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How to Build a Rock Box!

Wondering how to build a rock box or pebble pit play area? This post shares how we made ours, which started off as a DIY sandbox and ended up being a DIY rock box! I’m also sharing why we used rocks instead of sand. 

How to build a rock box or pebble play pit for hours of entertainment

Today I’ve got a fun end-of-summer project that I’m sure we’ll get use out of well into the fall…a DIY rock box! Whether you can this a rock play garden, a rock box, a pebble pit (the cute name our daycare calls theirs), or a pebble sensory box, it doesn’t matter. It’s just a box full of small pebbles. 🙂

Now that our community pool has closed, we wanted something to keep Mo entertained, especially on the evenings after work. Mike was the brainchild behind this project, except he wanted to make it a DIY sandbox.

I was not terribly keen on this idea because sand boxes can be super messy and difficult to keep clean. Since we have such a small space, I didn’t want to be dealing with sand all over everything.

little girl playing in a DIY rock box

If you have a bigger outdoor space (or if you’re just not as annoyingly high maintenance as I am), you can definitely use sand. Rocks were also great for us because the entire area around the deck and garden is finished off with rock landscaping. The landscaping uses a smooth river rock, but the pebbles blend in nicely when Ramona inevitably dumps them out. Here’s to hoping I don’t have to deal with too much cleanup. 

So if you’d like to make one of these for a kiddo in your life, here are the steps we took to make an easy DIY sandbox or gravel pit play area. We designed the size specifically for a little nook in our yard between a deck post and the HVAC area. But you can use these measurements and put it anywhere. Or tweak to make your own!

Here’s our supply list:

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  • Sides: (2) 2” x 4” x 38.5” and (2) 2” x 4” x 35.5”
  • Sides: (2) 2” x 6” x 38.5” and (2) 2″ x 6″ x 35.5″
  • (2) pieces of attic decking—you can also use scrap wood, plywood, whatever, cut to the total size of the box, ours was 38.5″ x 38.5″



And here’s how to build a rock box!

Step 1: Measure, mark, cut, and sand the lumber

The first step is to decide on the size of your DIY rock box play area. We knew we wanted ours to fit snug into a little spot between a deck post and our HVAC unit area.

I had a plant there before, and the area was already finished off with river rock landscaping. We removed the rock landscaping and just moved it to another area of the yard. If you’re putting your play area on top of grass, it’s likely the grass will just die from lack of light. 

Our overall measurements for the play box were 38.5 inches x 38.5 inches. The cut list we used is above in the supplies section. We used 2×4 and 2×6 stacked on top of one another to form the sides. We chose this because we thought the 2×6 stacked on top of one another would be too deep. It worked well for our garden beds, but pairing a 2×6 with a 2×4 for this project ended up being the perfect depth.

area for the DIY rock box
pieces of lumber

Mike also picked up some attic decking for the base. You can use pretty much anything similar. Keep in mind that it will be painted and largely hidden below the rocks, so you don’t have to be too picky. While I had a lovely nap one Saturday afternoon, Mike did all of the cuts (best husband). 

Then he used our orbital sander to clean everything up so it was nice and smooth. One round of medium-grit sandpaper and a finishing round of fine-grit sandpaper should do the trick, but you don’t have to be too picky. After all, this will be painted, go outside, and be filled with dirty rocks. 🙂

attic decking pieces
base of the box

Step 2: Drill pocket holes & form stacked sides of the rock box

We chose to use pocket holes to join the pieces for each side and then to join all four sides. To do this, I used my Kregjig K4 to drill 3 pocket holes on each 2×4 piece like so. Then I attached each of the 2×4 pieces to a 2×6 pieces to form four stacked sides.

I know drilling pocket holes and using pocket hole screws against the grain of the wood is frowned upon. But it was still the best, quickest, and easiest way to join the pieces for the stacked sides. I also chose to put the 2×4 piece on the bottom purely for a more seamless look on top and so the pocket holes would be hidden under rocks. 

drilling pocket holes in the wood
pocket holes
kreg bluekote screws
drilling pocket holes in the wood
sides for the DIY rock box

Step 3: Prime and paint the rock box

It seems weird to prime and paint and this step, but I did. Just seemed easier to finish the pieces separately. And given the play box is pretty big once it’s assembled, I think I was right. I did one coat of primer on each side piece (just to prevent any bleed through from knotty areas), and then one good coat of the outdoor opaque finish.

For the base pieces, I skipped the primer since this will be largely hidden. Instead, I just gave it once good coat of the outdoor opaque finish to seal it. I used a brush—a roller would have been much faster!

sides for the DIY rock box
painting the base of the rock box
painting the base of the rock box
painting the base of the rock box

Step 4: Drill side pocket holes and join stacked sides

I drilled three pocket holes on one end of each of the side XX” pieces. On the inside. Then we attached them all together to form a square. None of our bar clamps were long enough for this task, so Mike held everything in place while I drove the pocket hole screws.

joining the sides of the DIY rock box
sides of the play box

Step 5: Finish building the box

To finish building the base, we flipped the square sides upside down and laid the base on it. We lined up the sides and then drove 1 ½” Spax outdoor wood screws down all along the perimeter of the box. I also finished up painting the top and sides at this point.

Spax wood screws
Spax wood screw bit
Spax wood screws
bottom of the easy DIY sandbox
drilling spax screws
finished diy rock box

I ended up drilling a few holes in the base for water drainage. (We want to build a cover for this, but we haven’t gotten around to it yet.) This was probably unnecessary since there is a slight gap in the middle that water can escape from. Better safe than sorry, though, and a few extra drainage holes won’t hurt anything.

Here’s the spot with the landscaping rocks cleared out, and then with the rock play box structure dropped into place. Fits like a glove!

area for the rock box
DIY rock box in a townhouse backyard
DIY rock box in a townhouse backyard

What can I use instead of sand in a sandbox?

Well, I’m glad you asked! I hate sand, too. Whether it’s your neighbor’s cat you’re worried about, or the sand getting wet and icky, or just the idea of messy sand…you’ve got options.

Our easy DIY sandbox quickly turned into a neat gravel pit play area with the addition of sand pebbles. We used sand pebbles from Lowes because they seemed a bit smoother and more polished-looking than the pea gravel. Which was right next to it. And honestly, they looked pretty similar. The sand pebbles were a few bucks more expensive, though.

dewalt drill
drilling holes in a bucket
DIY rock box in a townhouse backyard

All in all, we used five or six bags. We rinsed the sand pebbles before putting them in, too. An easy way to do this is to drill a few holes in the bottom of a 5-gallon contractor bucket. Then rinse them that way. You can set them out on a tarp to dry in the sun, or you can just dump them in.

The approach we ended up taking was setting a portable fan on the rock play box and using a shovel to “turn” the rocks, exposing more wetness every 15 minutes or so. Until the sun came out, that is. That dried the rocks really quickly!

For more kids projects, check out my dollhouse bookcase build, my modern kids table and chairs, my DIY water play table, my toddler step stool, and Ramona’s nursery!

Our Finished DIY Rock Box!

And here is our finished DIY sandbox turned gravel pit play area/DIY gravel pit/pebble play pit/ DIY rock box/whatever you want to call it. It’s definitely a hit with little miss. She was so cute playing in it, doing her favorite activity: putting rocks in one bucket, then dumping them in another bucket. Repeat. The mess was pretty minimal, too. 

I’ll make sure to update this post when we get around to building a cover! But as of now, we’re just planning to do something simple on hinges. Possibly that we can hook to the fence when it’s open. We’ll see what I come up with. Until then!

DIY rock box in a townhouse backyard
DIY rock box in a townhouse backyard
little girl playing in a DIY rock box
little girl playing in a DIY rock box
little girl playing in a DIY rock box
little girl playing in a DIY rock box
little girl playing in a DIY rock box
cute toddler on a swing

**Update!** We added a lid to our DIY rock box!

Update! Before winter really hits, we finished up the lid for this project. It’s a pretty simple design that Mike knocked out in a few hours at naptime. The most time-consuming part was sanding all of the rough furring strips, to be honest.

He based the lid on the overall measurements of the rock box, using a vertical slatted approach with horizontal support pieces on the top and bottom, plus an additional support piece running at 45 degrees across the entire lid. The slatted pieces are 1×4, and the three support pieces are 1×2.

I then finished it using the same finish I used for the rock box—Behr opaque outdoor stain and sealer. It’s amazing the facelift this stuff gives to knotty, rough wood. Now we’ve got a place to store all of the outdoor toys and protect it at least a bit from the elements. Until next year!

Lid plan for DIY rock or sand play box
Lid plan for DIY rock or sand play box

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collage that says how to make your own DIY rock box with images of the process
Brittany Goldwyn
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