Need advice on hanging vanity

[Phil Thien]

I am going to build a hanging vanity for by full bath. I plan on using a 3/4" back with a French cleat securely attached to the vanity and the wall.

The top is one of those cast "marble" vanity tops. It is 19" deep and 25" wide. It has a built-in backsplash.

I want the box to be as stury as possible. So I'm going to put the back into a grove in the sides and bottom (all 3/4" plywood). The back will be inset 3/4" into the cabinet to allow room for the French cleat.

The problem I'm having is visualizing a way to handle a top of the vanity cabinet itself (where the marble top will sit). I could just make a complete 5-sided box (back, two sides, top and bottom) and then cut a hole large enough for the sink bowl. But I suppose I'd also have to drill some holes for the faucet, too.

Or should I build a frame out of hard/softwood instead?

I think the plywood top would make the cabinet stronger, but it seems kinda unconventional.

Any tips? Links to photos of how someone else did it will lead to extra credit. :)

[Jim Becker]

You need to build the piece such that it's designed to handle the type of loads that will be placed upon it. In effect, this is a "cantilever" design

Question: Will the vanity only be supported at the back or is there one or two walls to support toward the front?

Question: How tall do you feel the cabinet will be relative to storage or is it just a surface to mount the sink, etc.?

Oh, Mark Singer has a lot of experience with this format of vanity...hopefully, he'll comment. I'm going to PM him to let him know about this thread.

[Jamie Buxton]

The weight of the vanity is going to be trying to rotate the vanity around the bottom rear corners. That is, it will be trying to peel the top away from the wall. That means it will be trying to bend the material you're using for the back. If you put a top on the box, it will help keep the back straight. So yes, I'd put a top on the box.

[Phil Thien]

Fast replies. Thanks.

There will be no storage. Just the weight of the cabinet and the sink (with water). It will be approx. 24" high, 24" wide, and 19" deep. The French cleat will be 3/4" plywood. And I will secure the vanity at the bottom with two screws into studs so the entire thing can't lift of the cleat accidentally.

I guess the question boils down to how to make the top (including the joinery) so as to maximize strength.

I was thinking of a 3/4" plywood top. I would use a 1/2" rebate so I could maximize glue area and keep the top flush with the top of the cabinet. Like in the pic I've included. The pic is the joint between the top and the side. The back would be set into a 3/4" grove around the entire permiter (both sides, top, and bottom). So it should be pretty securely locked together?

[Jim Becker]

Phil, I actually think that you should base this piece on a torsion box principle in that it will give you great strength, including less chance for "twisting", without a huge amount of weight. Obviously, you'll need to modify to accommodate the plumbing. One other thing, your cleat should be beefy and there needs to be proper support/blocking in the wall to support the piece. Further, even though you'll hang the vanity on the cleat, you'll also need to make provisions for screws/lag bolts to directly fasten to the wall for both additional support and to insure it doesn't move. You have enough depth to do that as the torsion box doesn't need to be the full 24" thick. In fact, this can be a "wrapped" piece with the basic structure wrapped with veneered goods for mitered corners, etc. I'm looking forward to your end result!

[Mark Singer]

The best way is to use a french cleat as you stated and use light stainless, metal or wood legs on or near the front to transfer the load. See attached link

http://www.sawmillcreek.org/showthread.php?t=38135&highlight=balboa

[Phil Thien]

Phil, I actually think that you should base this piece on a torsion box principle in that it will give you great strength, including less chance for "twisting", without a huge amount of weight.

The piece I was envisioning was the equiv. of an upper cabinet in a kitchen. The only difference would be that it would be deeper (approx. 19") and there would be a vanity sink on top of it (approx. 20-25 lbs. empty--certainly heavier with a bowl full of water). The cabinet would be 24" high and 24" wide.

How would I do this with a torsion box? Would that be the top? Or the back?

[jason lambert]

Stone is something I know I have built every vanity in my house. The thing with a stone top to remember is that the base can't move. There can be no twisting or anything over time, if a corner lifts it will cause the rock to crack. I would recommend instead of a solid top use several 2x4 or what ever to cross braces. Make sure the top is perfectly level. The trouble with a solid piece of wood under rock is rock will absorb moisture and water, it will actually soak throught the rock if left sitting, you can help this by sealing regularly or some cleaners have a wax in them which helps seal the rock also some rocks are better than others. If the bottom has no air flow like sitting on a piece of plywood it will trap moisture against the wood and may cause warping, also you will see dark spots in the top depending of the characteristics of the rock and the amount of moisture trapped. In general rock tops need to breath below them.

[Jim Becker]

Jason, this can still be handled by a torsion box topped by a couple stringers to insure that the stone doesn't have full contact with a sheet goods surface. This is not a traditional vanity and has to be built in a way that it will be self-supporting as it cantilevers out from the wall.

[jason lambert]

Yes I aggree as long as the slab is not totally on a sheet of wood.

[Chris Friesen]

The weight of the vanity is going to be trying to rotate the vanity around the bottom rear corners. That is, it will be trying to peel the top away from the wall.

I agree with the general idea, but the torque acts all along the back wall not just at the bottom rear corners.

Due to that torque, the bottom rear edge of the vanity will want to press into the wall (this force is resisted by the wall itself), and the top rear edge of the vanity will want to pull away from the wall. The cleat must resist this outward pull in addition to the downwards pull from the weight of the vanity.

The top of the vanity won't see any special stresses when compared to a standard one. The main difference is that the vertical elements of the vanity case will need to transmit the downwards force to the back wall of the vanity rather than the legs; this may inspire/require some design differences as compared to a standard model.