On Mar 23, 10:50 am, "RicodJour" wrote:
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.

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.


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.

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 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 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 **** 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.

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.

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

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.


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