Bathroom Remodel etc etc [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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02-24-2008, 03:03 PM
Hello everyone,

I am starting a remodel of the Master Bath and thought I could simply lurk on this site and get the information I would need. But no, as soon as I took the old tile off of the bathroom counter a mortar bed was exposed. The mortar bed is 1 inch thick on top of 3/4 inch plywood. I am not smart enough to seach for an existing thread (the searches come up empty).

1. Is this a common install, the house is about 8 years old?
2. Does this mortar bed need to be removed or simply cleaned up and leveled?
3. What would you level it with?
4. I will be putting in Travertine 12 X 12 what type of mortar would you recommend they be set in?

I did buy a profile blade and have experimented on the travertine and it works great, if all you need is a 3/8 inch radius bull nose. This will be the terminating edges that are exposed to the front.

I would also like to keep this thread alive as I will be remodeling the rest of the bathrooma and will no doubt need help.

I will install a kerdi drain for the shower and a drop in tub next to it (the same lay out that exist now. I will tile the shower, tub base and walls with Travertine. I will replace all of the drywall with backer board. Then tile the floor in travertine.

1. Does any one have an opinion about the ceilings - Tile or no tile?

Here is a picture of what is now.

Thanks in advance for any assistance.


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John Bridge
02-24-2008, 03:58 PM
Hi Phil, Welcome aboard. :)

The mud bed looks pretty good. If it's not all cracked up you can re-use it.

Or you can remove it and double up the plywood for the travertine install.

Do you know that travertine can be damaged by acids found in the kitchen, i.e., catsup, lemmon/lime/orange juice, vinegar, and other items? I hope your travertine is not polished. Better for it to be honed. :)

02-24-2008, 04:13 PM

1. This is a very common (I would sat the best) install.

2. If you think the integrity of the mortar bed is in tact then I don't seeany reason not to use it as the substrate for the new tile as long as it will accomodate your new sink. For levelitys sake, I think it would take no extra time to float a new countertop using the existing plywood as long as the cut out will work for the new sink. You can use a variety of methods to grind of the thin-set if that is the route you choose. I think I would use a carbide disc othe grinder to take down the thinset. Go about this lightly and as soon as you see the grey of the mortar bed through the white of the thin-set stop. If it was floated correctly the only leveling required should be from the removal of the thin-set.

3. I think if you skim it with thin-set, let it set up a bit, then re-screed it using the cap-metal as your guides will give you the desired levelity (this is assuming that it was floated level in the first place).

4. There are a ton of good thin-sets to use. I would use a medium bed (it has a bit more sand in it to keep the stone from sinking while it sets) with a 1/2"x1/2" notch to make give you a bit of room to make it dead flat. Make sure that whatever you use is modified.

02-24-2008, 09:15 PM
I had to read multiple times to finally see the light. I will buy a 4" diamond cup grinder and level the old thinset. After that I will put a thin coat of thinset to fill in and do very little leveling.



Will post pictures after the grinding and thinset.

02-24-2008, 09:31 PM
Back off the diamond cup wheel. Use a carbide sanding disc. The ones you would use for sanding a slab. The diamond cup wheel is going to really dig.

02-26-2008, 10:16 PM
Here are a few pictures after grinding off the old thinset and covering it with a thin layer of modified thinset

Thanks again for the advice



03-05-2008, 08:19 PM
I am only posting this to show progress. As far as the countertops go I first used too wet and then too dry thin set. I am learning while able to stand and not on my knees. Soon will be the bath, shower and the floors though. I pray I am better by then. I did use the profile blade to bullnose the front and then 180 grit sand paper on an orbital sander. I learned pretty quick that the front facia pieces needed tape to hold them in place. Other than that no questions yet just slow progress. My real job keeps me kind of busy.


03-05-2008, 08:30 PM
Looks like your doing a fine job Phil.

Keep us posted.

03-10-2008, 09:04 PM
The picture is a generated layout of my bathroom. I have removed all of the existing tub and walls.

The tile will go up 80 inches on a 96 inch wall. I will install 1/2" board (concrete, hardi or something like it) to support the wall tile. If this is wrong please advise.

The existing sub floor is 3/4" strand. The home is relatively new and all this is in good shape. As shown on the diagram the sub floor is suported by manufactured I beams which are 12" high. They are set 16" apart with a max length of 12' as they go under the counter. I can install any heigth in the shower tub area for floor stregthening but am limited by wood flooring on the closet and bedroom side in the walk through area. There was tile in the toilet area with, what looked like, 3/8" hardi board.

My question is will 3/8" hardi board (or any other recomended product) strengthen the sub floor enough?

Should I have thicker sub floor in the shower and tub areas?

Thanks in advance for any help.


03-10-2008, 09:13 PM
Hardi or cement boards Do Not strengthen the sub floor.

you need to add more ply to it and them finish it with 1/4" tile backer board if your putting down tile on the main floor.

please check your floor Deflection ( to see if your floor passes for Ceramic
or Marble that you are putting down.

03-10-2008, 09:18 PM

The deflection tool does not work with engineered I beams (at least that is what it says) I put in the figures as if it was douglas fir and it comes up real high L1020 but once again it says don't use this tool if you use engineered I beams.



03-10-2008, 09:23 PM
the Mod's cx or bbcamp can answer your Engineered I beams questions for you.

one will be along son to possibly help you more.

03-10-2008, 10:08 PM
Welcome, Phil. :)

It would be pretty unusual to have a design with 12" engineered joists for a 12' span. You understand we're talking about the longest unsupported span of the joists, without regard to anything that's in the rooms above, yes?

The only way to determine the design deflection of those joists is to determine the brand and type by looking at the stamped information on one of them. Then get an accurate height and unsupported span measurement and either call the manufacturer or look at their website.

For a natural stone installation the website will do no good most of the time because the chart will go only to L/480 deflection criteria and you need L/720. There is frequently a phone number stamped on the members, too.

Once that's determined, and if adequate, you must still add another layer of subflooring to what you have. I would add no less than half-inch to what you have. It's never wise to tile over an inadequate subfloor just to try to match the height of an adjacent floor covering. You can always transition to what you have.

My opinion; worth price charged.

03-11-2008, 07:34 PM

Took a while for me to digest what you said. The span is really about 13 1/2 feet for the joist. It is a GPI 20 (georgia pacific) product. They are 11 7/8" high on 16" centers. They do indicate that with my install dimensions the GPI 20 will achieve minimum L480 at 18 foot 8 inches. You need software called "FASTbeam" to determine what the L reading is with parameters different than the ones on the chart or call them. It can only go up with a shorter span. I will call them tomorrow.



03-12-2008, 09:20 AM
Georgia Pacific engineers have given me a L 1260 for my joist and subfloor. Based on 40 PSF live load and 10 PSF dead load. I exceed the minimum for travertine. I now have to put in the 1/2 " plywood and 1/4" hardi board on top of my existing 3/4" strand sub floor. This will create about a 1/2 inch transition difference between existing wood flooring and the tile.

1. Is a 1/2" height difference a big deal or not (can it be taken care of in any way)?

2. Do I need more sub flooring than what I have indicated?


03-12-2008, 12:08 PM
1. It's pretty simple to make a wooden reducer to transition from tile to wood flooring.

2. No.

My opinion; worth price charged.