I have a 12" overhang, no plywood, no extra supports and it's fine. Installed 11/2002.
Ask this question over on the kitchens forum for more input :)

It will be fine untill the time someone sits on it, or a leans on it, then it could break. No one will recommend an overhang over about 6" without support. Plywood is ok but metal tubing attached to the cabinet and extending into the overhang area will give you the best support.

Tom: You mention that 6" maybe okay without support and thereafter there is a risk. Is 5/8 plywood sufficient support for a 12 to 13" overhang?

I suggest anything over 8" to have support. Generally that is the homeowner or contractors responsibilty. Over the course of time, something will happen with a large overhang. Not only you may need to replace the counter if it breaks, you or someone else can get hurt

Thanks to those who have provided input. Stoneonecorp. Is 5/8 plywood under a 12 to 13" overhang sufficient??

Well I dont do much 2cm in Boston, but I will try my best...
I still think you need support brackets. I THINK(not sure) they will only put plywood where the cabinets are and not on overhangs. I would think thats because on the overhang you would be able to see the underside of the gramite/plywood. Once again, I dont really work with 2cm, so I am taking educated guesses here

I'm in the same boat with a soapstone counter top...

And don't want the brackets, so we are having a 1/4" steel plate made that will be 3" in from all edges. The plate will be attached every 6" with 3" deck screws to the top of the knee wall (which is to transfer/hold the lifting tipping load).

It's not installed yet, so I can't say it's the way to go...but it's how we are proceeding.

We haven't done ours yet, either. But my plan was to get 1/4" steel plate, probably 4" x 18" and use a router to cut recesses in the cabinet tops. Then I'll place these supports approx every 2' along our 8' counter, with 9" under the granite.

Just a word of advice, do not compromise safety for asthetics.....Not saying that you are in this particular case but in general....I hear people all the time say "I dont want supports there" Better to be safe always

I have a 42 inch peninsula supported on one end by the cabinet box and a 12 inch square support pillar on the other end. 30 inch span between cabinet and pillar and 12 inch overhang on pillar. Both granite fabricator and kitchen contractor said 5/8 inch wood underneath was sufficient. Do not anticipate anyone standing on it.
Been up for 2 years.

I have a peninsula with 15 inch overhang on one side and 12 inch overhang on the end. My architect specified 2 steel "L" shaped supports coming from the floor and supporting the overhang. They are hidden in the cabinet. My GC is putting 2 additional flat metal sticks (they look like yardsticks with ridges) to support in between the L shaped rods.

We added six 10" "L" brackets to our 12" bartop overhang. What made it work without triangle supports or corbels is that the fabricator cut a 3/8" slot in the underside of the granite countertop for the horizontal piece. The contractor routed out a 3/8" dado in the vertical plywood wall for the vertical portion of the bracket. After the countertop was in, we added a maple veneer to the 42" x 87" vertical wall, and then added Shaker-style board and batten strips over the veneer.

Bottom line - the 12" counter overhang is completely supported, and there is nothing visible!

Where does one purchase 1/4 inch steel plates to support the stone?

The plywood support is just fine. The only problem with it is that you see it from the edge on both sides. So, unless you plan to run a molding or something to hide the plywood, then metal brackets are the way to go.

You go to a welding shop and have them made. 1/4" thick by about 3-5" wide, depending on what flat stock they have. They will make little countersink holes for the screws if you tell them exactly where you want them. Secured to a knee wall the way mjohnson suggested is great!

If you will not have a knee wall and are routering the top of the cabinets, you will DEFINITELY need to add some additional bracing inside the cabinet. A 1x or 2x added inside the cabinet to receive the screws and to carry the weight of the flat metal plate.

I am definitely going with the steel bars. My Silestone dealer says my 12 inch overhang definitely needs support. They recommend at least 3 for my 8 foot countertop, but we're doing 4- 1 toward each end and 1 on each side of the sink where the overhang is most vulnerable.

I called "steel fabricating" companies (in the Yellow Pages) and they all carry (and had in stock) 1/4 inch thick "rolled steel flat bars". They come in 20 foot lengths and in 2, 2.5, and 3 inch widths. The cost per bar ranged from $22 to $30, and the company I am using charges $1 per cut. They cut while you wait. I did not ask about hole drilling because we can do that ourselves. All 4 will cost under $35!!

I am thrilled that I don't need corbels. Had them, hate them. No matter where you put them, they are always in the way of the chairs and/or the knees!

Unless you are getting a sweetheart deal on the granite, I'd upgrade to 3 cm. If you're going to all the trouble to provide support at least consider a slab that looks substantial (thick enough).
Susan ~

I have a 7 foot granit top overhang. The granite overhangs about 15 inches in the center and curves around with a 12 inch overhead on the ends. The countertop that the granite is glued to is only six inches wide which runs across the 7 foot area. We finally found some steel supports that hold 1,000 pounds but found out the part the granite is glued to is plywood and we are not sure that the steel supports would work if not screwed into solid wood. Please help. I have been trying to resolved this problem for two months. It now has a 2x4 in the center for support.
Thank you so much for any advice.

We have about 4 feet silestone overhang about 20inches deep. Supported by 3 steel bars anchored to the base cabinet. No plywood.

Wood is not really a suitable support for large overhangs of stone.
You would have to use inch thick plus thickness wood to provide enough support.
If the stone manages to flex even a tiny amount, it cracks.
Like glass, it is strong but brittle.
Add in any weak spots in the stone and you are asking for a failure.

Steel is a suitable strength member for stone.
It is both strong enough, and when installed correctly will greatly reduce the chances of failure.
Steel epoxied into slots in the stone is about as good as it gets.

I have a granite countertop on a peninsula and am adding a granite slab for a breakfast bar which will start just under the lip of the existing countertop and extend out 12 inches and run about 5 feet. I would like the supports to be as hidden as possible and like the idea of epoxying steel rods into grooves cut into the granite but I don't understand how to attach the slab to the cabinet. I've read through the ideas here but don't understand what I should do in my situation. I'd appreciate any help. Thanks!

My builder and granite supplier both tell me that I will not need any support for a 12-inch overhang of my 3cm granite countertop. They also tell me that if I use brackets/corbels, then the overhang can extent up to 12 inches beyond the tip of the bracket/corbel. Thiss seems to be contrary to what I am reading here. Any thoughts on this? Thanks!

Get the guarantee in writing.

Granite is a far from uniform material.
Some types tend to have fewer flaws and can withstand more overhang, others are more likely to have fissures and hidden weak spots that require more support.

You'll hear different information from different fabricators. Everyone seems to have their own way, to some degree.
We had granite installed a couple of years ago which included an island with a 12" overhang and a raised bar top with the same overhang. Our fabricator made relatively flat (think they're about 1/2" thick) steel bars to support it. The bars fall shy of the ends of the overhangs by about 4 inches. Our granite simply sits on top of the bars and are secured with silicone, though the weight of the stone will keep it pretty much in place on its own. The bars were recessed into the wood and screwed down so that they sit flush with the cabinet top.
The bars in the island sit inside the cabinet. They added wood cleats 1/2" down front and back for the bars to rest on. Nothing to knock your knees on and they're painted black to match our stone. We're very pleased.
Don't know if they make them available without a granite purchase but it couldn't hurt to ask. Check the link I've attached.
Hope this helps.

Here is a link that might be useful: The Stone Works

We have a 6'8" granite counter 1" thick the last 3'8" of which is a breakfast bar with a 12" overhang on 2 sides (back & end). It is supported by nothing more than the base cabinets it's mounted on. 5 years of daily use by teens & 250 lb DH and no problems. No one has ever sat or stood on it. But that being said, I'm a safety first person and now a bit concerned after reading this thread!

Hi,

I had this same dilemma when I installed my breakfast bar with a granite countertop. I didn't want to use corbels or other supports because I didn't want folks banging their knees and I don't like the look. I like that "free float" look also. So, I actually purchase a custom cut metal plate, screwed it to top of the breakfast bar supporting wall, and then just layed the granite right on top. Make sure that your wall I had to go to a specialty machinist shop to get the metal plate (roughly 10 gauge), and they laser drilled holes and countersunk the holes so that I could screw flush into the metal. This is not sheet metal. It's a very thick, very heavy metal plate. I had screw holes countersunk and offset every 8 inches along the sheet metal. Also make sure that your top 2x4 is securely mounted. If you can add a 2x4 between each stud (directly under the top board, side nailed into the studs). Then, you can screw through the metal sheet securely onto not just the top 2x4, but also the 2x4 directly underneath it, giving you a very sturdy base to lay the granite on. You don't want the weight of the granite to rip the top 2x4 off.

You can see the whole project at http://www.thegoodrumfamily.com/ayrlee.kitchen if you look at the pictures under the Saturday section and you can see the metal sheet, and see a small section how the top 2x4 is reenforced with another 2x4 underneath.

Here is a link that might be useful: Ayrlee Kitchen Project

Hi,

I have a kitchen island 7feet and 2 inches long and 2 feet three inches wide. It has one column of drawers on either side of the island but the middle is free floating with no support..just three drawers along the top bridging the middle. This design should have never come to fruition as I'm told you can't have that much granite without support but I did not know that when I bought and within 1 year I noticed the middle of the island was warping and bowing downwards. The builder has come in to support with 3/4 plywood and new granite but the plywood support even though it has edging is noticable and doesn't work aesthetically. Is there something I can do with metal supports instead of this plywood? It would be almost 5 ft of 3/4 inch granite that needs supporting.

I would rather not have to replace the island counter for the bull nose edge (to cover the plywood) as my sink side counter is not bull nosed and that would require 2 new pieces of granite.

Any help would be greatly appreciated!!

I found bikerdave's post really helpful, Thanks! Here's my dilemma, in case anyone has any suggestions: I have a granite countertop/bar already installed in my kitchen. It's about 6' x 18" with a 12" overhang going along the entire 6'. Right now I only have 2 large support brackets holding it along the wall (it is sitting on top of a 6' long wall reinforced with 2x4. I will be tiling under the bar (where your legs would go if you were sitting at the bar) and trying to decide what to do with the supports. Since my granite is already cut, I think the steel bars idea is not good for me (the spaces can't be drilled out of the underside of the granite now). So after reading this forum I can see two possibilities. Either install new corbels or the use large steel plate idea from bikerdave. The corbels will be an eye sore and will look weird in conjunction with the surrounding tile. Plus I'm not sure if the tile should go under the corbels or around them. So I think I will take the granite off and install an entire sheet of 10 gauge steel. Any thoughts or ideas about going forward with this?

You can still do the steel L-brackets without the cutout for them on the granite--as thin as they are, they would be far less noticeable than corbels, and you could tile over the L-brackets on the wall to hide half of them at least.

bikerdave's plate would require the granite counter to be removed, the plate installed, and then the granted re-installed on top of the plate...

I would agree that the "L" brackets would be your best bet, probably economically as well as aesthetically. I believe they're mounted to the 2x4 studs within the wall. If you have drywall covering the knee wall now, they would just cut slots out to set the bars into it. Ideally, they would be flush with the drywall, so that one could lay the tile right over the installation.

During our conversations with our granite providers, they mentioned that they began supporting stone overhangs with the steel "sheets" mentioned previously but had an experience with one warping over time. At that point, they began using the flat steel bars.

Has anyone heard of milling an 1/8 slot on the granite x 1/2 deep and adding a steel brace inserted in with epoxy. The steel 1/2 inch would have to buckle to bend and being in granite that is a strong composite.

I see this done very offend by granite fabricators but have not seen this idea shown on this thread.

Answer to Patrick JordanÂs question. The process of adding steel strips to in the fashion you described is called 'rodding'. This process is to add strength to the stone slab... not practically for the strength of overhang... that's another matter. The fact is that porousness and veining has a lot to do with strength and Roding helps to shore up these types of situations.

Here is a link that might be useful: The Amastin Company

I'm about to have a soapstone (1.25" thick) counter intalled with a 15" overhang , 6" long. My fabricator is planning to embed 5 steel rods , each long enough to span most of the cabinets in the countertop before extending into the overhang. Stacy, others...are you suggesting that this rodding, isn't sufficient?

You might want to check out granite countertop brackets from the Original Granite Bracket Company

Its a SIX year old post.............

It is now 6.5 years and I read it! I am about to install a Centerline (not OGBC but similar) steel bracket on my 15.5" overhang so it is good to read these kinds of threads. Thanks Kevin.

Need advice please. have island 10ft long island x 4ft 2" (50inches)wide. overhang will be 12 inches down the entire 10ft length. have 24"d base cabinets plus another 12"d set of base cabinets back to back. (36 inches of base cabinets that granite will sit on). question is how many support posts will be needed down the 10ft length of overhang ?(14inch overhang) Will one support post on each end be sufficient or do I need 3? can't add metal supports into top of cabinets, not enough space between the cabinet doors and top of cabinets. no room for corbels. support posts are the only option. would like one on each end vs adding one in middle. help!

See Centerline brackets for info on their applicable products. We used these two years ago in our new kitchen. We have a 10' long "bar top" with a 12" overhang. You could dance on it and not worry about it falling. I put the brackets about 18" apart. Suggest you show your plans to Centerline and have them decide best approach.