Thread: Granite countertop overhange

I know what the requirements for granite countertops are, however I need something in writing from a good source. Anyone have a link or something they can post?

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You will want to reference the Marble Institute of America and their design manual.

I had one several years ago but gave it to another inspector when I moved and retired. Wish I still had it as they are no cheap.

"I know what the requirements for granite countertops are"
Would you list them here so I can see if I remember them correctly?

Also, a good search of the archives should be able to find when I referred to them before, probably will even have section numbers in the MIA Design Guide.

The Marble Institute of America (www.marble-institute.com) recommends that stone 1¼ inches thick should supported with corbels if the cantilevered portion exceeds 10 inches or is cantilevered more than 1/3 the overall width of the stone. Unsupported stone slabs can break off causing injury. Repair or replace the stone countertop installation to reduce the amount of unsupported cantilevered stone.

Richard, a few Q&A's that may help you here.

Granite FAQ

Granite can be cantilevered up to 14" if it's a large piece with sufficient support on the fixed end. It should never be cantilevered where it might receive excessive stress, however, such as where someone may be tempted to sit on it or use it as a step stool to change a light bulb. In these cases, it must always be supported.

It's always best to assume the worst and add proper support on any extension over 6". An unsupported span of no more than 36" is usually acceptable as long as the stone is supported on both sides of the span.

Here is an example of an island top with overhang. There are a lot of variables due to the type of stone, grain runs and grade.
Don't rely on too many assumptions because stone is stone.

Originally Posted by Marcel Cyr

Richard, a few Q&A's that may help you here.

Granite FAQ

MC:
the link appears to be yet another tradesman who flaunts his ignorance of industry standards.

Well perhaps Mr. Miller you can contribute more accurate facts about the product from your experience.

This is what I use from the marble institute.

Unsupported overhangs shall not exceed 6" on 3/4" countertops or 10" on 1-1/4" countertop, supports/corbels must extend 1/2 the overhang depth, supports should be placed 6" from the countertop edge and be separated a minimum 30".

Spans and Cantilevers. In designs where part of the countertop is spanning between supports, the length of the span shall be limited to 2'- 0" (600 mm) for ¾" (20 mm) stone thicknesses and 3'- 0" (900 mm) for 1¼" (30 mm) stone thicknesses. In designs where the countertop is cantilevered or overhanging the supports, the cantilever shall be limited to 6" (150 mm) for ¾" (20 mm) thick countertops and 10” (250 mm) for 1¼" (30 mm) countertops, but in no case may the cantilevered portion represent more than 1/3 of the width of the countertop. Cantilevered countertops exceeding these dimensions will require corbelled supports beneath the stone.

See page 3 and 23

http://www.marble-institute.com/cons...countertop.pdf

Jeff Euriech
Peoria Arizona

That looks like a very nice kitchen.