"It is between the builder and the stone supplier." With the exceptions of preschoolers, I can't think of many people more unqualified to design supports for stone. A stone supplier knows all about importing, transportation, and sales but is unlikely to have much framing experience. A builder has a huge conflict of interest which is getting things finished as quickly and cheaply as possible. A perfect example of builder conflict of interest is their lack of installing an uncoupling membrane between the concrete slabs and the tile on houses built here in Florida. I get calls monthly on "tented" tiles, those which have lost the fight with the concrete and have been shoved into a pyramid. Why didn't the builders install the uncoupling membrane? Because it can't be seen, they can't charge for it, and because by the time the tiles tent, their checks will have cashed. They even do the cost/benefit analysis on these types of items. Often it's less expensive to just repair the damage than to do it right the first time. Might my recommendations be a little overkill? Perhaps. But I'll gauran-dang-tee it will never fail. They're your kids; make your call. This post was edited by Trebruchet on Fri, May 23, 14 at 9:52

============================================= Get a steel fabricator involved and you can have any type of overhang that you can envision. It won't be cheap, but it WILL be sturdy. Bear in mind that the cabinets that the steel is attached to need to also be designed for actual support, as in no 3/8" backs trying to hold corbels, etc. And those cabinets should be fully anchored to the floor, possibly with connections to the joists depending on the size of the cabinet/pedestal. When you have a large overhang and small central type support, the power of leverage comes into play and magnifies any potential force that gets applied to the top, and if the whole isn't engineered as a system, having someone lean against it could possibly crash the whole thing to the floor with the resultant casualties to property and even possibly life. =========================================== This is what we have. Our bar sits on three steel corbels that were custom made by a friend of our granite fabricator. They are attached to a specially built wall that backs the cabinets in that section. The wall was originally the height of the bar but when they installed it, it really cut the view between the kitchen and great room and so there was much discussion (and delay) while a solution was found ie the corbels. The wall is anchored both to the floor and to the back of the cabinets. The counter is about 26" deep with overhangs from 20-24". It is shaped sort of like a Nike check. I drew it free form on the back of a credit card receipt and Kinko's enlarged it to just over 8 feet long. Let's say the drawing was pretty small and it took a bit of persuading at Kinko's and I had to sign a waiver and pay up front LOL but they did it. Here's the wall before we cut it down: After it was cut, and you can see where the original steel plates were to be set in the wall to support the overhang as other posters have shown. and the finished kitchen. The bar is rock solid. You could sit on it and it's not going anywhere (however don't let me catch you doing that - we are not taking any chances)

My island ended up being 118" long, so almost 10 feet. When I found my slabs, it was approx 120" long at one end and slightly less at the other end (it wasn't a perfect rectangle). The way my island is configured, one end is comprised of base cabinets while the other end has legs and space for seating. My fabricator's plan was to keep the island as long as possible during cutting... though we were both aware that depending on inherent stone qualities, the final piece may range anywhere from 117"-119" long. My contractor did not permanently install the legs of the island until day of counter installation. We got lucky and the island ended up being closer to 119" than 117"... I wanted it as long as possible. As others have mentioned, the length of your island will depend on your stone slabs. I have seen a few that were longer than mine at the yard, as well as many that were smaller. Planning ahead with your fabricator helps too. I visited twice, when they were templating and during cutting. Here's a photo of my super white quartzite:

I was told by my granite fabricators that any overhang over 10" requires supports. Mine are spaced just under 3 feet apart. I have a quarter oval with an 11"-15" overhang depending upon the curve. Although my supports leave about 6" of overhang, the farthest point of the curve in the middle is more like 9". I am pretty sure based on that, that your 30" long supports just 2 feet apart should be plenty sufficient. Best wishes.