Concrete countertop build

Building and polishing a concrete countertop can yield stunning, durable results if done right. Here's a step-by-step guide to take you from start to finish:

Step-by-Step Guide

1. Design and Build the Mold
Use melamine (smooth side in) to build the mold to your desired dimensions.
Ensure it is level and tightly sealed using silicone caulk on interior edges (smooth it out for clean corners).
Add reinforcement inside (rebar grid or mesh suspended in the center).
2. Mix and Pour the Concrete
Mix according to the bag instructions or custom ratio (common: 1 part cement, 2 parts sand, 3 parts gravel).
Use a water reducer for smoother concrete without weakening it.
Pour into the mold and vibrate the mold with a rubber mallet or palm sander to release trapped air bubbles.
3. Screed and Trowel
Use a straightedge to screed the surface level.
Trowel the surface smooth after 20–30 minutes, depending on temperature.
4. Cure the Concrete
Cover with plastic to retain moisture.
Let it cure for at least 48–72 hours, or up to 7 days for best strength.
Carefully demold after curing.
5. Polish the Concrete

Dry or Wet Polishing
Wet polishing keeps dust down and prolongs pad life.
Dry polishing is messier but more convenient indoors.
Steps:
Start with coarse diamond grit pads (e.g., 50 grit) on an angle grinder or concrete polisher to remove surface imperfections.
Progress through finer grits (100, 200, 400, 800, 1500, 3000) for a polished, glossy surface.
Use a concrete densifier after the 200–400 grit stage to harden the surface.
Finish polishing through the higher grits.
6. Seal the Countertop

Clean and let the surface dry completely.
Apply a penetrating sealer or food-safe topical sealer depending on use.
Buff to desired finish.
Optional Finishes

Integral color or stains for custom look.
Embedded items (glass, metal) added during pour for design.
Edge profiles shaped into the mold or ground post-cure.