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How Do You Make a Waterproof Storage Box?

While you may not have thought of this subject, if you enjoy your outdoor space, you may just wonder about this at some point. People use wooden boxes outdoors for all kinds of uses, whether for storage or even as planters on the deck. If you don’t have a storage shed, a box is a great place to store smaller yard tools, such as clippers, loppers, bulb digging tools, and others.

Some people store them under a deck while some use them as a kind of seat when the tools inside are not needed. You may have a storage box built from treated lumber, which helps prevent moisture damage, but it won’t be entirely waterproof.

Basically, all you need to make a waterproof storage box is the materials for the size you want and make a hinged lid. You can waterproof the pieces ahead of time to save time.

How to Make a Waterproof Outdoor Storage Box

The best thing is to use wood that is naturally resistant to moisture for the box’s construction, such as cedar or redwood. You need to let the wood you plan to use for the box rest indoors for two to three weeks to ensure that any moisture that the wood has absorbed will evaporate. This is especially important if you have recently built the box.

Use caulk to seal any joints when you have finished assembling your box, then use waterproofing paint or stain. Sanding the wood inside and out will give the waterproofing substance a much better surface to attach to, increasing the box’s waterproofing.

The next step is to apply silicone caulk. Protection such as gloves is needed because some people are sensitive to silicone, and you’ll need your fingers to smooth out the caulk. Of course, you won’t know if you’re sensitive until you get a reaction, so it’s a good idea to protect yourself beforehand.

Apply a bead to fill any cracks, either in the joints or wood. Smooth it out with your finger. Dipping your gloved finger into water first will help you remove excess caulk and also allow you to create smooth, clean lines. Let the caulk dry according to the manufacturer’s recommendations. Depending on the caulk used, this could last from a few hours to a few days.

Oil-based varnish comes next. Using your gloves again, apply the varnish according to the maker’s instructions. Apply it all over the box, inside and out. Be prepared to apply several coats, as you need to keep applying coats until the wood stops absorbing the varnish. Once this happens, it’s important to keep the wood wet with the varnish for at least ten minutes, then you can wipe off any excess with a cloth. Allow the varnish to cure, which usually takes 24 hours.

After the varnish has cured, sand the box inside and out with 220 grit sandpaper or something similar. Then apply two or three coats of the varnish. You’ll need to allow the 24-hour period of curing between each coat. Your box is then finished with the exception of providing some sort of method to keep it from touching the ground if it is to be used underneath your deck.

How Do You Make a Storage Box with Hinged Lid?

For a simple box, you’ll need the wood of your choice, a saw of some type, about two boxes of 1-1/4 inch wood screws, and some type of screwdriver. Use screws that are rated for outdoor use. You’ll also need four 18 x 4-inch plywood or panel board, two boards 1 x 2 x 6 feet, three hinges, and a clasp hinge to seal it. For tools, you’ll need a drill, table saw, miter saw, a pocket hole jig, and a tape measure.

Cut the panels into 32-inch lengths. Use the pocket hole jig on two of the leftover ends. Drill on the short ends and two holes on the longer ends. Also, use the tool on two of the main panels on one of the long sides. Screw the main pieces together, including the base, then make a frame of the narrow boards and screw them onto the box from the inside.

Make sure your top panel is the same size as your bottom. Cut two 6-inch strips from the narrow lumber to form handles. Screw them onto the top from the inside. Place your hinges and clasp where you want them and fasten them in. If you need to store some garden tools over the winter check out my article What’s the Best Way to Store Garden Tools?

How to Waterproof an Existing Outdoor Storage Box?

If your storage box is already made, you can get an inexpensive waterproof cover to keep water from harming the box or the contents inside. They are usually made in various sizes to fit your box, and feature drawstring closures to keep everything snug.

Otherwise, you can sand the box and treat it with oil-based varnish or weatherproof paint as described before. If the box had previously been painted, it would be a good idea to strip off the paint and start anew, especially if you don’t know what type of paint had been applied to the wood.

Can You Make a Storage Box Out of Decking?

You certainly can make a storage box out of the same lumber used for your deck. Not only is it useful, but it will make the box look like a part of your deck. The only hitch is that decking boards are usually fairly narrow, which will mean that you will need a lot more caulk to waterproof the box.

Other than that, you can easily construct a box out of the same wood that was used in your decking. Sand the box to roughen up the surfaces, and then use a waterproof paint, stain or varnish when it’s finished. You can put a waterproof cushion on top to make it into an extra seat, but that makes anything stored inside easily accessible.

I have added this video to help you with your outdoor storage box.


Making an outdoor storage box is an important addition, especially if you don’t have any other outdoor storage. It especially is useful for those with a small yard. You may not need many yard tools, but you do need a place to store them, or perhaps to store cooking tools for an outdoor grill. Whatever you choose to store in an outdoor box, you’ll find that once you have one, you’ll wonder how you got along without it.