Supporting Solid Surface Vanity Tops
Here is what we've done in the past. 1/2" thick 22" x 22" solid surface triangle glued to a 1/2" x 3" solid surface back cleat against the wall. We did groove the back cleat 1/8" deep to accept the triangle. (Still with me?) We also drilled (3) holes in the back cleat for fastening to the wall. The holes were lined with a steel bushing so the screw couldn't be over-tightened.
At the top of the triangle we siliconed 2 x 2 fir blocking on both sides to anchor the support to the vanity sub-top. We have seen similar designs built by other companies. The ones we've built in the past seem to be holding up okay.
In the past I've found that the major manufacturers (Corian, Avonite, Gibraltor, etc.) frown on this design and recommend a steel support clad with solid surface. Not a bad idea but lots of labor and lots of material.
From contributor M:
I actually see this architectural drawing often and handle it in a similar fashion as you described. Since solid surface material is not structural, it is fitting that the manufacturers suggest cladding a structural support such as steel.
To answer your question “is it sturdy enough?,” I say yes, from a non-engineering point of view, but with the experience of many successful installations. As I see it, the primary support of the vanity top is the wall cleat along the back wall and often one or two sidewall cleats. This type of vanity top often uses aprons, which allow the use of a structural lumber or plywood cradle that will add more support. The triangle support is needed to support the front of the countertop and the span along its length. The force applied to these triangles by leaning, sitting, or standing on the countertop (yes, it does happen) will be projected back to the wall at the triangle's lowest point. This is a vulnerable point and unless it is a masonry wall, I strongly suggest interior wall blocking at this area. The use of a back cleat, as you employ, also helps spread the pressure along a larger surface area, preventing the ½” solid surface from penetrating a sheetrock wall. Solid surface has a very high tensile strength, especially along the ½” axis. I don’t see it bending and I especially don’t see it crumpling under that amount of pressure.
All that said, the manufacturer's desire to have a steel support clad with solid surface is a safer recommendation that puts them less at risk. If cost were not an issue, I would also prefer to do it this way, but when an architect specs it, our hand is mildly forced to accommodate. If we insist on the more elaborate design, you can bet that someone else will estimate the design as drawn and win the project on lower cost.
Contributor P suggested looking into the Rakks brackets, which is a very strong “L” bracket made of “T” shaped aluminum. I use them for support at reception counters where clear knee space is essential. They are extremely strong. Attaching a solid surface triangle to these brackets is a viable option. The only downside is that each bracket will add approximately $50-$60 per support. You will, however, save on the back cleat and bushings.
From contributor J:
I like structural materials for structural installations. How about a steel support with a paint-affect finish to mimic or contrast with the solid surface? There's a few granite speckle, and other stone-look, spray paints out there. I used one on a wall accent shelf to go near, but not exactly adjacent, to a masonry fireplace surround, and this was acceptable for the purpose.
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