A lot depends on the material used for the countertop, if it's tile or granite then you can't have any flex.

For a 15 inch overhang I'd want to see brackets that extend out 11 or 12 inches under that 15 inch overhand, and a 3:2 proportion, or higher for the vertical leg, which would be a 16 to 18 inch vertical leg, or greater.

These need to be spaced according to the materials and dimensions at hand; two brackets might do for a 36 to 48 inch surface, I'd add one bracket for every 16-24 inch increment beyond 48 inches.

Hope this helps.

but if they're wood instead of plastic, they'll add considerable stability. You won't have to freak out when people are resting their heads in their hands with their elbows on it.

I had one in my trailer that was held up with wooden angle braces, about 42 inches long and only three braces, topped with Formica, and that thing felt rickety although it wasn't. I didn't ask it to do much, though.

You could do a cantilevered countertop with no supports if you have a beefy enough frame and enough of that frame not hanging free.

e.g. If the frame is 2x4's on edge, half-lapped with the uprights or sandwiched between multiple uprights with lag bolts, then you could sit on the edge of the frame without flexing, especially if you have 3/4" plywood on top, locking it together.

The problem then becomes with how to hide all that structure. If you're doing something like tile, it's easy. Granite? Not as easy.


For example, this would be a knee wall behind the island so that you could pull up bar stools.



Now if the island is just a single cabinet, or two cabinets back to back, you can't get away with as much overhang without some more work.

He has a 2x4 structure that is bolted into the cement floor. This structure surrounds three cabinets from three sides. The backside will have the overhang.

The frame, from the top view is about 93x30. Add 12-15 inches for the overhang.

We want that overhang secure because kids tend to hang from it.

If the frame is a single knee wall around the cabinets, you might want to add a knee wall behind the cabinets, which will take away from the backside, but will give some support to the overhang, and create a cantilever.

e.g.





Now, depending on what material you're using for the countertop, you could notch the top plates and use a half-lap with lag screws to build a supporting frame, and support 15" easily.

I will show it to him. Thanks!

What surprises me when I watch shows like Property Brothers and Love it or List it is that you rarely see any support at all.

Good luck with your project.

That required the corners to be rounded so the radius never exceeded 12 inches.

The client didn't want rounded corners OR corbels/supports so we opted for steel re-enforcement bolted to the cabinets..

We had a piece of 1/4 inch steel fabricated to cover the whole island piece including the over hangs - but held back 4 inches at the overhangs so you can't see the steel edges. We had the installer epoxy the granite to the steel.

I had another granite installer not flinch at a 12 inch over hang - which means the corners were like 15 plus inches (this was a peninsula with over hangs on only two sides). This a was a less vein-y type of granite.

It also depends a lot on the type of granite.

The more veins in the granite the weaker it is. In the first case I mentioned, the granite was very vein-y. Even with all their care, they still broke the sink-run piece when installing it. The piece bent like a piece of wet toast. The client happened to witness it and that's one of the reasons he demanded extra support for the island.

Granite will flex a lot - until it doesn't - and then it breaks.

Granite installers will sometimes epoxy in steel rods in weak spots (around cutouts) so the piece will not break during transport/installation. The rods have been known to cause problems later if they get wet and rust. Rusted metal swells - this can crack the granite. It's best to use stainless steel rods.

A lot of installers now save time/labor re-enforcing the slabs by transporting them in clamping racks made for this purpose.

My hubby settled on four thick corbels, and drilled them into a backboard that isn't going any where. Our main concern is a friend we have who is a big guy. If he pushes up on the table, we just don't know what the granite will do. But we have asked enough questions to feel comfortable that we're just being over-precautious. The island is built like a tank. It isn't going to budge.

Granite is good quality. We should be fine. I trust the company.

My older brother says I worry too much. That's why I have the gray hair and he doesn't.

I wonder if a dab of epoxy or liquid nails on the corbels might make sense. The installers will use silicone but that is more for side-to-side movement. Epoxy will make the granite one with the corbel. Ask the installer and maybe have a tube ready.

Thank you.