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.

I really appreciate your help Annkh, Hollysprings, and Trebuchet :) So, the thread I linked to below clarified a lot for me! The dishwasher isn't installed yet and I wasn't 100% clear on the installation requirements. I learned a few things: a. the dishwasher opening needs to be exactly 23-5/8" wide in order to prevent noise issues b. the dishwasher needs to be installed with no gap between its top and the countertop What that means is - 1. I cannot use the 20x20 L brackets mounted on the back wall because they would cause an unacceptable 1/2" gap on top of the dishwasher (noise issues) 2. I probably should not use cleats on the sides, because that would create gaps beside the dishwasher sides, which could lead to noise issues. That leaves an additional panel on the left hand side (bracketed to the wall/floor) as the only solution that will create an acceptable dishwasher install *and* countertop support. Now I have to evaluate how to deal with the resulting asymmetry (more panel on the left hand side of the dishwasher) and figure out if I still have enough hinge clearance on the left hand side of the fridge. Trebuchet - thank you for the instructions on how to attach a cleat to 5/8" particleboard - that is very useful info that I will use elsewhere in the kitchen install :) Annkh - I have room at the back, not the sides. Hollysprings - bingo with your comment on how gaps will affect dishwasher install. Here is a link that might be useful: Help with noisy Miele Diamond?

The Marble Institute of America recommends that 3cm granite needs additional support over 10" cantilever overhang and that 2cm granite over 6" cantilever overhang. However, the fabricator is warrantor of your counter and it is widely practiced and accepted that 3cm of 12" overhang is acceptable without additional support. Here is a link that might be useful: The Amastin Company- Concealed Overhang Support

Update: After the advice on this thread, We went with the single tier. The island back was built out a little more to give us more room behind the sink. Everything turned out great. The Granite is Lennon which has whites, browns, greys, and some copper/bronze. Also, there have been a few posts lately about granite costs/overages and trying to reduce budget by going with limited slabs. If you want a nice uniform look, I would suggest picking out multiple slabs so you can get a nice match/book match. See below how my granite vendor accomplished this. Other experts on here can go into other details. I love the way everything turned out. Can't notice the seam in the middle of our island unless you broke out a magnifying glass. There is a seam right in the middle but you cant see it.