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 03-15-2020, 08:16 AM   #1
zink88
Registered User
 
Join Date: Mar 2020
Posts: 15
Subfloor Support Bathroom Remodel

I am replacing a garden tub and small fiberglass shower with a tiled shower that will measure ~ 3.5' x 8'. The floor joists are 9” x 1.5” (not 9.25”) and the span is 13'-6” spaced 16” on center. Existing joists are stamped #1 and #2 SPF. House was built in 1994.

Flooring is 1/2” OSB nailed to joists and a second layer of 5/8” plywood on top in the area where the tub and shower were not located. Floor squeaks/groans/pops quite a bit. Plan is to use use 12” x 24” tile on the floor.

I plan to sister the joists from underneath to reduce deflection and have removed the ceiling in the living room below. Two of the joists crown higher than the others causing a crowning of at least 1/4” in the middle of the floor. I plan to

(1) remove both layers of subfloor
(2) level the joists by planing where necessary
(3) add sister joists (screw & glue to existing joists)
(4) glue and screw 3/4” plywood to the joists
(5) add another layer of 1/2” plywood screwed into subfloor only (not the joists)
(6) use Ditra between floor and tile outside of shower

The wall and doorway separating the bedroom from the bathroom are in the middle of two joists. If I remove the 1/2” OSB and 5/8” plywood back to the wall and doorway, I will need to provide support for the transition from the bedroom to the bathroom and to support the walls. In the picture below, the blue lines represent the existing joists and the red lines are what I am thinking for the new support... Two pieces of “blocking” between the two joists and then one or two pieces of lumber running parallel to the existing joists to support the subfloor in the bedroom and the new subfloor in the bathroom.

There would be no changes to the flooring in Area 1. Area 2 would be the new 3/4” plywood and second layer of 1/2” plywood. In Area 3 (underneath where the vanity will be installed) between the two joists I would like to only remove the existing 5/8” plywood and leave the 1/2” OSB which would continue to support the wall.

(1) Could I lay 1/4” plywood on top of the 1/2” OSB so as to match the height of the new 3/4” subfloor and then lay the 1/2” plywood over the top of both Area 2 & 3?

(2) Could I do the same in Area 3 between the wall and the joist at the back of the toilet (left-hand side of the 4th picture below)?

I have attached pictures of the area to be turned into a shower and the exposed joists from the room below along with a picture indicating how I plan to handle the transition between the bedroom and bathroom.
Attached Images
    
__________________
Jim
zink88 is offline   Reply With Quote
Sponsored Links
Unread 03-15-2020, 09:26 AM   #2
cx
Moderator emeritus
 
cx's Avatar
 
Join Date: Jul 2001
Location: Boerne, Texas
Posts: 89,826
Welcome, Jim.

First question I have is, "Do you plan to install ceramic tile in any of the areas you're describing?"
__________________
CX

Y'ALL NEW VISITORS READ THIS HERE!
cx is offline   Reply With Quote
Unread 03-15-2020, 02:22 PM   #3
zink88
Registered User
 
Join Date: Mar 2020
Posts: 15
Plan is to tile the bathroom floor with porcelain tile. Possibly as large as 12”x24”. Shower will also be tiled. The bedroom will remain carpeted.
__________________
Jim
zink88 is offline   Reply With Quote
Unread 03-15-2020, 03:09 PM   #4
cx
Moderator emeritus
 
cx's Avatar
 
Join Date: Jul 2001
Location: Boerne, Texas
Posts: 89,826
In which case removing and replacing the entire subfloor is your best bet. Some added blocking under the partition wall is also a good idea while you're at it. Sounds like you intend to remove that vanity and I'd certainly want the new subfloor to extend under there, too.

I can find a span table indicating that your existing joist structure meets the code required L/360 deflection, but adding some sister joists while you have access from both above and below certainly makes sense.

As for your leveling plan, your tile installation doesn't care at all whether your subfloor is level, it cares only about it being flat. And those large format tiles care a great deal about flat.

My opinion; worth price charged.
__________________
CX

Y'ALL NEW VISITORS READ THIS HERE!
cx is offline   Reply With Quote
Unread 03-15-2020, 03:57 PM   #5
PC7060
...unrepentant, detail focused, over-analyzer.
 
PC7060's Avatar
 
Join Date: Jan 2013
Location: Virginia
Posts: 2,830
Agree with CX, and I have to say I’m envious of the lack of obstructions. Will make sistering the joists must simpler.

What type of supply line is that to the left side of floor joist picture?

Looks grey and am hoping it’s not polybutylene. Your house would have been at the tail end of the period it was in use.
PC7060 is offline   Reply With Quote
Unread 03-15-2020, 04:47 PM   #6
zink88
Registered User
 
Join Date: Mar 2020
Posts: 15
Quote:
Originally Posted by CX
In which case removing and replacing the entire subfloor is your best bet. Some added blocking under the partition wall is also a good idea while you're at it. Sounds like you intend to remove that vanity and I'd certainly want the new subfloor to extend under there, too.
Yes, I will be removing the vanity. I was hoping to avoid the need to add blocking/support for the wall where the vanity is as there is a plumbing drain from the vanity running between the two joists where blocking/support would be needed. If I remove both layers of subfloor to the joist running under the vanity (about 9" from the wall on the bathroom side of the wall) and remove only the 5/8" layer of subfloor all of the way to the wall, I could leave the 1/2" OSB running under the wall to the first joist that runs under the vanity and would continue to have the current level of support for the wall between the bathroom and bedroom. If I then add 1/4" plywood on top of the 1/2" OSB to the first joist, the floor level would be the same from the wall to the first joist (Area marked as #3 in the pictures) as the new 3/4" plywood added on top of the joists over the rest of the bathroom (Area marked as #2 in the pictures). I could then cover the entire floor from wall to wall with 1/2" plywood. Area 3 would have 3 layers of wood measuring 1.25" and Area 2 would have 2 layers of wood measuring the same 1.25 ".

Do you see this approach as a problematic for the tile installation and, if so, why?
__________________
Jim
zink88 is offline   Reply With Quote
Unread 03-15-2020, 04:52 PM   #7
zink88
Registered User
 
Join Date: Mar 2020
Posts: 15
Quote:
Originally Posted by PC7060
What type of supply line is that to the left side of floor joist picture? Looks grey and am hoping it’s not polybutylene.
Yes, it is polybutylene. At least I have copper rings instead of plastic rings. We are the original owners and fortunately have not yet had a leak. We may be benefiting from the fact that we are on well water with no chemicals added.
__________________
Jim
zink88 is offline   Reply With Quote
Unread 03-15-2020, 05:01 PM   #8
PC7060
...unrepentant, detail focused, over-analyzer.
 
PC7060's Avatar
 
Join Date: Jan 2013
Location: Virginia
Posts: 2,830
I’d certainly replace the accessible sections with PEX since you’ve got wide open access. Can’t tell from the picture but you may have to remove it to sister that last joist or two anyway.

I had polyB in one house but was able to get replumbed in copper as part of the insurance settlement. Having that stuff in your house in my area is a big issue when selling house.
PC7060 is offline   Reply With Quote
Unread 03-15-2020, 05:07 PM   #9
cx
Moderator emeritus
 
cx's Avatar
 
Join Date: Jul 2001
Location: Boerne, Texas
Posts: 89,826
In remodel work you sometimes gotta do what you gotta do, Jim. The areas to be tiled will be the more critical, but I'd try to get a useful subfloor everywhere I could while I had the option.

My opinion; worth price charged.
__________________
CX

Y'ALL NEW VISITORS READ THIS HERE!
cx is offline   Reply With Quote
Unread 03-16-2020, 03:27 PM   #10
zink88
Registered User
 
Join Date: Mar 2020
Posts: 15
Since my floor is already barely above the L/360 deflection requirement and the intent with sistering of the joists is to stiffen it further, I have read that it is not necessary to have the sister joist supported at each end by the wall plates.

(1) Can I fasten a 12' board on the existing joist which spans 13'-6" which would take me to within 9" of each wall...or should I get even closer to the supporting walls?

As can be seen in the pictures below, my joists have a bow from top to bottom in the 9" dimension. In addition, some of the joists were not fastened plumb on a 90-degree vertical.

(2) What is the best method to mechanically fasten the new sister joist to the existing joist to get as much contact between them as possible? Clamp and screw? Clamp and nail and then screw or carriage bolts?

This will most likely be a one-man operation with me screwing in scrap 2x4s to the bottom of the existing joists at each end to support the new joist while I maneuver it into position to attach to the existing joists.

(3) Given it will be a one man operation, is there a particular adhesive you recommend that will not skim over before I complete the fastening?
Attached Images
  
__________________
Jim
zink88 is offline   Reply With Quote
Unread 03-16-2020, 07:22 PM   #11
PC7060
...unrepentant, detail focused, over-analyzer.
 
PC7060's Avatar
 
Join Date: Jan 2013
Location: Virginia
Posts: 2,830
Jim,

12’ is great the 13’-5”. You’ll find that it’s nice to have a little room on each end to allow you to work them into place.

I usually screw a 2x4 off to the bottom of the joists on each end to have something to rest the new joists on while I’m setting them (see below) Once the sisters are installed, you remove the 2x4.

Sometimes you have to jam a temporary board under the bottom of the sisters to force them up into alignment where you want em (also shown below)

Name:  0999D892-7EE6-4FF8-AE39-C0C6418A38A8.jpeg
Views: 174
Size:  47.5 KB


Skip the clamps and use 3” deck screws with 1/4” or 5/16” washers alternating top and bottom 3rd of joist every 18”. I always use washers when glueing and screwing sisters in place to ensure the sistered joist is pulled in snugly. The washer are cheap and easy to place on the screws once you get the hang of it.

My go to adhesive used to be Locktite PL 3 series in the big tubes; very strong but a pain in the butt to gun. On my addition subfloor, I recently used Great Stuff polyurethane spray foam adhesive and really liked how easy it is to apply and how far it goes. You have to buy the foam gun applicator but you can get a decent one for around $18 on amazon.

Last edited by PC7060; 03-16-2020 at 08:07 PM.
PC7060 is offline   Reply With Quote
Unread 03-17-2020, 10:35 AM   #12
ss3964spd
Moderator
 
ss3964spd's Avatar
 
Join Date: Jul 2005
Location: Fairfax, Va
Posts: 2,981
Send a message via Yahoo to ss3964spd
The 12's will be more than sufficient, you could probably get by with 10's. Don't even try to get either end into those pockets - not likely to happen, not even by trying to "roll" them in.

Since you have to replace the ceiling drywall, and slide it into that space between the joist bottoms and the crown, be certain that the joists you add are not deeper than the existing.

Be careful if you have to jack up a new joist to deal with a crown. If you use too much force it could push the subfloor off the existing joist.

The two times I sistered a bunch of joists I used a combination of clamps, 2X4 scabs, long 2X4's and a floor jack, 1/2" nuts-n-bolts-n-washers, and thick PL adhesive.

I like PC's fastening ideas better.
__________________
Dan
---------------------------------------------------------------------------------
If I recall correctly my memory is excellent, but my ability to access it is intermittent.
ss3964spd is offline   Reply With Quote
Unread 03-17-2020, 03:43 PM   #13
zink88
Registered User
 
Join Date: Mar 2020
Posts: 15
Thanks for all of the answers so far.

Quote:
Originally Posted by SS3964SPD
Since you have to replace the ceiling drywall, and slide it into that space between the joist bottoms and the crown, be certain that the joists you add are not deeper than the existing.
Since my existing joists are only 9" deep, I had planned to rip 0.25" from each new sister joist. Most of the flooring is going to be removed and replaced as part of this process as detailed in my first messages above.

(1) The partition for the toilet and closet walls will make installing tongue & groove subfloor difficult...so I was planning to use 3/4" plywood that is not tongue and groove and gap 1/8" all around, screwed and glued to the joists. Then a 1/2" layer of plywood screwed into the subfloor (but not the joists) also gapped 1/8" all around. Sound correct? Should both layers of plywood be Exterior grade (Exposure 1) BC sanded pine?

(2) Use the Great Stuff polyurethane spray foam adhesive for both the sistering of joists AND the subfloor to the joists instead of the PL adhesive? Does the Great Stuff adhesive expand anything like the Great Stuff foam used to seal cracks and holes?
__________________
Jim
zink88 is offline   Reply With Quote
Unread 03-17-2020, 05:14 PM   #14
PC7060
...unrepentant, detail focused, over-analyzer.
 
PC7060's Avatar
 
Join Date: Jan 2013
Location: Virginia
Posts: 2,830
You may want to consider using 2x8 for the sistering; plenty strong for sistering that short of a span. I did exactly that to stiffen bouncy true 2”x10” joists on an old house I’m currently renovating. Made a huge difference to floor but was very easy to install.

Re the Great Stuff adhesive, it does expand but not to the same extent as the stuff for cracks and gaps. Sticks well to surface, wet, dry or dusty. The PL tends to drip down and is hard to compress; this stuff squeezes out easily under compress. I’ve used it for foam to concrete, wood to wood and subfloor to joists. Just keep the tip clean and it feeds fine. I’ve got a can that’s been on the gun for months, comes out kinda slow now but still workable.
PC7060 is offline   Reply With Quote
Unread 03-17-2020, 05:51 PM   #15
PC7060
...unrepentant, detail focused, over-analyzer.
 
PC7060's Avatar
 
Join Date: Jan 2013
Location: Virginia
Posts: 2,830
After discussing the storage of the Great Stuff adhesive on the previous post, I’d figured I’d do a health check on the can I’ve had on the gun since January. I didn’t mention previously that keeping the cans warm is a key element to success storage. To that end I keep my near the furnace and was able to pull this one, shake for 60 seconds and gun out a nice controller bead.

I’ve attached a few pictures showing initial 1/4 bead expanding to 1” over 10 seconds and after 5 minutes you can see it reverts to very sticky glue. The last picture is an example of a tight bead I forced between framing and subfloor in area I previously boxed in to make room for a toilet. Course if would have been better if I’d remembered to apply the adhesive before I banged the joists into place but who’s perfect!

Edit: the bottom picture is flipped sideways but you get the idea.

Name:  2709E30B-80C6-49D6-AE70-179276109BE6.jpeg
Views: 154
Size:  62.6 KB

Name:  3399728C-CCB0-44A0-BB01-6EFD46739E19.jpeg
Views: 151
Size:  62.7 KB

Name:  6F0B72CA-6397-4B4B-8F3D-1171BCF8369E.jpeg
Views: 146
Size:  63.7 KB

Name:  3E734775-7D1C-4E19-BBA7-A9095B11C0EB.jpeg
Views: 147
Size:  40.1 KB

Last edited by PC7060; 03-17-2020 at 06:03 PM. Reason: Added picture
PC7060 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
Bathroom remodel, looking for subfloor recommends jheretico Tile Forum/Advice Board 5 07-21-2019 10:03 AM
Bathroom Remodel Floor support Question Baseballhack Tile Forum/Advice Board 4 09-18-2017 09:53 AM
Bathroom Remodel - Subfloor Jschen Tile Forum/Advice Board 9 03-05-2016 07:56 PM
Bathroom Remodel - Subfloor Prep Furiousdog Tile Forum/Advice Board 10 08-19-2013 05:50 AM
Bathroom Remodel Subfloor Q's candlman Tile Forum/Advice Board 20 08-17-2006 10:42 AM


All times are GMT -6. The time now is 11:32 PM.


Sponsors

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