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Unread 01-29-2020, 10:07 PM   #1
Dawson14
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Entry Way Tile Project Help

Hi all, first time post. I've done lots of "researching" and this site always comes up in youtube videos and articles, so I figured I'd ask for advice here . I am currently prepping for an entry way tile project and would like to do it right. I have some questions to ensure the underlying sub floor is adequate for the tile I will be installing.

Project Scope:

- Retile 1st floor entryway of a 1956 Ranch Style home with full basement with 8" x 19.75" natural stone quartzite tiles.

Entry Way:

- Dimensions - 15' 6" x 5' 3"

- Joist Layout - Parallel with the 15' long side. 2x10's every 14 inches cross braced with metal brackets. There is a metal beam that runs under the entryway joists after 10' 7".

- Current Sub Floor - Original 1/2 inch plywood secured to joists with additional 3/4 inch plywood nailed into 1/2 plywood (not sure if glued?)

What is been done so far:

- I have ripped up the old 12"x12" tile. I found that the original sub floor once had some sort of flooring that was adhered to the 3/4" plywood using adhesive. It appears when the owners remodeled and put down tile, they put down a super thin coat of thinset right over the remaining adhesive and then laid the tile so no backerboard. The tile was incredibly easy to pop up with a crowbar. I only had to break one tile to get under the rest. They all came up intact. I am assuming the thinset could not bond properly to the plywood due to the adhesive residue. What is more surprising is that the grout was actually in great condition. There was only one spot where there was cracking and chipping which I at least found surprising after finding out how the tile was installed.

The "Plan" and the issues:

- I plan to rip up the 3/4" plywood top due to it 1.) having old thinset still stuck to it and 2.) having adhesive residue.

- I am not sure if the builders back in the 50's would have glued to the two plywood layers together. I hope not because I am not quite sure how separating the layers would go. If it is, what do you all recommend I do? I REALLY want to avoid having to rip up subfloor all the way to the joists.

- The next step is to put down NEW plywood on top of the 1/2". What I am unsure about is the thickness of plywood I need to use. The old tile was already about 1/8" - 3/16" above the 1st floor hardwood. With that said, I plan on putting down modified thinset on the new plywood, then 1/4" hardie backer, then more modified thinset, then tile. I am guessing (correct me if I am wrong), that will increase the height by about another 1/2". I am worried about having to cut doors, cut trim, and the step up being really large into the entry way from other rooms. I would like to minimize this as much as possible....if possible.

- I know that hardiebacker requires at least a 5/8" subfloor beneath it as it doesn't provide any structural support. With already having a 1/2" subfloor after removing the 3/4", could I do another 1/2" or possibly a 3/8" inch layer without compromising the integrity of the floor to try to offset the increase in height due to materials? This is the biggest concern I have. What are the risks associated to going to 1/2" or 3/8" if any?


Thanks in advance for any feedback I receive. I have pictures on imgur, but when I signed up it said I needed to post 3 times to include links....so not sure if I can add or not since this is my first post.
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Unread 01-30-2020, 08:41 AM   #2
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Welcome, Dawson,

Yeah, given what you've got it'll be a challenge to keep the height down.

The 1/2" ply is nearly useless as a subfloor - it just flexes too much between joists. You could try adding another 1/2" ply layer but you're going to have a rough go of getting the new layer properly attached to the old layer so that they behave as a single, thick layer - there's just not much meat in 1/2" ply for screws to get a good bite to draw the two layers solidly together.

Do you have access to the underside of this floor from the basement?
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Unread 01-30-2020, 09:35 AM   #3
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Welcome, Dawson.

We prefer that you not link to third party photo storage sites at all, but you can attach photos from storage on your computer at any time using the paper-clip icon above the Reply dialog box.

I can only echo Dan's comment about the existing nominal 1/2" subfloor layer. Basically worthless in that application. If the surface is in pristine condition (unlikely) you might consider lanimating a second layer of similar plywood to the existing using a full spread of wood glue and about a brazilian screws.

That not being an option, the next best choice, aside from removing the existing subfloor, would be to install a new layer of nominal 3/4" exterior glue plywood with no face of grade lower than C and fasten it to the joist structure as though the existing half-inch material was not there. That would essentially give you a single layer subfloor that exceeds most tile substrate manufacturers' recommendations. You could do the same with your proposed nominal 5/8ths" plywood, but I would want all I could get in one layer.

In either case you would then install your CBU or a thinner membrane, prior to your tile installation.

Make the floor suitable for a ceramic tile installation, then make your transitions to other flooring as necessary.

Removing the existing "subfloor" sounds like a better plan to some of us.

My opinion; worth price charged.
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Unread 01-30-2020, 03:29 PM   #4
Dawson14
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Quote:
Do you have access to the underside of this floor from the basement?
I do not. It’s a fully finished basement under the entry way.

Quote:
You could try adding another 1/2" ply layer but you're going to have a rough go of getting the new layer properly attached to the old layer so that they behave as a single, thick layer - there's just not much meat in 1/2" ply for screws to get a good bite to draw the two layers solidly together.
So sounds like I need to put a new 3/4” layer down on top of the 1/2” and live with the lip, or I rip up both layers to the joists and lay down new 3/4” straight into the joists. Am I hearing you correctly? I’ve heard that if I rip up all the original subfloor to the joists, I am going to have to put in new “joists” or “blocks” so that the subfloor edges are resting on bracing. I doubt the joists are lining up exactly with the edges of the non load bearing walls. Are there any good videos or articles that explain how to properly do this that you know of?
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Unread 02-03-2020, 08:51 PM   #5
Dawson14
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CX and Dan, thank you for your feedback. I appreciate the help so far. I'm done with demo (pictures attached) and I'm nearing the installation of the new sub floor.

I have some final questions and was hoping someone could provide me some direction. The new sub floor will be 19/32 plywood since apparently what I ripped up was 19/32 and not 23/32 like I thought. I measured and installing 23/32 was going to cause door issues with added backer and tile. With that said, I'm hoping to get some clarification with the quote below.

Quote:
Originally Posted by cx
the next best choice, aside from removing the existing subfloor, would be to install a new layer of nominal 3/4" exterior glue plywood with no face of grade lower than C and fasten it to the joist structure as though the existing half-inch material was not there. That would essentially give you a single layer subfloor that exceeds most tile substrate manufacturers' recommendations.
I am planning on doing what you suggested, however I'm a little confused since I've read that I should screw the second layer of sub floor into the 1st layer and not the joists due to deflection. Can you explain the different methods? I am assuming since you stated that the 1/2 sub floor is basically worthless so the second layer of 19/32 is essentially THE sub floor. If that is the case, would I still screw into joists AND the other sub floor to try to make one solid piece?? The top layer I removed was nailed down around the edges and then stapled to the bottom 1/2". You can see the 1/2" subfloor now in the pictures I attached.


Two final questions:

1.) Do I need to space the new sub floor so that the seams don't align with the bottom layer seams (the original was not spaced this way. The breaks were in the same place width wise). IE: The bottom layer seam would be in the middle of the new 4x8 layer on top.

2.) Do I need to have any gaps between the new sub floor sheets? The original installation did not.
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Unread 02-03-2020, 11:16 PM   #6
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Quote:
Originally Posted by Dawson
I am planning on doing what you suggested, however I'm a little confused since I've read that I should screw the second layer of sub floor into the 1st layer and not the joists due to deflection.
That part has nothing at all to do with deflection, it has to do with movement transferring from the joists to the top layer of subflooring. I think it a rather nebulous thing myself, but it can't hurt.

But that only applies when you have an actual first layer of subflooring that is useful, which you have not. What you'll be doing is installing your single layer of plywood subflooring as though there was nothing there but joists and an unwanted spacer.

I would still recommend you use nominal 3/4" plywood for your subfloor. Make your subfloor suitable for tile, then make your transitions as necessary. There are substrates thinner than your 1/4" CBU if that will help.

1. You definitely don't want any seams in the new layer to align with any seams in the existing. It appears to me in your photo that all your new plywood will be in single spans across your entire floor with no seams except those perpendicular to the joists and you'll be able to stagger those a full half-sheet.

2. Yes, you want them gapped an eigth-inch or so. It's somewhat less important in your application than perhaps in new construction, but do it anyway. Your new T&G subflooring panels may be of a type that tends to gap itself, which is good.

Pay no attention to what was there before. Those were the same folks who installed the half-inch square-edge plywood as your original subfloor.

My opinion; worth price charged.
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Unread 02-03-2020, 11:46 PM   #7
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Quote:
Originally Posted by CX
But that only applies when you have an actual first layer of subflooring that is useful, which you have not. What you'll be doing is installing your single layer of plywood subflooring as though there was nothing there but joists and an unwanted spacer.
Makes perfect sense. Thank you

Quote:
Originally Posted by CX
I would still recommend you use nominal 3/4" plywood for your subfloor. Make your subfloor suitable for tile, then make your transitions as necessary. There are substrates thinner than your 1/4" CBU if that will help.
Fair enough, Ill check out Ditra and see if that will give me enough to clear the front doors.

Quote:
Originally Posted by CX
Your new T&G subflooring panels may be of a type that tends to gap itself, which is good.
Yeaaa....so it never even dawned on me about T&G subflooring until I read the other guys newbie thread (also the 2nd layer I removed was not T&G) and just saw your comment. The new 19/32 I picked up is not T&G. Home Depot does not have any T&G 19/32, only 23/32. Is T&G a must have?

Here is the link for the 23/32: HD T&G 23/32

Quote:
Originally Posted by CX
Pay no attention to what was there before. Those were the same folks who installed the half-inch square-edge plywood as your original subfloor.
You have no idea how much this statement rings true for this house. Every single upgrade/renovation previous owners did is a nightmare. Complete amateur hour hackjob.
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Unread 02-04-2020, 08:42 AM   #8
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While T&G panel edges are not usually necessary for the second layer of subflooring, Dawson, that's because it's presumed that the second layer edges will be adequately supported by the first layer. In your case that's questionable and I'd want T&G edges where I could get them.

We understand that getting in that last sheet with T&G edges might be challenging, I'd want them wherever I could manage them. Where I couldn't use a T&G edge, I'd want to pre-drill the screw holes near the edges of both new sheets and try to pull the bottom layer up against the new layer as best I could.

My opinion; worth price charged.
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