Cut the two bottom boards (A and E; see Figure A) to length. Cuts made at the lumber mill are usually rough, so trim the ends of all the boards before measuring.
I joined all the components with both trim-head screws and construction adhesive. Adhesive works better than wood glue on rough-sawn lumber and is more forgiving on joints that aren’t super tight. Apply a bead of adhesive and clamp the two bottom boards together. Scrape off the excess adhesive with a putty knife, and clean the rest with mineral spirits.
Install temporary cleats on the smooth side of the boards, which will be the inside of the container (Photo 1). Hold them in place with 1-1/4-in. screws. I used cabinet screws, but other types of screws would work just fine. Don’t worry about the screw holes left behind when you remove the cleats; the liquid rubber will fill them in.
A simple box with a rubber lining
I wanted a super-easy-to-build water feature, so I designed this wooden box that just about anyone can build with basic tools. What makes it work as a pond is a paint-on rubber lining. There are a few different brands of liquid rubber; I used Rubberize It! Universal Rubber from rubberizeit.com. It's ultra-stretchy and UV-stable, and it can be used on lots of materials, including wood, metal and concrete. It's amazing stuff, though expensive at $75 a gallon.
You can use liquid rubber to fix leaky gutters and metal roofs, seal RVs and trailers, and for many other applications. Ranchers love it for sealing leaks in metal water tanks. And we love it because it can turn just about anything, even a simple wooden box, into a water feature.
The width of 1x12s can vary slightly, so double-check the width of the bottom before you cut the ends and dividers (B and C) to length. The rough-sawn cedar I used was 7/8 in. thick. If you're working with material that's only 3/4 in. thick, you'll have to adjust the length of the sides.
All the trim parts are made from 1x6s ripped in half. If you don't have a table saw, check out our simple guide that lets you make perfect cuts with a circular saw. A few home centers sell 1x3 boards, so you wouldn't have to bother with ripping at all.
Mark guidelines for the dividers with a framing square 14 in. in from the ends of the bottom. Transfer that line to the inside of the sides (D). Face the smooth sides of the dividers toward the center compartment. That will ensure more even coverage of the liquid rubber in the compartment where it matters most.
Attach the ends and dividers to the bottom with adhesive and three 1-1/2-in. exterior-grade trim-head screws (Photo 2). Join the sides with adhesive and screws, three in each side of each end and divider. Space the screws about 10 in. apart along the bottom. The end caps hide the end grain and strengthen the corners. Secure them with four screws and adhesive. Cedar isn't as prone to splitting as harder woods, so I predrilled holes for screws only in areas where a knot was in my way.
Install four aluminum angle brackets (Photo 3). Cut them to size with a hacksaw or a jigsaw fitted with a bimetal blade. Drill two holes in each side, and secure them with adhesive and 3/4-in. screws.
Assemble the base with two 3-in. screws into each joint. I found it easier to center the base when the container was upside down. Hold it in place by driving in four screws at an angle. Flip the whole thing over and secure the base to the container with 3-in. screws driven down through the bottom of the container.
After removing the temporary cleats, drill four 1/2-in. drainage holes in the corners of the outside compartments and one in the middle. If you plan to install a water pump, drill a 1-1/2-in. hole for the cord. I used a hole saw. Figure out which side of the container has the best-looking wood grain and drill the hole on the opposite side about 3/8 in. down from the top edge.
If you're a regular weekend woodworker, you really ought to get yourself a pocket hole jig. But if you don't have one, here's a quick and easy trick that works well on soft woods like cedar: Start by laying out the face frame, rough side down, and marking two guidelines at each joint. Then drill 1/8-in. holes through the end grain at an angle so the drill bit pops out about 3/4 in. to 7/8 in. down from the end of the board (Photo 4). At that length, a 1-1/2-in. trim-head screw will travel about 3/4 in. into the adjoining frame section. If you mess up and drill at a funky angle, you can always drill another hole a little bit over, and no one will be the wiser because it's on the underside of the face frame.
Assemble the sides and the ends of the face frame with two 1-1/2-in. trim-head screws and adhesive (Photo 4). Keep downward pressure on both trim boards while driving in the first screw. A wood clamp on the seam works well as a third hand. Before installing the face frame dividers, measure diagonally from one corner to the other both ways to make sure the frame is square. If the frame is a little out of whack, adjust the frame until it’s square, and clamp it to your workbench to hold it square.
Tape off the top edge of the container, the power cord hole and the drainage holes on the bottom. Brush the rubber on thick into the corners, seams, screw holes and defects in the wood (Photo 5). It takes three heavy coats to make a watertight seal and at least three hours between coats. I applied only one coat in the two outside compartments because they'll be filled with soil rather than water. I also applied just one coat on the very top edge of the container. Avoid blocking the drainage and cord holes with rubber by mopping the excess out with a cotton swab or rolled up paper towel. The rubber needs to dry for a few days before it's ready for water.
Rough-sawn cedar isn't supposed to be smooth; hence the name. So resist the urge to sand, and embrace the imperfections. I applied a cedar-tinted wood finish made by Sikkens, but any exterior stain or clear finish would work.
Once the finishes are dry, clamp the face to the container and fasten it with adhesive and 1-1/2-in. trimhead screws spaced every 10 in. or so (Photo 6). Set the screws flush with the surface of the wood to keep water from pooling.
A water pump isn't necessary but does help the water stay fresh. Some pumps have suction cups to hold them to the bottom, but the rubber-coated wood may not be smooth enough for them to stick. I laid down a small chunk of Plexiglas at the bottom and stuck the pump's suction cups to that. Floating water plants with exposed roots will clog the pump filter, so only use potted plants, or plan to build some sort of additional screen or filtration system. A pump that moves 120 gallons per hour is plenty big enough for this situation.
Now it's time to fill up your new creation with water and plants. If the local nursery doesn't carry water plants, you can order them online. I got several at pondmegastore.com.