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I'm building a sandbox for my three-year old. It will probably sit on the deck, so it needs some kind of bottom. Ideally, we should be able to move the sandbox around the deck. Is it necessary for water to drain out of the sandbox, or will the sand absorb enough water? What should I use for bottom?

Ideas:

  • Landscape fabric: allows water to drain through, but may not be strong enough to move.

  • Regular plywood: allows movement, but may rot and does not drain.

  • Redwood plywood: I don't know anything about, but I saw it at Home Depot, and it may be more resistant to rot.

  • Edit: Combination: plywood with a few drilled holes, covered by landscape fabric.

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    Your concern about draining suggests it will be uncovered. Does your neighborhood have cats? Jul 26 '10 at 15:43
  • @Rod, I was planning to cover it in order to keep cats and other animals out, but I thought quite a bit of rain water might still get through. What do you think? Jul 26 '10 at 16:22
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    My experience is that a lid will keep the rain out fine, but you absolutely will forget to cover it properly at least once (especially when your daughter is 4 and can open it herself), and then getting the water out is a huge headache. Drainage is a must.
    – Rob Napier
    Jul 26 '10 at 19:20
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    +1 for @Rob's statement - drainage is a must for sure. I just wanted to make sure you had thought of the delightful presents from neighbourhood pets. Because nobody told me. :) Jul 26 '10 at 19:32
  • I'd consider building a double-walled box. Build the exterior box and secure to the ground (stakes?), layer with the landscape fabric, then add another box inside that. The interior box will retain the sand, the exterior box will retain and isolate the fabric.
    – Huesmann
    Jul 31 '20 at 15:17
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The sand will definitely not absorb/release enough water if it's ever open to the rain. If your box doesn't drain, you'll have a small pond (as we do if we ever forget to put the lid on).

Your landscape fabric idea sounds pretty good. I'd just build that on top of decking slats or something like Trex (which might be perfect for this). Some gaps between the slats will allow drainage. Look into what the decking material is treated with. I'm in the camp that believes that the fears of CCA pressure treated wood are overblown, but even I probably wouldn't use it in a sandbox for a three year old.

Keep in mind regarding sliding it around: Sand is heavy, especially when damp (100-130 pounds per cubic foot). We have a pretty small plastic sandbox in our yard and I can't move it without dumping the sand first (but then "small" to me is something that holds three boys :D and I'm sliding across grass). You might want to think about furniture glides if you can find something that will slide reasonably on your deck, or even castors. Those will require that your base be much more rigid of course.

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    I don't think you can even get CCA treated wood anymore. Everything you buy now is ACQ which does not contain arsenic and is much "safer" than CCA (if CCA was every really that dangerous in the first place) Jul 26 '10 at 15:13
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Since you are going to place it on a deck, move it around, want to keep water and cats out, I would just buy a plastic one with a lid. In my opinion its not worth the hassle. The wood alone will make it heavy and hard to move around, let alone with sand in it.

They are fairly cheap, we bought one a few weeks ago at a garage sale for $5. I know there is pride in doing it yourself, I wanted to build one too, but in the end, it may not be worth it.

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    It would have to be small one, then. My daughter requested an octagonal sandbox (her favorite shape), so I thought I would make each edge ~22 in long. That would mean 500–700 lbs of sand. Jul 27 '10 at 12:56
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I used a linoleum remnant for my kids and it lasted for 20 years. Now I can't find a remnant anywhere for my grand kids' sandbox. The linoleum worked great as it could still drain out the bottom and it kept the sand clean as they did not scrape up dirt when building their "roads" in the sand. I thought of putting outdoor remnant over the top of the sand as they could lift it and the cats and squirrels couldn't dig in it.

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Just thinking off the top of my head maybe a wooden (cypress) frame, put a metal grid across the bottom (maybe some kind of galvanized grid) and brace it with some pieces of cypress. Then put the landscape fabric over the metal grid and then fill with sand.

I almost said go with a straight metal grid but the weight of sand and children would probably be too much so the pieces of cypress would brace across the metal grid. This way you'd get good drainage and the ability to move it around (if you put it on casters).

Not sure how resistant redwood plywood is to rot or if they make cypress plywood.

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Use a tarp with lots of tiny holes poked through it. I used a meat tenderizer to poke the holes through. I simply cut it to size and stapled it to the bottom. Works great :)

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Landscape fabric because even if you was to put wood which would rot. Once sand was put in the weight would keep you from being able to move. Landscape fabric always easy to get and replace. Here is a great design to keep critters out and let the rain drain thru. Jae

great design I am making now

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    That design will keep big critters out. But mice and spiders can get in there easily. Plus, the permanent overhangs are prime black widow lairs - they seem to love being near wood piles and out of the sun.
    – Doresoom
    Apr 20 '15 at 21:05
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I thought of these good ideas but In my case the sand boxed area is enclosed outdoors and the ground is covered with pea gravel. Instead of removing the gravel I kept it as it has a cushioning effect for the knees and drains water thru to the soil beneath. After much thought I decided on the exact size piece of a well woven rug remanant BUT turned it upside down as the threads were so tightly secured only minimal sand can seep through. Then poured in 7 bags of white sand. This is working great so far. Should moisture cause mold I'll bleach the entire sand box. It appears that the layer of pea gravel causes the carpet and sand to stay somewhat aerated. So far my twin grandsons are loving it and are even able to add a "little" water without causing a big mess! So what do you think? Just me, Lisa

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  • Welcome to Home Improvement. It would be great if you would edit your post in put in some spacing to make it a bit more readable. At the moment, it presents as a wall of text and is hard to read. Also, since this is a Q&A forum, not a general discussion board, "what do you think" answers really aren't what we're looking for (check out the "answering" section in the help center to see what's expected). Frankly, just removing that part would make this a better answer.
    – FreeMan
    Jul 31 '20 at 18:15

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