Ceramic Tile Advice Forums - John Bridge Ceramic Tile

Welcome to John Bridge / Tile Your World, the friendliest DIY Forum on the Internet


Advertiser Directory
JohnBridge.com Home
Buy John Bridge's Books

Go Back   Ceramic Tile Advice Forums - John Bridge Ceramic Tile > Tile & Stone Forums > Tile Forum/Advice Board

Sponsors


Reply
Thread Tools Search this Thread
Unread 08-05-2021, 12:39 AM   #1
TileGuyCanada73
Registered User
 
Join Date: Aug 2021
Location: Canada
Posts: 46
Plywood underlay - Would any of these 3/4 options work?

I've got a 5/8" plywood floor on sleepers (2*4s at 16"-20" centers sitting on concrete). I'm going to add a 3/4" plywood underlay and then Ditra on top of that and then tile.

I'm having a hard time figuring out what plywood would be appropriate. My local Home Depot (in Canada) has these three options (I can't post links yet):
PureBond 3/4 Inch x 4 Feet x 8 Feet Sanded Aspen Plywood
West Fraser 3/4 inch 4 ftx8 ft Standard Spruce Plywood
AraucoPly Premium Pine Plywood ACX 3/4 inch x 4 ft. x 8 ft.


The PureBond looks fantastic in the store and is the cheapest option. Very smooth. No voids. Sits straight in the stack.

The West Fraser is very rough on both sides with a ton of voids.

I didn't get to look closely at the Araucoply but it looks like it is A/C graded.

I was hoping one option would just be labelled "Plywood underlay".

What am I really looking for?
Water resistant glue? One or two smooth sides?
__________________
Steven
TileGuyCanada73 is offline   Reply With Quote
Sponsored Links
Unread 08-05-2021, 08:06 AM   #2
Carbidetooth
Hmmmmm
 
Carbidetooth's Avatar
 
Join Date: Mar 2010
Location: Boise, ID
Posts: 1,635
A good choice among those would be the AraucoPly. I get it from local lumberyard and it is rated for underlayment. Labeled differently than domestic ply because it comes from Chile, IIRC. Nice stuff.

On HD site the PureBond is listed as "interior only"...no-go.
West Fraser is Canadian and after eyeballing on HD site, I'd guess it's CDX, but it should have a stamp that will tell you more.
__________________
Peter

Silicone (not silicon) Sealant Ranger
Carbidetooth is offline   Reply With Quote
Unread 08-05-2021, 10:36 AM   #3
TileGuyCanada73
Registered User
 
Join Date: Aug 2021
Location: Canada
Posts: 46
Thanks. That is very helpful. Still trying to wrap my head around the need for exterior grade plywood. If I use Ditra, is that still needed?
__________________
Steven
TileGuyCanada73 is offline   Reply With Quote
Unread 08-05-2021, 10:53 AM   #4
Carbidetooth
Hmmmmm
 
Carbidetooth's Avatar
 
Join Date: Mar 2010
Location: Boise, ID
Posts: 1,635
Yep, still required. Water and particularly water vapor are ever present or possible, be it crawlspace, wall cavity, floor, interior spaces, etc.

While Ditra may seem like a mitigating factor, there's always the perimeter, the seams etc.. Not to mention walls and ceilings can be sources of water.

Exterior glue has been a requirement in sheathing and decking for a long time. It'd be a mistake to assume you've found a chink in the armor of common building wisdom and code requirements.
__________________
Peter

Silicone (not silicon) Sealant Ranger

Last edited by Carbidetooth; 08-05-2021 at 12:02 PM.
Carbidetooth is offline   Reply With Quote
Unread 08-05-2021, 11:34 AM   #5
cx
Moderator emeritus
 
cx's Avatar
 
Join Date: Jul 2001
Location: Boerne, Texas
Posts: 94,054
Welcome, Steven.

It'll help if you'll put your geographic location into your User Profile so it appears with each post to aid in answering some types of questions.

For clarification, there is no exterior grade plywood. You want an exterior glue plywood with no face of grade lower than C. An exposure rating of Exposure 1 or EXT or Exterior on the grade stamp is what you want to see.

[Edit] And let me add that you can get a very good subfloor by adding nominal half-inch plywood, properly fastened, over your existing nominal 5/8ths" plywood. It'll be difficult to fasten your nominal 3/4" plywood to the thinner subfloor unless you pre-drill all the screw holes in the top layer.

My opinion; worth price charged.
__________________
CX

Y'ALL NEW VISITORS READ THIS HERE!

Last edited by cx; 08-05-2021 at 11:56 AM.
cx is offline   Reply With Quote
Unread 08-05-2021, 07:13 PM   #6
TileGuyCanada73
Registered User
 
Join Date: Aug 2021
Location: Canada
Posts: 46
Thanks all. This is making sense. CX, re "It'll be difficult to fasten your nominal 3/4" plywood to the thinner subfloor unless you pre-drill all the screw holes in the top layer." is that because the screws won't pull the two sheets together very well?
__________________
Steven
TileGuyCanada73 is offline   Reply With Quote
Unread 08-05-2021, 07:14 PM   #7
cx
Moderator emeritus
 
cx's Avatar
 
Join Date: Jul 2001
Location: Boerne, Texas
Posts: 94,054
Yep.
__________________
CX

Y'ALL NEW VISITORS READ THIS HERE!
cx is offline   Reply With Quote
Unread 08-05-2021, 08:16 PM   #8
Kman
Moderator
 
Kman's Avatar
 
Join Date: Nov 2006
Location: NW Arkansas, Ozark Mountains
Posts: 12,027
I would also recommend 1/2" ply. It'll be cheaper, easier to install, and will save you a little height.

Get some 1 1/4" screws to set it over the existing subfloor, and make sure none of the seams are aligned.
__________________
Kevin

The top ten reasons to procrastinate:

1.
Kman is offline   Reply With Quote
Unread 08-05-2021, 09:40 PM   #9
jadnashua
Veteran DIYer- Schluterville Graduate

STAR Senior Contributor

 
Join Date: Jul 2004
Location: Nashua, NH
Posts: 14,640
5/8" ply doesn't hold screws all that well, so by predrilling the second layer, there's no forces trying to act like a screw jack, holding the second sheet, and it can be snugged up to the bottom layer easier.
__________________
Jim DeBruycker
Not a pro, multiple Schluter Workshops (Schluterville and 2013 and 2014 at Schluter Headquarters), Mapei Training 2014, Laticrete Workshop 2014, Custom Building Products Workshop 2015, and Longtime Forum Participant.
jadnashua is offline   Reply With Quote
Unread 08-11-2021, 03:28 AM   #10
TileGuyCanada73
Registered User
 
Join Date: Aug 2021
Location: Canada
Posts: 46
Trying to prep a nasty floor

Hi All,

I'll be putting down 12"*24" tiles.

The floor assembly was:
- Concrete slab
- 2*4 sleepers
- 5/8" tongue and groove plywood nailed and glued to the sleepers
- 1/2" MDF
- Sheet linoleum

The adjacent room (which I am also tiling) is the same assembly but without the MDF or linoleum. It just had carpet on top. I'd like to bring them to the same level and I was planning on adding 5/8" plywood to that adjacent room.

I decided to rip up the lino and MDF because of some water damage and wanting to do things right. Of course, that is a mess. There are many spots where they used a lot of glue and I haven't been able to remove the MDF (It's pretty much a hammer and chisel project at this point.) There are other spots where I got the MDF off but it took a bunch of plywood with it. Also lots of areas where the MDF came up but left glue behind. It's about as flat as the Rocky Mountains right now.

My plan had been to get it flat and then put 5/8" plywood on top. I can do that but I am second guessing myself now. It's going to get messy to get to that point. I'll probably have to hit it with a belt sander.

I'm wondering if I would be better off pouring 5/8" of self levelling cement instead. My main concern about that is that I don't think it will help much for reducing deflection and I worry about the eventual crack causing a problem.

Perhaps I could split the difference and do 1/4" self levelling cement and then 3/8" plywood (screwed through to the bottom plywood?)

Taking the plywood off the sleepers is not an option (glued very well.) If needed, I could demo all the way down to the concrete and do new sleepers and new plywood. I was trying to avoid that because it will be easier said than done near the wall edges.
__________________
Steven
TileGuyCanada73 is offline   Reply With Quote
Unread 08-11-2021, 08:20 AM   #11
cx
Moderator emeritus
 
cx's Avatar
 
Join Date: Jul 2001
Location: Boerne, Texas
Posts: 94,054
Not sure why the "sleeper" system was used, but you might consider removing everything down to the concrete SOG (I'm guessing) and making a bonded mortar bed for your ceramic tile installation. More solid, more flat, exactly the correct height to match any adjacent flooring, etc, etc.

How large an area are you dealing with?

My opinion; worth price charged.
__________________
CX

Y'ALL NEW VISITORS READ THIS HERE!
cx is offline   Reply With Quote
Unread 08-11-2021, 08:33 AM   #12
Carbidetooth
Hmmmmm
 
Carbidetooth's Avatar
 
Join Date: Mar 2010
Location: Boise, ID
Posts: 1,635
Of your listed options, I think you'd be best to proceed with stripping underlayment, take hills off original plywood and then add additional plywood layer.

Is existing underlayment really MDF? That's a new one to me.
How are sleepers attached to slab?
Do you know if there's a vapor retarder (plastic) under existing slab?

CX makes a valid suggestion with mortar bed, but it's all gonna be significant work to prep this for tile.
__________________
Peter

Silicone (not silicon) Sealant Ranger
Carbidetooth is offline   Reply With Quote
Unread 08-11-2021, 11:11 AM   #13
TileGuyCanada73
Registered User
 
Join Date: Aug 2021
Location: Canada
Posts: 46
The thought has crossed my mind about going down to concrete but it's not really practical. This was a two car garage at some point and was converted about 30 years ago into an addition. A decision had been made to use the sleeper construction and there are multiple interior walls that are built on top of that floor. If I was doing the garage to living space conversion today, I might try to just level the concrete but that ship has already sailed.

There is a vapour barrier on top of the slab and then some sill plate foam on the bottom of the sleepers. The assembly has worked well with no signs of mold or mildew.

Sounds like I should keep chipping away at it get it as flat as possible (with divots being better than bumps. I'll use wood filler on the big divots and then do the 5/8" or 3/4" plywood overlay.

Here is a picture: https://imgur.com/pQ420ki
__________________
Steven
TileGuyCanada73 is offline   Reply With Quote
Unread 08-11-2021, 01:12 PM   #14
jadnashua
Veteran DIYer- Schluterville Graduate

STAR Senior Contributor

 
Join Date: Jul 2004
Location: Nashua, NH
Posts: 14,640
With foam sill seal underneath the sleepers, I wonder if a point load would cause deflection?
__________________
Jim DeBruycker
Not a pro, multiple Schluter Workshops (Schluterville and 2013 and 2014 at Schluter Headquarters), Mapei Training 2014, Laticrete Workshop 2014, Custom Building Products Workshop 2015, and Longtime Forum Participant.
jadnashua is offline   Reply With Quote
Unread 08-11-2021, 01:25 PM   #15
TileGuyCanada73
Registered User
 
Join Date: Aug 2021
Location: Canada
Posts: 46
Well that's an interesting and horrifying thought. It's a very thin layer of foam and so I think it will be OK if I beef up the sub floor and I also plan on using ditra.
__________________
Steven
TileGuyCanada73 is offline   Reply With Quote
Reply

Stonetooling.com   Tile-Assn.com   National Gypsum Permabase


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
nasty situation lati_cz The Mud Box 2 02-08-2018 02:03 PM
Nasty Nasty Hard Water Scum on my nice dark grout creature Cleaning, Restoration and Sealing 10 11-23-2011 11:28 AM
Ding Dong the am-nasty bill is dead. HS345 The Mud Box 45 07-04-2007 09:38 PM
Nasty Backsplash Susvc Tile Forum/Advice Board 9 03-30-2005 11:35 AM


All times are GMT -6. The time now is 06:25 AM.


Sponsors

Powered by vBulletin® Version 3.7.4
Copyright ©2000 - 2021, Jelsoft Enterprises Ltd.
Copyright 2018 John Bridge & Associates, LLC