So, my thought was to use three of these:

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EVERBILT 8 Inch Zinc Corner Brace

or maybe these:
Simpson Strong-Tie 7 Inch Reinforcing Angle

Basically I thought the brackets could be installed with the vertical part inside the cabinets and the horizontal part under the granite (a slot would need to be cut at the top of the cabinet to allow the bracket to poke through). Alternatively, the brackets could be on the outside (with internal reinforcing inside the cabinets for stability) - and hidden by the panels using routering.

I'm not sure how you would get the horizontal parts of the brackets totally snug against the granite so they are actually supporting?

Dh initially did not want to use real countertop steel countertop support brackets due to the cost. They do seem like one of those specialty kitchen products that are unnecessarily $$$ ? For example, the Freedom Hidden Countertop Bracket 12x12 would be $90 each plus horrendous shipping costs.

Looks like these bloggers used the cheap bracket support option as suggested by their Corian countertop fabricator (I know, Corian is not the same as granite). They used 12" brackets and quite a few:

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Full details here:

Here is a link that might be useful: Prepping For Corian Counter Installation

Thanks cal_quail. Those are a good option but would probably cost $500ish with shipping etc. Not sure if they are overkill structurally?

The pictured brackets are nearly useless; they have no triangulation. Bond a 3/4" thick cabinet-grade plywood to the back of the cabinets with construction adhesive and screws, then use brackets like these after you've veneered the plywood to match:

Here is a link that might be useful: Brackets

The pictured brackets are nearly useless; they have no triangulation. Bond a 3/4" thick cabinet-grade plywood to the back of the cabinets with construction adhesive and screws, then use brackets like these after you've veneered the plywood to match:

Here is a link that might be useful: Brackets

A lot of times when I am tempted to do the cheap thing, I remind myself what an ER visit costs.

You would not want that counter to crack and land on a guest

Trebuchet is absolutely right...those brackets pictured are useless as they will flex, and granite will not allow that. You need heavy duty granite brackets and they need solid wall support at all points to be effective. Also, reinforcement is best installed before the granite is in place, not after.

Here is a link that might be useful: Granite bracket

Thanks to those who provided specific input :) .

Lowes Canada doesn't source the Federal Brace 8-in x 2-in Plain Steel Countertop Support Bracket. Any suggestions for Canadian sources of those? Or equivalent?

Trebuchet, I assume I would need three of the Federal Brace 8-in x 2-in brackets? Could I install the plywood inside the cabinets (there is room)? Is there a reason why I wouldn't use the "L" shaped granite support brackets that don't have the cross-brace (knee knocking) like the example below?

What about this Ekena Millwork 2"x8"x8" Hamilton Bracket?

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Price is good. Cold-rolled steel and it's supposed to be appropriate for granite. Is there any way to evaluate the many different brands of cold-rolled steel granite brackets?

I am still trying to understand is shimming the bracket end(s) will be required to get a snug fit to the granite, and if so how would that be done?

Kudzu, that supplier doesn't ship to Canada unfortunately.

This post was edited by feisty68 on Mon, Dec 29, 14 at 13:32

Listen to those two, they make sense. The two "sided" brackets you show are suitable for keeping things from moving in the two planes you're NOT concerned about. They are weak in exactly the one vector that you need strength in, and that's down.

Since you are dealing with an absolutely brittle material that cannot withstand any bending whatsoever, you want something (anything: bracket, corbel, beam, post, whatever) that cannot be moved even the slightest bit by a strong person's best try at bending. Not an expensive common L bracket, beefy or not.

These Centerline Steel Hidden Front Mounting Brackets look better. Manufacturer recommends 12"X10" for 15" overhang. Three of them would be US$95.85, and shipping would be US$48.60 (gag) - that doesn't include taxes, brokerage fees, and duty.

In the photo below they removed drywall to attach to wood support. In my case I would build in structural wood support inside the cabinets, and attach the brackets to that. I already have solid wood finished panels to cover the vertical part of the bracket. Veneer is not sturdy enough for kids' feet kicking, etc.

Grubby_me, so are you saying that all of the L shaped brackets (with no cross-bracing) that are marketed specifically for supporting granite and made of thick steel are not appropriate?

For example, the Centerline Steel Hidden Front Mounting Brackets that I posted above meet ATSM A36 Standard Specification for Carbon Structural Steel. Doesn't that mean anything?

I am hoping that there are alternatives to knee knocking solutions. Many countertop professionals seem to use unobtrusive brackets??

feisty-
There are L-shaped brackets that will work, but they need to be of a different design than you want to consider. If the brackets I linked you to above can't be shipped to Canada, you need to find something similar that is available. You have quite an overhang and using the type of brackets you keep finding will end up in an unhappy outcome. I know that you don't want to spend a lot of money, but how much will it cost to replace the countertop after it cracks off?

P.S.: The ASTM standard refers to the quality of the steel; it has nothing to do with the suitability of the bracket to your application.

feisty:

"L" brackets without triangulation, even 1/4" steel, simply aren't strong enough. I've driven shims between the tops of these brackets and the bottom of granite. The granite didn't budge; the bracket flexed. This doesn't take an engineering degree to figure out.

I'm going to be blunt. You didn't design and budget appropriate support into your original installation. Now when you're told you need expensive brackets, you're looking for cheapies.

The back of the cabinet should be reinforced; there are plenty of ways to do this. Again, right isn't cheap. Plywood inside or out, it must be plumb when you put a level on it. When your top is level that makes the plywood/back and top perpendicular and not needing any shims.

This post was edited by Trebruchet on Mon, Dec 29, 14 at 23:55

Thanks Trebuchet and kudzu. I agree that the project implementation has been highly imperfect thus far. I really appreciate your opinions as to what brackets would be required for appropriate support. Also, it helpful to understand the details of how to get the right angle that is needed.

I wasn't trying to cheap out, but I was trying to understand why some granite support solutions were deemed acceptable while others were not.

I see that the Hardware Hut does carry the bracket that Trebuchet recommends, and that they do ship to Canada.

Here is a link that might be useful: Federal Brace 301 Brunswick Countertop Bracket

This post was edited by feisty68 on Thu, Jan 1, 15 at 16:56

feisty-
I think that's a wise choice. I know good brackets can seem pricey, but they're an inexpensive insurance policy. You won't regret it. Good luck.