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 06-19-2014, 02:50 PM   #1
bajpga
Registered User
 
Join Date: Jun 2014
Posts: 25
Leveling Upstairs Bathroom Floor

Hello,
I am renovating an upstairs 10' x 5' bathroom which originally had carpeting. To date, I've opened the 3/4" OSB floor (I had to retain the OSB top layer as it runs under the second story floor plates), sistered 2x6's to the 2x12 joists, added a second layer (from underneath) of 3/4" plywood (overlapping the top layer), then closed it by screwing the layers together 6" on center with ceramic coated deck screws. I did not glue the layers together. I've checked, and all is good on the deflecto.
After closing it up (yes, I should have checked level before starting, but expected a 10 year old house to have fairly true joists), I checked the floor level and discovered a ridge in the flooring caused by a couple of high joists and the effect is 1/4" to 5/16" out of level across the 5' span from highest to lowest point. So 4' of the 5' span is out of level. So, that's the problem I need help with.
What is the most effective way to flatten the floor WITHOUT opening the floor again?
**Note** I plan to use Ditra over the OSB.

1. Do I need to use hydroban or something similar over the OSB prior to putting down the Ditra?
2. Can I use medium build thinset to lay the tile flat and overcome the issue?
3. Do I need to use SLC?

I would appreciate any and all help.
__________________
John
bajpga is offline   Reply With Quote
Sponsored Links
Unread 06-19-2014, 04:33 PM   #2
cx
Moderator emeritus
 
cx's Avatar
 
Join Date: Jul 2001
Location: Boerne, Texas
Posts: 92,692
Welcome, John.

Your tiles care not a whit if your floor is level, they care only that it's flat. Is your floor flat?
__________________
CX

Y'ALL NEW VISITORS READ THIS HERE!
cx is online now   Reply With Quote
Unread 06-19-2014, 05:50 PM   #3
chuck stevenson
Contractor -- Schluterville Graduate
 
Join Date: Aug 2006
Location: Columbus, Georgia
Posts: 2,248
Quote:
Originally Posted by John
...To date, I've opened the 3/4" OSB floor (I had to retain the OSB top layer as it runs under the second story floor plates), sistered 2x6's to the 2x12 joists, added a second layer (from underneath) of 3/4" plywood (overlapping the top layer),...
Can you post a picture of " added a second layer (from underneath) of 3/4" plywood ".

Not sure how that would be done overlapping the top layer.
__________________
Chuck

No curb, walk-in shower.
chuck stevenson is offline   Reply With Quote
Unread 06-20-2014, 07:11 PM   #4
bajpga
Registered User
 
Join Date: Jun 2014
Posts: 25
Hi CX,

In answer to your question, no, the floor is not flat. Across the 5' span of the 10' x 5' room, the floor is level for about 14" from one wall to the first joist, then the floor drops 1/4" - 5/16" to the opposing wall. So I'm not sure how to proceed.

Thanks
__________________
John
bajpga is offline   Reply With Quote
Unread 07-17-2014, 06:19 PM   #5
bajpga
Registered User
 
Join Date: Jun 2014
Posts: 25
As noted in my original post, the top layer of subfloor is OSB. This will not be changed.
1. Can someone please recommend a thinset for the Ditra to OSB application.
2. Do I need to use Hydroban or Redguard over the OSB prior to putting down the Ditra?

Thanks
__________________
John
bajpga is offline   Reply With Quote
Unread 07-18-2014, 08:52 AM   #6
bajpga
Registered User
 
Join Date: Jun 2014
Posts: 25
As noted in my original post, I am using Ditra over OSB. This will NOT be changed to plywood.
1. Can someone please recommend a thinset for the Ditra to OSB application.
2. Do I need to use Hydroban or Redguard over the OSB prior to putting down the Ditra?

Thanks
__________________
John
bajpga is offline   Reply With Quote
Unread 07-18-2014, 09:19 AM   #7
cx
Moderator emeritus
 
cx's Avatar
 
Join Date: Jul 2001
Location: Boerne, Texas
Posts: 92,692
1. Your thinset mortar must meet the requirements of ANSI A118.11 to be used over plywood (or OSB in your case). That number will be on the bag. Every maker of tile setting products makes one or more such mortars.

2. Not at all sure why you'd wanna do that, but no, it's certainly not necessary.

But you must do all your leveling or/and flattening of your subfloor before you install the Ditra.

My opinion; worth price charged.
__________________
CX

Y'ALL NEW VISITORS READ THIS HERE!
cx is online now   Reply With Quote
Unread 07-18-2014, 09:28 AM   #8
Richard Tunison
Retired Tile Contractor
 
Join Date: Jul 2002
Location: Homosassa Springs, Fl
Posts: 2,689
From the Schluter instructions,,,,

For example, to set DITRA over plywood or OSB, a modified thin-set mortar meeting the requirements of ANSI A118.11 is used.

Any modified thinset in the 25 to 30 dollar range will be fine. Flexbond from H.D. is one such product. Many out there to choose from depending on your location.
__________________
Richard
Richard Tunison is offline   Reply With Quote
Unread 07-18-2014, 09:42 AM   #9
bajpga
Registered User
 
Join Date: Jun 2014
Posts: 25
Thanks CX!

On point No.2 - (Not at all sure why you'd wanna do that, but no, it's certainly not necessary.)....Since it is going over OSB, which is evidently a suspect subfloor and susceptible to delamination with moisture exposure, my thinking was to protect the OSB with RedGard prior to applying the thinset and Ditra. This way the moisture from the thinset wouldn't cause an issue with the OSB. I am already planning on using RedGard for the bath walls, so it might be prudent to use it for this application on the OSB.
Do you have any thoughts on this logic or approach?

Thanks,
__________________
John
bajpga is offline   Reply With Quote
Unread 07-18-2014, 11:17 AM   #10
cx
Moderator emeritus
 
cx's Avatar
 
Join Date: Jul 2001
Location: Boerne, Texas
Posts: 92,692
If your OSB has an exposure rating of Exposure 1 it is not going to suffer any such "delamination" when exposed to thinset bonding mortar.
__________________
CX

Y'ALL NEW VISITORS READ THIS HERE!
cx is online now   Reply With Quote
Unread 07-21-2014, 12:38 PM   #11
bajpga
Registered User
 
Join Date: Jun 2014
Posts: 25
Thank you CX.
My next question is about the type of drywall to use for the walls outside of the wet area. I am using Hardie in the tub area and will fir it out to be inside the tub lip and to be even with the bathroom walls.
Is it necessary to use a Type X MMR Board for the walls or can I use gypsum board?

Thanks
__________________
John
bajpga is offline   Reply With Quote
Unread 07-21-2014, 12:43 PM   #12
cx
Moderator emeritus
 
cx's Avatar
 
Join Date: Jul 2001
Location: Boerne, Texas
Posts: 92,692
Plain gypsum drywall is sufficient outside the wet areas.

A properly sized and used exhaust fan is a necessity in any bathroom with a shower as far as I'm concerned. If you don't currently have one, now is the time to install one.

My opinion; worth price charged.
__________________
CX

Y'ALL NEW VISITORS READ THIS HERE!
cx is online now   Reply With Quote
Unread 09-26-2014, 02:43 PM   #13
bajpga
Registered User
 
Join Date: Jun 2014
Posts: 25
Can someone please recommend a good screw for securing plywood layers together. I would like a screw that will pull the two layers together and not allow the head to burrow into the top player.
Will a Kreg S.S. pan head type screw work?

Thanks
__________________
John
bajpga is offline   Reply With Quote
Unread 09-29-2014, 05:10 PM   #14
bajpga
Registered User
 
Join Date: Jun 2014
Posts: 25
Leveling over Ditra

Can someone please explain why you cannot level the floor over the top of Ditra?
Why can one not use a medium bed unmodified mortar to properly fill the grids, add more mortar as needed and screed or trowel to flat or level, then let all dry before setting tile with the same mortar?
For my application, that would be adding no more than 1/4" of flattening/leveling material.

Thanks
__________________
John
bajpga is offline   Reply With Quote
Unread 09-29-2014, 07:49 PM   #15
cx
Moderator emeritus
 
cx's Avatar
 
Join Date: Jul 2001
Location: Boerne, Texas
Posts: 92,692
You want some sort of coated or plated fastener for that application, John, and you definitely want the screw head to pull into the top layer at least enough to be completely flush. Craig screws are not what you want.

One easily available deck screw you can get at many home centers is the Deck Mate brand and it would be good for your application.

One very good reason for not leveling or flattening on top of your Ditra rather than under it is that the manufacturer doesn't want you to do that.

The manufacturer of the thinset mortar also does not want you to use his product for flattening or leveling the substrate.

My opinion; worth price charged.
__________________
CX

Y'ALL NEW VISITORS READ THIS HERE!
cx is online now   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
Bathroom Floor Leveling diln76 Tile Forum/Advice Board 12 02-28-2009 07:11 PM
Upstairs Bathroom Floor mikeyg Tile Forum/Advice Board 4 08-05-2008 05:09 AM
Leveling Basement Floor in Bathroom + I'm New! Mr.T Tile Forum/Advice Board 7 01-05-2007 06:05 AM
Upstairs bathroom floor project Bjorn Tile Forum/Advice Board 18 01-12-2004 08:14 PM
Upstairs bathroom floor tdelker Tile Forum/Advice Board 41 08-25-2003 03:31 PM


All times are GMT -6. The time now is 07:02 PM.


Sponsors

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