Concrete Umbrella Base

• Gather the required materials and cut the parts to size.

Step 2 – Baseboard

• The first step is to make the baseboard. A piece of 3/4″ plywood works well, cut to 16″ x 16″ or just larger than the outside diameter of the lamp shade.
• Draw diagonal lines to find the center point. Use a 2 to 2-1/2″ hole saw to drill a hole through the base for the pipe to pass through.

Step 3 – Center Pipe

• Take a piece of galvanized pipe, 10″ to 12″ in length, and screw it to the bottom of the baseboard using a floor or ceiling flange. The galvanized pipe should be centered in the 2.5″ hole.
• If you’re using a length of PVC pipe, cut a hole that’s as close to the outside diameter of the pipe as possible for a very tight fit.
• Cap the top end of the pipe with a piece of styrofoam or insulating foam and clear packing tape.

Step 4 – Fix Lampshade to Base

• Put some modeling clay on the flat side of the lampshade as shown. Slide it over the galvanized pipe and press it down onto the baseboard. The clay will help seal the bottom of the mold and keep concrete from getting underneath the form and lifting it up during casting.
• Put a bead of 100% silicone around the outside edge of the form where it meets the baseboard. Be careful not to bump and dislodge the form. The silicone will cure in a few hours and help hold everything in place.

Step 5 – Foam Strip Reveal/Kick

• Creating a reveal at the bottom of the piece will help prevent chipping as the concrete is dragged around. This is one of the trickier steps, but it’s not completely necessary.
• Cut a long strip of 1″ insulating foam and cover all sides with clear packing tape. Use spray adhesive on one side and work the foam strip around the top edge of the form. Without the tape, the foam won’t make such a tight bend and will snap. Trim down the excess so the edges meet up.

Step 7 – Mix and Pour Concrete

• Clean: Remove any debris from inside the form and clean with soapy water or denatured alcohol.
• Decoration: Add decorative aggregate, inlays, or other decoration using spray adhesive. This piece had a little bit of decorative aggregate and a stone inlay on the top surface.
• Mix: Avoid a soupy mix! The ideal mix will have some body and you can hold it in your hand. Too much water and it will be running through your fingers. Too little water will make the mix gritty.
• Pour: Fill the form with concrete on a level surface. Don’t fill it all the way to the top! Fill it about half way up the foam strip. Leaving a gap will help the concrete drop out of the form later.
• Vibrate: Pick up one edge of the form an inch above the tabletop and drop it repeatedly to help the air bubbles rise to the surface. Tapping on the sides of the form will also help, but be careful not to dislodge the form.
• Cure: After the form is filled, cover it with plastic. This will help keep the humidity in the concrete and minimize cracking.

Step 8 – Demold

• Unscrew and remove the flange from the baseboard.
• Remove the foam strip by digging it out with a flat screwdriver.
• Remove the baseboard.
• Flip the mold over, place the edge of the mold on a board and gently drop it until the concrete is released.
• Saw off the galvanized pipe with a hacksaw or grinder.
• Polish the top with an orbital polisher.

Step 9 – Finishing

• Fill any air pockets with a color-matched slurry.
• Install furniture feet on the bottom of the piece by drilling small holes and fixing them in place with epoxy. This will help eliminate damage to flooring from dragging the umbrella base around.
• Drill a hole in the center of the concrete for drainage.
• Seal the piece to give it a nice shine and help keep it looking good for a long time.