Best Underlayment for Tile

LESLIE: Next we’re going to take a call from Alex in California who’s thinking of doing some tiling.

Alex, how can we help?

ALEX: We wanted to put tile on it and I wanted to know …

LESLIE: Tile where?

ALEX: All over the house.

LESLIE: OK, floor, wall, countertop?

ALEX: Floor.

LESLIE: OK.

ALEX: I’m sorry, floor; in the kitchen and …

LESLIE: No worries. You can put it in a lot of places.

ALEX: Yes. And I was wondering what kind of underlayment I should use if – would a linoleum work or do I need to get hardy backer stuff?

TOM: Well, linoleum is a lousy underlayment for tile.

LESLIE: Yeah, especially because it might react with your mastic or your adhesive and then might cause some sort of reaction that’s undesirable for the tile and might even cause it to crack or split.

TOM: Yeah, you could probably put down some new plywood on top of that first. You could probably put down some luan plywood if the floor is fairly stiff and then put thinset right on top of that and adhere the tile to it.

ALEX: Right onto the plywood?

TOM: Yes, on top of the plywood. Yeah, as long as you have a stiff floor. Now are these going to be wide tiles or are they going to be small tiles?

ALEX: Probably 18×18.

TOM: Oh, OK. Change advice. I think what you should do is put down a mud floor or you should put down DUROCK. You need something much thicker and much heavier if you’re going to put down an 18-inch-wide tile. You can have absolutely no flex in that floor whatsoever or your tile will crack.

ALEX: What’s the biggest tile I can use on plywood?

TOM: Well, that’s a fair question. I would tend to say not more than about a six- or an eight-inch tile. What do you think, Leslie? You know what I mean? Because the wider it gets the …

LESLIE: (overlapping voices) I think that’s probably a safe guess.

TOM: Yeah, the wider it gets …

LESLIE: The more area it’s covering. So as the floor below it flexes, the more chance you have an area of tile being put in a pressure situation where the tile might crack and not just the grout lines.

ALEX: Well, that pretty much answers my question because we’re trying to find a way around that hardy backer material because it’s so expensive.

TOM: Well, if you put the tile down and you don’t have a good surface, you’re not going to be pleased and then you’re really going to be looking at some expense. You’ll be calling us asking us how to take out those tiles and replace them. So I would recommend that you get a really strong floor to start with and then you’ll be happy with the job.

ALEX: OK, sounds good.

TOM: Alright.

LESLIE: And if you do get that hardy backer, make sure when you’re cutting it, make sure you use a mask because that stuff gets really dusty and really crumbly and you want to protect yourself.

ALEX: OK, now if I’m going to put the hardy backer down, how often – how far apart do I need to screw it down?

TOM: Well, if you’re going to use the smaller boards – if it’s a big sheet, like a 4×8 – then you put six screws across the middle and eight at the edge. But I would basically put screws about every, say, six to eight inches. You can’t put enough in that to make sure it’s really down all …

LESLIE: And the smaller sheets actually have notations on it so you know exactly where to put the screws.

TOM: And by the way, there are special screws that the hardy folks made for that. They have an extra wide head to give you more holding power.

LESLIE: And it even has a special bit, so it comes all with it.

TOM: Yeah, it kind of drills – right, it drills as you go through.

ALEX: Oh. Do I need to predrill?

TOM: No.

LESLIE: No, no.

TOM: These special screws have a drill tip kind of on the top of them.

ALEX: Oh, OK.

TOM: OK?

ALEX: Well, great. Thank you.

TOM: Alex, you’re very welcome. Thanks so much for calling us at 1-888-MONEY-PIT.