Granite Counter Support On Knee Wall

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Old 01-12-13, 05:44 PM
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Granite Counter Support On Knee Wall

Hello all,

I am having granite installed on my cabinets and have a question about support for a knee wall. There is a knee wall that is 74" long. On one end it is connected to an interior wall. On the other end it is not connected to anything. The knee wall is 2x3 construction with 1/2" drywall on each side. I screwed everything together with deck screws so it would be as rigid as possible. On one side there are kitchen cabinets which are screwed into the knee wall and interior wall so there is some added rigidity there. On the other side is the dining room. This wall is about 6 inches taller than the base cabinets. I want to put a granite shelf on top of it. I am thinking between 12-14". 2" will overhang on the kitchen side. 6.5" to 8.5" will overhang on the dining room side. The drywall is already installed, spackled and primed. The granite will be 1.25" thick. I am assuming they will silicon it to the knee wall during installation. The granite company expects any necessary supports to be installed prior to templating.

I'd like to hear your suggestions on how to support this wall. I know some people use wood corbels while others use metal brackets.

1) What do you think would work for my specs?

2) Also a lot of corbels I see at the Home Depot have a part on the back that gets hooked onto a nail/screw. I am assuming that I will need to actually drill holes into them and screw them into the studs for them to bear any weight. Are there certain corbels to look for and others to avoid?

3) How many corbels/brackets/other will I need to install and how should they be spaced?

4) Are there any issues that you can see with this wall only being 6" or so taller than the base cabinets? After the 1.25" granite goes in I will have about 4.75" of wall. I plan to tile this wall with the other walls above cabinets.

Thanks all.
 
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Old 01-12-13, 07:49 PM
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My landlady just did the exact same thing. The knee wall is already supported. You will need 4 support brackets under the granite, to the knee wall, on the dining room side. Put one on each end & space the other 2 evenly. They can be angled or L shaped. My landlady used metal brackets.
 
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Old 01-12-13, 10:33 PM
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None of the corbels I've found at Home Depot ever looked capable of actually supporting any weight. They do have some decorative metl shelf brackets that would probably give you enough support for the limited overhang. You could also go with a beefy L bracket and cover it with a decorative corbel.

The only places I've ever found load bearing corbels were ones I made or at my local specialty wood supplier.
 
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Old 01-13-13, 05:52 AM
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A basic "L" bracket won't have the strength to support the granite.

In my kitchen, I used 4 of these. Probably overkill, but it's certainly strong:
Cafe Counter Top Bracket - 10" x 10" Steel

I've since come across this company, and will probably be using their brackets for my next project:
Made of Metal - Support Brackets

In my kitchen, I cut the drywall out so the brackets were lag bolted directly to the 2x4 wall. Then I used joint compound to bury the bracket, so all you see is the angled bracket and the horizontal one holding the granite. I left mine the silver color, but they could have easily been primed and painted.


In my experience, the way you've stabilized your wall, especially with the connection to the cabinets, you should be fine.
 
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Old 01-13-13, 09:02 AM
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Here is a good industry document summarizing recommendations from the Marble Institute

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

In short, you can have up to 10" of Unsupported overhang on a 1.25" thick top, but only if the overhang is 1/3 or less of the total width of the countertop. So, at 14"' you have to keep the overhang under 4.66" to go without corbels.
 
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Old 01-13-13, 10:47 AM
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The granite people should have a bracket. What Zorftd used was not overkill.
 
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Old 01-13-13, 07:17 PM
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If I order support corbels like this:
4 1/2"W x 5"D x 10"H, Medium Traditional Corbel - CORTT2 - COR305 by Architectural Depot

How would I fasten it to a stud? I would imagine drilling holes through it and screwing it into a stud will negatively affect its appearance.
 
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Old 01-13-13, 07:56 PM
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Isn't there a bracket that gets mounted first, then the decorative part goes on afterwards?
 
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Old 01-13-13, 10:38 PM
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Solid wood corbels often come with mounting brackets/slots that hang on a couple of screw heads coming from the wall. Some designs may also have a recess cut out for a metal bracket that goes on first.
If you have a solid corbel with no mounting hardware, there are a couple of ways I've seen them mounted. 1) cut short t slots in the back of the corbel using a special router bit. 2) drill angled holes in the back of the corbel, then screw in bolts at a matching angle into the stud. Cut off the bolt heads and slide the corbel onto these angled pins. 3) screw in bolts straight into the stud, cut off the heads and then drill matching holes into the back of the corbel. Coat the bolts with epoxy and slide the corbel onto the bolts.

1 is the easiest but requires a special router bit. It also has the greatest potential for tear out if the slots aren't cut deep enough or the bolt heads are too small in diameter.

2 works well in terms of strength (I am currently using 4 such angled pins to support a 10" x 8 foot mahogany mantle) and is removable, but is very difficult to do with a precision placement.

3 is easy and strong but is permanent. No oops or repositioning.

The last thing I can think of is to lag a wooden baseplate to the wall that is the same dimension as the back of the corbel. Then glue the corbel to the baseplate. A properly glued wood joint like that will hold a heck of a lot of weight once it cures.
 
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Old 01-14-13, 03:39 AM
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Old 06-05-13, 11:42 AM
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Hi Guys,

As a professional installer I absolutely recommend using 1/2 inch thick hidden steel brackets. For a 14 inch overhang past the knee wall put about 10 inches of steel under the granite and 4 to cover the knee wall - a 14 inch bracket. The are several companies that sell these brackets. Don't let anyone tell you that 1/4 inch thick brackets are just fine. 1/4 inch deflects with a 30 lb load at 8 inches. If someone leans on the granite is very possible that a 1/4 inch bracket will flex and the granite will snap. 1/2 inch will not. We usually place our supports about 24 inches apart and have NEVER had a top snap. Here are a couple of brackets t check out.

Federal Brace, Carrier - nice bracket but not exactly hidden
Carrier Countertop Brace

Centerline, Stand Bracket - very strong and hidden
Granite Bracket - Standard with 4 off Set Mounting Holes for supporting granite overhangs and countertops.

Centerline, Forward L Brackets - the bracket I use most often
Countertop Support Brackets - Hidden Forward L Bracket for mounting granite countertops to cabinets or knee walls
 
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