1. Plywood expands and contracts more than concrete backer board. If water finds its way onto and into your plywood, the plywood will expand. The expansion will create a soft spot under the tile that will give in when someone steps on it. This will almost always cause cracks in your grout and in some cases will pop tiles up completely.
2. Plywood flooring is organic and can host mold, and rot out and weaken over time.
3. You need a table saw or circular saw to cut plywood. Backer board will allow you to lay all the tile you need with just a utility knife.
4. Screws…you will need more of them and they will need to be waterproof. As pointed out in the first reason, plywood expands and contracts and needs lots and lots of screws to anchor it securely to the floor. Depending on the thickness of the plywood, you will need to use upwards of 25 screws per square foot to make sure expansion is minimized. In addition, since plywood holds moisture better than backer board, your screws will rust out over time if your sub floor stays damp. Rusted screws will eventually give way to the expanding and contracting of the plywood and your tile and grout will fail with time.
5. Standard mortar doesn’t bond well with plywood. You will need to cough up more cash and buy the “white” latex based mortar or purchase an expensive additive that mixes in with the regular mortar. Even with these options, the bond isn’t nearly as strong as with regular mortar and backer board.
If you decide not to heed this advice and pursue a plywood base for your tile floor at least do the following:
• Buy the thickest plywood that you can, ¾ inch works well (this assumes you have at least a ¾ inch subfloor). Total thickness of floor under tile should be about 1.5 inches. Trust me, the thicker the better…or your grout and tiles will be more likely to crack.
• Get lots of outdoor deck screws
• Spend more and get the premixed white latex mortar
• Thoroughly clean and sweep the plywood prior to laying the mortar/tile
• Leave at least 1/8 inch gaps around each piece of plywood
• Most importantly…keep your house and floor dry!
Good luck and happy tiling!
Tags: tile floors