Granite counter top overhang

Sumar · 05-11-2010, 11:46 AM

I am building a granite counter top bar 6'x26" for my back yard. Never done this before. The rectangular piece of straight-edge 3/4" granite is going to sit on 3/4" plywood and the granite/plywood edge on all four sides is going to be finished with wood moulding to match my bbq moulding. This countertop is going to be freestanding, forming one arm of an 'L' shaped outdoor kitchen. On one long side and short side the granite/plywood worktop will have a 1' overhang The only support for the 6'x26" granite/plywood top is going to be a 5' long x 1' thick x 34" high concrete block wall (I am using standard retaining wall blocks 12"L x 8"W x 6"H, that I have left over from another project).
1.Is the overhang likely to put so much stresses on the granite slab when people lean on the overhang that the granite slab cracks? Do I need to support the plywood/granite overhang with angle brackets.
2. To prevent tipping I was considering attaching the plywood to the stone with inset screws to embedded plugs in stone and perhaps metal brackets at the other end. What do you guys think?

RoyalAcresRod · 05-12-2010, 06:14 PM

Maybe it's just me looking at the drawing wrong....but I'd be concerned with the retaining wall base...it's looks like it might fall over. Usually those blocks are supported by earth or gravel. What's going to hold the structure up?

rod

Sumar · 05-13-2010, 06:15 PM

Rod
You're. Correct. There is a chance of the wall topplin over. So I intend to support it with some frame under the top course.

RoyalAcresRod · 05-13-2010, 06:42 PM

I'm sure you're wanting to make good use out of the retaining wall material you've left from another project....but I urge you to rethink your plans. I believe your best interest would be served by constructing the unit from more conventional building materials such as CMUs (concrete masonry units), that you can face with stone of your choice.

I'm just real worried this structure will be dangerous.

r

Scuba_Dave · 05-13-2010, 06:46 PM

People lean against that I'd bet its going to topple over
You would need something to support the wall
Supporting just the top blocks with a frame won't do it IMO

Bud Cline · 05-14-2010, 05:32 PM

Sumar,

I too think you are kidding yourself with this plan.

You can buy CMU's with a chiseled face that look the same. If you use them the wall can be built and reinforced with re-bar inside the cells and filled with mortar. A cement base/footing should be poured first with "L" re-bar rising from the footing so as to fit inside the cells and be wire-tied to the additional re-bar that will be placed inside the cells ahead of filling them solidly with mortar.

What you are proposing can topple and seriously injure someone. Do you have kids?

Sumar · 05-17-2010, 12:21 PM

OK guys; I won't use the retaining wall blocks. Will use CMUs. But I still have the issue of 12" overhang to create the bar. Would 1/2" plywood with brackets underneath be sufficient support for 1/2" granite tiles? Also I have to cover up the edge with some kind of moulding suitable for outdoor use. If I can paint the moulding I can match my bbq's moulding. Thanks,

Bud Cline · 05-17-2010, 01:12 PM

When using CMU's things change for the better. You can get to the top course then turn two or more CMU's perpendicular to the course to create a support 16" wide for the granite. If a full 8" CMU is too much bulk a cap (3X8X16) could replace a perpendicular CMU at the top of the top course and it would turn to be perpendicular to the course with fillers below it to take up the 5" remaining that would need fill below it.

This is no place for plywood and that thought should be canned.

Let's try this and see if it works for me! Here's a rough sketch.

drtbk4ever · 05-17-2010, 01:46 PM

I'm confused now.

Are you putting 3/4 " granite on this countertop or are you putting 1/2" granite tiles on this?

Sumar · 05-17-2010, 02:52 PM

Bill - Have not decided whether to splurge on 3/4" granite sheet or to go for the cheaper 1/2" tile. Whichever I use it would be on plywood (1/2" or 3/4").
Bud thanks for the drawings - very clear. I assume the three blocks in the top course turned perpendicular do not need any securing.

Bud Cline · 05-17-2010, 05:36 PM

Quote:

Bud thanks for the drawings - very clear. I assume the three blocks in the top course turned perpendicular do not need any securing.

Depends! I wouldn't think so but iffin' it were me since I would be filling the empty cells with rebar and mortar I would probably go as far as to extend rebar into the cells of the support blocks and continue filling those cells also.