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 01-31-2019, 07:12 PM   #16
jadnashua
Veteran DIYer- Schluterville Graduate

STAR Senior Contributor

 
Join Date: Jul 2004
Location: Nashua, NH
Posts: 13,089
Trying to screw through a layer of slc is not going to work out well at all. IF you need it, it should be the layer above any ply.

If you're tearing out your subflooring, you can usually strengthen things below so that your new subflooring will be nice, flat and level.
__________________
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 01-31-2019, 09:52 PM   #17
Yes si
Registered User
 
Yes si's Avatar
 
Join Date: Jan 2019
Location: Houston Texas
Posts: 33
Thanks for replying Cx.
sorry about the useless pics. not sure how the orientation loaded that way either.
Yes I will be using deck mud. still not sure of whether ill be using traditional pre-slope /liner/ mud deck because I prefer the shower floor and main floor to be somewhat the same height.
My options feel limited after seeing Isaac Ostrom's video on Kerdi 7 day test and the follow up with the drain but I digress.

my reasoning for considering ignoring the existing 1/2' plywood and adding 2 layers of plywood on top is 2 fold.
one is because the long wall of the shower sits between joist and has dead load over it in the form of water heater. That wall backs up to a hall way and the plywood under the hall way runs under the shower wall and terminates in a joints almost in the middle of the proposed shower subfloor over a beam . I did add a joist under this loaded wall but i'm paranoid and afraid that there could still be movement .
the other concern is as follows:
note:The 1st pic in that last post is my attempt in outlining (in blue "marker") the area of unsupported plywood which shows a dip (in person) . Now when I say unsupported I mean no JOIST under the plywood. if you will please note the square of plywood showing in that outline is only a fourth of a total 16sf area (4'x4') the other forth is under the tile and lastly the other half on the opposite side in the other room. The only thing they did to support this area was to bridge the span (off centered) with a 2x4 on its side held up by two 2x4 "cleats".
because of the limited space with the plumbing there isn't much I can do for an ideal structural solution other then taking advantage of the existing cleats that span the width.
there is a wall directly under this space so, I did take advantage of the existing cleats to add another 2x4 except here I was able to stack blocks from the top plate of the underlaying wall to this stud/improvised "joist"
I realize its hard/impossible to visualize what I just described especially with my lack of knowing how to describe it.

Question is how to fasten the plywood? glue and screws to joist/no joist?
thanks again CX been learning a lot of your post
__________________
Jesse

Last edited by Yes si; 01-31-2019 at 10:12 PM. Reason: clarifying the area dimensions
Yes si is offline   Reply With Quote
Unread 01-31-2019, 10:08 PM   #18
Yes si
Registered User
 
Yes si's Avatar
 
Join Date: Jan 2019
Location: Houston Texas
Posts: 33
Thanks Jim.
yea I guess I thought I would pre-drill through the ply and SLC before screwing . but your suggestion makes sense. it's just that there are 3 joints that are off and plywood uneven in a such a small footprint that im not sure how the new plywood would conform to 1/2 ridges and valleys.
Btw,cutting out the 1/2 plywood will cause greater complications then its worth.
This nice elderly lady had her galvanized pipes burst upstairs caused much damage, then , my plumbers re-piped and forgot to attach washer machine drain hose and caused more damage, last thing I want is a leaky shower .
I can't wait to get past this stage.
__________________
Jesse
Yes si is offline   Reply With Quote
Unread 01-31-2019, 10:18 PM   #19
jadnashua
Veteran DIYer- Schluterville Graduate

STAR Senior Contributor

 
Join Date: Jul 2004
Location: Nashua, NH
Posts: 13,089
ANy time you try to screw multiple sheets together with wood screws, there's the chance of 'jacking' which is that the point of the screw turns a bit before it bites into the underlying layer and then acts like a screw jack. Because of the threads, this can leave a gap between the sheets. Plus, 1/2" ply won't allow enough 'bite' for the screw to pull things together before the threads strip out in the wood. If you're leaving the 1/2" stuff there, treat it like it isn't there and screw into the joists.
__________________
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 01-31-2019, 10:45 PM   #20
Yes si
Registered User
 
Yes si's Avatar
 
Join Date: Jan 2019
Location: Houston Texas
Posts: 33
Those are really good points, Jim. I will screw into joist.
if I double up on the plywood it will bring my final shower floor considerably higher. I wonder if that would be an issue stepping into and out of it?
__________________
Jesse
Yes si is offline   Reply With Quote
Unread 10-07-2019, 02:33 AM   #21
Yes si
Registered User
 
Yes si's Avatar
 
Join Date: Jan 2019
Location: Houston Texas
Posts: 33
3 layers of subfloor ?

3 layer subfloor help

Hello from Houston where you’re always wet...if it ain’t from flooding it’s from sweat.
So, I have another head scratcher (least for me) that I couldn’t find an answer to.
1st off , thank you who take the time to read and reply to post.
I appreciate you all and learn tons here.
Ok , Hope someone has ran into something like this.
It’s a 2nd floor condo , Bathroom remodel , tub to shower conversion,
On 12” deep open web truss joists on 24” o.c. that span about 25’ . I have to assume that there is some intermediate support to the trusses from below which i can’t confirm because it is another unit I don’t have access to. I realize only the manufacturers of engineered joist systems would know the deflection properties of their particular system but,
I’m just hoping for a close rule of thumb.
The bathroom is at the end of the joist span , in the corner of the unit with a common wall parallel to the long side of this 10.5’ x 5’ area with the floor trusses that also run parallel to the long side. The subfloor is 1.5” concrete with 1/2” plywood under. It might be helpful to know that it also has a truss rafter system and it appears that at least 3 walls are not load bearing (including the 2 parallel walls to the joist)
Since the joists are spaced at 24” o.c. only 2 joist are under the bathroom footprint . The common wall is 6” proud of the supporting joist and the opposite wall has a similar situation .
What I’m wanting to do is control the deflection between joist and need direction on how to address the space between joist. Being that the parallel walls to the joist sit at least 6”proud of the joist under it makes options difficult especially when thinking of installing blocking between joist. I don’t know what would keep the unsupported remainder 6” plywood “lip” under those walls from sagging under its own weight (making lining up blocks under the potential sag to the top chord a problem)
- [x] Would it be an option to just glue and screw 2 layers of 3/4” B Cx or t&g sturd-I-floor to the original 1/2 plywood and install detra then tile?
I only know the joist layout because there is a walk in attic behind the shower wall that sits about 1 foot lower that allowed me to cut access for a side view of the flooring system.
Thanks in advance.
Jesse
Attached Images
  
__________________
Jesse

Last edited by Yes si; 10-07-2019 at 08:14 AM. Reason: Was too long
Yes si is offline   Reply With Quote
Unread 10-07-2019, 08:08 AM   #22
cx
Moderator emeritus
 
cx's Avatar
 
Join Date: Jul 2001
Location: Boerne, Texas
Posts: 88,567
Welcome back, Jesse.

I don't know if this is the same bathroom project as the one from earlier this year, but I've combined your threads here so we don't lose all the previous discussion on subflooring.

If I understand your current situation, you've removed the "concrete" substrate and are down to the useless half-inch subflooring, which is now spanning engineered joists on 24" centers, making it even less useful than in your previous description/area.

Without the option of installing adequate blocking or additional joists to support the outside edges of your new subflooring, I'd say your best - perhaps only - option would be to add the two layers of plywood you're suggesting, counting on the rigidity of the plywood to support the cantilevered overhang beyond the existing joists. Certainly not a perfect solution, but you don't appear to have a lot of options.

And in this case I would recommend you actually glue and screw the second new layer to the first new layer with a full spread of wood glue to enhance the rigidity. The first layer would be fastened to the joist structure as though the existing half-inch layer were not even there. The second new layer would be pre-drilled for the fastening screws to prevent screw-jacking and make the fastening more firm for the gluing.

Keep in mind that all layers of subflooring must be oriented with the strength axis perpendicular to the joist structure.

My opinion; worth price charged.
__________________
CX

Y'ALL NEW VISITORS READ THIS HERE!
cx is offline   Reply With Quote
Unread 10-07-2019, 08:27 AM   #23
Yes si
Registered User
 
Yes si's Avatar
 
Join Date: Jan 2019
Location: Houston Texas
Posts: 33
Hi Cx. Thanks for the fast reply.
No it’s a different project. I can’t seam to get a break.
Yes you understood correctly.
Do you think cutting individual holes in the plywood big enough to add blocking one at a time starting around the perimeter could work?
Or would I risk in compromising the existing plywood in case it’s already warped enough to make blocking connections on the top cord therefore killing any chance for the 1st option of just screwing and gluing to existing plywood?
__________________
Jesse
Yes si is offline   Reply With Quote
Unread 10-07-2019, 08:43 AM   #24
cx
Moderator emeritus
 
cx's Avatar
 
Join Date: Jul 2001
Location: Boerne, Texas
Posts: 88,567
Understand. We can either leave the threads combined to preserve the subfloor discussion or separate your new project from the original. Your choice.

Without seeing exactly what you're working with my best guess is no, you could not really improve your situation by cutting holes in your existing subfloor, although removing the entire half-inch subfloor wouldn't hurt at all. I just don't see how you'd manage to install adequate blocking at those room edges without access to the adjacent apartment, which I presume is not yours.

I'd need to be onsite to help much more and we don't even know where onsite might be, eh? A geographic location in your User Profile is frequently helpful in answering some types of questions.

My opinion; worth price charged.
__________________
CX

Y'ALL NEW VISITORS READ THIS HERE!
cx is offline   Reply With Quote
Unread 10-07-2019, 09:05 AM   #25
Yes si
Registered User
 
Yes si's Avatar
 
Join Date: Jan 2019
Location: Houston Texas
Posts: 33
I don’t mind them being combined so long as it doesn’t hurt chances of getting feedback on this current situation.
But I value your input and since I currently have your attention, it’s a moot point.

Regarding making holes in the existing subfloor, the idea is to install blocks 1 hole at a time to avoid a cantilever effect and then cut out the the rest of the old ply completely.
But , your point is another concern.
The project is Uptown Houston ( Galleria area). Bering st to be exact.
Lots of townhomes and condos in the area.

Here is another question, say I left the existing plywood and glued and screwed double layer of 3/4, how would I minimize potential future shower walls to shower floor separation ?
Do I try and tie the framing and flooring together?
__________________
Jesse

Last edited by Yes si; 10-07-2019 at 09:19 AM. Reason: Missed a word
Yes si is offline   Reply With Quote
Unread 10-07-2019, 09:12 AM   #26
Yes si
Registered User
 
Yes si's Avatar
 
Join Date: Jan 2019
Location: Houston Texas
Posts: 33
Here is something else to consider. I attached a pic.
The existing plywood in this area only has nails in the corners.
Attached Images
 
__________________
Jesse
Yes si is offline   Reply With Quote
Unread 10-07-2019, 09:24 AM   #27
cx
Moderator emeritus
 
cx's Avatar
 
Join Date: Jul 2001
Location: Boerne, Texas
Posts: 88,567
Quote:
Originally Posted by Jesse
...say I left the existing plywood and glued and screwed double layer of 3/4, how would I minimize potential future shower walls to shower floor separation ?
'Fraid I don't understand the question, Jesse.

While that subflooring may make it easier to work in that area, it's looking more and more like something I'd want gone before installing my permanent subflooring.

Quote:
Originally Posted by Jesse
The project is Uptown Houston
You have my most heartfelt sympathy.

My opinion; worth price charged.
__________________
CX

Y'ALL NEW VISITORS READ THIS HERE!
cx is offline   Reply With Quote
Unread 10-07-2019, 09:28 AM   #28
Yes si
Registered User
 
Yes si's Avatar
 
Join Date: Jan 2019
Location: Houston Texas
Posts: 33
Like you mentioned, I’m worried about being able to properly fasten blocks under those walls especially because I do Not have access below (separate unit).
Geez talk about a coin flip. Heads you lose , tails you lose.
__________________
Jesse
Yes si is offline   Reply With Quote
Unread 10-07-2019, 09:37 AM   #29
Yes si
Registered User
 
Yes si's Avatar
 
Join Date: Jan 2019
Location: Houston Texas
Posts: 33
What I saying is I’m concerned about the new sub floor perimeter relying on the old plywood for support especially around the new shower floor. If there is a risk in between the joist sub floor sagging here could be disastrous, don’t ya think?
__________________
Jesse
Yes si is offline   Reply With Quote
Unread 10-07-2019, 09:40 AM   #30
Yes si
Registered User
 
Yes si's Avatar
 
Join Date: Jan 2019
Location: Houston Texas
Posts: 33
Ty for your sympathy. I’ve been working word of mouth in this area since the beginning of the year. I’m starting to feel sorry for myself. But, I got moufeses to feed.
__________________
Jesse
Yes si 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
Glue for plywood layers in subfloor gimel Tile Forum/Advice Board 10 03-14-2013 04:25 PM
WTF? 5 layers of 1/2 inch subfloor? LunchBox Tile Forum/Advice Board 1 01-01-2013 10:00 PM
subfloor layers and ditra bman1978 Tile Forum/Advice Board 12 10-20-2009 08:40 PM
Subfloor layers wouldheart Tile Forum/Advice Board 13 01-10-2006 09:06 PM
Subfloor layers (how many) bmulcahy Tile Forum/Advice Board 3 11-15-2005 01:14 PM


All times are GMT -6. The time now is 09:10 AM.


Sponsors

Powered by vBulletin® Version 3.7.4
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Copyright 2018 John Bridge & Associates, LLC