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 12-23-2016, 10:01 AM   #1
texas777
Registered User
 
Join Date: Dec 2016
Posts: 12
sufficient for marble tiling

Hi all,

I have 2x8 joists running about 6.5'' long spanning 24'' (max) in a small 36 sq foot bathroom. Part of the room is keeping it's existing subfloor, because it's tied in with the adjacent room. The remaining half has a new subfloor (old removed to updated pipes, etc).

I'm interesting in marble tiling and want to make sure it's feasible and what measures I can take to strengthen the structure (cross-blocking with hangers?, blocking underneath shower pan border?).

I'm also curious why many seem to recommend double wood subfloors. I had never heard of this until visiting the forum. What benefit does this offer? Is it better than using one single thicker sheet (7/8'' or 1'')? Is there a specific size of each plywood sheet that is recommended?

Thank you for the help!
Attached Images
  
__________________
David
texas777 is offline   Reply With Quote
Sponsored Links
Unread 12-23-2016, 10:31 AM   #2
cx
Moderator emeritus
 
cx's Avatar
 
Join Date: Jul 2001
Location: Boerne, Texas
Posts: 89,551
Welcome, David.

The Marble Institute of America (MIA) requires a double layer of plywood subflooring regardless the joist spacing for any natural stone tile installation. The double layer is required so that there are no places where a subflooring joint extends all the way from the joist top through the surface.

Quote:
Originally Posted by David
I have 2x8 joists running about 6.5'' long spanning 24'' (max) in a small 36 sq foot bathroom
A bit confusing there. Your joists have an unsupported span of only 6 1/2 feet (rather than inches)? And the 24 inches is the joist spacing, perhaps?

At least part of your new subflooring is inadequate, being oriented with the strength axis parallel to the joists rather than perpendicular. That needs to be corrected before you add another layer of nominal 1/2" exterior glue plywood over the entire floor.

My opinion; worth price charged.
__________________
CX

Y'ALL NEW VISITORS READ THIS HERE!
cx is online now   Reply With Quote
Unread 12-23-2016, 11:45 AM   #3
texas777
Registered User
 
Join Date: Dec 2016
Posts: 12
Thank you CX for the quick and informative reply.

Yes, you're right that the joist span is 24 inches and the joist span is 6.5 feet.

I will make sure the plywood's strength axis is perpendicular to the joists.

Is it worthwhile to add cross blocking to tie the joists together in certain places (ie. along the shower pan perimeter)?

Is there any concern of reusing the existing/old subfloor in conjunction with the new subfloor (which appear to be solid)?

Merry Christmas!
__________________
David
texas777 is offline   Reply With Quote
Unread 12-23-2016, 02:27 PM   #4
jadnashua
Veteran DIYer- Schluterville Graduate

STAR Senior Contributor

 
Join Date: Jul 2004
Location: Nashua, NH
Posts: 13,329
You'd want blocking to support the unsupported joints, but any additional blocking won't buy you additional strength on a distributed load...it does help with point loading, but not a distributed load which is held up by the joists. If you want to strengthen the joists themselves, you either need to shorten their span or add material by doubling/sistering them (which is harder to do when plumbing, wiring, ductwork, etc. is in the way).

If the old and new subflooring is the same thickness, replacing the old may not buy you anything UNLESS by putting in a new sheet, you can add T&G panels that will support the edges OR, if the existing sheets don't span at least three joists...it's not very strong to just hang the ply between one set of joists spanning only one bay - it will just be hanging by the fasteners verses being supported in the middle.

When you add the second layer, you want offsets and adequate screws. There's an article in the liberry (sic) that describes the proper method.
__________________
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 01-05-2017, 10:51 AM   #5
texas777
Registered User
 
Join Date: Dec 2016
Posts: 12
Does the need for the double plywood subfloor change if whether CBU or mortar is used? The plan is to have a mortar bed to level the uneven floor.

Height of the bathroom and the adjacent room is a concern, so would prefer to leave out the second plywood layer if possible for minimizing height difference from room to room.
__________________
David

Last edited by texas777; 01-05-2017 at 11:21 AM.
texas777 is offline   Reply With Quote
Unread 01-05-2017, 12:04 PM   #6
Houston Remodeler
Pondering retirement daily

STAR Senior Contributor

 
Houston Remodeler's Avatar
 
Join Date: Oct 2009
Location: Houston Texas
Posts: 28,195
No,

The plywoods are installed then the floor is flattened as desired.
__________________
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 01-05-2017, 12:47 PM   #7
cx
Moderator emeritus
 
cx's Avatar
 
Join Date: Jul 2001
Location: Boerne, Texas
Posts: 89,551
Quote:
Originally Posted by David
The plan is to have a mortar bed to level the uneven floor.
If that is to be a reinforced mortar bed of a minimum 1 1/4" thickness with welded wire mesh in the vertical center, the MIA will, I believe, accept that over a single layer subfloor.

My opinion; worth price charged.
__________________
CX

Y'ALL NEW VISITORS READ THIS HERE!
cx is online now   Reply With Quote
Unread 01-09-2017, 01:11 PM   #8
texas777
Registered User
 
Join Date: Dec 2016
Posts: 12
shower curb - 2x4 on edge

Hi,

My contractor is planning on building the shower curb with a single 2x4 on edge. It's a small shower in limited space. I'm more familiar with the curb base being built from 3 stacked 2x4s. Is there any concern that a single 2x4 isn't strong enough to support the weight of the shower enclosure? Thank you.
__________________
David
texas777 is offline   Reply With Quote
Unread 01-09-2017, 01:26 PM   #9
cx
Moderator emeritus
 
cx's Avatar
 
Join Date: Jul 2001
Location: Boerne, Texas
Posts: 89,551
David, it'll help if you'll keep all your project questions on one thread so folks can see what you're working on and what's been previously asked and answered. We can give it a more generic title any time you'd like to suggest one.

It'd help if we knew what type of shower receptor waterproofing system you intend to use, but in general that single 2x4 might be adequate if it's tall enough and if your contractor knows his business. Supporting the shower enclosure won't be a problem and you will not allow anybody to poke mechanical fasteners of any kind through the waterproofing of your curb.

My opinion; worth price charged.
__________________
CX

Y'ALL NEW VISITORS READ THIS HERE!
cx is online now   Reply With Quote
Unread 01-09-2017, 02:18 PM   #10
Davy
Moderator -- Mud Man
 
Davy's Avatar
 
Join Date: Jan 2003
Location: Princeton,Tx.- Dallas area
Posts: 32,224
Sometimes having a narrow curb is desired, especially in a tight shower. I have built many showers with a ripped down 2x6 for a curb. I cut it down to about 5 inches. The pan liner goes over the wood and then I wrap it with lath and mud it. Makes for a strong curb.
__________________
Davy

www.davystephenstile.com
Davy is offline   Reply With Quote
Unread 01-10-2017, 02:41 AM   #11
texas777
Registered User
 
Join Date: Dec 2016
Posts: 12
Thank you CX and Davy for the helpful responses.
__________________
David
texas777 is offline   Reply With Quote
Unread 01-17-2017, 12:23 PM   #12
texas777
Registered User
 
Join Date: Dec 2016
Posts: 12
Is cement board on the curb considered a bad practice? Should I insist on on mud and lath for the curb?

My contractor is insisting on the 2x4 edgewise curb.

CX: Can you elaborate a little more on this comment? "a single 2x4 might be adequate if it's tall enough and if your contractor knows his business"
__________________
David
texas777 is offline   Reply With Quote
Unread 01-17-2017, 12:42 PM   #13
cx
Moderator emeritus
 
cx's Avatar
 
Join Date: Jul 2001
Location: Boerne, Texas
Posts: 89,551
1. It is not acceptable practice in a traditonal mud/liner/mud shower receptor construction.

2. It's not likely to be tall enough for some types of shower receptor construction, David and some tile contractors, in my experience, are not well versed in the other building trades, such as carpentry.
__________________
CX

Y'ALL NEW VISITORS READ THIS HERE!
cx is online now   Reply With Quote
Unread 01-17-2017, 05:36 PM   #14
jadnashua
Veteran DIYer- Schluterville Graduate

STAR Senior Contributor

 
Join Date: Jul 2004
Location: Nashua, NH
Posts: 13,329
Code calls for a minimum drop of 2" from the top of the curb to the drain...with a conventional shower pan construction, that's almost impossible to achieve with a 2x4 on edge.

Once the liner is wrapped over the 2x4, how would you install cbu without piercing the curb? Since the CBU isn't waterproof, how would you apply anything on top of it with it buried in the deckmud that would prevent moisture from wicking up and out of the curb? Classic situation where moisture gets in there, the wood swells, the tile/grout crack, and things fail.
__________________
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 01-18-2017, 01:07 PM   #15
texas777
Registered User
 
Join Date: Dec 2016
Posts: 12
Starting to think about tile and grout.

Current proposal:
*1/8'' grout line
*unsanded grout (Bostick)
* carrara 3x6 tile on shower wall
* 1'' hexagon on shower floor
* 3'' hexagon on bathroom floor

I understand that 1/8'' grout line is at the midpoint between sanded and unsanded grout, but I know sanded grout is not recommended for marble.

Any feedback is appreciated!
__________________
David
texas777 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
Set back from edge for a hybrid tub (nailing flange and finished front edge) stephenson Tile Forum/Advice Board 8 01-16-2013 02:45 PM
Tiling a varying-height shower curb; Penny tile OK on top of curb? smcquaid Tile Forum/Advice Board 6 01-07-2012 09:02 PM
Edge of Marble curb chipper Tile Forum/Advice Board 2 12-16-2006 08:44 PM
2x4 on edge for curb Rob Morita Tile Forum/Advice Board 2 06-28-2005 04:13 PM
floor tile with a pillow edge ( soft radius on edge) cas Tile Forum/Advice Board 1 01-20-2004 10:12 PM


All times are GMT -6. The time now is 10:39 AM.


Sponsors

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