Support brackets for granite overhang?

15 years ago

I've read online that if you have a granite overhang of 12 inches or more, you should have some type of support brackets installed. I've got a 7' long peninsula that will have a 12 inch granite overhang: the cabinets are 24" deep. Since it's right on the cusp, I'm not quite sure what to do. My granite is being installed next week, but the fabricator did not mention any type of support to me.

Featured Answer

stacywomble

15 years ago

Hopefully this will help future readers looking for answers. The post by Buehl is all over the conditions of needing support as recommended by the MIA (Marble Institute of America).
This is for "Single-Level" counters with cantilever overhang:
For 3cm stone: any overhang over 10" will need additional support; spaced every 36" or less.
For 2cm stone: any overhang over 6" will need additional support; spaced every 24" or less.
For "single-level", the goal is to support the cantilever. We do this with CONCEALED SUPPORT. Single-level concealed supports use the mass of the supported material to "reach out" and support the un-supported material.

"Raised Bar" support is of a completely different breed. Unlike "single-level" support, "raised bar" supports support the whole darn top. (Gosh, I need to write an article explaining all of this stuff!) There is a rule called the "2/3rds Rule" which says that in dealing with overhang, that 1/3rds overhang much be supported by 2/3rds of the width of the overhang. (Example: a 36" wide counter should have 24"(2/3rds) of support (cabinetry) with 12"(1/3rds) overhang.) Raised bars blow this rule out of the water so we have to look at it differently. ALL RAISED BAR COUNTERS NEED SUPPORT! We use "SB" support to support raised bar overhang up to 12" and "SBS" supports to support anything over 12" and up to 18" overhang. We Do Not recommend overhang over 18" on either "single-level" or "raised bar" counters.

Let me address Rodding. The process of grooving the bottom of the material and epoxying in steel rod is an acceptable practice in suring up weak areas of material (such as in front of and behind sink or cooktop cut-outs or even fissure veins) but is NEVER an acceptable method of supporting cantilever overhang (I know this is going to ruffle feathers of some fabricators) but let me repeat "NEVER". The fact is that, as a method of overhang support, it actually weakens overhanging material. You will not find this recommended by the MIA as an acceptable overhang support method.

Here is a link that might be useful: The Amastin Company- Concealed Overhang Support

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Comments (11)

Kathy F
15 years ago
The fabricators I've been talking to have all said that if I don't want corbels or other visible support, they could install rods in the slab. These rods would only be visible from underneath and would be adequate support for even a 15" overhang. Perhaps your fabricator is planning on doing this and didn't specify? I would ask.
remodelfla
15 years ago
You can either rod your stone or you need braces for sure. We used the Freedom Brace by Federal Brace since I did not want corbels or anything hanging down. we were only able to get a bit under 14" depth for our overhang. But you can't go without anything there.
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EllenMel
Original Author
15 years ago
Do fabricators normally charge additional for installing rods? As far as the Freedom brace, how is it attached to the cabinet? My existing cabinets are being refaced before the granite is installed: is this something that should be done before the peninsula is refaced?
Buehl
15 years ago
Use the "6 & 10 Rule"
For 3cm stone: any overhang > 10" will need a corbel or other support. how much? Overhang inches - 10" = # inches for support
For 2cm stone: any overhang > 6" will need a corbel or other support. how much? Overhang inches - 6" = # inches for support

....with a corbel or support every 30" of unsupported overhang

If you don't want corbels or legs, consider the "CounterBalance" system instead.

Thread: Kevin - 'remember the 6 & 10 rule'
Thread: granite fabrication questions..what do you think!

Minimum recommended overhangs (NKBA): Table-height: 18"
Counter-height: 15"
Bar-height: 12"

Here is a link that might be useful: Thread: Stone Information and Advice (& Checklists)
MCMesprit
15 years ago
I agree with all the previous posters. Another consideration: will there be a seam in the granite? We just had installed a two-tiered island. The second tier has an overhang a bit more than 10" but it didn't need any support (rods or corbels) because the entire tier is one piece. We needed to purchase an additional slab to accomplish this, but it was well worth it.
remodelfla
15 years ago
My situation is different because I had a pony wall that the braces attached to. I know that make braces for a variety of applications.

Here is a link that might be useful: Federal Brace countertop supports
jterrilynn
15 years ago
Here's another idea, scroll to the bottom for pictures.

Here is a link that might be useful: progress pictures
zinnah
15 years ago
I used flat aluminum bar stock 1/4"x3" about 12" oc screwed to top of pony wall. Got an overhang of 12" with 3 cm granite.
warmfridge
15 years ago
You can get all kinds of interesting corbels, if you want to go that route.

Here is a link that might be useful: Corbels
sdishii
13 years ago
Stacy,

So since I have 36" depth of cabinets I can have 12" overhang with no support? Our island is going to be around 9'x 4'. Does it matter if it is 2 or 3 cm granit? I was just going to do the 3 cm, but my husband likes the mitered 2 cm to look like 2". Is the mitered 2 cm going to be a broblem? We can't use corbals because there are back cabinets all the way across.