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Old 04-09-2019, 08:28 AM   #1
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Adding support to concrete wall for granite top


I am looking at building a pavilion with concrete walls columns (see attached pic). What I want to do is extend the short walls on each side of the pavilion to be about 8 ft long, and then add granite for counter/bar top. My issue is that the concrete is apx 5ft tall, so I can't add the granite to top of the wall. What I was thinking of doing is bumping put the concrete blocks about 40" up the wall, so the granite can be place on there (vs making the entire wall double thickness). Curious about the support though. Can the concrete block bump out like 8-12" and still support granite top? Looking for some suggestions/advice.

Thanks,
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Old 04-09-2019, 08:44 AM   #2
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Re: Adding support to concrete wall for granite top


Build a cantilever in the concrete wall.
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Old 04-09-2019, 09:05 AM   #3
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Re: Adding support to concrete wall for granite top


Thanks. So the cantilever is built into the wall so the only thing you see sticking out is the shelf that the granite would sit on?
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Old 04-09-2019, 09:15 AM   #4
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Re: Adding support to concrete wall for granite top


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Originally Posted by rambo1224 View Post
Thanks. So the cantilever is built into the wall so the only thing you see sticking out is the shelf that the granite would sit on?
You might get to the same place with just a steal shelf bolted to the concrete. Some of it would be seen from a distance or if you are short.
https://www.countertopbracket.com/Co...teel-p/fmp.htm
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Last edited by Nealtw; 04-09-2019 at 09:20 AM.
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Old 04-09-2019, 09:29 AM   #5
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Re: Adding support to concrete wall for granite top


If you're gonna use brackets like Neal linked, you should embed your fasteners (probably some kind of threaded insert?) in the concrete when you pour your columns.
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Old 04-09-2019, 09:30 AM   #6
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Re: Adding support to concrete wall for granite top


Thanks. Besides steel or cantilever, could I offset a row of the concrete block (40" up the wall), so there is enough overhang for the granite to lay on? Wasn't sure how much I could offset it by for it to have enough strength to support the granite
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Old 04-09-2019, 09:40 AM   #7
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Re: Adding support to concrete wall for granite top


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Originally Posted by rambo1224 View Post
Thanks. Besides steel or cantilever, could I offset a row of the concrete block (40" up the wall), so there is enough overhang for the granite to lay on? Wasn't sure how much I could offset it by for it to have enough strength to support the granite
I don't have enough experience to comment on block, usually they put plywood under the granite and that would be bolted down.

But you need a block guy for better info.
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Old 04-09-2019, 10:56 AM   #8
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Re: Adding support to concrete wall for granite top


you could but it'll eventually fall off/down UNLESS its attached to steel reinforced full-height invisible columns ino,,, hate paying for the same ground 2x
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Old 04-09-2019, 02:58 PM   #9
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Re: Adding support to concrete wall for granite top


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Originally Posted by rambo1224 View Post
Curious about the support though. Can the concrete block bump out like 8-12" and still support granite top? Looking for some suggestions/advice.
Maybe give a little more info, like a sketch. You're building poured concrete, or all CMU? How wide is the counter? 24" open below with no supports desired, or 18" wide bar height? With the granite, since its not mechanically fastened, the amount of unsupported overhang will be determined by the width of the support.
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Old 04-10-2019, 10:48 AM   #10
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Re: Adding support to concrete wall for granite top


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I don't have enough experience to comment on block, usually they put plywood under the granite and that would be bolted down.
I believe that plywood-under-granite is an east coast vs. west coast thing. On the west coast they use a plywood support. Here on the east coast they use a thicker slab and no plywood underneath.
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Old 04-10-2019, 10:57 AM   #11
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Re: Adding support to concrete wall for granite top


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I believe that plywood-under-granite is an east coast vs. west coast thing. On the west coast they use a plywood support. Here on the east coast they use a thicker slab and no plywood underneath.
I guess you work with whats available.
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Old 04-10-2019, 01:17 PM   #12
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Re: Adding support to concrete wall for granite top


Here in middle America we too use plywood backer when inside, but outside may not be the best idea.
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Old 04-10-2019, 01:19 PM   #13
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Re: Adding support to concrete wall for granite top


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Here in middle America we too use plywood backer when inside, but outside may not be the best idea.

Does your granite leak?
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Old 04-11-2019, 08:32 AM   #14
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Re: Adding support to concrete wall for granite top


Out of curiosity, how do the "plywood backing" folks mount undermount sinks? Over here they make cuts in the bottom of the slab and screw the clips into the cuts, with the clip right on the flange. Do y'all screw to the slab, or to the ply, using a spacer (or maybe a clip with a vertical extension) against the flange?
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