How to raise a cubby house off the ground for a sandpit beneath?

globetrotter

Hello,

Have purchased a cubby house and would like to raise it off the ground to a height of about 1m as I would like to incorporate a sandpit beneath. Have a few ideas in mind but not exactly sure which approach would be most ideal and wanting some advice/recommendations. The cubby house is 2.7m x 2.5m. My intention is to have 9 posts dug at a dept of 600mm and at a width of 180mm using 90mm x 90mm H4 treated pine posts. To build the subfloor I was going to have two bearers and about 5-6 joists. Am not exactly sure which way the bearers should run and how they should attach to the posts.

Also how should the joists be attached to the bearers, just nailed in on an angle, bugle screws or joist hangers?

And what would the recommended size of the bearers and joists be?

Tagging @MitchellMc for ideas.

Picture below is the idea that I have.

Thanks in advance

MitchellMc

Welcome to the Bunnings Workshop community @globetrotter. It's fabulous to have you join us, and many thanks for your question about elevating a cubby.

That sounds like a reasonably solid plan. I'd suggest constructing the frame from 190 x 45mm L/M Outdoor Framing MGP10 H3 Treated Pine, and the joists from 140 x 35mm Outdoor Framing MGP10 H3 Treated Pine. That's on the beefier side, but I believe it's good insurance on elevated structure for kiddies. I'd have a central beam of 190 x 45mm and have the joists connect to it and the fame with Pryda Joist Hangers - To Suit 35 x 140mm. They can be nailed or screwed in. I'd recommend bolting the frame to the posts. You can mirror the top frame down to the base, retaining your sand and adding rigidity to the structure. Instead of using the H3 framing timber, it would be best to swap out for 200 x 50mm H4 treated pine sleepers as that timber will contact the sand.

You could run two bearers if you'd like instead of the one and swap the 140mm joists to 90mm. My preference would be the design I've proposed. I've created some renderings for you to illustrate the construction steps better.

Remember, with an elevated structure that kids will use, installing rated shock pads in any potential fall zones is important. Although it's only one meter, that's enough to cause significant damage.

Please let me know if you have any questions.

Mitchell