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 07-19-2022, 04:01 PM   #1
zimm0who0net
Registered User
 
Join Date: Aug 2010
Location: Tucson, AZ
Posts: 37
Ditra over plywood with impervious foam on back

About to Ditra an entire 2nd floor. One room goes over an outside area. The 1-1/8" plywood subfloor has a 2" closed cell foam sprayed underneath it as insulation. I know the rule is modified under ditra and unmodified over ditra, but I'm wondering if this might be an exception. I'm not sure the latex in the modified thinset will cure properly given that the moisture can't escape up (through the ditra) or down (because it'll hit the foam after going through the plywood).

Thoughts?

Also, is there a lot of difference in unmodified thinsets? I thought they were basically just portland and sand. So why does Mapei alone have six different products in that category?
__________________
Rich
zimm0who0net is offline   Reply With Quote
Sponsored Links
Unread 07-19-2022, 04:29 PM   #2
jadnashua
Veteran DIYer- Schluterville Graduate

STAR Senior Contributor

 
Join Date: Jul 2004
Location: Nashua, NH
Posts: 14,989
FWIW, today, not that many modified thinsets still use latex. Because the plywood still moves with seasonal changes, you would want to use the specified modified thinset. The ply will absorb some of the excess moisture, so I don't see a problem, but you could call Schluter and ask their tech support for confirmation. The moisture issue occurs when you have two impervious surfaces sandwiching the modified thinset...you don't have that...the ply will deal with any excess moisture.
__________________
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 07-19-2022, 04:44 PM   #3
zimm0who0net
Registered User
 
Join Date: Aug 2010
Location: Tucson, AZ
Posts: 37
Ok, so you're saying that even though the ply and the mortar are between two impervious surfaces (the foam and the ditra), the plywood will act as a "sponge" (for lack of a better term) and let the thinset dry properly.

That makes sense...
__________________
Rich
zimm0who0net is offline   Reply With Quote
Unread 08-01-2022, 07:58 AM   #4
pdeluca
Registered User
 
Join Date: Apr 2020
Location: Florida
Posts: 3
In response to your question "So why does Mapei alone have six different products in that category?" MAPEI is a tile mortar manufacturer so we continue to add new products as the industry changes and evolves. MAPEI makes some tile mortars only sold at Lowes, some are thinset mortars for smaller tiles, and others are for large format tiles with non-sag non-slump properties.
__________________
Patty
pdeluca 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
Heated Garage floor with 3" pink foam board, What is easiest subfloor plywood +hardi? rollandelliott Tile Forum/Advice Board 29 06-27-2014 06:38 AM
Plywood subfloor, foam, and that 1/8" Gap metal121 Tile Forum/Advice Board 3 10-30-2008 05:59 AM
underlay requirements over insulated concrete? (plywood/OSB/foam board) dougabowski Tile Forum/Advice Board 3 04-12-2007 05:00 PM
Ditra- exterior on impervious surface Jeffrey (dsnbld) Tile Forum/Advice Board 29 01-12-2007 10:01 PM


All times are GMT -6. The time now is 10:51 AM.


Sponsors

Powered by vBulletin® Version 3.7.4
Copyright ©2000 - 2022, Jelsoft Enterprises Ltd.
Copyright 2018 John Bridge & Associates, LLC