rubyvine_gw

granite fabrication questions..what do you think!

rubyvine
March 21, 2010

So this marble lover is finally able to embrace the granite countertop thing. After a year of searching I came across a beautiful granite called Titanium Black. As I posted earlier (but can't find), I am wondering if anyone has info about and/or experience with this stone?

My layout includes an island that is 117in x 37.5in. There will be a 13.5in overhang along the back for stools and an 8in overhang on the two sides. My fabricator, who is very reputable, says I do not need any supports for the larger overhang. I have questioned them on two occasions and they keep telling me it is fine to do this and that they do these overhangs often. This is NOT what I have read here.

Also, they showed me a thin 6in line along the top of one of the slabs and said it was a "crack". They are planning to start using the granite for the island an inch below where the crack ends. Again, they have a very good reputation, I have seen there work and have also read good reviews about them on this site.

So to all the granite experts, what do you think?

Thanks so much for your help!

Comments (18)

  • azstoneconsulting

    Your Fabricator - however reputable - IS WRONG!!!!

    The rule of 6 & 10 is very clear - depending on whether you are using
    2CM or 3CM - 13.5 inches of unsupported span is CLEARLY EXCESSIVE
    and IF the stone breaks after install - and you or he has NOT put supports
    under the stone (ie; corbels, or counterbalance plates) YOU WILL LOOSE!!!

    Remember that:
    IF you are using 2CM stone ANY unsupported span of
    6 inches or more REQUIRES SUPPORT FROM UNDERNEATH - corbels or counterbalance plates

    IF you are using 3CM stone ANY unsupported span of
    10 inches or more REQUIRES SUPPORT FROM UNDERNEATH - yes - you guessed it...
    corbels or counterbalance plates...

    This iS NOT ROCKET SCIENCE - yet Bonehead after Bonehead STILL insists
    that you don't need any support - because "That's the way we've always
    done it" - well - NEWS FLASH - the "That's the way we've always done it
    Defense Argument" does not hold up in court when YOU as the consumer
    are SUEING your reputable Fabricator fro installing an assembly that had
    INADEQUATE SUPPORT.....
    I ought to know - I do LOTS of work as an Industry Expert Witness in lots of cases that go to hearing.....

    Do it right NOW - rather than doing it OVER the SECOND TIME.....

    it's your choice - NOT your reputable Fabricator's

    hth

    kevin

  • rubyvine

    Thanks Kevin! That is what I have always read here and I am so glad you set me straight. I guess that was what my gut was telling me, even thought they assured me TWICE. I think we will go with wooden corbels that we will put in ourselves after they do the install. If I remember correctly the formula to use is: overhang-stone thickness (so 13.5 in overhang - 3cm granite = 10.5 in wooden corbles). Does that sound about right?
    Also, what do you think about using the cracked slab. They will throw out the cracked top part and starting using the stone from an inch below where the crack ended. I am not sure if this granite (Titanium Black) is particularly fragile or not. Have you heard of it?
    Thanks :)

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  • azstoneconsulting

    Using a slab that's been cracked from handling can be done - you just
    have to avoid the cracked areas and either NOT use them - or
    have the ability (as a Fabricator) to repair and re-enforce the cracks..
    it can be done - but it's a PITA and should only be done as a last resort...

    Check out the Tyler Morris Corbel Wizard - My rule of 6 & 10 is there too...

    as far as the corbels for your project - anything bugger that 3 1/2 inches
    is going to be fine - this will put you within MIA specs and THAT is where
    you WANT TO BE!!!! the 10 1/2 inch corbels will be overkill - but they'll work fine....

    Spacing should be NO MORE THAN 16 inches apart IF you want optimum support
    of the assembly - I would NOT space out corbels any farther apart than 24 inches on center....

    Oh yeah - Titanium Black IS pretty brittle stuff - once it's in your house - I
    think you'll be fine - from a Fabricator's point of view - it's a PITA - but
    it is WAY COOL when installed and it goes into service!!!!

    Enjoy!!!!

    hth

    kevin

  • annkathryn

    Are counterbalance plates equivalent to rods? For overhangs of 6+ inches, would rods be sufficient to support the granite?

  • azstoneconsulting

    Rods are NOT ANYWHERE NEAR the equivalent of counterbalance plates when
    it comes to supporting an overhang ... the counterbalance plates are DEFINITELY
    the way to go!!!!!!

    Counterbalance plates are 3/8" thick and come in two lengths - 9 3/4"
    and 11 3/4". Both lengths are 3 3/4" wide.

    i wrote an article in this subject for Stone Business Magazine - a re-print of
    it is available for free by going to Natural Stone 101.com

    remember that rods are usually much smaller dimensionally - in 3CM - most guys
    (me included) use Stainless Steel that is 1/2" tall by 1/4" thick. the rods in this
    style of application are set into the stone so the 1/2" dimension is up on it's edge...

    here is a quick tutorial on "RODDING"......

    The use of "rodding" has been embraced by many Fabricators to gain
    an increased measure of strength in a piece of stone - similar to the way the
    re-bar is imbedded in concrete in highway construction. The rods are used
    around areas that are prone to breakage - such as undermount sink openings,
    and cook top cutouts. Rodding is primarily done in order to get a piece of
    stone FROM the Fabrication Shop - TO the jobsite where it will be installed.
    Once the piece is installed - the rod will stay there and act as a re-enforcement,
    and help to prevent breakage of already weak-end assembly.

    As far using the rods in lieu of corbels or counterbalance plates - I would
    NOT advise it, as the counterbalance plates are much better suited
    to support an overhang assembly.... That's how I would do it - I'd
    use the counterbalance plates for the overhang and rod everything else....

    Anyways - Rods are inserted into the back side of the stone running along
    the long axis of the piece.

    FYI - The examples shown here are for a 3CM thick stone application - IF you are doing 2CM
    thick stone, the "norm" for rodding stock is 1/4" round stainless steel...

    First - the 1/4" x 1/2" steel is ready to be "set" into the slot that's been cut just
    a little more than 1/4" wide

    like so........

    "Flowing" Epoxy is mixed up and poured into the slot after it has been cleaned out and
    dried ...

    like this....

    The rodding steel is set down into the slot so that the 1/2" dimension will be up
    on it's edge - making the assembly more rigid..

    The steel rod is then pushed down into the wet epoxy so that the glue encapsulates the
    rod.....

    Excess glue is scraped off the back side of the stone so that when it dries,
    very little will have to be ground off to render the back side of the countertop
    really smooth...

    thus endeth the lesson!!! HA!

    hth

    kevin

  • annkathryn

    Wow! Thanks so much for the lesson, Kevin.

    I had a fabricator tell me that an 8" overhang (2cm granite) would be ok with rods, but it looks like I'd better insist on corbels or counterbalance plates.

  • needsometips08

    Oh, so that's what those lines on the back of my granite are!

  • rubyvine

    Can't thank you enough Kevin for sharing all that good info ya got floating around in that head of yours! :)

  • sreeb

    Rods will only add strength when the are in tension, hence they would be used when spanning an unsupported area.

    You could use them on an overhang if you installed them in the top surface. That may not be the look you are seeking though.

  • azstoneconsulting

    Rubyvine - thanks for the kind words - I'm glad to be able to help....

    Sreeb- This will not work - as it is NOT approved by MIA as a suitable method.
    It WILL fail - rodding is an inferior method of support for overhangs - as opposed to
    corbels and counterbalance plates - it's just that simple.

    The first time you apply a dead load to the overhang without any corbels
    or plates underneath - and the unsupported span exceeds 6 inches
    in 2CM stone, or 10 inches in 3CM stone - the risk factor of fracturing
    the stone at the overhang increases exponentially........

    I have been doing this for over 25 years - you can either do it right - or
    do it wrong. Relying on rods alone to prevent a fracture is not only wrong -
    IMHO - it's just plain dumb - besides - you cant add "tension" to rods in
    a stone top assembly - It does work in post tensioned concrete, as that type of
    application HAS the ability to apply tension before the pour and after, but in this type
    of application - applying tension is impossible to do - does that make sense?

    hth

    kevin

  • riverspots

    My fabricator was also suggesting I needed less support than I felt comfortable with. For my situation, an 11 ft island with overhangs going around the corner, they thought 5 corbels would do it. I've put in 9, though a few of them were partially for looks. But it is an overhang, afterall, and exactly where folks are going to lean and I'd rather prevent cracks than worry about getting them fixed.

  • azstoneconsulting

    Riverspots-

    Now THAT'S what I'm TALKIN ABOUT!!!!!

    If more people would look at the issue of overhangs the way you do,
    I would not have so many failures to look at and make money on consulting!!!

    HA!

    kevin

  • petepie1

    So what can you do after your granite has already been installed? Install a corbel underneath? Is there any low-profile corbel or other solution that won't show as much? I have a "boxed in" island approx. 60" long with a 15" overhang on the back for stools -- so the granite overhang is supported on each end by the ends of the island, but spans about 50" in the middle (15" deep) without support. After reading this thread, I'm thinking some extra support under the overhang is needed.

  • rubyvine

    petepiel-I think corbels are the only option once granite has been installed, but Kevin would know best. I checked out the corbles on the Tyler Morris web site and there were some really plain/low profile corbels there. Good luck!!

  • benjayva

    Bumping this for those of us in this time of our renov...awesome info

  • marjoriest

    We are planning to put in a small peninsula with counter height stool/chairs for my children to sit at for snacks and homework advice while I cook. (I am tired or running from the kitchen to the dining room to explain algebra!) My KD said that a 9 inch overhang should be enough and the granite fabricator suggests 2-3 5-7" corbels. Would any other support be necessary?

  • titan7

    Not to steal your thread, but I wonder if I am doing this correctly also. My overhang will be 12 1/2" x 48" on the penisula and we are adding 3 corbels 2" wide, 10" tall and 7 5/8" deep. That leaves 4.8" of unsupported granite, we are using 2mm. Would I gain anything by go to a deeper corbel or is it overkill if I am under the 6" limit with 2mm.

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