Rodding Granite Countertops |
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issue time:2006-06-22 11:05
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In 2000, the Marble Institute of America (MIA) had laboratory tests conducted to determine the conditions under which rodding granite countertops may be beneficial. This information was first published in April 2000 and later incorporated into the MIA鈥檚 Dimension Stone Design Manual, VI.
The laboratory tests measured the flexural strength of 20 reinforced and two unreinforced samples of 3" x 48" x 3/4" granite. Additional tests were conducted on granite samples 26" x 30" x 3/4" with a 20" x 26" sink cutout and three 1-3/8" faucet cutouts. The reinforcing materials used were polyester resin, epoxy, rectangular steel rods, square steel rods, round steel rods, and fiberglass sheeting employed with the granite samples in a number of combinations.
Test results indicated that threaded round steel rods significantly strengthen the stone by 50% in load and 600% in deflection. Round rods with fiberglass on the bottom face produced the highest values, increasing the ability to withstand load by 300%, and increasing deflection over unreinforced stone by 1600%. There was no meaningful difference in using either a polyester resin or epoxy as the adhesive to set the rod.
The test results indicated that the MIA revise its recommendations on rodding granite for use as a countertop material.
MIA recommends:
Inserting threaded round steel rods (stainless preferred but not required) secured with epoxy or polyester resin (epoxy preferred but not required) in the bottom face of granite countertops along both sides where cutouts are required.
Applying fiberglass mesh to the bottom face of the granite at the cutouts.
Caution: It is not appropriate to use a rodding technique to repair granite countertops. The National Building Granite Quarries Association specification for repairing granite (endorsed by the MIA) states, 鈥淎llowable Patching: Chips at the edges or corners may be patched providing the structural integrity of the stone is not affected and providing the patch matches the color and finish of the natural stone so that the patch does not detract from the appearance.鈥� Cementing a broken granite countertop together is not an accepted practice.
What does this mean for the fabricator/installer? Rodding granite countertops at the weakest point, i.e., at cutouts, can significantly reduce waste and breakage when moving and installing the countertop. If the countertop was installed with proper support, rodding is not necessary.
See the Image for the Test Results
This technical bulletin contains general guidelines. The Marble Institute of America and its Member companies are not responsible for any use or misuse that causes damage of any kind, including loss of rights, materials, and personal injury alleged to be caused directly or indirectly by the information contained in this document.
(www.marble-institute.com)
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