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 09-09-2020, 09:55 AM   #16
cx
Moderator emeritus
 
cx's Avatar
 
Join Date: Jul 2001
Location: Boerne, Texas
Posts: 90,914
The infamous TYW basement closet is a frequently recommend here on the forums to reduce joist span to eliminate excessive deflection, Jack. Very effective and frequently otherwise useful.

If you were to shorten the unsupported span of those joists by two feet, and if those joists are of good species and grade, and if you call or visit your mom regularly, I think you would have a structure that would meet the L/360 deflection minimum required for your ceramic tile installation. Our Deflectometer doesn't include the 7.5" height you have for joist calculation, but we have a couple members here who can do the calculations if we actually knew the species and grade of your joists. Absent that, I'd extrapolate the data the Deflectometer is capable of and be comfortable that I'd achieved better than L/360. See my warranty information below.

If you elect to sister your joists as well you need not have the ends of your sisters supported from below so long as you've fastened them adequately to the existing joists with construction adhesive and mechanical fasteners.

The addition of a minimum of nominal 1/2" exterior glue plywood with no face of grade lower than C over your existing board subfloor would then give you a suitable subfloor for a tile installation substrate, including a waterproofing membrane, and ceramic tile.

My opinion; worth price charged.
__________________
CX

Y'ALL NEW VISITORS READ THIS HERE!
cx is online now   Reply With Quote
Unread 09-09-2020, 11:21 AM   #17
jadnashua
Veteran DIYer- Schluterville Graduate

STAR Senior Contributor

 
Join Date: Jul 2004
Location: Nashua, NH
Posts: 14,046
To achieve the desired benefit when sistering joists, you must have a minimum of 2/3'rds of the middle with the sister. More is nice, but doesn't add all that much.
__________________
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 09-09-2020, 12:56 PM   #18
Kman
Moderator
 
Kman's Avatar
 
Join Date: Nov 2006
Location: NW Arkansas, Ozark Mountains
Posts: 11,591
You would take the span, minus the depth of the closet, because now the joists are shorter. Plug that number in now as your unsupported span.

The joists width can be a combination of the original joists plus the sisters. Yours is a full 2", and if you add a nominal 2x of the same height, you would just make the joists width 3 1/2".
__________________
Kevin

The top ten reasons to procrastinate:

1.
Kman is online now   Reply With Quote
Unread 09-09-2020, 08:17 PM   #19
johnston101
Registered User
 
Join Date: Sep 2020
Location: Baltimore, MD
Posts: 12
Nice! Thanks everyone!
__________________
Jack
johnston101 is offline   Reply With Quote
Unread 09-24-2020, 06:59 AM   #20
johnston101
Registered User
 
Join Date: Sep 2020
Location: Baltimore, MD
Posts: 12
help with plywood underlayment

Hi.

I'm planning on installing Ditra on an existing covered porch built around 1920.

The subfloor is 3/4" floorboards running perpendicular to joists. They look like they have old black glue and some paint on them. See pic.

Questions are :

1) Do I lay my new plywood underlayment that is going on top of floorboards perpendicular to floorboards or joists? I read perpendicular to joists is best, but then it will be parallel with floorboards.

2) Will Liquid Nails Subfloor product stick to this old black glue? Do I need to sand it? I really dont want to sand it. It could be something nasty.

Thanks for help!
Attached Images
 
__________________
Jack
johnston101 is offline   Reply With Quote
Unread 09-24-2020, 07:43 AM   #21
e3
Registered User
 
Join Date: Jan 2003
Location: mi.
Posts: 4,868
Send a message via Yahoo to e3
Wink

remove them altogether.
__________________
Eric
Noble Company
e3 is offline   Reply With Quote
Unread 09-24-2020, 07:56 AM   #22
cx
Moderator emeritus
 
cx's Avatar
 
Join Date: Jul 2001
Location: Boerne, Texas
Posts: 90,914
Jack, please don't start new threads on the same project. Just results in confusion and duplication of effort on the part of our all-volunteer army of helpers. Keep all your project questions here so folks can see what you're working on and what's been previously asked and answered.

All layers of structural subflooring must be oriented with the strength axis perpendicular to the joists. Period.

If those boards are in bad condition, Eric's suggestion may be your best approach. You don't care whether Liquid Nail will stick to the boards or not as you will not be using any glue between your layers of subflooring in this application.

What have you decided to do to improve your joist deflection?

My opinion; worth price charged.
__________________
CX

Y'ALL NEW VISITORS READ THIS HERE!
cx is online now   Reply With Quote
Unread 10-11-2020, 03:18 PM   #23
johnston101
Registered User
 
Join Date: Sep 2020
Location: Baltimore, MD
Posts: 12
Sorry about that.

We resolved our deflection issue by doing the closet idea on each wall underneath. We also sistered new joists to the existing. All good to go!

Right now the Ditra is down, but we have a few questions before the actual tile process.

Do we need an expansion joint down the center of the floor? This is an exterior floor (porch) that is 14' x 8'. The tile is Quarry Red Flash 6x6 Daltile that is 1/2" thick.

Second question is, there are ridges on the back of the tile going one direction. Do these go a certain direction relative to the trowel lines?

Thanks!
__________________
Jack
johnston101 is offline   Reply With Quote
Unread 10-11-2020, 04:50 PM   #24
e3
Registered User
 
Join Date: Jan 2003
Location: mi.
Posts: 4,868
Send a message via Yahoo to e3
Might check with Schluter to verify that it is suitable for exterior applications. I heard that it is no longer recommended for it.?
__________________
Eric
Noble Company
e3 is offline   Reply With Quote
Unread 10-11-2020, 06:07 PM   #25
jadnashua
Veteran DIYer- Schluterville Graduate

STAR Senior Contributor

 
Join Date: Jul 2004
Location: Nashua, NH
Posts: 14,046
While Ditra can be made waterproof if you band the seams, it does have pockets in it that can hold moisture which won't be good in an area that has freeze/thaw cycles.

One thing not potentially addressed is the height of the steps. Code wants them all to be within some minimum differences...otherwise, it can become a trip hazard. Adding more stuff on top of the landing could become a problem.

I did not see that you ever indicated if you have any slope on that deck. That can make any moisture penetration worse as it won't tend to mostly run off.
__________________
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 10-11-2020, 07:44 PM   #26
cx
Moderator emeritus
 
cx's Avatar
 
Join Date: Jul 2001
Location: Boerne, Texas
Posts: 90,914
Current online Ditra Installation Handbook does not appear to contain any information at all about exterior installations, as Eric suggests. My most current (2013) Printed Handbook had exterior installations, which still required at least a plywood subfloor and an exterior rated CBU for the Ditra installation over a properly sloped surface.

I believe the Noble products, sheet membranes, that Eric (e3 above) would recommend in your application also require a CBU over a wood framed subfloor and it still must be properly sloped. I'm sure Eric will correct me if that's not the case.

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
Tiling a Porch Taylor Tile Forum/Advice Board 2 01-08-2017 04:51 AM
Tiling a porch Saltworks Tile Forum/Advice Board 7 08-08-2016 10:33 AM
Opinion needed - porch tile layout herbk Tile Forum/Advice Board 4 10-13-2004 07:01 PM
Tiling a porch Unregistered Tile Forum/Advice Board 2 07-02-2004 05:40 PM
Tiling an outside porch cnrhome Tile Forum/Advice Board 13 04-08-2002 08:17 PM


All times are GMT -6. The time now is 08:11 PM.


Sponsors

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