Supporting Marble Countertop

by Kyle Laughlin
(Los Angeles, CA)

QUESTION

I recently had a 3/4" slab of carrera marble with an 1 1/8" mitered edge installed over my washer and dryer. Beforehand, I had a 5/8" sheet of plywood installed, supported on three sides. The marble fabricator/installer did not glue the marble down to the plywood and put a tile backsplash around the marble. The plywood seems to be sagging in the middle, not fully supporting the weight of the slab.

Today I noticed slight, light colored (almost white) cracks in the middle of the mitered edge. I have not put very much weight on the counter. Am I going to have an issue with this slab cracking? If so, what should I do to prevent a bigger issue? I have about an 1" gap between my washer and dryer. The width of the slab is 57" and 39" deep. Please advise. -Kyle

ANSWER:

Kyle, you should install some sideways 2x4 or metal cross bracing under the plywood that extends from wall to wall at or near the front and again half way back.

You need a completely solid and stable base for the marble. That plywood will fatigue and continue to sag putting stress on the center of the slab. Eventually that little crack you have will break through the whole slab.

If you can fit it, I'd also fit a pole or support in between your washer and dryer from the floor to the plywood base or to one of the cross pieces.

Good Luck,
Ryan