DIY Tank Cover

Form a hexagon by using three each of the 18 ¼-inch and 21 ¾-inch pieces. The 18 ¼-inch pieces will sit between the ends of two 21 ¾-inch pieces to form tight 60-degree angles.

Using a 1/8-inch drill bit, drill two pilot holes one inch from both ends of the 21 ¾-inch pieces and angled into the ends of the 18 ¼-inch pieces. Secure together using 12 – 2 ½-inch decking screws.

Lay six 20-inch pieces on top of the base form. The ends will be flush with one another. Drill two pilot holes one inch from both ends of the three pieces lined up with the shorter base pieces. Secure together using 12 – 2½-inch decking screws.

Now that you have two layers, drill two holes using a ½-inch drill bit on the top edge of each board making up the top layer. Each hole should be 3 to 4 inches from the end and 1 ½-inch deep. Alternate the location as you add each layer so you do not hit the same spot as the lower layer.

Once you have the holes bored out, secure the layers together using 12 – 2 ½-inch screws. Use wood glue between the layers for added support.

Tip: Wrap a piece of painter’s or masking tape on the drill bit where you should stop drilling as a guide.

Repeat steps 2, 3 and 4 until you reach the desired height. Do not fasten the final layer yet. Use this layer as a form for Steps 6 and 7, and then secure it to the other layers.

Center the hexagon form around the area you are covering. Use a shovel to mark a perimeter. Remove the form and dig a 4 to 5-inch deep trench around your mark. Dump two to three bags of pond pebbles into the trench for drainage and then rake level.

Lay five 1- x 6- x 31-inch pieces side by side and two 1- x 6- x 13 ½-inch pieces on either end on a flat surface. Leave one-quarter inch between each slat to allow for expansion from moisture. Use decking screws as spacers.

Place the last hexagon form centered on top. Trace the inside of the hexagon onto the 1- x 6-inch boards, leaving about a one-quarter to one-half-inch gap for easier removal.

Trim the pieces you’ve traced, using a circular saw. Once the boards are cut, reassemble, again leaving one-quarter inch between each slat. Check to make sure they all fit nicely within the hexagon form.

Secure the boards using the final 1- x 6- x 31-inch board set across and centered over the seven slats. Drill two pilot holes for every slat and secure using 14 – 1 ½-inch decking screws.

Once you’ve secured all the hexagon layers together, drill four pilot holes in each of the six 16 ½-inch pieces, about one inch from the outer corners. Attach the pieces to the inside of the hexagon two layers down using 2 ½-inch decking screws. Rest the floor you built in Step 7 on top of the ledge.

Place the unit on top of the prepared site and level. Cutting at a 29-degree angle, cut the 1- x 2-inch x 8-foot pieces of lumber into six 20-inch long pieces. Repeat the process of cutting and flipping the board over. You may need to adjust the angle slightly to get a tight fit.

Use wood glue to secure the 1-inch x 2-foot pieces to the top of the hexagon flush with the outer edge. Let glue set according to directions. If you do not use 1-inch x 2-foot pieces as a top edge, fill exposed holes with exterior wood putty.

Tip: Before you stain your new cover, wait several rains so the waterproofing stain will soak into the wood.