some basic questions

I work at HD and I have installed tile before in my own home and learned something new everytime. I feel knowledgeable but I only know what I have experienced. So I get stumped sometimes with odd questions from customers.

1. Can you install tile on a wood subfloor? Why/why not? I had a contractor tell me that he does it all the time and never had a probem. Contractors are the last people I would trust though.

2. Do you have the butter the back of the tile? Do you have to put thinset under the backer board?

3. What is the largest tile size you can use on a wall and do you have to do anything special when using a size larger than 12x12? I ask this because it seems like the heavier tiles might not stay in place?

4. Why would grout break up shortly after installing the floor?

5. When do you recommend Ditra over hardibacker?

Sorry if this this is a bit much but I don't want to fall into the HD sterotype that is always assumed. I want to actually know what I am talking about when dealing with my customers. I love this forum btw!

Jen,

You're right, those are very basic questions. It's a shame your employer throws their associates into the deep end without teaching you guys anything. I'm happy your are taking the initiative to improve your knowledge of how tiles are installed. Not many will do that, and many won't be working there long enough to make a big difference.

1. Technically you can install tile over a double layer plywood subfloor that meets certain standards. It can work in dry areas. Not a very good method though. I don't recommend it.

2. A. You do not have to butter the backs, but it's a good idea that could save a job if the thin set was not spread correctly or allowed to set too long.

B. YES, thin set under cement board for floors is critical. Guaranteed to fail if you skip this step.

3. The size is limited to the ability to manage the size of the tile in the given space. Larger tiles are more difficult to work with, just as small mosaics take more time too.

4. Grout cracks tells you there is movement somewhere.

5. Ditra over Hardie or any other CBU is not necessary, it's dumb & a waste of money. (Don't tell Mike Holmes though.)

"Sorry if this this is a bit much but I don't want to fall into the HD sterotype that is always assumed. I want to actually know what I am talking about when dealing with my customers. I love this forum btw!"

If there were more people like you working at the orange place, I would actually recommend going there.

Jaz

[Edited by JazMan on Wed, Mar 10,2010 at 9:22 pm EST]

[Edited by JazMan on Wed, Mar 10, 2010 at 9:22 pm EST]

Jen,

Good for you for posting here. Don't be a stranger.

1) No, you can't lay tile directly on a wood subfloor, ever. The subfloor is the first layer on the joists, on top of which the walls are placed. Anything else on that is an underlayment. Can tile be laid on a properly prepared double layer plywood floor? Yes, but as Jaz pointed out, it's very particular to the details for it to be longstanding. On a subfloor, though, no, but with an appropriate underlayment, (including cement board, or Ditra), yes.

2b) Here's why you need the thinset under the cement board: When you screw it down, there will be small voids between the plywood and the cement board, it's unavoidable. Cement board is not structural, it doesnt make the floor any stronger and without the thinset underneath to fill all those voids and provide an even supporting bed underneath, setting on a dry laid cbu is like setting on a 1/4" thick floor. It might take a while for the cbu panels to fatigue, but they will and then the tile will show it. Using beads of construction adhesive instead of thinset is even worse than dry laying it. You also need to tape the joints, but suggest that people do it as they set their tile so as to not create bumps of hardened thinset to ride over as they set their tile. Taping the panels makes the floor act like one large monolithic sheet of cement board over it.

3) Consider this, 20 sf of 6x6 vs. 20 sf of 12x12 vs 20 sf of 18x18. They each weigh the same so ultimately they each exhibit the same force per square inch or square foot on the wall. Do you need to do anything special with larger tiles? Yes. If it is a dry area, you could set the 6x6 with mastic but you'd want to set the 12x12 or the 18x18 with thinset. If it was a wet area, you'd treat them all the same and set them with thinset.

Thinset only comes in bags. Mastic comes in buckets. If it comes in a bucket, it's mastic, no matter what it says on the bucket.

5) I think you meant "when to suggest Ditra instead of Hardi," right?

Ditra beats cement boards hands down every time. Lower floor build up, allows the addition of plywood to stiffen the floor while still keeping the height build up low, lighter, cuts with a utility knife, no screwing it down, no joints to tape, I could go on and on. You only sell one unmodified thinset, Customblend, which is not the best one out there. Anyone who buys Ditra would be better off buying a better quality unmodified thinset somewhere else.

Other stuff

Premixed thinsets> These are just mastic with sand mixes into them. They need air to dry and placing a tile on them is like placing the lid on a bucket. It says in very vague terms on the bucket 2-3 days drying time for 8x8 or smaller and extended drying time for tiles larger than 8x8. That extended drying time could be weeks. Do whatever you can to sway people away from it.

Every place that sells Hardi has one of those little Hardi in a plastic water filled case things. It's pretty misleading in that people walk away confusing "unaffected by water" with "waterproof." Hardi, Durock, Wonder, etc do not waterproof the walls where they are installed. You need to install a moisture barrier behind them, either 4 mil plastic or 15 lb roofing felt if it's a wet area. The other option is to paint the walls with Redgard instead. Either way, you don't waterproof just by installing a cbu.

Marble and Granite Mortar> This is just Custom's name for thier medium bed mortar. Thinsets can only be build up to 3/8" but M_G_M can be built up to 3/4". That comes in to play with large tile or stone of varying thickness like slate. You don't need to use this to set you basic 12x12 granite or marble or travertine. A basic white thinset such as versabond will do.

WOW! This is great info. I have definately learned something new. I am going to pass this on to everyone else that I work with over here and hopefully they will do the right thing. After all that is what we are suppose to do over here at the Orange Box.

I feel absolutly horrible about not knowing these details already because I walk at least one customer a week through their tiling project.

I totally bleed orange and I want to do a better job at insuring that a customer has success. Everyonce in awile I get odd questions that I don't know the answer to so I appreciate your responses.