Wood sizing for kids play structure
 

I need to build a freestanding 3'x4' platform about 4' off the ground as a base for a slide and steps. DIY guides I find online tend to use 3x4 or 4x4 posts for the vertical pieces and 2x6 for the deck framing. That's what I was planning to do but looking at instructions for the hardware kits you can buy they're using 2x4 for everything.

example here: https://www.playstarinc.com/Content/...0PS%207720.pdf

Based on that I'm thinking of using 2x6 for the vertical supports and 2x4 for the deck framing due to the small size. Will that still be solid or should I stick to the original plan of using the same sized materials as a full size deck?

3'4' is tiny, that's basically a small table. You will be fine with 2x6s as your base.

IMO, I would have no problem framing the floor with 2x4, but I think the choice of using 2x4s or 2x6s as the vertical post is not a good one.

The reason is that they are plenty strong vertically, but at only 1.5" wide in the "2x" direction, provide pretty mediocre bending resistance from side-to-side. The directions you link to use a bunch of corner brackets/ties to try to tackle this. They have also used additional 2x4s on the perpendicular direction to help prevent side to side bending.

The cost for the 2 8' 4x4 posts you'd need (get them cut in half at Home Depot) is peanuts and will make for a much sturdier/less bouncy feeling platform. It will probably cost less than the extra brackets to beef up the 2x6 corners.

-Mark

I just built one using a hardware kit and my own lumber. Just my two cents, if you want to build it quick and hassle-free, stick to the plans. It will list all the wood you need to buy, and also show all the cuts you need to make. Once you start switching lumber sizes to save a couple bucks, it'll cost you more time when making the cuts because you can't just follow the cut sheet anymore. You'll have to modify the dimensions on the cut sheet to make it match your new lumber sizes.

I built one a couple weeks ago. My main structure is 5'x5'. I used true 4"x4"lumber instead of typical the 4x4 that's actually 3.5"x3.5". I got the job done but the change in post size affected the sizes of many of the other cuts, so I had to be careful when following the cut sheet. Overall, the structure is very heavy and sturdy.

Good catch on the brackets, I didn't factor those in when I was comparing lumber sizes.

Unfortunately due to the size and shape of the space I'm working with I can't buy a kit, otherwise I would have gone for that.

A few changes to make but it's 90% complete and feels super solid, thanks for all the input.

https://scontent.fyvr3-1.fna.fbcdn.n...61&oe=5F51AF48

Nice job!

Just like on fence posts, you should put little caps on the top of your 4x4 posts as that is the weakest part for weather protection and they'll rot a lot quicker if rain hits the end directly.

-Mark

Thanks! I bought some caps (purely for cosmetics, good to know they're functional too) but I haven't put them on yet as I want to add some trim pieces where they meet the decking as well just to tidy things up a bit. I also only have 1 screw left, and I think they need 2 each.

I also need to sort out the best way to shorten it a bit, as it sits the slide is way too steep for my toddler and she comes screaming off the end every time. I think the easiest way would be to cut the bottom stair off and the bottom of all the posts since I already put carriage bolts through for the deck frame and I don't want to leave big exposed holes in the posts.

^ we added a ~12” block under the bottom end of our slide to reduce the slope. The kids still come out hot but that definitely made it safer.

My dad would've jerry rigged that slide to a ladder and called it good.

I started shimming it up with offcuts just to see how much adjustment is needed, she's getting better at not needing our help to stop with it boosted up about 4" but much more than that and the drop is too much for her. Dropping it by one step + some shims would land it anywhere from 7-11" higher than it is now.

I just don't want to drop it too much and then the kids are bored of it within a few years and I end up like every dad with this huge unused thing sitting in my yard. I might be able to boost it back up later with some concrete deck blocks but idk how stable that would be with a 4' high floating structure.

I'm also trying to figure out if I should add something by the opening of the slide on the outer side. I have no idea what I could put there I just don't like the thought of a kid falling the wrong way and missing the slide.

I'm wondering why that pool isn't at the bottom of the slide lol

It's too small or it would be. Eventually I plan to put a slip n slide at the end though.