Sanity Check for Tiling Bathroom/Laundryroom [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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08-02-2004, 06:06 PM
Hi guys, incredible website. Learned a lot from reading a lot of historical threads.

Just wanted a sanity check on our plan for tiling a bathroom/laundryroom (just seperated by a pocket door which will be tiled)

We have some linoleum on 5/8" plywood which is nailed over joists that are 16" o.c..

The joists are about 12' long before they hit the support beams that cross orthogonal in the middle of the house.

Our plan is to:

1. Rip up the linoleum (don't want to, but after reading this website realise that this is necessary)

2. Lay down construction adhesive ontop of the 5/8" plywood and lay in another 5/8" plywood and nail in spiral nails 6" along the joists

3. Cover the plywood with tiling thinset and then tile 12"x12" filled and honed travertine, starting from the center.


a) Do we need a membrane (kerdi or otherwise) in the bathroom over the second 5/8" plywood? We're going to have a shower and I'm worried that moisture might an issue.

b) Are the joists sufficient support for the two layers of subfloor with travertine 12"x12" tiles? Seems fairly solid when I walk over it.

c) Can we just go plywood - tiling thinset or do we need something more?

Insights or references to relevant threads are very much appreciated!

Thanks again,


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08-02-2004, 06:11 PM
Hi Tim and welcome to the Forum. Glad to have you with us.

Tell us what size joists your have, i.e., 2X8, 2X10, etc.

08-02-2004, 06:14 PM
Sorry, I should have gotten that. They are 2"x9"

Just did a calculation: L / 558.

Not good enough for travertine. Is it possible that our travertine is rated at a better deflection? Should I bother asking the dealer?

08-02-2004, 07:21 PM
Is there a way to decrease the deflection by adding more joists?

How about using smaller tiles? Will that have a better deflection rating?

John Bridge
08-02-2004, 08:14 PM
Hi Tim, Welcome aboard. :)

The minimum deflection requirement for stone tiles is put out by the Marble Institute. We don't have any influence there. ;)

Yes, you can certainly improve the floor by adding material. Our chief engineer, Bob Campbell, will probably meander in here and 'splain all that.

One thing. When you add the second layer of plywood, do not nail into the joists, only into the subflooring.

One other thing. You will need either a membrane or cement backer board on top. :)

08-03-2004, 12:00 AM
Hmm, ok, may need to sister the joists. Yikes.

How about if we use smaller tiles? We are adding another 5/8" of plywood .. doesn't that decrease the deflection?

Kirk Downey
08-03-2004, 12:27 AM
I seem to remember advice here that one shouldn't nail into the joists - something about letting the wood joists expand and contract while allowing the plywood to do the same at a different rate and distance.

Am I wrong?

Kirk out

08-03-2004, 06:01 AM
Using smaller tiles doesn't change the deflection requirements. Adding plywood doesn't help the joists, but is good for the between the joist deflection in the plywood.

2x9 is an odd size. Is this an older house?

You don't nail the second plywood layer to the joists. The reason for this is to avoid transmitting joist movement to the tile setting surface. It is absolutly essential for a tile-on-plywood application, but is less important for backerboard or Ditra applications. It is a good habit to get into (not nailing into the joists, that is), if you plan on doing this for a living.

I agree with John, you need a membrane or backerboard. Stone floors are troublesome enough without adding the tile-on-plywood headaches.


08-03-2004, 02:41 PM
Actually it's 9.25 ala 2x10

It looks like I need to sister the joints. Not looking forward to it, as it's only about a 3' crawlspace, but c'est la vie.

Strangely enough, I'm having a hard time finding someone around here (Vancouver, BC) that actually understands deflection.

However, I can certainly see that it could be an issue and I certainly don't want to take the chance of having to re-install all that travertine..

08-03-2004, 04:29 PM
Also, I was thinking of using the Kerdi Schluter system for the shower. Is this a good idea?

I've watched the videos and they seem fairly straightforward. Just a couple of questions, though:

a) Is it Drywall - Thinset - Membrane - Thinset - Tile on the walls?

b) Are the videos fairly authoritative or are they missing anything?

Thanks again,


John Bridge
08-03-2004, 06:58 PM
Hi Tim, :)

Vancouver is and has been lumber country. I'll bet your 2x9s are actually 1-1/2 or 1-5/8 by about 9-1/4 to 9-38. They are 2x10s. :)

The Schluter Kerdi shower system is tops. Nearly every shower I build (about one a week) is done that way. Yes, you have the correct sequence of events, and yes, the video is authoritative. It is produced by the company that makes and backs the products.

Plus, the guy that sells Schluter products to many of our visitors is a transplanted, border jumping Canuck. His name is David Taylor. His company is Tile Experts. You'll find a link in our store. ;)