Floating vanity question

[Guilliaume woodworks]

I have client that wants a floating vanity. 30"wide 20"deep . This usually isn't a problem, I would use solid 3/4" back properly anchored to cabinet  walls,top,and bottom. But.....they are putting a 5" thick concrete countertop.I asked client to provide me with the weight of top,she's gonna call tomorrow,however I'm sure it's really heavy. And she's absolutely against any leg for support "cab has to float" she said firmly. Other than that its a basic euro style box with a single slab door & slab end panels. Painted with white high gloss lacquer .    Any ideas for supporting this cab to accommodate countertop load? I'm thinking really hd shelf type bracket that has 45* brace?  Any input would be great.  Oh yeah, btw I am using 3/4" birch ply for cab box & back.

 

[ajones]

Hi I think you have to fabricate a steel gallows type bracket and hang it all on that..

 

[jonny round boy]

The density of concrete varies, but averages (according to google) at 150 lbs/cubic foot.

Your top at 30 x 20 x 5" comes out at 1.736 cubic feet, so the weight will be in the region of 260 lbs, plus the weight of the sink.

What is the wall made of? Unless it's a really solid masonry wall, you might have problems getting a secure fixing for any kind of bracket.

 

[ajones]

The density of concrete varies, but averages (according to google) at 150 lbs/cubic foot.

Your top at 30 x 20 x 5" comes out at 1.736 cubic feet, so the weight will be in the region of 260 lbs, plus the weight of the sink.

What is the wall made of? Unless it's a really solid masonry wall, you might have problems getting a secure fixing for any kind of bracket.

J did you allow for the hole where the sink is fitted in the top? [poke] [big grin]

 

[jonny round boy]

The density of concrete varies, but averages (according to google) at 150 lbs/cubic foot.

Your top at 30 x 20 x 5" comes out at 1.736 cubic feet, so the weight will be in the region of 260 lbs, plus the weight of the sink.

What is the wall made of? Unless it's a really solid masonry wall, you might have problems getting a secure fixing for any kind of bracket.

J did you allow the the hole where the sink is fitted in the top? [poke] [big grin]

Yes, that's the extra 0.41 lb I subtracted when rounding down. Should cover the tap hole, too.  [tongue] [big grin]

 

[bigjonh]

I would recommend Rakks product line of support brackets. We use them a lot for floating shower benches. I believe they have a range of countertop supports as well. They are very strong and finished well. If it was me, I would open the wall, get some solid blocking in there, mount my brackets and counter top as a separate unit. Then hang my cabinet underneath with some modification to go around the brackets. That way the countertop doesn't depend on the cabinet at all for support.

 

[Jonhilgen]

We install metal L-brackets during framing stage and install extra blocking between studs.  That way the vanity has something strong, yet is barely visible (unless you get down on your knees to look).  I've installed many vanities this way and have yet to have any issues.

 

[GPowers]

Concrete counter might have a foam or hollow core and just 5" thick edge.

 

[Guilliaume woodworks]

Great input guys!    She found out the weight is 145lbs, and it is solid throughout . I think it must be some kind of fiber reinforced or light weight concrete judging by Johnny r. Boys calculations(thank you btw). Anyway 145lbs is still heavier than I'm comfortable with installing cab w/out some kinda metal braces. The wall it's hanging from is traditional 2x framing with 1/2" dry wall, and I checked stud layout and got lucky. I'm able to anchor to three studs, and we are going to open up wall to plumb for wall/backsplash mounted faucet. So I could install brackets at that time directly to framing. Also I'll check out big join recommendation of rakks product. Thanks and appreciate everybody advice! Fog rocks!

 

[Tinker]

Great input guys!    She found out the weight is 145lbs, and it is solid throughout . I think it must be some kind of fiber reinforced or light weight concrete judging by Johnny r. Boys calculations(thank you btw). Anyway 145lbs is still heavier than I'm comfortable with installing cab w/out some kinda metal braces. The wall it's hanging from is traditional 2x framing with 1/2" dry wall, and I checked stud layout and got lucky. I'm able to anchor to three studs, and we are going to open up wall to plumb for wall/backsplash mounted faucet. So I could install brackets at that time directly to framing. Also I'll check out big join recommendation of rakks product. Thanks and appreciate everybody advice! Fog rocks!

I would still put in some solid blocking between studs.  That is a lot of weight to hang all from one level.  Eventually, those studs will start to bow towards the weight.  In a case like you are describing, i would tend to over build than to try to be exact on my estimate of support. 

Don't forget, the cabinet will have some weight.  Sooner or later, somebody will lean on the counter and there go your close calculations.
Tinker

 

[leakyroof]

Great input guys!    She found out the weight is 145lbs, and it is solid throughout . I think it must be some kind of fiber reinforced or light weight concrete judging by Johnny r. Boys calculations(thank you btw). Anyway 145lbs is still heavier than I'm comfortable with installing cab w/out some kinda metal braces. The wall it's hanging from is traditional 2x framing with 1/2" dry wall, and I checked stud layout and got lucky. I'm able to anchor to three studs, and we are going to open up wall to plumb for wall/backsplash mounted faucet. So I could install brackets at that time directly to framing. Also I'll check out big join recommendation of rakks product. Thanks and appreciate everybody advice! Fog rocks!

I would still put in some solid blocking between studs.  That is a lot of weight to hang all from one level.  Eventually, those studs will start to bow towards the weight.  In a case like you are describing, i would tend to over build than to try to be exact on my estimate of support. 

Don't forget, the cabinet will have some weight.  Sooner or later, somebody will lean on the counter and there go your close calculations.
Tinker

  Totally agree, OR, someone will sit on it[kids and drunk adults do the strangest things..... [embarassed]]

 

[Tinker]

Great input guys!    She found out the weight is 145lbs, and it is solid throughout . I think it must be some kind of fiber reinforced or light weight concrete judging by Johnny r. Boys calculations(thank you btw). Anyway 145lbs is still heavier than I'm comfortable with installing cab w/out some kinda metal braces. The wall it's hanging from is traditional 2x framing with 1/2" dry wall, and I checked stud layout and got lucky. I'm able to anchor to three studs, and we are going to open up wall to plumb for wall/backsplash mounted faucet. So I could install brackets at that time directly to framing. Also I'll check out big join recommendation of rakks product. Thanks and appreciate everybody advice! Fog rocks!

I would still put in some solid blocking between studs.  That is a lot of weight to hang all from one level.  Eventually, those studs will start to bow towards the weight.  In a case like you are describing, i would tend to over build than to try to be exact on my estimate of support. 

Don't forget, the cabinet will have some weight.  Sooner or later, somebody will lean on the counter and there go your close calculations.
Tinker

  Totally agree, OR, someone will sit on it[kids and drunk adults do the strangest things..... [embarassed]]

That's exactly what i had in mind.  [scared]

 

[Tinker]

After I posted about solid blocking, as i was driving to work, I thought more about what i might have done.
I think i would try to distribute the load over a longer section of the studding than just solid blocking behind the counter.

A horizontal header a couple of feet below and another above the counter.
Then wide diagonal blocking from corner to corner of each of the header. 
Tinker

 

[Guilliaume woodworks]

I've given this a lot of thought and asked all my woodworking buddies. Probably the the best cabinet maker I know,whom I highly respect, gave me some interesting advice. He said that getting the cabinet anchored to the wall properly isn't the biggest concern. The problem is the cab walls separating from the cab back,because all the shear weight is almost entirely on the walls. Which made sense. I'm using 3/4 pre-fin birch ply for entire case including back. To reinforce joint between walls and back I'm doing shallow rabbet on walls,top&bottom to receive back.mainly to remove pre- fin for better glue bonding. Then use dominos and screws all around four sides. My theory is for cabinet to sag,the dominos would have to rip through back.Also I'm debating installing a piece of L metal  anchored to studs as a cleat for cab to sit on.hope I explained this right. Anyway would like your feedback(+ or -). 

 

[Tinker]

My feeling is that, since the whole works are floating, and the stone top is the heaviest unit, the top should be self supporting.
The cabinet below should be anchored strongly enough to support everything.
The wall behind must be solid enough to support all with no flex or even gradual movement over time.
If the wall is not strong enough, the entire project will fail.

I have not constructed cabinetry with such characteristics as you project.  I have build concrete forms and solved scaffolding problems that were close to what you have described. The architects gave me the masonry problems. It was up to me to figure how the construct. My inclination has always been to be safe on the over construction side.  Under construction and I might not have been a part of this discussion.
Tinker