To reply for concerns regarding countertops, our news column has specialized a series, named Countertops. Here is the news today.
Q: Do you have a documented standard on the maximum length of countertop pieces?
A: There is no established maximum length of individual pieces. Maximum length is influenced by stock availability, stone soundness, thickness, cutouts, handling equipment, and in some cases, jobsite conditions. To arrive at a general rule for maximum length would be impossible.
Q: Is there a standard that limits the amount of bow in a slab?
A: Yes there is, but it is not going to help you. The only standard that I am aware of for slab warpage is the NBGQA (National Building Granite Quarries Association) Architectural Specifications. In section 3.2 (Flatness Tolerances) of this document, the “out of -plane” tolerance for polished or honed finish granite is a maximum of 1/16” within a 4’-0” length. The document doesn’t indicate that this is to be a uniform profile, so the 1/16” variation could all occur within one foot of the 4’-0” length. And it allows both concave and convex warpage. Theoretically, you could have a countertop with a slab with a 1/16” concave bow resulting in a full 1/8” of lippage at that seam, but the slabs would meet the NBGQA specifications.