Floating Vanity with Granite Top

[Brian Livingstone]

Hi,

I am planning on building a floating vanity, about 5 feet long, 2 feet wide, 2 feet high.  10 square feet of countertop in total, weight of the granite top should be about 200 pounds.  The wall I am attaching it to is 2 by 6 construction.  I am going to build the box out of 3/4 inch plywood, with a 3/4 inch back and top.  Should be nice and solid with all domino construction.

I was thinking I might put a piece of angle iron to hold up the cabinet, but maybe this is overkill.  I think I will simply remove the drywall from behind where the vanity is going, reinstall 3/4 inch plywood in its place with a 3/4 inch lip to hold the back edge of the vanity, and then screw the vanity to the 2 by 6 through the two layers of plywood.  Sound solid enough ?

Thanks.

Brian

 

[roblg3]

I recently built a "floating" cabinet similar.  I did not have any heavy granite top though.  200 pounds sound light for that much stone??  if you did the math i trust you, but sounds shy...What i did was to make the back the full outer dimension so the sides when weight loaded would be pushing on the large 3/4 back to spread the point load.  My cabinet sides did NOT land on top of studs and I didn't want to push a thin load on just drywall when groceries were bound to be placed on top of this thing at some point.  So the top sat on the ledge of the full back and on top of the sides which also sat on the back.  the bottom carried nothing so whatever with that piece since the sides carried the weight of the drawers

 

[shaun.mcc]

I think I would go the angle iron route with integral brackets welded to the iron that sister the studs or maybe three brackets that sister the studs then come out like shelf brackets to support the cabinet from the top and the granite from the bottom - if that makes sense. You have a lot of weight between the floating vanity, contents, sink, granite...not to mention someone potentially leaning against it or sitting on it. Be sure to show some pictures as you progress

 

[WastedP]

Just for quick math, I figure on 30 lbs per sf for 3cm stone and quartz as a rule of thumb.  I'd rather overbuild it than underbuild it.

Hafele's Hebgo brackets are great for floating vanities and ADA countertops with aprons and no cabinets below.  I have hung the vanity first, then installed the brackets inside the vanity, lagged to studs (or zip-bolted to metal studs) through a full 3/4" back.  I have also built vanities that had slots in the back so the brackets were attached to the wall first, then the cabinet slid over the brackets and screwed to the wall.

 

[Brent Taylor]

I agree with the use of the angle iron on the  bottom  and brackets to support the top. I have used this method before and am a strong believer in over kill, wouldn't want it to fall on anyone,  with that much weight you would crush a small child. Better to be safe, than cheap or lazy.   

 

[Tinker]

I agree with the advice already given that it is better (translated=safer) to ver build.  The floating vanity can be anchored to the framing.  I don't think the granite can be safely anchored to anything except what will be holding it from below.  Any anchoring will be holding the vanity AND the granite.  the granite, i think, is free weight.
Tinker

 

[rmwarren]

Just a thought, I did a floating vanity in a small bathroom and realized I could still install legs that would not be visible as long as I inset them about 6-8" back from the front of the cabinet. The only way anyone can see them is to get down onto their knees and look.

Only works if you don't view the vanity from very far away, in my case there is only a narrow space between the cabinet and the shower, so not a problem. You can see the cabinet here from the hall:

[attachimg=1]

And this is as far back as you can get from it in the bathroom itself - standing with my back to the shower door:

[attachimg=2]

RMW

 

[AndyG]

Strike a line at finished height across stud's. Cut 5 1/2 inch x 20 inch "L" brackets from 3/4 plywood and glue and screw to each stud ...install drywall now or later..if later fill with 3/4 plywood between each one so drywall isn't complicated...now wrap with 3/4 and veneer and set top. Watch plumbing centers. 2x6 can be added to horizontal or double the 3/4 .

 

[Tinker]

Just a thought, I did a floating vanity in a small bathroom and realized I could still install legs that would not be visible as long as I inset them about 6-8" back from the front of the cabinet. The only way anyone can see them is to get down onto their knees and look.

Only works if you don't view the vanity from very far away, in my case there is only a narrow space between the cabinet and the shower, so not a problem. You can see the cabinet here from the hall:

[attachimg=1]

And this is as far back as you can get from it in the bathroom itself - standing with my back to the shower door:

[attachimg=2]

RMW

Doing it that way, doesn't it still require extra framing.  Either the wall or under the bottom of the cabinet.  Won't the legs distort the bottom of the box if not extra support from somewhere?

I have never built a floating cabinet, but have done some fireplaces open on three sides.  Extra support had to come from somewhere.  i always used extra weight of the back part of chimney as counter balance to hold down the extended angle iron. Or a steel leg close to ouer corners of the openings.  (I always hated three sided openings or straight thru openings.  Could never guarantee they would not smoke up the house. I always discussed the alternatives as well as solutions if they did not work.) I have done porch decks that were hanging out into space.  with legs set back from outer edge of the deck, it required extra framing at top of legs to spread the support across entire underside of deck. Extra frame support at the house wall to use house as counterbalance. I all cases, neither decks nor chimneys have fallen down yet.  :
Tinker

 

[rmwarren]

Just a thought, I did a floating vanity in a small bathroom and realized I could still install legs that would not be visible as long as I inset them about 6-8" back from the front of the cabinet. The only way anyone can see them is to get down onto their knees and look.

Only works if you don't view the vanity from very far away, in my case there is only a narrow space between the cabinet and the shower, so not a problem. You can see the cabinet here from the hall:

[attachimg=1]

And this is as far back as you can get from it in the bathroom itself - standing with my back to the shower door:

[attachimg=2]

RMW

Doing it that way, doesn't it still require extra framing.  Either the wall or under the bottom of the cabinet.  Won't the legs distort the bottom of the box if not extra support from somewhere?

I have never built a floating cabinet, but have done some fireplaces open on three sides.  Extra support had to come from somewhere.  i always used extra weight of the back part of chimney as counter balance to hold down the extended angle iron. Or a steel leg close to ouer corners of the openings.  (I always hated three sided openings or straight thru openings.  Could never guarantee they would not smoke up the house. I always discussed the alternatives as well as solutions if they did not work.) I have done porch decks that were hanging out into space.  with legs set back from outer edge of the deck, it required extra framing at top of legs to spread the support across entire underside of deck. Extra frame support at the house wall to use house as counterbalance. I all cases, neither decks nor chimneys have fallen down yet.  :
Tinker

Wayne, in my case the top was small, probably < 4 SF, so the total weight was not an issue. I added some 3/4" ply between the studs and screwed the 3/4" back to it top/bottom, then the legs just carried the load on the outer edge.

RMW

 

[Tinker]

That makes sense.  With 3/4" backing and plywood sides, that takes up a lot of strain.  I think in the OP's case, with 10sq ft of stone (2.5cm/almost 1" thick) and a single thickness of what ever for the bottom, a whole lot more needs to be considered. Somebody recommended steel brackets.  I think that will only help. 

To original poster:  I assume drawers or doors are involved.  Especially drawers will add live weight to the temporary loading. You don't have to pay attention to all of my recommendations.  As a mason, i always had a tendency to over spec any carpentry i got involved in. ???

Tinker

 

[JimD]

A vanity of 3/4 plywood with an inset 3/4 plywood back will be very strong.  I would pocket screw and glue the back on and make sure it is a tight fit.  With those precautions, I don't think steel brackets are necessary.  At least the top screws shouldn't be drywall screws.  1/4 lags would be better but at least #12 screws.  drywall screws can be brittle and are pretty thin.  The load will rock the bottom into the studs as long as the top screws hold.  Friction with the wall holds cabinets up as long as the fasteners keep the cabinet tight to the wall.  It would probably be fine with a fairly wide 3/4 strip at the top and bottom. 

I like the idea of hidden legs, however.  Cantilevered loads tend to sag over time (anybody been to falling water (Frank Lloyd Wright).  That would be the biggest benefit of steel.  It essentially does not creep - sag.