Need Granite Top Advice

[Jay Hart]

I occasionally volunteer to build a project for a local brain injury group. Currently I am designing a “coffee bar” for their main meeting room. So far, so good but this time they found a counter top company that offered to donate a granite top for the bar. I am not a professional and have never dealt with granite before. I guess the one thing I know is that it is heavy.

I would appreciate it if some of you knowledgeable gentlemen would take a look at the attached drawing and offer an opinion as to whether the structure is adequate to support the weight. The materials being used are ¾” poplar for the stiles, rails and nailers and ¾” ply for the panels.

[Lee Schierer]

Your design looks good. Your top if it is 1" thick is going to weigh about 200-250 pounds (Granite weighs 150-170 pounds per cubic foot). All the weight will be compressing the vertical pieces and most of them are put together to make corners. As long as the construction is well made, the wood should hold the weight no problem. The stone will want to be very flat so insure that when your cabinets are mounted that the top surface where the ganite will be is perfectly level.

[Jim Becker]

I think you are fine...the weight is spread out quite a bit.

[Jay Hart]

Jim, Lee,
Appreciate your confirmation. You can bet that it won't be me hauling in that top

[Joe Chritz]

Remember the weight is distributed among all the stiles so the actual weight on any particular part is actually not that much.

The design looks fine.

Good for you for doing the project. I recently had an acquaintance go through a lot of therapy after a vehicle accident and the work they do is truly amazing. Hats off to you.

Joe

[Jamie Buxton]

Jay --
In your drawing, are the two hovering rectangles intended to be the granite? If so, you might want to talk to your granite supplier. When I've built kitchen cabinets for granite tops, it worked the following way...

The basic granite material is 3/4" thick or so. The fabricator doubles it over at the edge to make it look 1 1/2" thick. He expects that there will be a sheet of 5/8" ply covering the top of all the base cabinets. The edged granite rests on the ply, and the doubled-over edge conceals the edge of the ply. The granite gets installed on blobs of polyester or epoxy resin. The installer levels the slabs by tappinging down on the slab, flattening the blobs as necessary. If he needs to lift up a slab, he runs a wood screw up through the 5/8 ply to jack up the slab.

If your fabricator works the same as mine, you just need to add the ply on the cabinet tops, and maybe adjust the height of your cabinets if you're particular about the height of the completed furniture.

[terry hansen]

Having just redone my kitchen with granite tops - research showed me granite in the south is typically sold as 3cm and not often built up with an additional edge unless you specify additional thickness. Granite on the other coast is often sold as 2 cm and then has a built up edge. My granite installer placed the granite on top of the cabinets I built of 3/4 birch ply and preferred to not have a solid top of ply to install to. The reason being the granite is not smoothed on the underside and the minor variations seat better by shimming on supports if needed. woodweb.com is a good resource for additional information. cabinets need to be level and plumb so granite doesn't crack.

[Jim Becker]

Jamie, my granite fabricator supplied full inch and a quarter thickness for all four tops for our addition. The only 3/4" material was for back splashes. They were just fine with my cabinet design which was pretty much similar to the OP's picture above...still used the blobs of adhesive on the 2-3" wide components installed for the purpose.

[Jason Roehl]

The only thing I see that I would think might be a problem is the long section inside--where you only have 3/4"x3" material laid flat. I would think that you would want some sort of rail on edge under that so that you don't have a ~3' section virtually unsupported on one side. It may also be that the angle of the drawing obscures a rail you already have designed in there...

[Johnny Fischer]

Jay,
First of all, my hat is off to you for the kindness of charitable work for those in need.
One good deed deserves another.
I use to be a professional granite fabricator, install, etc.
Granite comes in increments of 2cm and 3cm thicknesses.
2cm being 3/4" thick and 3cm being 1 1/4" thick.
If all you base cabinets are properly secured together then you wont have a structural support problem.
Remember something. Factory built cabinets (usually) are built from 1/2" plywood, so 3/4" ply will defineately support your project.
With that said, back to the granite.
In regards to 2cm granite a customer sometimes request the look of the thicker 3cm granite as a finished product. The fabricator will use 2cm (3/4"), cut 1 1/4" to 2" wide strips of the same material and laminate (glue w/ (Kemmi) stone epoxy) the two peices together. At this point they profile the edges to give it the look of the 3cm stone.
In reality, its a waste of time as by the time the fabricator is finished w/ this procedure the customer could have got the thicker 3cm for the same price.
Install the (2) seperate pieces together. Level out your larger piece w/ shims. Slide your other smaller piece up to it and level it off that piece.
Once your happy w/ that, ever so slightly slide the small piece back just far enough so you can pump the joint full of super glue gel.
Slide back to gether and use a flat edged razor to remove the excess gel before it dries.
Walk away from it at this point.
After the glue has dried use another flat razor blade to remove any additional glue on top. There are companies that sell tintable stone epoxy kits to fill the joints but I dont think you need to go to that extent.
On the inside of the cabinet apply a bead of clear silicone touching the stone and your cabinets. This along w/ the weight of your top will keep it from going anywhere.
Good luck and God speed.
Hope this helps

[Johnny Fischer]

Forgot to mention this one.
On an average, 2cm weighs approx. 22# per sq. ft.
3cm weighs approx. 30# per sq ft.
Depending upon the type and density of the stone.
Darker colors tend to be alittle heavier.