How to Cut a Cultured Marble Countertop to Install a Sink

Lead Image
  • 2-4 hours
  • Intermediate
  • 70-300
What You'll Need
Measuring tape
Rotary saw
Masonry saw blade
Vice grips
Old blanket
Sanding block

Cutting a cultured marble countertop to fit can be a challenge for the novice do-it-yourselfer. Why? This type of countertop is made from components such as marble dust, resin, catalyst and pigments, all of which are very hard and brittle and yet easy to mar or scratch. Once this surface is scratched, it will be difficult, or impossible, to remove these scratches. The material, because it is brittle, is also easily chipped and splintered from the spinning saw blade. Cutting a material this hard and brittle requires not only care and patience but special cutting blades and a surface that is free from sharp edges that could scratch or gouge your countertop.

Step 1 – Protecting the Countertop Finish

You'll need to place your countertop on a surface such as a work table, with the countertop surface resting on the table. To avoid scratching or marring its surface, place an old blanket or other soft material beneath the countertop surface.

Step 2 – Measuring the Countertop for Cutting

When measuring the countertop for cutting, use a pencil and measuring tape, yardstick or straightedge. Make your measurement marks on the unfinished side of the countertop to avoid scratching it or leaving marks on the finished surface that cannot be removed. Draw straight and even lines you will be able to follow with your saw blade.

Step 3 – Securing the Countertop for Cutting

In cutting the countertop, you'll be applying lateral pressure that can easily make the countertop slip and can result in mistakes in cutting. One wrong cut, and you will have ruined the countertop and will likely need to replace it. To avoid these mistakes, secure the countertop. Clamp it to the table it's resting on. If you don't have clamps, your can use vise grips. Once you have clamped it, test it to be sure the clamps are holding it securely from moving.

Step 4 – Cutting the Countertop

In cutting with your rotary saw, be sure the blade you use is a sharp masonry blade. Push the saw slowly and carefully so that the blade follows the pencil lines you drew. Be sure it cuts without chipping or splintering the countertop finish. As you reach the end of your cut, reduce the forward movement of the saw until it is barely moving. Splintering or chipping, caused by too much pressure on the saw will be more likely here.

Step 5 – Sanding the Countertop

When you've finished cutting, begin smoothing the cut surfaces with a fine grade of sandpaper. You'll need to glue some of these edges to the cabinet or base on which it will rest, so you'll need them to be smooth, level, and to have square, sharp edges. To get this type of finish, use a sanding block. Avoid sanding near the finished countertop surface where you could inadvertently scratch the finish. Avoid using power sanders that can make these surfaces uneven and can make gluing difficult.