DIY Tiler needs help

Hi--

Stumbled across this forum looking for help and need some feedback.

I have an older house (1920). In the 1/2 bath on the 1st floor (abt 5'x6') I'd like to remove the parquet floor and install tile (I have a little boy and a husband, if ya know what I mean).

The existing parquet seems to have a layer of plywood underneath. If I understand correctly, I should remove both the parquet and the plyood, and then install the exterior grade plywood on top of that before adding a water barrier and then tiling. I THINK I understand the instructions posted in the article on this site "Installing Tile Over Vinyl, Wood, & Concrete."

What I don't know is this: how do I know if the floor is strong enough to handle the weight of the tiles plus the plywood substrate? I have not picked the tile yet but want to use the 1"x1" tiles that come on sheets and would be more period-appropriate for the house. I can look at the joists from the basement but don't know what the requirements are that I should be looking for.

Thanks for your feedback. I'm hoping to do this project myself. But I don't want to end up costing myself and arm and a leg 'cause I screwed up something big!

Catherine

You determine the strength of the structure by measuring the size of the joists, the length they span between supporting beams or walls and how far apart they are spaced. When you have that info, you input those values on a span table. The AWC has a good one, but you can just post that info here and we'll let you know. I'm doubting you will have a problem but better to be certain.

Yes, remove the parquet, and who knows what else is under there. 90 years could be many layers until you get to the actual subfloor, which in your case will be planking. From there you would install 1/2" bc plywood, then 1/4" cement board, then your tile. 1/2" plywood gets installed with the grain direction crossing the joist, 1/4" perimeter gap, 1/8" gap between panels, fasten every 6" around and every 8" within, and only to the planking, not the joists. Cement boards have the instructions on them, thinset under, screw with cbu screws every 8", tape the joists as you tile, also maintain the 1/4" perimeter gap.

'd like to remove the parquet floor and install tile (I have a little boy and a husband, if ya know what I mean)

Umm, no, I don't know what you mean. Hey Bud and Jaz, either of you feeling kinda like the Geico cavemen after that comment? Hey Cathrine, how do we know it's really not YOU with the problem? Nah, my daughter shares a bathroom with her 3 brothers. I'll leave it at that.

And therein lies the reason you were once considered for bear-bait!

Yeah, I left that fodder in for you all on purpose. I figured a female was probably in the minority here.

Anyway, I am confused about the substrate & cement board.

1. What is "bc" plywood?
2. In that article I referred to, 1 1/8" think plywood was mentioned, much thicker (seemingly rediculously so IMO) than that 1/2" you mentioned.?
3. Is the cement board the waterproof layer, or is that an additional layer?

Looks like I have parquet then plywood then subfloor. I will measure joists and post that tomorrow.

Thanks guys.

Catherine

Hi Catherine,

1. B/C is a grade of plywood. You need C/C or better, so B/C is fine. Sometimes you can't find it graded that way, so also look for "underlayment".

2. 1 1/8" total thickness is when you install tile direct over plywood. We don't recommend doing that though. But your case is different anyway cuz you have an older home with a subfloor made of planks. You need min. 1/2" ply over the planks and continue as per Bljack's directions above.

3. Cement board is not waterproof nor is a waterproof floor necessary. Is there any special reason you may want the floor to be waterproof like a shower floor?

How thick is that plywood under the parquet?

Jaz