[Ron6519]

I would like to install a floating vanity for my bathroom. The counters will be solid surface, quarts or granite. Will a floating vanity (assuming installed correctly) provide enough support for the weight of the counters? What kind of extra structural support might I need?

The support would depend on the weight involved. The weight involved would depend on the size of the vanity and how it was constructed.
Do you have any plans for this unit?

 

[Ron6519]

sorry, forgot dimensions.

Its going to be 48"W x 18"D x ~16"H . It will be installed in a corner, so support on two sides is possible. The counter is about 3/4" thick.

Does it matter if the supports are visable? If not, you can weld up "L" brackets and bolt them to the framing and sit the vanity on top.
If you don't want to see them, you'll integrate the brackets into the vanity structure.

 

[Ron6519]

yes, i would like to keep it hidden. I was thinking of using large L brackets, or integrated shelf brackets. Shelf brackets (triangle vs simple L) would be much stronger, but are harder to hide. I have yet to find available brackets in the correct size, 18". I would like to be able to support the entire depth. Largest bracket I've found is 12". Welding my own is an option, but my access to a welder is limited.

My second choice would be a french cleat. How well would a french cleat work in this situation?

I would have the brackets fabricated by a welder myself unless your certified.
If using a french cleat it would need to be the Charles De Gaulle of french cleats.