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 > Professionals' Hangout

Sponsors


Reply
Thread Tools Search this Thread
Unread 04-13-2011, 07:27 PM   #1
pgc555
Registered User
 
Join Date: Aug 2009
Location: Chicago NW Burbs
Posts: 1,226
Phil's SLU Thread

I know that we have been down this road with CBU. Yes, plywood of coarse adds structural advantage and No, CBU "technically" doesn't.( I still think that
when it's laminated to the plywood with the thin set under it and then mechanically fastened, it DOES add something) But, that debate it for another thread and day.

My question now is, Does SLU ADD ANY structural advantage? OR, is it just the
same as CBU. I'm saying SLU WITH some kind of mesh ( plastic or metal ). It would
seem to me that this cemetitious SLU would act as a "stiffener" to the plywood it's installed over and by doing so, would be structurally valuable.

I'll get some popcorn and come back and watch this one flush out
__________________
Phil,

http://www.edgestripkits.com/
pgc555 is offline   Reply With Quote
Sponsored Links
Unread 04-13-2011, 07:33 PM   #2
Houston Remodeler
Pondering retirement daily

STAR Senior Contributor

 
Houston Remodeler's Avatar
 
Join Date: Oct 2009
Location: Houston Texas
Posts: 28,201
If you pour a layer of SLC over plastic sheeting or paper and let it cure you'll find out rather rapidly how easily it crumbles when bent. So my guess is it has even less tensile or deflection strength than CBU.
__________________
Paul1

For when DIY isn't such a good idea...
Houston TX area Kitchen & Bath Remodeling


http://CabotAndRowe.com
Houston Remodeler is offline   Reply With Quote
Unread 04-13-2011, 07:51 PM   #3
dhagin
builder, anti-builder, rebuilder -- Retired Moderator
 
Join Date: Mar 2009
Location: oahu
Posts: 13,162
Same as backer in that substrates need to be structurally sound before installing. I'd argue that it does, same as backer, increase mass and as such provides more resistance to applied loads. (tried to thread the needle there )

But until someone specifically tests for this sort of thing, we can't count on any structural advantage. SLU compressive strengths can be very high, though. Custom's Levelite is spec'd at 4600 psi at 28 days, compared to standard residential concrete at 2500 - 3500 psi.
__________________
dana

"the road to hell is paved with osb, mastic, pre-mixed latex 'grout' or 'thinset', "
dhagin is offline   Reply With Quote
Unread 04-14-2011, 04:47 AM   #4
bbcamp
Registered User
 
Join Date: Jul 2002
Posts: 30,274
Compressive strength is of little value in bending, which is what you are doing to a subfloor. Both SLU and CBUs are brittle, meaning that cannot take much bending. While there is some strength in each product, the amount gained is offset by the increased dead load on the structure.
bbcamp is offline   Reply With Quote
Unread 04-14-2011, 06:48 PM   #5
mctile
Fort Collins, CO. Tile Contractor
 
mctile's Avatar
 
Join Date: May 2006
Location: Fort Collins, CO.
Posts: 989
If lath is applied to the subfloor will this not add to the tensile strength of the layer of SLU? Or, being that the lath is in-between the subfloor and the layer of SLU, will the lath see little force acting upon it with the tensile force acting on the subfloor and the compressional force acting on the layer of SLU?
__________________
Matthew



Fort Collins Colorado Tile Installation
mctile is offline   Reply With Quote
Unread 04-14-2011, 10:40 PM   #6
pgc555
Registered User
 
Join Date: Aug 2009
Location: Chicago NW Burbs
Posts: 1,226
Matt, Are you ASKING those questions? or Are you ANSWERING my question with those questions?????
__________________
Phil,

http://www.edgestripkits.com/
pgc555 is offline   Reply With Quote
Unread 04-14-2011, 10:57 PM   #7
mctile
Fort Collins, CO. Tile Contractor
 
mctile's Avatar
 
Join Date: May 2006
Location: Fort Collins, CO.
Posts: 989
Definitly asking. Just wondering how much (if any) lath in conjunction with SLU would help with tensile strength of a subfloor. I have often wondered if when lath is bonded to a subfloor and an SLU is poured on top and the layer of SLU is thinner than the subfloor if the lath does anything for the tensile strength of the subfloor/SLU layer due to the lath being on the top half of the subfloor/SLU layer.
__________________
Matthew



Fort Collins Colorado Tile Installation
mctile is offline   Reply With Quote
Unread 04-14-2011, 11:12 PM   #8
pgc555
Registered User
 
Join Date: Aug 2009
Location: Chicago NW Burbs
Posts: 1,226
You bring up a good point. Ditra filled waffles act to help with compression
(deflection) right? JB you may have to get in on this.I THOUGHT that was
the way it was presented in the workshop (I could be wrong) That is why
it is rated for 19.2" o.c. joist spacing over single plywood - F148-09

Would then SLU with lath be a similar result?

I'm still just asking not presenting this as true.
__________________
Phil,

http://www.edgestripkits.com/
pgc555 is offline   Reply With Quote
Unread 04-14-2011, 11:17 PM   #9
cx
Moderator emeritus
 
cx's Avatar
 
Join Date: Jul 2001
Location: Boerne, Texas
Posts: 89,799
Quote:
Originally Posted by Phil
Ditra filled waffles act to help with compression
(deflection) right?
If I understand what you're suggesting (not at all sure), no, that wouldn't be correct. Ditra will have absolutely no effect upon the design deflection of the subfloor at all.

The Ditra waffles filled with thinset mortar will have quite sufficient compressive strength in the the vertical direction, the direction perpendicular to the plane of the membrane, but in no other direction. That's part of the design. Indeed, that's the whole concept of the design.

My opinion; worth price charged.
__________________
CX

Y'ALL NEW VISITORS READ THIS HERE!
cx is offline   Reply With Quote
Unread 04-14-2011, 11:29 PM   #10
pgc555
Registered User
 
Join Date: Aug 2009
Location: Chicago NW Burbs
Posts: 1,226
Cx,
I stand corrected in my thinking and yield to the gentleman from Texas
__________________
Phil,

http://www.edgestripkits.com/
pgc555 is offline   Reply With Quote
Unread 04-14-2011, 11:40 PM   #11
cx
Moderator emeritus
 
cx's Avatar
 
Join Date: Jul 2001
Location: Boerne, Texas
Posts: 89,799
Might wanna check with Herr Schluter to be sure I'm correct before you concede the point, Phil.
__________________
CX

Y'ALL NEW VISITORS READ THIS HERE!
cx is offline   Reply With Quote
Unread 04-15-2011, 02:36 PM   #12
pgc555
Registered User
 
Join Date: Aug 2009
Location: Chicago NW Burbs
Posts: 1,226
Cx,
That's why I invited JB to the party.I would take his word as solid.I'm sure you would also?
__________________
Phil,

http://www.edgestripkits.com/
pgc555 is offline   Reply With Quote
Unread 04-15-2011, 02:58 PM   #13
John Bridge
Mudmeister
 
Join Date: Mar 2001
Location: Rosanky, Texas
Posts: 67,905
Send a message via AIM to John Bridge
CX probably knows more than I do about compression.

Actually, that's what you guys are talking about. Tensile strength is stretching, and that would occur on the bottom of the panel, not the top. Ditra couldn't possibly make a difference because the small squares of thin set are not even connected; they've got air between them.

ANYthing bonded to the surface of the plywood is going to add something. The question: is that something valuable? Not really.
John Bridge is offline   Reply With Quote
Unread 04-15-2011, 04:26 PM   #14
Steve Taylor
Registered User
 
Join Date: Jul 2010
Location: So. California
Posts: 274
An un-coupling membrane works by allowing differential movement between the single layer of plywood and the tile assembly. So, no it does not contribute to the structural strength. In TCNA F-185 SLU is applied over a single layer of plywood, when re-inforced with lath, and is suitable for tile installation. We can not bond tiles directly to a single layer of plywood because of too much deflection. The addition of the SLU, re-inforcment and installed tile reduce the deflection; as demonstrated by the Robinson Floor tester. It does not contribute to the overall sructure performance of the floor, so we are reluctant to say that it has imporved the structural strength of the floor. However, it does allow installtion of tile.

The same argument holds for backerboard.
__________________
Steve
Retired Tile Industry Chemist
Steve Taylor is offline   Reply With Quote
Unread 04-15-2011, 05:21 PM   #15
John Bridge
Mudmeister
 
Join Date: Mar 2001
Location: Rosanky, Texas
Posts: 67,905
Send a message via AIM to John Bridge
Hi Steve. Glad to have met you at Coverings.
John Bridge 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
Phil's roll in shower project firepilot Tile Forum/Advice Board 95 03-31-2012 09:07 AM
Why use lath with SLU? pgc555 Professionals' Hangout 14 01-04-2012 08:25 PM
Phil's Shower Project 420benz Tile Forum/Advice Board 98 04-26-2010 05:00 PM
Phil's Main Bath Redo paral Tile Forum/Advice Board 39 02-03-2010 12:00 PM
Phil's Kitchen Floor Project flipr Tile Forum/Advice Board 60 07-19-2009 09:21 PM


All times are GMT -6. The time now is 02:57 AM.


Sponsors

Powered by vBulletin® Version 3.7.4
Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.
Copyright 2018 John Bridge & Associates, LLC