Failure Number 13       Inadequate Countertops

The Residential Stone Countertop Installation published by the Marble Institute of America is wonderful. Thank you to Vincent Migliore and the Marble Institute of America for publishing this document.  I have shared the document with the Woodwork Institute of California and Nevada for the purpose of coordinating proper rough tops required for stone slab countertop installations. I have also asked the Ceramic Tile Institute of America, Inc. to supply the proper rough top requirements for ceramic tile and thin stone assemblies.  The Woodwork Institute of California and Nevada requires mechanical fastening of cabinets to studs in walls using 3-inch long number 14 sheet pan screws.  As contractors, you should verify the cabinets are adequately anchored to the wall.  A minimum ¾ inch penetration into wood studs and a minimum 3/8-inch penetration into metal studs is required.  Where the proper anchorage is not provided, the splash joint will crack at the intersection of the cabinet deck to the vertical splash on the wall.  In addition, sinks and overhangs or cantilevered countertops require adequate support.   We currently have failures on countertops with fractured countertops with stone slabs where the stone slab is not properly supported.  One project utilized particleboard for the rough top.  Then the stone top was leveled using screws through the particleboard. The particleboard has sagged since original installation and the stone slab has fractured directly above the screw support used to level the countertop.

We have investigated slab countertops where the slab was installed cracked. 

We have investigated slab countertops where fill was not uniform and where bullnose edges were poorly fabricated. I recently investigated a granite slab countertop where oil or fat had been uniformly wiped into the horizontal slab countertop and the owners wanted new granite slab countertops from the fabricator at no charge.

Sealing of stone countertops is currently being addressed through the seminar going on simultaneously with this seminar.

Installation of stone tile over backer board has previously been addressed under Failure Number 8 discussion of backer boards.

The most successful countertop installation method with stone tile is following Assembly Method C511 in the Handbook For Ceramic Tile Installation.

We sincerely caution against direct bond of stone tile to plywood, oriented strand board called OSB, or particleboard.