Adding tile flooring on second floor

[JP.mpls]

I'm going to do a bathroom remodel this winter, including a new tile floor.

I know the standard method used to include "floating" the floor, or adding a half inch of cement base.

My cousin told me he used purchased cement board as the base, just like on the shower wall. I'm assuming it is glued and screwed down.

Has anyone on the forum tried that.

If you had professionals do a bathroom, what did they use?

Thanks, JP

 

[wmc1000]

Cement board is the standard to use as an isolation barrier when installing tile - see article -
https://todayshomeowner.com/flooring/guides/installing-tile-over-a-wood-subfloor/

 

[Fermion]

In our new house build we are putting porcelain tile in the upstairs bathroom. The sub floor is 1-1/8" plywood but we are putting down 1/4" thick hardi board concrete board on top of that with a thin set mud. The tiles are about 3/8" thick so the total thickness will be around 3/4" after accounting for the mud under and on top of the concrete board. This should match up nicely with our planned 3/4" solid hardwood flooring outside the bathroom.

https://www.homedepot.com/p/James-Hardie-HardieBacker-0-25-in-x-3-ft-x-5-ft-Cement-Backerboard-220022/100183556

 

[jrgators]

I'm going to do a bathroom remodel this winter, including a new tile floor.

I know the standard method used to include "floating" the floor, or adding a half inch of cement base.

My cousin told me he used purchased cement board as the base, just like on the shower wall. I'm assuming it is glued and screwed down.

Has anyone on the forum tried that.

If you had professionals do a bathroom, what did they use?

Thanks, JP

We are actually having our upstairs bathroom redone. It had tile but we are replacing with heated floor and tile. The demo of the existing showed the original builder did not use cement board for those tiles but the replacement work is using cement board.

 

[skyking1]

I use Schluter Ditra uncoupling systems.
https://www.schluter.com/schluter-us/en_US/Membranes/Uncoupling-(DITRA)/Schluter%C2%AE-DITRA-&-DITRA-XL/p/DITRA
I poured Self Leveling Concrete (SLC) over the electric heat wire, and then the ditra.

 

[OldShooter]

Yes, lots of information and videos on their site: https://www.schluter.com/schluter-us/en_US/ We just moved in to our new house and the tile setters used Schluter products exclusively.

 

[Winemaker]

The main thing is to make sure the sub floor doesn't move one iota. Two years ago, I tore out 9x9 tile that was attached to lauan veneer over plywood using adhesive. Our entrance way, 1st floor bath, hall way, kitchen, breakfast room, and laundry room took me almost two months to do the demo, chiseling each piece of tile, one at time, without tearing up the plywood. The lauan was also a *itch to get up as in the high traffic areas, it was stuck pretty good. We never had a problem with tiles coming up, I had issues where DW dropped a jar, or pot and broke tiles. Make sure you have extra tiles so they match. And tiles do go out of style.

 

[calmloki]

About 25 years ago we had tile done in this house, including the upstairs bath floor and a landing about 10'x10'. The 12"x12" bathroom tiles have all stuck down with zero issues, but at the bath to landing doorway and a bedroom doorway on the landing we've had some cracking in the grout. 1/2" cement board was used over 3/4" plywood in both locations and I think the plywood joints may have been too close to some cement board joints allowing flex. In the garage upstairs we used 1 1/4" T&G plywood and I'd pretty much bet you could set the tile right to the ply and not have issues (not that you should).

 

[ERD50]

I've tiled three bathroom floors, had to rip up tile from one room, and the old tile was just done over the plywood sub-floor (two layers, so any seams over-lapped). No tiles were cracked, no water damage, and it was a bear to get them ripped up.

So in all three bathrooms, I just did thin-set over the sub-floor. Was still like new when we moved, ~ 15 years later.

When I tiled our 3-season room, I went all the way. Cement board set into thin-set and screwed down every x" (forget the distance, but it was a LOT of screws). Many 'pros' skip the thin-set. But because that was a larger floor, and larger 12" tiles, and would be subject to expansion/contraction from summer heat/humidity, and possible frost in winter, I didn't want to take a chance. Also like new 15 years later.

Cement board on the floor sure won't hurt, but for a smaller space, indoors, and with smaller tiles, I don't think the extra cost, time, effort gets you anything.

-ERD50

 

[JP.mpls]

I use Schluter Ditra uncoupling systems.
https://www.schluter.com/schluter-u...ng-(DITRA)/Schluter®-DITRA-&-DITRA-XL/p/DITRA
I poured Self Leveling Concrete (SLC) over the electric heat wire, and then the ditra.

Thanks Skyking, I'm considering this.

If not, I'm going with cement board.

JP

 

[JP.mpls]

I've tiled three bathroom floors, had to rip up tile from one room, and the old tile was just done over the plywood sub-floor (two layers, so any seams over-lapped). No tiles were cracked, no water damage, and it was a bear to get them ripped up.

So in all three bathrooms, I just did thin-set over the sub-floor. Was still like new when we moved, ~ 15 years later.

When I tiled our 3-season room, I went all the way. Cement board set into thin-set and screwed down every x" (forget the distance, but it was a LOT of screws). Many 'pros' skip the thin-set. But because that was a larger floor, and larger 12" tiles, and would be subject to expansion/contraction from summer heat/humidity, and possible frost in winter, I didn't want to take a chance. Also like new 15 years later.

Cement board on the floor sure won't hurt, but for a smaller space, indoors, and with smaller tiles, I don't think the extra cost, time, effort gets you anything.

-ERD50

ERD,
Thanks for telling me what you did. My existing tile is loose and grout is cracking.
Thinset directly to plywood subflooring.

My floor framing is spaced fairly wide apart. They are very long premanufactured truss beams. Used to create an open floor plan on the main level. I suspect the wider spacing isn't as stable.

I'm most likely going to use cement board with screws and thinset to make the floor more stable and solid.

It sounds like it is common practice these days.

Take care.

 

[ERD50]

ERD,
Thanks for telling me what you did. My existing tile is loose and grout is cracking.
Thinset directly to plywood subflooring.

My floor framing is spaced fairly wide apart. They are very long premanufactured truss beams. Used to create an open floor plan on the main level. I suspect the wider spacing isn't as stable.

I'm most likely going to use cement board with screws and thinset to make the floor more stable and solid.

It sounds like it is common practice these days.

Take care.

Yes, if it isn't stable, you'll want to beef it up. Screwing the cement board into wet thin-set on the plywood really locks it in. What I read was that stepping on the dips or weak spots will cause that section to move a little, and eventually wear around the screw and allow movement. The thin-set locks that all in and fills dips. And stagger any seams.

Good luck! It's not too bad a project, until you get older and working on your knees gets tougher and tougher. And when it turns out well, it's pretty satisfying.

-ERD50

 

[skyking1]

ERD,
Thanks for telling me what you did. My existing tile is loose and grout is cracking.
Thinset directly to plywood subflooring.

My floor framing is spaced fairly wide apart. They are very long premanufactured truss beams. Used to create an open floor plan on the main level. I suspect the wider spacing isn't as stable.

I'm most likely going to use cement board with screws and thinset to make the floor more stable and solid.

It sounds like it is common practice these days.

Take care.

adding another layer on top of the subflooring is not going to cure the structural problems presented by the long spans.
Floor stiffness is described by a measure of deflection based on standard loads.
Standard deflection is L/360. This is not sufficient for tile application, according to the experts at John Bridge forums. The tile Council states it as a minimum, but most tile pros will want at least L/480 or greater on really long spans.
The issue is the long span can deflect enough to break grout and tile, while still meeting the L/360 specification.
If you knew the floor joist size and span, it is easy to calculate the deflection based on standard tables for the material.

Bottom line is you may not want to pursue tile over that area.
Another layer of subfloor will not help with span, only with joist spacing.

 

[ERD50]

...
Another layer of subfloor will not help with span, only with joist spacing.

I'm curious about that. While cement board/thin-set may not add much in terms of a structural support (but not zero), why wouldn't screwing (and gluing?) another layer of plywood help?

Doubling the thickness provides an 8x reduction in deflection (cube factor). The numbers are a little different depending on how the bridge is supported (loose, just lying on supports, or secured to the support), but IIRC, the difference is minimal.

Or by "Another layer of subfloor ", were you thinking that flimsy 1/4" luan stuff, and not a full 1/2" ~ 5/8" plywood/OSB?

-ERD50

 

[Fermion]

Also curious about that. Glued and screwed 1-1/8" T&G plywood is going to be more rigid than 3/4" for the same joist spacing.

 

[ERD50]

... My existing tile is loose and grout is cracking.
Thinset directly to plywood subflooring.

My floor framing is spaced fairly wide apart. They are very long premanufactured truss beams. Used to create an open floor plan on the main level. I suspect the wider spacing isn't as stable. ...

Re-reading this, I'm also curious about what the span is, and what the subfloor consists of. How many layers of plywood, what thickness?

-ERD50

 

[Fermion]

Boise gives the L/360 (minimum), L/480, and L/960 spans for different joist sizes, although they also mention stiffness can be modified by thicker glued and screwed subfloor.

https://www.buildsite.com/pdf/boisecascade/BCI-Joists-Technical-Notes-2105342.pdf

 

[Ronstar]

I used concrete board on our small guest bathroom - glued and screwed to 3/4" subfloor. There are special type of screws for concrete board. Then thinnest mortar and tile.

 

[skyking1]

it does help a small amount, but think of the physics.
Data is from the weyerhauser MTP-W7000 West Specifier Guide
For a good tile base of L/480
for the 9.5" 5000 1.7 series @16" OC you can span 15'7"
the 11 7/8" joists will span 18'7" with the same series and conditions.
Move up to the 14" deep joists and you get 21' span
The 16" deep joist goes 24'5"
All of that based on:
"Span values assume 23/32" minimum plywood/OSB rated sheathing is glued and
nailed to joists for composite action (joists spaced at 32" o.c. require sheathing
rated for such spacing - ⅞" plywood/OSB)."

So when you add a thin layer, even some 5/8" ply on the alternate direction glued and screwed with the joints all mixed, you need to think about it as 5/8" of material over the 20' of span.
They add *inches* of joist depth to achieve a longer span.
The other thing that added layers does is increase the dead load and that ADDS to deflection on the long dimension.
Don't expect added sheeting to fix that direction, It is best for local stiffness between the joists.
It absolutely does cure those joist spacing problems.

 

[skyking1]

So joist depth is the answer and the question.
If you really want a stiffer floor that is already relatively a thin section, you do get some help by adding joists and cutting the joist loading that way.
If an existing 14' span @24" OC meets L/360 the bare code minimum, cutting out the sheet rock and adding joists in between those for @12" OC will get a great floor, around L/720.
is it fun? oh heck no you have to pull out the wiring and if there is plumbing crossing those joists that really complicates things.
This OC reduction has its limits too. At some point joist depth rules the day, no matter how many you add.

 

[street]

I use Schluter Ditra uncoupling systems.
https://www.schluter.com/schluter-us/en_US/Membranes/Uncoupling-(DITRA)/Schluter%C2%AE-DITRA-&-DITRA-XL/p/DITRA
I poured Self Leveling Concrete (SLC) over the electric heat wire, and then the ditra.

This.

 

[ERD50]

So joist depth is the answer and the question. ...

OK, I was looking at 'span' as the distance between the floor joists (16", 24"?), not the length of floor joists between supports.

Agree, sub floor isn't going to help much with that, using the cube estimate, adding 3/4" to a 2x10 (9.5") joist is about a 25% improvement, less if there are seams at 4' or 8'?

((9.5+.75)/9.5)^3 ~ 1.256 

OP needs to fill us in on the details, I think.

-ERD50

 

[skyking1]

One more post on the joist subject:
You can cut huge holes in IJoists and not reduce the strength and deflection properties.
Let's use Weyerhauser for the example. Boise is less expensive and similar and I can put up those links too.
https://www.bc.com/wp-content/uploads/2019/06/West_Spec_Guide.pdf

If you only use the table on page 7 for cutting holes, you are missing a lot.
They are quite limited and address all possible conditions.
If you examine each joist span specifically, you can cut many more and larger holes using the ForteWeb software.
https://www.weyerhaeuser.com/woodproducts/software-learning/forte-software/

boise's version is BCcalc.
https://www.bccalc.com/Account/Login

Using those softwares, I can keep all of the plumbing and hvac in an 11 7/8" joist space.

For example,on the short span side of the house it is 13' 6" and I can cut out the whole web in the middle, an 8"x14" hole for one return duct, and another 8" round hole near one end too. The chart won't allow that, only addressing the specific conditions with the software.
I have no tile plans and L/360 is fine. That particular joist is:
Total Load Deflection L/993 (0.161") 36.3%
Live Load Deflection L/1241 (0.129") 29.0%
I could do that span with a 9.5" joist easily, but the other side of the house is 18'6" span and I also want to keep everything between the subfloor and sheetrock, so I am committed to the 11 7/8".
At one point I had considered using the 14" deep joists, until I found that software.

 

[JP.mpls]

Re-reading this, I'm also curious about what the span is, and what the subfloor consists of. How many layers of plywood, what thickness?



-ERD50

ERD,
I'm not there yet, but I previously repaired some flooring issues by my slider door before having wood floors installed.

I think it is 3/4" plywood in questionable condition. Built in 1984. I'm going to add more deck screws, and replace any damaged or delaminated plywood.

I could decide to add. 1/4" layer on top, or even replace all of it once I remove the tile.

The trusses are further apart than 16". I suspect 24" spacing.

Right now my plan is to screw down cement board.

Thanks for your comments.

 

[Fermion]

Seems easy enough also to just measure your deflection in the floor with a 4 foot straight edge and knowing your weight. Stand at the 2 foot mark on one foot, see how many pieces of paper you can slide under the straight edge in the middle.