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profenx 11-27-2009 07:48 PM

Island Overhang
Hey ppl,

I would like some advice with my kitchen island. It's ~72" x 42" granite countertop (i believe 2cm)

My contractor says that it'll be fine to have an 18" overhang but what i'm reading from various sites is 10"-12" overhang max. So now i'm worried.

I have a drawer, sink, and dishwasher cabinet on this island. That leaves 18 inches overhang. I was worried about it so I purchased 3 corbels ~ 4.5" d x 9" height x 5.5" wide. This will still give me ~13" unsupported overhang. I dont want to worry about it falling over or cracking if someone by chance jumps on it to sit or something.

Cabinets is made of maple and the rest is made of plywood.
plywood (as an underlayment?) will be placed under the granite that will span the majority of it. I'm not sure if the 42" includes the 2" overhang on the cabinet side or not. It's a pre-fab 42"

Is their enough support for my overhang?

On an off note, how do I install an undermount sink if there is plywood under the granite?



Just Bill 11-28-2009 05:57 AM

There are a lot of factors involved, but for 3/4" thick material, I doubt that 18" is safe.

Kyle Keever 11-28-2009 09:15 AM

There are several ways to support the overhang. You can use corbels like you are considering and with 3/4" ply a 13" overhang should be fine. If you don't want corbels you can dato steel brackets into the plywood sub top that cantilever off the cabinet tops to increase the rigidity of the plywood sub top. Make sure you have a hole in the sub top that is larger than the sink you want to undermount in the granite. It will be hard to remove the plywood after the granite is in. Make sure you plan for your valves as well by leaving a hole in the plywood sub top in those locations. Same goes for insta hot, soap dispenser etc.

profenx 11-28-2009 04:02 PM

Thanks for the replies.

If i place brackets on the plywood underlay, would these be outside the cabinets like the corbels or can they be inside?

Maybe i can do both the corbels and the steel brackets to be safe.

will 3 corbels be enough for the 72 inches? I didn't want to use corbels at first cuz in most pictures i've seen, the corbels run all the way to the edge while mine don't.

Thanks again,


Kyle Keever 11-28-2009 04:34 PM

1 Attachment(s)
Corbels usually do not have to go to the edge to give support. With the plywood sub top attached to the island which is attached to the floor the plywood itself will resist sagging because it is in a cantilever condition. If you add a corbel that reduces the distance of the cantilever the stiffer the plywood will be where it is unsupported. Corbels take up knee space at a bar so I try not to use them when possible. You can use flat steel for support that is hidden in the sub top. For example take 1/4" x 2" flat steel and attach it to the frame of the cabinet (one of these every 24" or so). These flat steel pieces will be slightly shorter than the plywood subtop. Dato out slots where the steel is in the bottom of the plywood sub top. Install the plywood over the cabinet and steel and then your finished top over that. Hope that makes sense. If you need more support use thicker steel, 3/8" thick possibly. You could also install a sub-sub plywood top that is within the frame of the cabinet that would allow more attachment points for the steel. Either way the only way you will be able to see the steel members is by looking up under the "bar" area. I usually paint that out.

profenx 11-28-2009 04:57 PM

I see! the diagram helps a lot. I thought we were talking about L brackets.

this makes perfect sense in strengthening the plywood and top. I'll go with the corbels and some steel reinforcements.

I also think ~1" will be for the front overhang which will reduce my seating area overhang. This will be good.


I'll just have to make sure no one sits on the counter overhang just in case.

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