Kitchen Island question?? Cabinet experts please come in!!

My daughter wants me to build her a Kitchen Island that will be approx 11' by 8' ( L shaped). It will hold a stove top and will have a back splash behind it. On top of the back splash she wants to have a granite Counter top. My concern is what is going to hold up the 1 foot over hang that she wants to have. I am sure that I can make the back splash approx 6" wide but what should I use to hold up the over hang?
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if she wants it to look like it's floating with no support, I'd have brackets welded up from square steel tube and sandwich the tubes between layers of backsplash and granite top.
if she's ok with visible brackets, go ahead and buy, make or steal something that works with the rest of the design of the piece and her kitchen.
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Actually, one foot overhang is okay, no supports needed (at least that's what my granite guy told and sold me). Tom
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tom wrote:

That was my reaction at first, but thinking about it I'm getting the impression that he's talking about a short counter on the back side of the island, 18 inches wide with only 6 inches of structure underneath.
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Yes, taking a second look at the original post, I may have misunderstood the design. If so, some type of bracket...Maybe the OP could speak up again? Tom
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bdeditch wrote:

Steel should be holding up the overhang. Various stone people will tell you that the maximum overhang is anywhere from 6" to 12". It's granite, it's expensive and not a DIY repair, you might have somebody who doesn't know any better put their full body weight on it - be conservative.
Here's a reasonable workup on the matter, with one caveat. One poster mentioned cutting into the granite to install steel rod. You don't want steel rod, and it's nuts to weaken the granite to make it stronger. Further down the page is a picture of some plate steel strips let into the plywood sub-counter - a _far_ preferable installation.
http://ths.gardenweb.com/forums/load/kitchbath/msg0223352910274.html?8
R
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"bdeditch" wrote in message

In short, you need a design that incorporates support, but not knowing your design, it is almost impossible to advise you.
I would draw up a proposed plan and head to a local cabinet shop and see what they advise based on your drawing. Here's why:
IME, and simply put, you need _support_ of some type for the overhang, regardless of the material you are using for your countertop.
A 3/4" plywood substrate is quite sufficient to support a 3/4" thick granite "countertop" overhang of 12", providing the plywood substrate is sufficiently deep (front to back) to be properly "cantilevered" from the supporting base/island cabinet.
In doing a granite overhang on an island, I try to use the old "1/3 to 2/3" cantilever rule as a bare minimum, and much more if I can get away with it:
IOW, as a MINIMUM for 12" overhang, I want at least 36" of granite over +/- 36" of well fastened plywood substrate, supported by a minimum of 24" of countertop.
Your problem is that your "countertop", in this case the top of your backsplash, is only 6" deep and you're attempting to "cantilever" 12" of a roughly 18" deep slab of granite.
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Swingman wrote:

You're concept of how a cantilever works is okay if you're talking about materials with the same modulus of elasticity. Unfortunately wood and granite behave far differently. Wood and plywood can take a fair amount of flex. Granite has no such flexibility. A 3/4" plywood sub-counter is certainly "strong" but it is not stiff in the way granite is stiff, and it is brittle. In other words the plywood will simply flex and the granite will be forced to take all of the load and it will crack. It doesn't matter how far back that plywood sub- counter extends, it will not change the amount of flex as it can not change the modulus of elasticity of either material.
If you want to omit knee braces, corbels or any other type of visible support, you need a stiffer material with a higher modulus - steel. The steel should be thick enough that you can stand on the end of its full cantilevered length. In other words the steel supports should be designed to take _all_ of the load so that the granite can do what it is there for - look pretty - without being required to be structural as well.
Robatoy's suggestion of using a thicker, engineered (man-made) stone with let-in steel is certainly a good way to go, but it is also frequently a more expensive way to go as letting into the stone requires more labor and entails more risk. The thicker stone adds a lot more weight to the countertop, which may or may not be a problem structurally, and you're paying for that extra stone that you'll never see. The engineered stone also limits the choices you'll have in stone. The idea is to add strength and stiffness. Cutting into a thin slab creates stress concentration points, and let-in braces are weakening the stone in order to strengthen it - that doesn't make sense to me.
R's comment about idiots doing stupid things on stone cantilevered countertops should not be discounted. I once swung a hammer at an idjit painter's ankles that was _standing_ on the cantilever! He jumped off, and started yelling at me, and I told him that the only reason I didn't swing at his head was because I couldn't reach it.
Cantilever's are one of the few things where I tell people to purposefully over-build things, as deflection and stiffness are of paramount importance. Doubly so with a stone countertop.
R
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"RicodJour" wrote in message

... and "if" you give some folks a keyboard and a forum you end up with a pedant.
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Swingman wrote:

You're right. I was overly wordy in pointing out you were giving bad advice. My apologies.
R
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"RicodJour" wrote in message

LOL ... so "wordy", AAMOF, that you obviously fell in love with your own words and failed to comprehend that to which you were responding ... a common failing among pedants.
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Correct. Now apply that same standard to a plywood substrate. Just to clad the bottom of a slab of granite would be a waste of time. If 3/4" stone (either e-stone (quartz-based) or g-stone (genuine granite) is used, one MUST build a support which on its own will support the load. The 3/4 stones are NEVER allowed to take a structural role in a cantelevered application. 'Real' granite is full of fissures and can snap at any time... the risk of 'fissures' is virtually non existant in e-stone. A 12" overhang is safe in 1 1/4" e-stone..ASSUMING the bar top is anchored in such a way that it can't tip on a fulcrum further away than 1/3 from the load. (That is a guide-line.) If the top is 18" wide, I would spec a support at 6" and 12" along it's length no further than 24" apart. The support at the opposite edge from the load can be closer than 6" from the edge.

Any stone shop worth its salt can let in a 1/2" thick metal bracket with sufficient radii along the sides and end of the slot to minimize stress-risers. The thicker material won't require a glued-on (visible line) edge and an added edge in a flexing situation like a bar top is not a good idea. All the dicking around to properly support a 3/4" slab will evaporate the savings in materials quickly. So, even though one is not supposed to count on a structural component in a floating application, it sure is nice when the strength is there to begin with.

The increased weight is a worthwhile investment to get the strength and stiffness. Not to mention a much better look.
In granite, 3/4" is a non-starter. An invitation to disaster in a suspended bar application. As I mentioned before, the investment to properly support that brittle shit would be way more money than an upgrade to 1-1/4"
I have 21 choices in my granite palette, but 60 in Quartz. The uniformity of the patterns and non porous surface AND it's raw strength make for a far more durable surface than granite. When hit with a very hot pan, the possibilty of moisture in granite can create quite a catastrophic failure.

Doesn't to me either. The letting in of a bracket will only be doable in 1-1/4" e-stone material.

When using 3/4". make sure that clown can tapdance on the substrate before you apply that thin skin of granite. 3/4" is for low-cost vanities.
r
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Robatoy wrote:

I use assorted engineering programs for figuring deflection and such. With a 350 pound load on 3/4" plywood on a 24x24 base, the deflection is less than a 1/16th. You are conservative and I'd never dream of telling you that was a bad thing.

Right. In that link I posted some of the replies indicated it was possible to cantilever the stone by itself. That's a bad idea until you get into thick stuff, 2"+ depending on the stone, which would not be suitable for a countertop.

The 1/3 cantilever rule of thumb is fine for wood joists and such, but it's misleading as soon as you change materials or have dissimilar materials trying to act in concert. I pointed that out to someone and they got mad.

With just that one comment you've made it clear you know what you're talking about. I don't doubt that you'd do a fine job letting in for a brace/bracket. It's not _you_ I'm worried about. You and I both know that some "stone" guys would hog out a let in brace with their wet skilsaw and knock out the pieces with a hammer - no one would ever see it, right? In general, most people asking the question about how to support a stone cantilever wouldn't know what to avoid. You do.

I thought we agreed that there should be no flexing in the stone at all. ;) Out of curiosity, what's your ballpark percentage upcharge going from 3/4" with a laminated edge to 1 1/4" granite?

Okay, we did agree. Thought I was losing my mind for a second! I can't argue with you there.

You may be right, but what's your opinion on the suitability of the OP's island with respect to his floor capacity? Right - I don't know either. When I hear of an L-shaped 8' x 11' island, I think of possibly exceeding the floor's design load. Personally, I think the OP shouldn't go a step further until he determines what the floor is designed for and how this, presumably fully loaded, island will affect deflection and bounce. Your 1 1/4" engineered stone top alone would weigh almost 550 pounds and that's on only 34 SF of floor. The standard design load, live and dead loads, for a first floor is on the order of 55 PSF. 15 PSF for the structure, ~15 PSF for your countertop, leaves only 25 PSF reserve for cabinets and contents, appliances and people. That island could _easily_ exceed the allowable floor load. At the very least you'd have lots of deflection and a bouncy floor.

It sounds like you're a dedicated stone installer. I'm not. I gotta buy the stuff, and it's easier and cheaper for me to cut the plywood and add some steel bracing as required. Of course I am not locked into the plywood as any such decision must be based on the stone used.

No argument about the homogeneity and overall durability of the engineered stone, but some people _like_ the random swirls and patterns of real stone. And face it, no one's ever come to you and said, "I don't care how it looks, I just want it to last forever." The choice of stone vs. laminate or Corian is an aesthetic decision. I can't tell people what to like. I can only warn them of the consequences, and in that we're on the same page.
I'm kind of surprised that you only have 21 natural granites. Since China and India opened up the floodgates the choices are almost unlimited. Are the 21 granites your way of keeping your life simple and not overwhelming customers?

It flashed across my mind when the idjit painter was up there that I didn't want to hit his toes, which was my first thought. I figured he'd pull his foot away and I'd bust up the countertop, so I swung at his ankles. :)
R
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"RicodJour" wrote in message

In your rush to show us your ass, you missed the point entirely.
In the OP's case, the advice of applying a rough approximation of the cantilever principle has NOTHING to do with "dissimilar materials" and EVERYTHING to do with attempting a 12" overhang from a 6" counter top!!
Since you missed/ignored it, know that your new hero, who's ass you've been kissing publicly in this thread, clearly stated the same thing:

The concept of the wREC is not to attempt to blow us away with "wordy" (your own admission), self imagined intellect, but to provide _practical_ advice for the OP to use in solving his problem.
Try to keep that in mind ...
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Swingman wrote:

You're acting like a little kid.
Bridger gave the correct answer immediately, which was essentially this:
http://i.timeinc.net/sunset/i/home/2007/02-Feb/0207kitchens_color_e.jpg
That's not exactly it, but it does show the _only_ way the OP could support such a raised top above a backsplash, and as Bridger noted, it could be sandwiched inside to conceal it.
I went off on a tangent, agreed, but the first answer the OP got was correct. What did I need to add to that? The thread drifted - like that's never happened before.
I was responding to _your_ comments about cantilevering as they are misleading. You wrote: "A 3/4" plywood substrate is quite sufficient to support a 3/4" thick granite "countertop" overhang of 12", providing the plywood substrate is sufficiently deep (front to back) to be properly "cantilevered" from the supporting base/island cabinet."
Quite sufficient? Really? Using plywood to support stone is insufficient in any cantilever situation.
And you wrote this: "In doing a granite overhang on an island, I try to use the old "1/3 to 2/3" cantilever rule as a bare minimum, and much more if I can get away with it."
That's where the dissimilar materials come in. The plywood over the base cabinets can be infinitely stiff and the freeboard end of the plywood cantilever will still deflect more than the granite. You need to come up with a new rule of thumb - like don't use wood to support a thin stone slab cantilever.
I've read enough of your posts to know that generally you do know exactly what you are talking about. This was not one of those times. I was not trying to piss you off. If someone is in error, it _should_ be pointed out. You do it all of the time. I learn as much as I instruct on most newsgroups, and I like that part, even if sometimes the learning is at my expense.
BTW, Robatoy doesn't jump down someone's throat if they disagree with him. He treats me with respect, I treat him with respect. Unless you have something of a technical nature to add to the OP's question, instead of defending your wounded pride, is it okay if we just let this thread die? Thanks.
R
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"RicodJour" wrote in message

Like all blanket statements, both erroneous and demonstrating a basic misunderstanding of engineering and construction techniques.
You're correct on one count, however ... with that, no more needs to be said.
EOT ..
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After 20+ years of manufacturing and installing countertops in all kinds of acrobatic applications, the only failures I have encountered have been human failure. Like the kid doing his girlfriend on the bar section when mom & dad are away. 10 feet of 18" wide granite will crush just about anything on the way down from bar height. The static load isn't what concerns me most. It's that guy who tosses 3 cased of beer on the very corner of a bartop who makes me over-engineer structural integrity. That includes the people who will buy that house some day.
I strongly recommend large angular brackets at strategic intervals. They can be physically smaller when you use tubular steel. They do not have to reach all the way to the edge of the bar, the distance of setback depends on whether you plan on using 3/4" or 1-1/4" granite. Engineered stone is much more reliable in this application, btw. Along with other many good points, Swingman hit it right on the nose when he discussed cantilevering. The brackets move the tipping point (fulcrum) forward.
Countersinking 1/2" steel brackets into 1-1/4" engineered stone is by far the slickest look. E-mail me a sketch and I'll post some ideas back to you.
r www.topworks.ca
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That is not an island, its a whole continent.

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I certainly don't claim to be a cabinet maker or solid surface guru, but had some experience years ago in the metal trades. Quarter inch by 18 inch steel plate is about $150 for 8 foot lengths (google it). Have a local shop or friend weld some brackets on it to attach it to your cabinet frame to avoid tipping with the cantalever and you should be able to dance on it. Hold it an inch or so back from the underside edge of the granite and it is almost invisible. HTH
Jerry
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