How would I hang 150lbs+ on a wall?

[03mustangdude]

Dont really like any new vanities so I was discussing doing a "floating " marble top and a shelf underneath for a bathroom i'm redoing.

Shelf isnt an issue its maybe 60lbs

Marble top is.

60x18.5 150lbs+ without a sink on top.

So would I put some plywood underneath and support it with brackets?

Would I do some kind of metal contraption where its all connected and attached to the studs?

I'm curious if its possible.

Going in a corner

Doing plumbing into the wall so no worries about cutting the top.

Any ideas?

[diablo rojo]

You're definitely going to need a structure underneath. If you want the floating look, you'll need to channel into the wall/studs the exact thickness of the marble, and probably 2 3/4 deep in the wall (accounting for drywall thickness). You'll still need a metal (maybe wood) grid under it, with a few angled supports tied to the wall closer to the floor. 60" is a big slab though you may end up having to shave it closer to 48".

My. 02.

[juiceweezl]

Dont really like any new vanities so I was discussing doing a "floating " marble top and a shelf underneath for a bathroom i'm redoing.

Shelf isnt an issue its maybe 60lbs

Marble top is.

60x18.5 150lbs+ without a sink on top.

So would I put some plywood underneath and support it with brackets?

Would I do some kind of metal contraption where its all connected and attached to the studs?

I'm curious if its possible.

Going in a corner

Doing plumbing into the wall so no worries about cutting the top.

Any ideas?

You can screw something that looks like C-channel into the studs. It'll need to be fairly thick steel and have enough bearing to support the marble. You'll also need to have screws or something to lock it in place. I have shelves in my house like this, but they are obviously much smaller. No reason you couldn't fab of buy something similar to work. We have 1/4" diameter wood screws that I use all the time that will support 300 #'s in shear. If you put a screw like that in each stud of the channel, you'd probably be fine.

[03mustangdude]

http://m.homedepot.com/p/Crown-Bolt-3-4-in-W-x-9-16-in-H-x-96-in-L-Aluminum-C-Channel-with-1-16-in-Thick-56870/100338033

This kind of c channel?

I can put a solid metal piece under it since it'll be hidden but can't cut marble.

[diablo rojo]

http://m.homedepot.com/p/Crown-Bolt-...6870/100338033

This kind of c channel?

I can put a solid metal piece under it since it'll be hidden but can't cut marble.

That's a good example, but you'll need a much deeper channel.

[Big A]

These guys seem to think that a frame and L-brackets bolted to the studs is enough.

http://www.legacybrackets.com/granite-support-tips.html

[03mustangdude]

Would one of those heavy duty brackets that's rated for 500lbs wor you might be able to tell it's there but maybe not. 3 of those into the studs. 1/2 plywood on top. Then marble.

[juiceweezl]

That's a good example, but you'll need a much deeper channel.

Correct. The top flange is just as important as the bottom flange.

[ceyko]

These guys seem to think that a frame and L-brackets bolted to the studs is enough.


http://www.legacybrackets.com/granite-support-tips.html

Yeah, I'd buy into this if I pulled drywall - reinforced the hell out of the wall and then put drywall on. It's one of those deals where doing that is a PITA, but if you have problems, trying to double up studs and improving later is going to be real difficult with plumbing in place...etc...etc.

[Tremor14]

If it were me i would definitely pull the sheet rock and reinforce all the wat across with some 1/2" or 3/4" plywood. Will also give you a chance to mark the studs correctly and add some if you dont have enough. Depending on the age of the house, the rock may be in bad shape is it is.

[8mpg]

I wouldnt float it

[juiceweezl]

Yeah, I'd buy into this if I pulled drywall - reinforced the hell out of the wall and then put drywall on. It's one of those deals where doing that is a PITA, but if you have problems, trying to double up studs and improving later is going to be real difficult with plumbing in place...etc...etc.

Studs spaced at 16" on center can carry the load with the proper fasteners installed directly into the face of the stud, even through the rock. The thickness of the rock will create an eccentric load on the fastener, but it's likely on 1 layer. That gap isn't enough to create a problem if you're placing fasteners at each stud. Again, you want the screw to be in the center of the stud and be a legit screw. This is what I use:

http://www.strongtie.com/products/connectors/sds.asp#tables

It's a 1/4" wood screw that has an allowable shear load of say 390 pounds with a 14ga or 12ga steel side plate. That's using a 2 1/2" screw. I'd use a 3" screw since going through the rock, and you'd get close to that value even though it's an eccentric load. That's in straight shear though (axial/gravity) supporting the weight of the top. Withdrawal loads are 150 lbs./in of thread penetration. Again, it'd be closer to 300 pounds per fastener allowable load if you hit the middle of the stud.

The fasteners will hold, and a 2x4 will support that load in bending as long as it's 16" on center or less and standard height. The bigger issue is finding a channel that can support the load/fasten to the marble.

[ceyko]

The fasteners will hold, and a 2x4 will support that load in bending as long as it's 16" on center or less and standard height.

*nod* - I know you're most likely right - but I'd be paranoid if I was doing the installation with my own stuff...etc. DIY'ers (at least me) tend to overdo it ..."just to be sure"....although, sometimes I think I over-think stuff too.

[juiceweezl]

*nod* - I know you're most likely right - but I'd be paranoid if I was doing the installation with my own stuff...etc. DIY'ers (at least me) tend to overdo it ..."just to be sure"....although, sometimes I think I over-think stuff too.

I, and most of my colleagues, hate the terms 'overdo' and 'over engineer' which are commonly used in the building industry. Something should simply be designed and constructed to resist loads from all components and foreseeable forces that may act on it. In this case, OP referenced a 150# countertop. He goes on to say that he may put plywood underneath it, and logic tells us that at some point, someone is going to lean/press down on it or even sit on it. You could factor in some numbers like 200# concentrated load on the edge. Then, if you had the depth of the counter, you could calculate the moment on the back side to determine the fastening pattern/system. The good news is that when you see a screw like the one linked above, it's been tested, and the published values include a 2.5 or 3 times factor of safety minimum. We've been building with wood long enough to have established values for it as well, so we know what it can take in bending. All in all, neither the wood nor a fastener like above would be the limiting factor. In this case, it'll be the interaction/bearing of the bracket to the slab that will define if it will work.

All that being said, the term we like is 'redundancy' and I try to build things myself with it built in.

[03mustangdude]

Ok my game plan is as follows:

Heavy duty brackets 16in on top 10inches against the wall , 4 in total 3 against wall and one on the side. 2 can support 600lbs

Found some heavy duty screws like the ones linked that can support 480lbs

1/2 plywood underneath attached to brackets 4 holes per bracket

Will test out with 300lbs of weights before putting down 100% silicone and dropping the marble top on.