How to Form Cast-In-Place Countertops

You might have a preconceived idea of a cast-in-place kitchen countertop as a plain gray concrete slab. This is typically not the case. With the many coloring agents available, it’s possible to make a concrete countertop any color imaginable. By combining colors, you can make a concrete kitchen countertop look like a much more expensive stone countertop. By pouring, or casting, the concrete countertop in place, you don’t have to worry about moving a heavy slab. One disadvantage, though, is the concrete must cure, which may take as long as 30 days.

3/4-inch plywood
Circular saw
Drill and drill bits
Screws
Screwdriver
Melamine board
Electrical tape
Wire mesh
Tin snips
Concrete mix
Paddle attachment for drill
Trowel
Polisher/grinder
Various grit pads for polisher/grinder
Concrete sealer
Paintbrush

Instructions

- 1
  Measure 3/4-inch plywood pieces to cover the base cabinets then cut them to size with a circular saw. The plywood helps distribute the weight of the concrete evenly across the countertop.
- 2
  Pre-drill holes through the plywood and into the cabinet uprights spaced 4 to 6 inches apart. Secure the plywood with screws set below the surface of the plywood.
- 3
  Create the forms for the concrete with melamine board placed with the shiny side facing the concrete. For the width of each piece, allow at least 1-1/2 inches for the countertop, plus enough melamine to attach the form to the 3/4-inch plywood during installation. Cut the melamine with the circular saw. Attach the pieces to each other at the corners with screws. Secure the melamine form to the plywood with screws as well. Take care that the depth of the form is the same throughout.
- 4
  Place electrical tape along all of the seams. Be careful not to create any wrinkles in the tape that might show in the poured concrete. The tape helps the concrete release from the melamine forms and keeps the concrete from leaking out of the forms.
- 5
  Cut wire mesh or other reinforcement material to fit the inside of the countertop form with tin snips.
- 6
  Mix the concrete with a color additive, if desired. Add the amount of water recommended on the concrete mix packaging. Stir the mixture well with a paddle attached to your drill.
- 7
  Pour a 1/2-inch layer of concrete into the form then work it into all of the corners. Place the wire mesh on top of the concrete then pour the remaining concrete into the form and smooth it in place with a trowel. Continue smoothing the concrete until it is hard to the touch. Follow the package directions for curing time.
- 8
  Remove the melamine form from the concrete countertop. Use a polisher/grinder to smooth the concrete surfaces. Start with coarse-grit pads and finish with fine-grit to provide a shiny surface.
- 9
  Apply a concrete sealer with a paintbrush once the concrete cures. Follow the package directions for drying times.

How to Build Frame for Base Cabinet for Cooktop

How Much Overhang for an Undermount Sink?

Kitchens