We are doing kitchen upgrade- keeping our cabinets but replacing laminate countertops with granite. Our island is a bit unusual- two 18 " cabinets with a 30" opening between them, so my husband who uses a wheelchair can wheel underneath. We'd like to add 10" to either end of the island, making it a total of 86" long. The width is 36", with the cabinets being 26" and a 10" overhang. We know we need to add extra support for the granite. We are thinking of using two corbels on each end to cover the 10" overhang. Then using the counterbalance brackets I've read about on this forum for the 10" overhang on the long side. My questions are: are 2 of the brackets enough support, or would I need 4 brackets to support the 86" length? And do I need any extra support for the 30" opening between the cabinets? We'd like to get this worked out before the granite guys come to measure and template. Thanks for any suggestions.

We have a 60" long x 18" wide overhang with our island. Our granite guy said we didn't need to support it, but I beg to differ and supported it just in case. We drilled a 3/4" plywood sheet (just smaller than the entire island)into the top of the cabinets and then routed in 1/2" steel bars (these were also just smaller than the island) and drilled these into the plywood. The granite was laid on top (and glued/epoxied). Although you can't see the plywood unlesss you bend over or are sitting under the overhang, we chose to cover the edges of the plywood with thin strips of wood that matches our cabinets, so it looks like the support extends as part of the cabinets. We did all this because we wanted a clean look with no corbels, etc. It is great (I had to stand on the island to change a light bulb) and I am very happy that I chose to support it...now I don't have to worry!

Folks- Let me just point out that the stone (3CM most likely in this application) will need to be adhered to the pony wall and the cabinet assembly with an adhesive of some sort - latex caulk, silicone, polyester or epoxy (I use latex caulk and sometimes silicone) to "freeze" the stone assembly to the substrate. The stone (IMHO) should never be just "set dry" on any substrate. The overhang intel from MIA is indeed designed to deal with the fulcrum effect that a piece of stone will develope - when more of it's mass is not supported by a substructure - ie: pony wall or cabinet assembly.... I am NOT an Engineer.. (I should have been cuz I love the structural stuf and all) but alas - I am just a Fab-Ri-Mi-Cator that's been doing this Natural Stone gig for 24 1/2 years now. and I have seen, done & learned a lot over the years. We are ALL in the learning curve at all times - it is just that some of us have been in the curve longer than others..... Thanks for all of your kind words - I hope that you'll benefit from my ramblings. You can also check out my consumer education website at natural stone 101.com. I will be posting pod-casts on various topics on Natural Stone that are brought up by consumers. kevin

cawfee, I've seen large tables made of 2cm granite, without any plywood. (!) They've never cracked. I've seen many renovators who overkill things, just to be sure. Most do. In fact, they all do. Otherwise things would crack or move later. How many simultaneous dancing 200-pounders do you want to support on your countertop, this is the question. I've seen kitchens that were more solid than the walls and the house. How many future earthquakes and foundation cracks will your house live through before your countertop also cracks, this is the question. At some point you have to let go of the wish to overkill, and call it good enough. This is up to you. Sooner is usually the best time. Otherwise you go crazy trying to do ever better. So, "... Obviously, this needs supports ..." is true, to an extent, but what to do next is up to you , and up to your sense of overkill -- Part 2. "... seen mention of 2x1 rectangular steel pipe as supports (12-16 inches apart)..." Search on the term box girder to reassure yourself about "... rectangular steel pipe..." It's the strongest. For its size. But, this following statement isn't knowledge: "... I know I need to support at least 12 inches of the overhang (13-14 to be safe)..." It's a judgement call or a hunch, like most other rules of thumb. You choose "... plywood sit on top of these metal pipes or are the pipes routed into the plywood..." You choose because it doesn't matter. "... screwed down to the cabinets or is the weight of the slab sufficient to hold them in place..." golly, is the weight of the slab a lot of weight? do you want to drill a hole and screw it down just for greater overkill? -- Here it appears you want to save 0.75": " ... lower profile of the 2x1 over the 1 3/4 ..." I'm not sure what you are referring to. I read a lot. I remember a lot. If I don't know what you are referring to, I'll bet that the other readers also don't. I'll bet that most pro installers don't. I think you need to be more diligent about your descriptions. For your slab, nobody knows " ... how much deflection can granite handle ..." Therefore, nobody knows "... What wall thickness ..." But, in my estimation, there is nothing wrong with getting heavyweight wall thickness tube ("square pipe") since overkill is the objective. But, not much is lost if you get lightweight wall thickness tube. All you lose is a bit of the excess overkill. In Engineering, it's called a margin of safety. But it's the same thing. If you are willing to crack a few slabs under very tightly controlled conditions you will know factually how much weight cracks them (and how much microdeflection they will take). It's just a stone from a quarry. It's not a processed material from a factory made and "scientifically studied" material with "known" properties. Don't ask for answers that won't be good numbers. Anyone can invent a numerical answer for you if keep insisting on having numerical answers. How much overkill is enough? Hard to tell, not seeing anything from my keyboard here. Do you know anything about the flex in your floor? This is a big thing. This is the one thing that I recommend you to go look into before proceeding.