7 steps to install marble kitchen countertops

Marble kitchen countertops usually come in slab form, with one slab sometimes covering an entire countertop surface.

Marble kitchen countertops usually come in slab form, with one slab sometimes covering an entire countertop surface. More often, however, two or more marble slabs are joined together with epoxy to make a countertop surface.

Carefully remove any existing countertop materials and disconnect all gas and plumbing lines before removing appliances.

Make sure all cabinets are level, flush and securely fastened to both the floor and the wall. To avoid excessive shimming and wide gaps that call for a lot of filler material, make sure that the cabinets are within ⅛ inch of level over a 10-foot span and the walls are within ⅛-inch of a true plane (plumb and without excessive curves).

Some marble kitchen countertops do not require any underlayment – the cabinet frames are strong enough to support the slabs. But, for installations with large overhangs or many large, open cabinets, you may need to support the countertop with a sheet of ¾-inch exterior-grade plywood or ½-inch cement board laid over the cabinet frame and use decorative brackets under the overhangs to support the weight.

For installations with large overhangs or many large, open cabinets, you may need to support the countertop with a sheet of ¾-inch exterior-grade plywood or ½-inch cement board laid over the cabinet frame and use decorative brackets under the overhangs to support the weight.

Use kraft paper or something stiffer yet still lightweight to create an exact template of the countertop and other surfaces to be covered with marble, including backsplashes. Precisely mark any openings for sinks, cook tops or any other cuts that will have to be made in the marble slab. If you’re installing a new sink, be sure it will fit in the sink cabinet and is in the right position before creating the template. This will allow you to make any necessary alterations to the cabinets to ensure a perfect fit. Be sure to include any overhangs in the template.

After your customer has made all color, pattern and edge selections, take the template to your local Home Depot or other material supplier and order the countertop to size. If the new countertop will need more than one slab, the supplier will be able to advise you on the best locations for seams.

Installing marble kitchen countertops

Before you begin, drape plastic over the cabinet fronts to protect them from adhesive drips or and from workers leaning against them with tool belts, belt buckles, etc.

Step 1

When installing multiple slabs on kitchen countertops, begin with the end pieces first and then insert any middle sections between them. Shim the front edges to make sure they are flat and level along the entire edge. Place shims at solid points on the cabinet tops – not in the middle of a long trim or filler piece. Be sure everything fits snug, square, level and flush. Slight variances can be sanded away with a power sander.

Step 2

Once the slabs fit correctly, remove them and place the silicone adhesive. Place quarter-size dollops every 6 inches over a plywood substrate. If your installation doesn’t require a substrate, place smaller beads on top of the cabinet frames so that excess silicone does not ooze out from under the slab.

Step 3

Carefully place the slabs in place again by setting the back edge down in place first, then lowering the rest of the slab onto the silicone. Be careful not to slide or push the slabs around, which would smear the silicone and result in a less-than-ideal seal. Clamp the slab down in several places to hold the entire assembly in position.

Install backsplashes after the slabs have been set and clamped.

Apply an enhancer-sealer to the countertop after installation. The enhancer will make the colors more vivid and the sealer will protect the stone.

Step 4

Once the slabs are level and tight to each other, apply strips of painter’s tape along both sides of each seam. Apply as close to the edge as possible to prevent excess epoxy from oozing onto the marble surface. Most epoxies need pigment mixed in to match or complement the marble color. Mix the pigment in slowly until the desired color is achieved and then pour the mixture over the seams and use a putty knife to force it into the joints.

Step 5

Overfill the seams, as any excess can be sanded off after it dries. Mix slightly more epoxy than you think you will need and make sure you completely fill the seams, as any gaps or cracks can be difficult to re-fill and color matching another batch of epoxy can be tricky.

Step 6

While the epoxied seams are drying, run a smooth bead of clear silicone adhesive between the cabinet tops and the bottom of the countertop to seal these seams. Once everything is completely dry, remove the tape and sand or carefully scrape away or remove any excess epoxy and/or silicone adhesive.

Step 7

Apply an enhancer-sealer to the countertop after installation. The enhancer will make the colors more vivid and the sealer will protect the stone. Advise your customer to re-apply the enhancer-sealer about every year or two, or when they notice spills do not wipe away easily.