Do seriously consider a countertop with rounded corners for that small a kitchen. If you're going to use the dark metal bar chairs shown in your first pic, you could probably use dark metal brackets to support a bar no longer than the one in your first pic. Pick a sturdy pair with as little knee-knocker potential as possible.

Reinforce the cabinet back internally, all the way to the floor, by adding at least a layer of 1/4" plywood internally, and blocking in the toe area under the backing. You may need additional solid wood corner bloke glued in place as well. Order matching fillers or profiled stock from your cabinet company. Cut them to the size that you need for your design.

Mark the position for your posts, and Hilti drill the floor for threaded rod if concrete. Epoxy into place inside the sleeve, and drill the posts using a drill press to keep hole absolutely vertical and centered. Semi the same procedure on crawl space, but a bit harder with the positioning. You will need pilot holes through the subfloor to be sure that it doesn't interfere with any wiring or joist etc. Then washers an lock nuts.

Use pocket hole jig to drill reinforced island back and posts to accept the screw creating the box frame for support. Make sure it is all level and plumb, which is MUCH harder than you think it is. Create cross bracing at the mid point as well using the pocket screws. It all has to be perfectly level in order to support the stone flat up against it.

Stone fabricators shouldn't touch cabinets. Your cabinet installer does the alterations. There isn't a material around from laminate to butcher block that I would allow to span that distance without intermediary support.

We did something similar.

I am not sure why the cabinets look two-tone!

The cabinets were moved into a new configuration. I actually copied the idea from a magazine picture. A carpenter custom made the " leg". The curved area allows for 4 people to sit there.

Do you have a steel framework projecting outwards from the center post?

The 1/3 2/3 cantilever rule comes into this as well. With 25" of base cabinet, any overhang over 12" will need some type of support. Maybe invisible steel. Like Counter Balance brackets.

But when you have as much overhang as you originally planned, you definitely need a more complex support, as the center of gravity is no longer on the cabinets. The ability of quartz to resist deflection is greater than granite. But it still doesn't bend. It breaks. I've seen dented floors that thankfully were not broken feet. I like belts and suspenders. Especially where 1500lb counters are concerned.

Hi Tracylstephens! I’m in process of designing an island with 24 x 102 inch base and a 20-24 inch overhang with posts. I found a website to buy steel brackets that are strong enough to withhold the span. The site has videos and guidelines for amount of flat brackets needed for the span, length, install etc. I’m personally thinking of having a 2 x 4 framed wall built for the back of the cabinets and getting the flat support brackets long enough to span from the cabinets over the framed wall and recommended length for over hang. I plan to back the wall with plywood and a matching cabinet skin (1/4 inch) then add decorative board and batten design with two posts. Sophie Wheeler- does this sound like sufficient support (thanks for your wisdom). I’m a rookie but have been researching it. Also, I found Rubberwood posts on Wayfair that are on sale.... any thoughts on Rubberwood (super inexpensive that I would paint to match) vs alderwood? I can’t remember brace site off hand but I just googled island support. I read lots of horror stories on not supporting the overhang properly and how some countertop installers don’t care about installing it safely. Countertops are very heavy and if they aren’t supported properly someone could get hurt. My mom’s island countertop overhang wasn’t supported properly and someone was leaning on it and it fell off!!! Thank gawd it was just a heavy duty Formica!!

You need to make your own post. Probably not going to get responses to a 5 year old thread.