Cantilevered granite shelf?

[paredown]

Thinking about using a granite offcut that I have and cantilevering it. (no brackets below).

I've seen versions of this on commercial stone jobs--they would edge drill for bar stock, epoxy in bars, and then do the same on concrete.

I'm thinking about trying something like this, but attached to a standard 2x4 stud wall--so threaded bars into studs, granite drilled to fit non-threaded ends, then epoxy and slide in place.

Stone calculator puts this at about 110 pounds, it is long enough that I can catch 4 studs, so the load would be carried by those alone.

I've got a local stone guy who I think has the ability to drill, so the questions would be:

1) crazy idea or might be cool?;
2) anyone seen appropriate dohickeys for threading into studs;
3) if I think about this as 25 pounds per stud (sheer), what kind of force is the cantilever putting against the wall. (I'm not worrying about wall surface--it is hard shell plaster, so fairly tough.)

Thoughts anyone?

(These are the things I think about while nailing down flooring....)

 

[paredown]

Found this thread on Woodweb where they talk about doing this with 60 pound solid oak shelves, and it worked out well. Wood is easier to drill than stone though...

They used Allthread cut to length.

http://www.woodweb.com/knowledge_base/Floating_Shelf_Installation_Methods.html

 

[rlitman]

How wide will this shelf be? Are you using 2cm or 3cm thick granite?

 

[paredown]

How wide will this shelf be? Are you using 2cm or 3cm thick granite?

Sorry--shelf width is 12"

granite is 1.25" thick--so about 3cm in 'new' measurements

 

[rlitman]

Sorry--shelf width is 12"

granite is 1.25" thick--so about 3cm in 'new' measurements

I've never seen granite that's 1.25" thick. Try measuring it more closely.

Anyway, I think you'll quickly discover that this will not work. I suggest hidden steel brackets, like this:
https://www.countertopbracket.com/Countertop-Support-Bracket-Steel-p/fmp.htm

You can cut a rectangle out of the sheetrock around the studs and patch over these brackets with some creativity to hide the vertical component.

 

[PugetDude]

1/2" rebar pins-about 10" long
Drill the back edge of the stone about 7-8" deep.
Drill 3" deep 1/2" holes in the studs at a couple of degrees over 90 to the wall and pound in the rebar
Dry fit first...make sure the pins don't bottom out on the rebar. Adjust the pins with a ball pein hammer until the shelf slides over snugly.
Overfill the holes and slather the pins with epoxy, slide the shelf over the pins sticking out of the wall.
Prop up the shelf with a couple of 2x4's until the epoxy dries.
Display your anvil collection.

 

[Viper98912]

I think it's a neat idea, but concerning. I personally think you also need to consider the load of that friend of yours that's going to come over, marvel at your granite shelf, then turn around and put his elbow on your granite to talk to you, along with the rest of the weight of his 200+ pound body, bringing your granite crashing down.

I think it's cool but I'd still put down some support of some sort.

 

[paredown]

I've never seen granite that's 1.25" thick. Try measuring it more closely.

Anyway, I think you'll quickly discover that this will not work. I suggest hidden steel brackets, like this:
https://www.countertopbracket.com/Countertop-Support-Bracket-Steel-p/fmp.htm

You can cut a rectangle out of the sheetrock around the studs and patch over these brackets with some creativity to hide the vertical component.

Corrected, measured with caliper-- 1.20" ~3.048 cm Absolute Black polished one side. Hard to get any more exact, since the caliper catches on the stone's roughness...

Why do think it will not work? Weight? Physics?

They do similar installations on commercial projects (admittedly into poured in place)...

(Thanks for the link to the brackets--I may get there. Cutting the plaster wall is a ***** though--hard to get straight cuts to sink brackets below...)

 

[paredown]

1/2" rebar pins-about 10" long
Drill the back edge of the stone about 7-8" deep.
Drill 3" deep 1/2" holes in the studs at a couple of degrees over 90 to the wall and pound in the rebar
Dry fit first...make sure the pins don't bottom out on the rebar. Adjust the pins with a ball pein hammer until the shelf slides over snugly.
Overfill the holes and slather the pins with epoxy, slide the shelf over the pins sticking out of the wall.
Prop up the shelf with a couple of 2x4's until the epoxy dries.
Display your anvil collection.

A bit primitive but definite style points!

 

[paredown]

I think it's a neat idea, but concerning. I personally think you also need to consider the load of that friend of yours that's going to come over, marvel at your granite shelf, then turn around and put his elbow on your granite to talk to you, along with the rest of the weight of his 200+ pound body, bringing your granite crashing down.

I think it's cool but I'd still put down some support of some sort.

It would not really have much on it--it would be a hall display, possibly the place to toss keys, or the last mail pickup. I can't imagine much being placed on it as far as weight.

 

[rlitman]

...Why do think it will not work? Weight? Physics?

They do similar installations on commercial projects (admittedly into poured in place)...

Yes. Physics.

I do not believe you will be able to drill such deep holes in a piece of granite without breaking it or drilling out a side. That alone is a deal breaker.

On a normal kitchen countertop, without any bore holes to compromise the stone, a 10" overhang is the most that is recommended. You're starting out past that, and don't have the rest of the stone to counterweight the shelf.

In a commercial project, this could be done with a stone veneer over steel armature. But it would still require better attachment to the wall than just a few rods inserted into studs.

It would not really have much on it--it would be a hall display, possibly the place to toss keys, or the last mail pickup. I can't imagine much being placed on it as far as weight.

And when someone leans on it and breaks bones as it falls? Anyway, I don't see how it could support its own weight, so that's a moot point.

 

[PugetDude]

A bit primitive but definite style points!

I've done several log mantles this way- some of them weighing as much as your little granite shelf.
No issues; I actually stood one on one doing some stone work above the fireplace.
If you're hitting 4 studs, the load per stud is negligible. Only issue is keeping it from sagging until the epoxy filling the voids sets up. .

 

[Viper98912]

It would not really have much on it--it would be a hall display, possibly the place to toss keys, or the last mail pickup. I can't imagine much being placed on it as far as weight.

Now that I picture this, it's not as wide as I was picturing. Maybe you'll be fine. Just need to add a little reinforcement possibly. Or router-out the bottom side and glue some channel under it. But the routing might make it weaker?

And as a general rule of thumb, darker colors are denser, so they're a little more robust against cracking.

 

[Sureshot]

1/2" rebar pins-about 10" long
Drill the back edge of the stone about 7-8" deep.
Drill 3" deep 1/2" holes in the studs at a couple of degrees over 90 to the wall and pound in the rebar
Dry fit first...make sure the pins don't bottom out on the rebar. Adjust the pins with a ball pein hammer until the shelf slides over snugly.
Overfill the holes and slather the pins with epoxy, slide the shelf over the pins sticking out of the wall.
Prop up the shelf with a couple of 2x4's until the epoxy dries.
Display your anvil collection.

I would definitely try this. How much are you paying for the granite?

 

[YukonXL04]

Thinking about using a granite offcut that I have and cantilevering it. (no brackets below).

I've seen versions of this on commercial stone jobs--they would edge drill for bar stock, epoxy in bars, and then do the same on concrete.

I'm thinking about trying something like this, but attached to a standard 2x4 stud wall--so threaded bars into studs, granite drilled to fit non-threaded ends, then epoxy and slide in place.

Stone calculator puts this at about 110 pounds, it is long enough that I can catch 4 studs, so the load would be carried by those alone.

I've got a local stone guy who I think has the ability to drill, so the questions would be:

1) crazy idea or might be cool?;
2) anyone seen appropriate dohickeys for threading into studs;
3) if I think about this as 25 pounds per stud (sheer), what kind of force is the cantilever putting against the wall. (I'm not worrying about wall surface--it is hard shell plaster, so fairly tough.)

Thoughts anyone?

(These are the things I think about while nailing down flooring....)

I have some granite cutoffs as well. Not sure what I want to do with them. Thought maybe a soldering station or something.

 

[redneckcharlie]

Yes. Physics.

I do not believe you will be able to drill such deep holes in a piece of granite without breaking it or drilling out a side. That alone is a deal breaker.

On a normal kitchen countertop, without any bore holes to compromise the stone, a 10" overhang is the most that is recommended. You're starting out past that, and don't have the rest of the stone to counterweight the shelf.

In a commercial project, this could be done with a stone veneer over steel armature. But it would still require better attachment to the wall than just a few rods inserted into studs.



And when someone leans on it and breaks bones as it falls? Anyway, I don't see how it could support its own weight, so that's a moot point.

My company does granite fab. I only do it for our projects. I only use 3cm material as well. A 10-12” over hang isn’t an issue with 3cm material without any support. I routinely do 16-18” overhangs on bar tops. On those applications I use 1/4” flat stock that is mortised in to the wall top and glued to the underside of the material. The number of supports depends on the load it’ll see. Also, drilling the slabs with holes from 1/8” up isn’t an issue either. Professional diamond hole saws are readily available.

 

[paredown]

I would definitely try this. How much are you paying for the granite?

It was free to me from a kitchen project in a high end house. Best price, really.

Thanks to everyone who weighed in.

I did find a second bracket supplier who makes a really cool one--you open up the wall and face mount to the side of the stud and only a bar projects through the drywall to support the stone. (I still don't want to try that with the plaster walls... but it is a cool solution.)
https://www.countertopbracket.com/category-s/1823.htm

I also found the dowels I was thinking of for stone installation--pictures show it joining blocks:
http://www.masonpro.com/products/residential/stone-anchoring-setting/

 

[CraigStu]

So redneckcharlie are you anywhere Pamona NY? Looks to me like paredown needs to get to know you.

 

[engineer2]

3 cm is the standard countertop thickness now. It used to be 1-1/2".
Absolute black is very fine grained and strong. Commonly used for laboratory countertops.