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Discussion Starter #1
Hello all, I am new to this community, and some of this info has been very helpful. I am about to lay Slate tile in my kitchen that has already been purchased, and noticed now (maybe too late) that the flooring may need reinforcing. The kitchen is on 2x8 joists (not sure wood type) @ 16'oc , with a span of about 9'6" between foundation wall and center beam. I thought I would originally be OK due to the fact that the tile I ripped out was a heavy 1/2" ceramic tile, but the more I read, the more I get nervous. I removed the existing tile, and existing underlayment (3/16? plywood) and am now left with 1/2" ply. My thought was to use a 1/2" backer and then apply the tile, but I am now second guessing all of this. Please let me know if there is anything I should do before moving further ahead. I appreciate your time in advance.
Thanks!
 

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Tileguy
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Hi Dave,

You're right thinking you have some extra work to do if you wanna install that slate in your kitchen. (I'd think again about your selection, but.....) Your subfloor isn't even stiff enough for regular ceramic or porcelain. And, your joists are a little short of minimum spec for natural stone too.

You didn't include enough info but, are you sure the subfloor is only 1/2"? If so, how did that happen? Was there ever a thicker layer of ply over the subfloor that was removed in a remodel in the past? How old is the house? Where is the house located?

Jaz
 
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Slate would have been one of my last choices for natural stone flooring.
To brittle, and one of the most porous stones there is so a lot more work to seal it before laying, even the thin set can stain it.
I find homes built on the cheap many times with 1/2 subflooring. All it does is act like a shim over the joist when you add a thicker real subflooring over it because it sags and bounces so much between the joist.
 

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Discussion Starter #4
Thank you for replying! We are located in a small suburb south of Buffalo, NY. The original part of the home was built in the early 1800s... but this part of the home was added on in the 1970s or 80s and the tile must have been put in when this addition was put on.
We are going for a farmhouse type feel, and that is why I chose slate... not the best choice now that I have looked into it more, but also too late, seeing we opened the boxes to inspect each tile upon delivery.

I removed some flimsy underlayment that came up with the 1/2" tile, but I really think the subfloor is only 1/2", I will confirm tonight though.

Moving forward, what is my best option? I know I must double up on the subfloor (at least), and then use either a Ditra like product or backer board of some sort, but generally speaking, is there something more that I should do short of adding walls in the basement?
Thanks for your time!
 

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Tileguy
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Dave,

It's sometimes difficult to measure ply accurately because plywood is thinner than its stated size. 1/2" ply is usually 15/32", 5/8" is 19/32". People often mistaken 5/8" thinking it's 1/2".

However, it's also possible that the addition was built with 1/2" with 5/8" over it, but at some point the top layer was removed. That would be wrong, but who knows?................

Starting with your joists, you should stiffen them by either sistering them, or shortening the span with a supporting wall or a beam. Then install some underlayment grade ply. The thickness depends on what the subfloor measures, but I'm leaning towards 5/8" or thicker.

Then you'll install your favorite concrete backer or a membrane like Ditra. :thumbsup: Check back when you know the details.

Jaz
 

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Discussion Starter #6
Hello Jaz, thank you very much. The sub floor is as you suspected 5/8"... I was able to pull a vent back. So should I still do another layer of 5/8" or can I get away with something less... And after doing that, is 1/4" backer ok? I was trying to keep the height down due to this kitchen's adjacencies so every little bit will help.

Damn, I wish there was a warning on the slate when I was looking.
Thanks again for your help, it is much appreciated!
 

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Tileguy
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You need another 5/8" underlayment grade, (no cheapo CDX) installed correctly with 1/8" gaps etc. You also need to stiffen those joists. Is the underside easily accessible?

1/4" backer is just as good if not better than 1/2" for floors. I would consider Ditra though. Ditra will save you about 3/16" too.

Damn, I wish there was a warning on the slate when I was looking
Well, you bought this slate where?

Jaz
 
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Tileguy
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Great! :censored::censored::censored:

Here I am, (and others) we volunteer our time by spending many hours a week trying to help people to understand how tile projects should be done. We want to promote doing the work correctly and save the public from a failure and many thousands of dollars.

We do all the work per se. Management manages how the site works and sells advertising to maintain the site and hopefully make a profit. We just feel good that we help the industry with never a thank you.

So I look at one of my answers and there is an ad inside the box of my answer promoting a tile company a few miles away from me. :censored::censored: It's bad enough that it looks like I am endorsing "L.L.". and dozens of other products I don't necessarily like. So, if I'm the average visitor it looks like I am endorsing this company because it's "inside" my post. There's something wrong with that, no?:whistling2:

Jaz
 

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Discussion Starter #9
Hey Jaz, I don't see an ad, so no worries. Thanks for your time. I plan on using the 5/8", reinforcing and I'm not sure on the underlay yet... I want to do it right, but I also need to watch what I am spending, the Ditra seemed expensive. I appreciate your help, and good thing I didn't listen to the people at the big box stores, they said I'd be fine with what I have and just a layer of backer. Feel bad that so many people listen to them as pros. Thanks!
 

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Tileguy
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Dave,

There was no ad in my post either a few minutes ago, there was one in yours. It keeps changing.

You can be assured you will have a hard time finding a pro at the big box stores. They will not hire one even if they could find one that was willing to work there.:no: Ask which way to the restroom and that's about it.

Ditra is worth more than concrete backer, but it's not that much more for your project, is it? It might add a hundred or so? It'll be easier, thinner, waterproof and can save you from a failure under the right circumstances. But ok, backers work fine too. I used to charge about the same for both methods installed, sometimes 25-50 cents more for Ditra. How many sq. ft. is the room net? Not how many ft. of slate you have.

Jaz
 

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Discussion Starter #11
one more question - slate under cabinets?

Hello again, I hope Jazman can help me one more time... We have chose to replace all the cabinetry in the kitchen as part of this remodel, so my question is, do I tile the entire room and then put cabinets on top, or do i build the cabinet base level up with plywood to match the tile and backer and tile up to the face of the toe kick on the cabinets?
I have seen both ways suggested.
Thanks again for all your help!
 

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Age old question.
Dealing with a dishwasher?
Plywood under the cabinets to lift them and tile in the area under the dishwashers has worked for me in the past.
Once again slate is a brittle, porous natural stone, poor choice to a kitchen.
I'd even seal it before installing it. Even the thin set and grout can stain it.
 
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Tileguy
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Thanks,

You can do it either way.

As a tile setter I'd rather install the tiles all over before the base cabinets are installed. Of course if there's ever an issue and the floor needs to be replaced, there a small problem.

You can install the tiles after the cabinets and save 20-30 sq. ft. But it'll take more time to install less tiles, plus always a chance to damage the new cabinets.

You need to shim the cabinets either way.

Jaz
 

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Tileguy
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OK so, we couldn't talk you outa using that slate for your kitchen. I will amend my answer then.

Install the base cabinets first, shimming them 3/4" +-. This way if someone needs to rip out the slate and the CBU you won't necessarily have to remove the cabinets first.

Farmhouse look you want, farmhouse floor you'll get. At least yours are gauged so you shouldn't trip on them. Breaking up I'm not so sure. :whistling2:

Jaz
 
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Discussion Starter #15
a few more question... thanks!

so Jazman,
laying my additional subfloor this weekend and have a couple questions if you have time,

after rescrewing existing subfloor, do I screw and glue additional plywood subfloor? or just screw? if glue, what type? adhesive or wood glue?

do i hit or avoid joists below?

do I run ply opposite direction of joists or opposite direction of existing subfloor?

do i leave 1/8" between sheets?

as for the backer (chose durock 1/4") ... do i have to tape? some say yes, some say no? can i tape while laying tile?

every question has 12 different answers when I search online.... ugh.

enjoy your weekend!
 

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Tileguy
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Dave,

NEVER glue the underlayment to the subfloor.

Screw the new to the subfloor, use 1 1/4" flooring screws. The only issue I see is that your subfloor is very wimpy and the screws may not "bite" as well as you'd like. See how that goes.

Subfloor and all underlayments ALWAYS go perpendicular to the joists, always. That is their strongest axis. Be sure of offset both ways from the sub of course.

Always leave 1/8" gap in sub and underlayment and min. 1/4" at perimeter and any vertical object.

Yes you have to tape the seams of CBU's. The only exception is factory edges on Wonderboard brand, cuz of the way the edges are wrapped. You can tape as you install although I never liked to do it that way. I kept moving the tape with the trowel.

every question has 12 different answers when I search online.... ugh.
Tell me about it.................:censored: Anyone who ever wanted to give advice can do so online. I have found that You Tube is awful. I like it, but it's a dangerous place. So many idiots there.

But my criticism is not just for amateurs. There a certain nationally known DIY show guy who has or has had a TV show who doesn't know his rear end from the hole in the wall. (when it comes to tile and flooring in general). He has sold books and has videos etc.

Jaz
 

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Discussion Starter #17
Hey Jaz, thanks again for all your help. We successfully laid the ply and cbu. I'm taping this week and then laying my tile next weekend. Figured you've been so helpful that I'd ask for your recommendation on mortar to lay the slate tiles? Again they are a Brazilian Black 12x24 Slate tile. I found products at Home Depot and lowes for stone or large format tiles but wasn't sure if I should spend the extra money if something else can do the same job? This floor has gotten to be expensive so I'd like to save where I can, but don't want to sacrifice what I have done already by buying an inferior product. Thanks!

Oh and any other tips or words of wisdom to prep or lay the tile?

I will definitely send you a photo once this is complete, you've been a huge help!
 

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Tileguy
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Dave,

Well yea you need to use mortar that is intended for large/heavy natural stone. Which mortar were you thinking about? Last time I looked neither HD nor Lowes carried expensive mortars. The most is what (?) $30 a #50? I don't think they carry specialty mortars that can cost $120-140 for a #40. (and you don't need those anyway). :huh:

So look for what is known as 'medium-bed' mortar, aka granite & stone or similar.

Oh yea, I like pics.:yes:

Jaz
 

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Tileguy
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Numbers 1 - 2 - 4 & 5 are very good for your slate.

# 2 & 4 are standard type medium bed. The other two are a little more hi-tech.

Personally I'd would probably select # 2 or # 4, but If I had the time to read all the data, I might choose any of the 4.

# 3 Versabond, is an entry-level but decent mortar, but you need a medium bed, so leave it at the store.

Jaz
 
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