How to Build White Concrete Countertops

White stone countertops look beautiful in a kitchen, but the price tag often makes them an unrealistic option. White concrete offers a practical alternative that captures a similar look at a fraction of the cost. With the right materials and techniques, you can build precast concrete countertops in a garage or workshop and install them once fully cured. This approach keeps the kitchen clean and functional while the work happens elsewhere.

This blog explains the full process, from building the forms to sealing the finished slabs, and highlights the techniques that help produce a smooth, polished white finish.

Building the Forms

Precast countertops require rigid, watertight forms. Melamine-coated MDF or particleboard is the most common choice because the smooth surface helps produce a clean finish.

Cutting the panels

The panels for the bases and sides are cut according to a layout drawn before beginning the project. A track saw or circular saw can make the base cuts, while a table saw handles the long, narrow side strips. When making thin countertops, the form sides can be relatively short. For example, a one-inch countertop only needs sides slightly taller than one inch.

Assembling the forms

The side strips are pre-drilled to prevent splitting. Screws secure the sides to the base panels, forming a box shape. Each form is labeled with its measurements to keep track of multiple slabs.

Sealing the seams

All interior seams are sealed with 100 percent silicone. This prevents leaks, protects structural integrity, and helps create slightly rounded edges inside the form. Once sealed, the forms are cleaned with a vacuum and wiped down so no dust or debris transfers into the concrete.

Preparing Reinforcement

Thin concrete slabs need reinforcement to prevent cracking. Fiberglass mesh designed for countertops is ideal because it adds tensile strength without the rust risk associated with metal.

The mesh is cut to size for each form and set aside to be inserted halfway through the pour. Keeping it centered in the slab is important for structural performance.

Mixing White Concrete

Water and pigment

Using cold water gives a longer working time, especially useful in warm environments. White concrete mix accepts pigment, and adding white color packs enhances brightness and consistency. Pigment is mixed into the water first before adding dry ingredients.

Mixing

Concrete is added gradually while the drill mixer runs. A corded drill is recommended because it delivers steady power for extended mixing times. Water amounts follow the manufacturer’s instructions, but adjusting slightly for flow can help with surface quality. A mix that is too dry tends to trap air pockets, resulting in pitting on the finished slab.

Pouring the Concrete

The concrete is poured into the forms and pushed toward all corners. Once the forms are half full, the reinforcement mesh is placed in the center, gently pressed in, then the rest of the concrete is added until the forms are level and slightly overfilled.

A straight board acts as a screed to strike off the surface. After leveling, the slabs need vibration to release trapped air. A simple method uses a reciprocating saw (no blade), pressed against the form edges. The vibrations draw bubbles upward, reducing voids in the finished surface.

Curing the Slabs

The slabs cure inside their forms for several days. Spritzing them with water a few times a day helps maintain moisture, promoting a slower, stronger cure. Rapid drying can weaken the slabs or increase the risk of cracks.

Once cured, the forms naturally pull away from the concrete. Screws are removed, sides come off easily, and the slab can be lifted with help. Removing the form reveals the finished

top surface, along with any small imperfections that need filling.

Grinding and Smoothing

The bottom side is ground first to flatten inconsistencies. Edges are eased by hand with diamond sanding blocks. The top surface—the visible face—requires more attention. A polisher fitted with diamond pads removes melamine and silicone imprinting and exposes a clean, smooth surface. Small pinholes left by trapped air are common, even with vibration. These are filled later.

Filling Voids

A patching slurry fills pinholes and surface defects. A white powder-based filler blends with added white pigment to match the countertop tone. The slurry is spread across the surface and pushed into all voids.

After drying, the excess is sanded away. A drywall sanding block is effective because it removes the filler cleanly without cutting too aggressively into the surrounding surface. This step can be repeated if any voids remain.

Sealing the Countertops

A high-quality concrete sealer is essential for stain resistance, scratch protection, and water resistance. Countertop sealers rated for food contact and high heat are the safest choices. Three coats typically provide strong protection, and the slabs should sit for 24 hours before installation.

Installing the New Tops

The old countertops are removed by cutting caulk lines and unscrewing brackets. The precast slabs are then set into place. A one-inch thickness allows them to fit neatly under the existing backsplash without modifications. Once installed, the smooth white concrete surface brightens the kitchen and eliminates seams that were present in earlier materials.

White concrete countertops offer the look of stone with long-term durability, water resistance, and a clean, modern finish. With proper planning and careful mixing, the final result resembles high-end materials at a significantly lower cost.