Designing Kitchens and Bathrooms - Kitchen counter top thickness?

I want to know what materials I should construct a new kitchen counter top that will have porcelain tiles as the surface?

I was thinking 3/4 inch exterior ply, and then 1/4" cement board. Can I find edge trim for the one inch plus top, or will I have to cut from the tile pieces? If I used materials that offer bull nose trim would the bull nose work with the one inch thicknes?

I plan on screwing the cement board to the ply, and should I also use THIN SET?

Thank You,


Dale

Most tops are actually 3/4" thick, but the edges are built up to 1 1/2" Plywood not recommended, breathes too much, use industrial grade particle board, what goes over that depends on what your finish layer will be. For tile, stone, etc., but not including granite slab(it needs no underlayment) you should use a backer board, glued/screwed. If Formica, it can go directly on the particle board with contact cement.

Just Bill,

When you say GLUED cememt board do you mean with THIN SET? Partical board DOESN'T like screws, and since I will be adding the 1/4" cememt board do you STILL feel plywood should NOT be used?

Thank You for your input, FOR SURE.



Dale

I wouldn't use particle board under tile. On my house I used 5/8 plywood, 1/4" cement board [w/thinset] and tile. I used a hardwood banding instead of tile edging.

The only issues I've had with my countertop is the white grout :eek: I should have used something darker ;)

Mark - I used 3/4" particle board under tile for my kitchen countertop. I didn't use cement board just the particle board. I painted around the sink cutout before I tiled. When I demo'd the kitchen 15 tears later the particle board was just like when I installed it. I also used a lighter contrasting grout which I regretted. I cut it all out and regrouted.

Screwing particle board is no big deal. Just predrill and countersink.

I think 3/4" plywood would also make a suitable substrate. I don't understand "plywood breathing". I thought it was dead. :).

Wood expands/contracts(breathes) with different weather/humidity conditions, somes woods more than others. Plywood warps if it gets damp. Particleboard is much more dimensionally stable than plywood. But really swells if it gets wet, which is a good reason for the backer board and sealing around the sink area. I do that too, but did not mention it.

Particle board is specifically excluded as an underlayment anywhere under ceramic. How thick to go with your substrate will depend upon what you use for an edge treatment. Locally, I can get oak counter trim that has a 1.25" leg to cover the substrate, which really only allows 5/8" plywood and 1/4" cement board or 5/8" followed by 3/8" and then Ditra. Either combo is 1 1/8" thick but when long cabinet spans are involved, the second is the significantly stronger option.

Counter trim tile is tile that is bent at about a 75 degree angle to give a drip edge to contain spills. Once again, you need to consider what thickness will be covered by the leg over the substrate.

My most recent countertop, I used Schluter Step Rondec CT. It has a 1.5" leg to cover the substrate and some long cabinet spans, up to 36" by 24, so I laid the plywood overtop, traced the shape of the openning from below. Then I used the waste from the countertop ply to reinforce the plywood from below. Your 4'x8' piece will be cut to more like 25" x8' so the remaining 23" x 8' piece can't be used for much else. The strength axis of the ply is along the long edge so it needs to be cut that way. So this countertop had essentially 1.5" of plywood, though only 3/4" of it was exposed substrate. Then I thinsetted and screwed 1/2" hardi over the top giving me 1.25 " in height.

The rondec CT has a channel to accept about a 15/16" piece of tile along the front edge and because the edging is metal, there won't be any problems with edge chipping. Since this was a glazed pocelain with a beige bisque, grinding a bull nose was not an option, but you could do that with a solid body unglazed porcelain.
http://i2.photobucket.com/albums/y3/bljack/edgetrim.jpg