Kitchen island granite overhang support
mamaleo1013
8 years ago
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geoffrey_b
8 years agoRelated Discussions
Neet help on 12' granite overhang support on kitchen island
Comments (13)I know this is not going to help the original questioner posted in 2007 and I sure wish I had found this question back then... But for those of you looking for "THE" answer... hear you go. The Amastin Company, Corryton TN, has been providing steel support bars in supporting hard surface counters to the East TN market since 1995. In this particular case, which is a common one, Amastin offers a 31" long x 2-1/2" wide x 1/2" thick steel support bar that would bump and mount into the back of the front face frame, notch and recess flush across the back cabinet mounting strip. This support would overhang 8" leaving it approx 4" from the counter edge making it virtually hidden. Amastin has the overhang support thing figured out and if you have any questions or in need of custom support advise... Amastin is place to find the answers. Here is a link that might be useful: The Amastin Company- Steel Support Bars...See Moregranite island support for overhang?
Comments (4)The Marble Institute of America recommends that 3cm granite needs additional support over 10" cantilever overhang and that 2cm granite over 6" cantilever overhang. However, the fabricator is warrantor of your counter and it is widely practiced and accepted that 3cm of 12" overhang is acceptable without additional support. Here is a link that might be useful: The Amastin Company- Concealed Overhang Support...See MoreSupport for Granite Island Overhang
Comments (30)I review the plans of everyone working on my house. [...] My general contractor and the granite fabricator/installer will warrant their work, and like everything else going into my house, I want to double check, and I want them to justify their plans if they differ from what I have learned from Professor Google. We don't have their plans though, if that sketch was given to you as their plan for support, then you are in trouble and need to hire another professional. To evaluate their plan we need to know what system they plan to use to limit flex. Make a wall beyond the cabinets, or close in the ends. for additional support. I am not a huge fan of walls that dissect long pieces of granite unless the people building the walls really understand what they are doing. I think the post is a much better idea that accomplishes substantially the same thing as a wall. ----------------------------------- When we talk about supporting granite we are talking about one thing. Limiting the tensile pressures. Granite, just like concrete, has great compressive strength and rotten tensile strength, when granite flexes you get compressive force on the concave side and tensile force on the convex side. Moving from theory to reality in granite we really have to do three things, (1) limit flex, (2) limit movement and (3) avoid isolation. Many inexperienced people will address movement and flex while ignoring isolation and when that happens you get the result that Joseph posted above. If we look at the brackets that are often used for granite islands we can see that their real purpose isn't to stop movement but to avoid creating a fulcrum so that the entire sheet of granite moves together. http://www.countertopbracket.com/countertop-island-support-brackets-hidden-p/ib.htm I guarantee you that something heavy placed on that overhang will cause the countertop to tip slightly in that direction, but the brackets ensure that the movement is carried past the edge of the cabinets so that the entire piece moves rather than creating a fulcrum at the back of the cabinets that isolates the overhang from the cabinets. Too much movement must be avoided because then you get the shock of the cabinets moving which can be bad so walls in long islands may be necessary but when they are you must avoid isolating them. In other words, in Joseph's example above had the brackets been extended and tied into the cabinets in such a way that the entire piece was tied together or tied to the cabinets sufficiently that everything moved together, the break is unlikely to have occurred. Technically the brackets in Joseph's post above did exactly what they were designed to do. They eliminated breakage at the fulcrum...They just created a new fulcrum because their designer didn't understand the problem. From a physics stand point, a post is nothing but a very short wall. You can get substantially the same results from a post that you can from a wall, by adding cost. Essentially the white arrows would be a wall while the red arrows will be a post. So long as the post doesn't flex more than a wall (which it will compress less than a wall), mechanically you can achieve the same thing. However, you create more isolation points, all of the red arrows need to either have very little movement at all, or be tied together in such a way that they move together (note the arrows actually form a circle). Achieving no movement is much harder than tying them together in such a way that the limited movement extends through the area. A 2" tubular frame under the entire granite surface would absolutely be preferred, as that is the best way to carry movement to the entire counter. My original advocacy for plate was in opposition of L brackets rather than a tubular frame, to avoid isolation. I think you can achieve much the same result with a steel plate (a 36" steel plate is roughly equivalent to about 20 brackets) but I am not opposed to a tubular frame, especially if you are going as deep as 2". Anyway, this is just my 2 cents. In the end, to evaluate the solution that your contractor is using we need to know that....See MoreNeed help! Supporting granite overhang on island
Comments (20)Thank you, Joseph! I think the issue is that we have a much larger overhang than 15" planned. It is currently spec's for 41" (but is supported on the ends by 6x6 posts.) Of course, I never realized it was so wide. I am fine making it shallower, but was hoping to preserve one seating spot on each end. How do I support the center of the countertop (which would be about 8' between the posts at a depth of somewhere between 30"-41". Does that make sense? I was looking at cantilever brackets, but no one says how far of an overhang can be supported. My dad thought 4" Channel irons could work, but I have no idea....See MoreVith
8 years agolast modified: 8 years agogeoffrey_b
8 years agomamaleo1013
8 years agoUser
8 years ago
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