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Old 12-18-2006, 08:17 AM   #1
jkealty
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Maximum Granite Bartop Overhang

I will be putting a granite top on an L shaped bar I am building. The current top is 3/4 oak plywood 15-1/2" wide. I would like to install 3/4" granite on top with a 6" to 8" overhang. I would prefer to not have to install any additional support for the overhang. Does anyone know what the recommended maximum unsupported overhang for granite is?


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Old 12-18-2006, 09:12 AM   #2
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i do not know for sure, but one of my coworkers showed me his new house and his 1.25" thick granite slab overhung by 18 inches without support.
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Old 12-18-2006, 09:46 AM   #3
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JK,

Welcome to the forum.

This topic gets a lot of debate. Do a search using granite overhang and you'll get some threads to review. Here is one link that might start you off:

http://johnbridge.com/vbulletin/showthread.php?t=43841

Any other questions, please feel free to ask. And if you need help, please try to keep your project questions all in one thread, it will help us to have the background handy. Good luck!
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Old 12-19-2006, 07:05 AM   #4
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Thanks for the help.
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Old 12-20-2006, 08:11 AM   #5
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My quartz countertop over hangs the bar by 12 inches. The supports are hidden behind the bullnose. The supports consist of sections of steel square tubing screwed to the bar every 12 inches or so. I'll try to post a picture of the supports as soon as my camera battery charges. I would be afraid of having much overhang with out some kind of support but I am by no means an expert.
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Old 06-01-2010, 09:02 AM   #6
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The Rules

There really shouldn't be much debate. The rules are solid (get it?... solid?...) however they've never really been documented.
The Rules:
Single-level bar with overhang: Natural stone requires “adequate” additional support of overhangs more than 10" for 3cm and 6" for 2cm. Otherwise, there is a general "2/3rds" rule... Any overhang not being counter-balanced by 2/3" of the counter depth, will require additional "adequate" support. Example: If one had a 36" deep counter, 1/3 (12") is allowed unsupported overhang with 2/3 (24") being counter-balanced support. However, The Amastin Company recommends additional support of any overhangs over 12".
Raised-bar overhang: A different animal than single-level and requires a different way of thinking. Overhang on a raised bar is usually opposite of the “2/3rds” rule. i.e.: Usually 1/3" of the counter depth is supporting 2/3" of the overhang. With this in mind, additional support is not only supporting the "overhang", they support the entire counter.
In the case of this thread’s question... They will have 6-8" overhang on one side, resting on a 4-1/2" wall, while the other 5-3" will overhang the other side of the wall. THIS WILL REQUIRE ADDITIONAL SUPPORT.
Since they are using 2cm granite, The Amastin Company recommends, and supplies, concealed steel support mounted flush to the top of the wall, set back from the overhang edge no more than 4", and supported every 24" on center.
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Old 06-01-2010, 09:28 AM   #7
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Stacy,

Welcome to the John Bridge Forums. The forum has literally tens if not hundreds of thousands of threads and they can be brought up and responded to at any time. You have dredged up a thread that is 3 1/2 years old. The original poster hasn't been on the forum since the day after their question was posted.

In my eyes, although your information is informative it will do little good in this case. Please be cognizant of the date of the thread and judge whether responding to it will be worth your time and effort. We value any expertise that any professional brings to the forum and if you want to stop by the Professional's Hangout and introduce yourself we would welcome that.

Brian
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Old 06-01-2010, 11:54 AM   #8
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But in any case it seems to have been a well-informed reply, Stacy. Welcome aboard.
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Old 06-01-2010, 06:02 PM   #9
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Welcome Stacy,

The M.I.A. has published guidelines for counter-top overhang support. Their recommendations for maximum unsupported overhangs/cantilevers are based on "structurally sound" stones, roughly stated by Stacy above. Not mentioned above is that some stones may need more or less support based on it's structural integrity.

For double cantilevered counter-tops, some type of steel support is typical and can be 'let-in' to the bottom of the stone and hidden in some cases.

...I know it's an old thread, but there is good reliable published information/standards and the MIA does go into some detail in their Dimension Stone Design Manual. The manual is available through their website... for a price.
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Old 06-01-2010, 07:16 PM   #10
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I think she He knows, this is from their website:

The Amastin Company supplies Steel Support Bars supporting hard-surface counter overhang such as Granite, Marble, Quarts, and Solid-surface such as Corian counters.
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Old 06-01-2010, 11:32 PM   #11
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Thanks for nice welcomings...

I did realize the age of this thread. However, I found this thread through a Google search and thought that if others found it as well, that I could possibly help with an answer. And I hope it does.

My support recommendations are bases upon the research of several documents and personal experiences since 1995. The MIA (Marble Institute of America) is one of the documents I keep in close view for updated changes. However, their recommendations are based on natural stone. I also have fabrication manuals for a number of quartz and solid surface brands such as Ceasarstone, Silestone, Cambria, Corian, Fountainhead, and so on. We also realize that there are some surfaces, particularly with natural stone, that are less porous and stronger than other materials. We rely heavily on good communication with stone fabricators to utilize maximum support for a particularly stone.

I am aware of a process in which steel rods are routed in flush with the bottom of stone counters. This is a process call “rodding” and is used to strengthen weaker stones or those which may have heavy veining. This process is not recommended as “adequate” overhang support… although; I get this question quite often.

When I stated that "they've never really been documented", I was referring to a copulation document of "general"-"rule of thumb" rules that come close to covering the bases of natural and synthetic stone as well as solid surface.

Between the recommendations of the MIA and the specifications of individual material manufacturers, there really shouldn't be much debate as to the "how to" of adequately supporting overhangs.

Thanks again for the kind welcoming and I hope I can be of help to someone…
Mr. Stacy
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Old 06-02-2010, 10:28 AM   #12
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Regardless of the dates, etc., it seems that the original poster didn't receive a qualified answer. Too late now, but others might benefit.
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Old 06-21-2010, 03:54 PM   #13
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Agree with Randy

It is more important to focus on the availability of a thread rather than the date it was posted. The area of countertop support is sufficiently void of accessible information and resources that the questions raised in threads often stay visible on search engines for years.

Just as Stacy referenced, these threads are easily found on search engines and when a visitor views them it is beneficial for all if they have usable information rather than a question left open.
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