Estimated Cost: $$$$
Total: 4 hours
This sand box is as rugged and durable as it is simple to build. Notching the 4 x 4 posts for the side pieces and using 2 x 10 stock for corner braces, this box will handle all the rough and tumble play youngsters can dish out. Heavy duty landscape fabric on the bottom allows water to drain out and keeps grass and weeds from creeping in.
This particular plan is for a large sand box, and you can adjust the dimensions in any way you like to make it bigger or smaller. Remember to calculate how many yards of sand it will take to fill your box before you build it (inside box width x inside box width x depth of sand). This box ended up requiring about .6 cubic yards of play sand to fill to depth of 6 inches.
Careful sanding and rounding over of all sharp corners are especially important for this plan, as you want to eliminate the chance for splinters as much as possible.
Cut four posts (A) to length according to plan. Then, set your table saw fence to 1" and run the posts through on two sides, reset the fence to 1 5/8" and run through again to make two notches to accept the sides (B) (see detail illustration).
Cut four sides (B) to length. Check the widths of all four sides to make sure they are the same. If there are some slight differences, rip them on your table saw to one width. In this case, we ripped all the sides to 9". Attach to posts with 3" deck screws and glue.
Cut corner braces (C) from leftover pieces of 2 x 10. In this case we cut two 45° angles at 18" apart; you can make them smaller if you wish. Place them tight in each corner and attach with glue and 3" deck screws.
Attach landscape fabric to the bottom of the box with ½" galvanized staples. Do not pull the fabric tight so the weight of the sand does not rip it loose when filled.
Turn the box over and check for square. Cut the tops (D) by measuring the distance from inside corners of posts, which will be the short points of the 45° miters on the top pieces. Spread glue on the corner posts (A) and top edges of sides (B) and attach with 3" screws on corners and 2" screws into the top edges of the sides.
If your miters do not meet tightly, you can drive screws through the edges of the tops (D) to pull them together.
Round over each corner (we simply traced the bottom of our glue bottle to get our curve) and if desired, rout a 1/8" roundover along all edges. You may forego the routing and simply break the edges with sandpaper if you wish. Sand the rest of the box thoroughly to eliminate the chance of splinters. Apply a waterproofing finish according to manufacturer instructions.
To figure out how much sand it will take to fill your box, multiply length x width x desired sand depth. In this case we had approximately 70” x 70” x 6”, which gave us 29,400 cubic inches. There are 1,728 cubic inches in a cubic foot and 27 cubic feet in a cubic yard, so our dimensions yield 17 cubic feet, or just over .6 cubic yards.