Determine the location and position for the sandbox, then spray-paint the outline on the ground. This sandbox measured roughly 4 feet by 8 feet; adjust dimensions as needed for a different sandbox size.
This project utilizes redwood lumber. Cedar can also be used. As a space for children to play in, you don't want to use treated lumber that hasn't been thoroughly dried, sanded to remove all possible splinters and painted with non-toxic primers and paints.
Cut frame lumber. Measure and cut a 4-foot length from each of the 2x12s. This will yield two 4-foot-long pieces and two 8-foot-long pieces.
Cut post lumber. Cut six pieces of 4" x 4" post, each 10 inches long. These will serve as the corner supports for the sandbox and will also support the lid.
Foam noodles serve as bumpers for the top edges of the sandbox. Use a utility knife to split the foam noodles lengthwise so they can fit over the edge of the sandbox. Cut the noodles to the appropriate length, slip them over the top edge of the sandbox. Secure the noodles with screws and washers, spaced about 4 inches apart.
Spread landscape fabric over the ground inside the sandbox and extending up the inside of the box. Pin the fabric down with landscape staples and staple it to the inside of the box with a heavy-duty stapler.
Fill the sandbox with play sand – not coarse sand – up to the top of the 4x4 posts.
To keep neighborhood cats from using the new sandbox as a litter box, cut eight pieces of 2x4 lumber, each 4 feet long. The finished lids should fit inside the sandbox, resting on the 4x4 posts.
Stand four of these pieces on end to form a box and screw together; repeat with the other four pieces. Drill pilot holes and secure a metal cleat to the inside of each 4x4 box, then install eye screws around the inside of each box. Tie colored rope to each cleat, then thread it through the eye screws to create a spiderweb pattern to deter cats and other animals from digging in the box.