it should work OK.

The big risk is the plywood absorbing the water from the grouting, an such, or just spills over time, and disintegrating. getting a decent bonding surface might be tough, but since it lays flat, you really don’t need all that good a bond anyway.

You could probably even seal the plywood with paint,(both sides, and especially the edges) or some such. Don’t use any oil based products, you will never get anything to stick to it.

now if you ever put them where they have to hang onto a wall or something, this will not work well.

The thin set you choose will also have a bearing on how well it works, buy the good stuff, don’t try to save pennies t Yes, flexibility is a problem, but if you build it real sturdy, this should not be a major problem. Build it poorly, nothing will work well.

I have put in a lot of tile countertops and backsplashes, to answer you questions about what excatly does the backerboard do? It keep water and mold issues under control and it also gives the screet something to stick to.

But I have done just as many countertops without backerboard as I have with it. Keep in mind that most floors do not have it, I normally put in right over the ply.

As long as your not pouring water on your countertops you should have any trouble. My bathroom floors have been tiled for 15 years over ply and I haven’t had any problems.

Cement backerboard, as you suggest, is for possible wet or damp applications such as behind shower walls. If you are using tiles for your counter, it may not be a bad idea to use backerboard there, since there is always the possibility of water leakage and resulting damage to ordinary plywood. After continued wet condition, plywood will delaminate, as well as encourage mold growth.

Use the backerboard.

The wood will expand and contract which will over time break the bond.

It may not be a big deal for the horizontal pieces but certainly the edge pieces and the trim around the sink will ultimately lose their grip and fall off.

The backerboard will also make the job have a more solid feel and will guarantee a longer lasting job.

A great resource for DIY tile is John Bridge’s Tile Your World at:

-http://www.Johnbridge.com/vbulletin/index.php

Doug

no,use a concrete composite that will fuse with all products to become one. I like Hardy backer and their instructions say to trowel thin set on counter top then set their product in it.

Then thin set again setting your product. Remember the ideal surface becomes one. In the old days,they nailed wire mesh,floated with motor and then set the tile,and believe me,when you tear out,it comes off in big pieces.

Also i reread and you have the answers correct as to the whys,don’t fudge.

plywood base if fine. . . . . . Make sure u use 3/4′ plywood. . . .

lic. Gen. Contractor

You could get away with not using it if you never planned on using your kitchen. The problem with plywood is it absorbs water and will begin to warp and bow. Eventually over time (can’t be sure how much time it would take could be a couple months or a couple of years) it will begin to warp and crack your grout etc. Backer board isn’t all that hard to work with and the HardiBacker stuff lasts forever. The only draw back is cost, a sheet of 3×5 1/2″ backer is around $10, and a sheet of 4×8 1/2″ plywood is around $10-11 but I believe it is worth it.

I would use the backerboard even though you probably don’t need to use it. I installed tile on my own countertops and used the backerboard because it stands up to moisture better, it adds strength, it’s not real expensive, and it doesn’t take long to install.

If you decide not to use the backerboard, just get the correct adhesive that sticks to plywood.

The thing that pissed me off was the cost of the green backerboard screws that they say you need to use.