Hall bath

[Thisstinks]

Hello,

I was a professional tradesman 25 years ago. I am now 56, my body was beat up then. Needless to say I have not tiled a bath in a long time. Things have changed; the last time I tiled a tub I used stucco rock in the stall then 15 pound felt, then chicken wire, then three coats of mortar before the tile. As I research I find that is rarely done anymore and Concrete Backer Units are used instead, which seems a blessings, but I am not so sure. Yet, that would make it a lot easer.

My project: The hall bath has (make that had) a leaky sink and shower for a few years. It does not have a window either. My project for it is to replace the sink and vanity, the fiberglass tub-shower with a cast iron tub using tiles walls. Add a skylight, replace the floor. Currently, I removed all the sheetrock the sink and vanity. Framed the rafters and joists for the skylight it is ready for headers and ready for me to cut through the roof. The structural part of the project I don’t have a problem with. Although, I welcome input.

My concern is the Cherry Blossom marble I purchased with the intent to use it in the shower stall and on the bathroom floor. What I am reading suggests rather strongly that I shouldn’t user it. But, I have it so what else am I going to do with it. What mortar do I use? What grout do I use? I’ve ordered Stone Techs Bullet proof for a sealant is there more that I need?

With our Lord's blessings take care,

Doug

[GraniteGirl]

Hi Doug

Welcome to the JB forums!

The marble should be OK if your bathroom does not see a load of traffic (you said it is a hall bath, right?) The trouble you will have with it will be etching and scratching, and the majority of that will happen through careless use and inappropriate cleaning methods.

You can prevent those things by implementing some simple rules like:

1. Pee IN the toilet - not around it
2. Wipe up spills of liquid soap, cosmetics and lotions immediately
3. Squeegee the shower after use
4. Liquid bath soaps are better than bar soaps, since they seem not to leave as much soap scum and thus clean up easier
5. Make a habit of using stone specific, pH neutral cleaners for the shower and floors.

I would suggest a narrow grout joint (less than 1/8") with non-sanded grout.

The sealer you have is great, but it will not prevent any wear and tear or etching in your stone. Also - it is important when you seal the stone that you work in a small area at a time and that you TOTALLY remove all excessive sealer or you will have a streak, smudge appearance to your tile that could be very, very tricky to remove.

Oh - and post PICHERS! We love pichers

[Rd Tile]

What do you have for a subfloor, slab or joist system, need to know if the floor will support stone without an issue, how many sq. ft.?

[Thisstinks]

Hi GranitGirl,

Some good advice, but squeegee? I thought a towel. What non-sanded grout?

The Stone Tech says 2 coats, but when I finished furniture I found 3 better. Would that be the case here?

I will post pictures take care,

Doug

[Thisstinks]

Hi RD Tile,

It is 3/4 inch plywood over 2x10s on 16 inch centers with a 12 foot span. The bath is small roughly a 7’ by 9’ area that includes the bath stall, linen closet, vanity and toilet. If I tile under the vanity the floor coverage in 35 sq feet 30 if I don’t. I plan on laying down Wonderboard over emulsion tar and felt.

Take care,

Doug

[Rd Tile]

Your joist system doesn't meet specs for stone, you also would need 2 layers of plywood and no tar paper needed under cementboards, you use thinset and screws.

[Thisstinks]

Hi Tile man,

They didn’t have a problem with it over at county. Why do you say it doesn’t meet spec? Can’t be the weight 30-35 sq feet of 3/8 marble and wonderboard isn’t that heavy, flex?

Take care,

Doug

[cx]

Welcome, Doug.

I've moved you to the Advice forum because this is project thread and we like for all our visitors to have access to the information that will be exchanged.

Nothing at all to do with being a pro or not a pro, just the nature of the thread.

In the Hangout, where you and all are welcome, we like to get into the more technical discussions/arguments about the trade. Not that we really argue, mind you, but...............

What Richie said about your floor.

The requirement for the joist structure for a natural stone installation is a deflection of no more than L/720.

The MIA requirement for subflooring for a natural stone installation is a double layer of plywood or OSB regardless the joist spacing.

[Thisstinks]

OK, thank you CX. So, it is flex then. This project just keeps getting more and more expensive like so many of mine do.

Take care,

Doug

[Thisstinks]

So, the question remains with me if adding the extra 3/4” plywood would help. Can I glue it with the older plywood then screw it to the joists with 3 inch galvanized screws? Do I really have to double up 5 2x10 joists? Sigh, I expect I do. This house is a money pit, then again so was my last.

Now, back to my question about mortar and grout. Suggestions please. I’ve read as for the grout that non-sanded won’t fill a 1/16” gap between the tiles, but sanded will. Yet sanded will scratch the marble. I don’t suppose there is a caulking gun solution to filling the gap? Something about smooching all that grout over the top of the marble bothers me.

One article I read told me that using a quick set mortar was best for my marble, but another I read said that particular product is discontinued. I know to use white mortar and to back butter, but what product?

Argh! I should stick to what I know.

With our Lord’s blessings take care,
Doug

[bbcamp]

Adding the extra 3/4” plywood would help, but you could get by with as little as 1/2". Do not glue it with the older plywood, just screw it into the plywood, not the joists with 1-1/2 to 1-3/4 inch galvanized deck screws. After that, you need some sort of underlayment, either backerboard or a membrane. Follow their installation instructions to the letter.

You really do have to double up 5 2x10 joists. At best, your deflection rating is L/540-something, you need L/720.

Non-sanded grout will fill a 1/16” gap between the tiles just fine.

Using a quick set mortar is the best way to get a DIYer into trouble. Use a regular modified thinset or medium set mortar, depending on the size of the tiles and flatness of the floor. Versabond (thinset) or Granite and Marble mortar (medium set) are available at HD.

[Thisstinks]

Hi Bob,

You are not very encouraging. I was hoping for a “You’ll be OK.” However, after pounding on the floor today I know you, CX and Tile Man Richie are right. (I am about ready to buy linoleum.) Since I need to add 5-6 2x10s to the subfloor Which is better doubling up the existing 2x10s or centering them for an 8” on center structure rather then 16”? It seems to me that the 8” centers would stiffen up the plywood subfloor considerably negating the need for the extra plywood. My only objection to the extra plywood layer is the height difference with the carpeted hall. I would answer that question myself, but John’s calculator doesn’t go to 8” (JOHN!) and I am too tired to go hunt the formula down. The doubled 2x10s gives me a L/1115.

I really want to thank all of you that have given your precious time to respond to my questions. May our Lord’s blessings be with you,

Doug

[cx]

Originally Posted by Doug

I’ve read as for the grout that non-sanded won’t fill a 1/16” gap between the tiles, but sanded will. Yet sanded will scratch the marble.

Un-sanded grout is suitable for joints that size, Doug. Some folks don't like un-sanded on floors at all, but it will work and is the grout of choice when the tile surface is sensitive to scratching, 'specially if re-finishing the stone surface is ever to be an option.

Adding your new joists midway between the existing is a good idea if you can support the new joists adequately at both ends.

That does cut down on the between-joist deflection, which is the most critical area for deflection issues. But the MIA still requires a double-layer plywood subfloor for all natural stone installations regardless the joist spacing. I suggest you do the extra joist in whatever way is most convenient to your individual situation.

My opinion; worth price charged.

[Thisstinks]

Hi CX,

You give me good advice, you would not be a moderator of this list without knowing your trade. So, I will not doubt what you tell me. I do question the MIA. With 8 inch centers the widest unsupported gap between joists is 6.5 inches. Only the rare occasion of a tile straddling a single joist every 12x12 tile will have 2 joists under it. That said I can see that rare occasion being a problem. So, as I need to remove 2 panels of T111 siding and cut through a rim joist to add joists to support this floor why not add 2 joists per bay having an effective 5.33 inch centers. No tile will ever have less then 2 joists under it, many will have 3. I will go that far to keep from building the bath floor 1.5 inches above the hall. Without the MIA would you consider that sufficient?

As for your opinion being worth the price charged absolutely more.

May our Lord’s blessings be with take care,

Doug

[bbcamp]

Doug, the 2 layers is as much for movement isolation as it is for stiffness.

Of course, this is your floor, your money, and your labor, so you can do it any way you want. Who knows, you may get lucky.