a gross weight around 900kg?  500kg (sauna) + 4 people (approx 90kg each). 

Have looked at the helpful post by Bunnings Team Member @MitchellMc re raising a kids cubby but not sure about our heavier load requirement. 

If I should just concrete the thing let me know that too! 

Cheers! 

[MitchellMc]

Welcome to the Bunnings Workshop community @ST79. It's amazing to have you join us, and many thanks for your question about building a platform for a sauna.

I'd encourage you to read through this recent discussion on How to build a deck for an outdoor barrel sauna? In that discussion, my colleague @EricL and I suggested how the sauna could be placed on the ground. Is there a chance that your sauna could be placed on the ground?

Any slightly elevated deck that is being built to bear the weight of a 900kg sauna needs to be designed to suit. There's plenty of information available for constructing a deck, and it's reasonably easy to follow and adhere to. Creating a platform structure that bears more than a standard deck starts to get quite complicated. This is where engineers come into play as they specialise in the structural integrity of constructions. Unless your sauna has been supplied with specific instructions on constructing the platform, I'd advise you to employ the services of a professional to design it for you. Keep in mind that from what I've seen, many saunas are designed to be placed on a flat compacted base or a concrete slab. If the manufacturer recommends placing it on a raised platform, then it might be best to look to them for further information on how that platform must be constructed.

Please let me know if you have any questions.

Mitchell