I want to know if it‘s necessary to use any special underlayment, or any additional steps required to successfully lay ceramic tile over a wood plank floor. Thanks!
yes, you'll need a good underlayment. The reason is that the independent movement of the planks as weight loads the floor will cause torque between two planks, cracking the mortar and the grout and perhaps the tiles themselves. Its enough work to lay the tile that you definately don't want to do this without the underlayment. And I'm a guy that will lay tile over a well secured vinyl floor, so I'm not one of those there's only one right way to do it people. But in this case, you'll be unhappy with the results without a sanded plywood or cement board underlayment.
The right way to do it would be to remove the flooring and lay down some hardi backer or some cement board. However - if your wood floor is very very flat, and you consider the areas where that wood floor + the thickness of your tile meets up with other floor surfaces (e.g. carpeting or door door thresholds), it might be the easiest thing to do. Tile is a lot of fun. Don't skimp on making the right cuts and be sure to use spacers. Depending on what kind of tile you use - go with a smaller (1/4 or less) spacer so you have less cleanup with your grout. [Edit - I definitely agree with Crazy Man below. The waterproofing layer is a definite! Make sure you give it adequate time to dry, and then make sure you let the mud (adhesive) dry completely before grouting.] You might also consider something other than ceramic tiles, although there are some newer styles that are quite nice. A sealed porcelain tile or slate looks so nice.
Not directly. There are products out there like Tavy Thinskin that say you can do this by applying the Tavy membrane first and then setting tile, but I've seen installations like this fail far too often. Plank floors move too much for an installation like this. They will inevitably crack the tile or the grout. If this is a plank subfloor then you are best to put down 1/4 durock concrete board before tiling. If it's less than about an inch thick, you should lay a sheet of exterior grade plywood and apply a Ditra membrane before laying tile. Concrete board adds no structural value so you need to make sure your subfloor is stiff enough to avoid flexing and causing cracks. If this is an actual finished hardwood floor, it really needs to be ripped out and proper subfloor for tile installed like I laid it out in the last section. There is another easier option but it can get expensive. There is a product out now that is basically a porcelain tile mounted on a plastic grid. You click the grid (and tile) together just like installing a laminate floor and then grout the joints with a flexible urethane gout. This allows the whole installation to float without any actual connection to the floor below. This newer system is greatly improved over the older systems where a tile was mounted on an actual laminate backer board. We had the opportunity to bring the product into our store, but we passed on it due to cost. I'd have to sell it for $8-$10 / SF. The grout isn't cheap either.
Yes you can, if in good condition. If you have hardwood over planks, then it won't move anymore than having cement board over planks will. 1.5 inches of wood in excellent condition doesn't have enough bounce to bother tile. Cement board is overkill in most jobs. And not that great of one in the first place. On the flip side, If it is not an overkill, then it probably isn't enough. Any tile that goes over the seams of the cement board, is at high risk for cracking. Tile in the center of cement board is very safe. Mine you if the joists aren't strong enough, it won't matter what the sub floor is or how many layers of cement board you have, you can't do tile. If the floor moves a 1/16th of an inch when 300 pounds is set in one spot, then you have to reinforce or replace the joists, nothing else will fix it. This is how most plank floors fail. Old floors often are built with 2x6 lumber spanning 10 feet. And then there is the new technology: Tile membranes. Cement board harden the floor so it doesn't move. Tile membranes create a floating layer for the tile to sit on. As long as the floor doesn't move more than an 1/8 at the extreme, the tile won't crack on top of a tile membrane. Tile membranes cost about 1.00 to 1.80 US dollars a square foot. The basic membrane is 1/8 of an inch thick. Due to price most tile installers have rarely or never used it, so be prepared to see skeptics. common membrane brands: Schluter?-DITRA is the favorite of TV shows like Holmes on Homes and is sold at home depot among other places. Homelux is sold at Menards
