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   Buy a TYW Shirt

Go Back   Ceramic Tile Advice Forums - John Bridge Ceramic Tile > Tile & Stone Forums > Tile Forum/Advice Board

Sponsors


Reply
 
Thread Tools Search this Thread
Old 06-05-2007, 08:15 AM   #1
AaronB
Registered User
 
Join Date: Apr 2007
Location: Kitchener, ON Canada
Posts: 10
Smile Structural Issue - Removing Plank Subfloor & Replacing with Plywood?

I'm planning a gut and replace on our main bathroom. Our house is a 40 year old bungalow. The subfloor is 3/4" T&G planks running diagonally across the joists. After reading a number of threads here I was planning on cutting out the planks and replacing with 3/4" T&G exterior grade plywood. I don't have the luxury of building up the existing subfloor as there would be too much of a lip when meeting the adjoining floor.

My question is - if I'm goign to be cutting out the existing subfloor and replacing it, will that cause any strucutral issues, specifically around support for the walls that surround the bathroom? ie. I'm not sure if the floor helps tie in and hold all of the walls together. I was planning on leaving 1/4" around the perimeter of the room for expansion purposes.

Any advice? Is my quesiton even clear?
AaronB is offline   Reply With Quote
Sponsored Links
Old 06-05-2007, 08:43 AM   #2
Brian in San Diego
AC Specialist -- Schluterville Graduate
 
Brian in San Diego's Avatar
 
Join Date: Oct 2005
Location: San Diego, CA (Northwest part of the city)
Posts: 10,760
Aaron,

Yes, your question is clear and the first part of your answer is no. The subfloor doesn't support the walls per se. The problem that you may experience and have to address is the lack of support for the edges of your new subfloor. You may have to do some blocking and make provisions for supporting those outer edges. Once that is done, you should be able to install your 3/4" exterior plywood.

It seems you've done some reading and I'm assuming you've run your joist dimensions through the deflecto. If so, (and you have enough structural support)then with the new subfloor you should be good for a ceramic installation. Stone requires two layers of plywood.

Brian
__________________
Brian
If that doesn't work, I'll always think it should have.
Brian in San Diego is offline   Reply With Quote
Old 06-05-2007, 09:06 AM   #3
AaronB
Registered User
 
Join Date: Apr 2007
Location: Kitchener, ON Canada
Posts: 10
Brian,

Thanks - that's great info. I was planning on blocking the perimiter to ensure that all points of the subfloor were supported. I was concerned that removing the existing subfloor would somehow weaken the structure or lead to "flexing" of the walls.

I've used the Deflecto and am clear for installing ceramics. I'm actually putting down a porcelain tile (3/8" thick, not glazed) with a DITRA underlayment so I am confident I won't have any cracking there. I just didn't want to go ahead, replace the floor, tile everything, then have sagging walls or something!

Thanks for the advice.
AaronB is offline   Reply With Quote
Old 06-05-2007, 04:37 PM   #4
jadnashua
Veteran DIYer- Schluterville Graduate
 
Join Date: Jul 2004
Location: Nashua, NH
Posts: 8,947
If your walls don't sit on a joist, you'll want to run blocking support underneath the wall, especially if the wall runs parallel with the joists.
__________________
Jim DeBruycker
Not a pro, multiple Schluter Workshops (Schluterville and 2013 and 2014 at Schluter Headquarters), Mapei Training 2014, and Longtime Forum Participant.
jadnashua is offline   Reply With Quote
Old 06-11-2007, 07:43 PM   #5
AaronB
Registered User
 
Join Date: Apr 2007
Location: Kitchener, ON Canada
Posts: 10
jadnashua - I think I get what you mean. If I'm cutting out the subfloor, and the wall is overhanging the joist, then I should block underneath the wall to support it, right?
AaronB is offline   Reply With Quote
Old 06-11-2007, 07:59 PM   #6
bbcamp
Registered User
 
Join Date: Jul 2002
Posts: 30,305
[quote]If I'm cutting out the subfloor, and the wall is overhanging the joist, then I should block underneath the wall to support it, right?[/QUOTE=AaronB]

Yep!
bbcamp is offline   Reply With Quote
Old 06-11-2007, 08:11 PM   #7
Rob Z
Guest
 
Posts: n/a
Aaron,


More often than not you can take out that old subfloor that runs under those NON-BEARING walls and nothing will happen. The walls are tied into the ceiling joists or the bottom chord of the roof trusses or raffters, they're tied into the walls they intersect, they are even held in place by the drywall or plaster that is on the wall on the other side from the bathroom.

I'm not saying that you shouldn't try to tie everything back together, but sometimes is next to impossible to get blocking into some or all of the space that you'll find under the wall you're describing.

One trick we use is to get the new subfloor in and fastened to the joists. Then we install Simpson framing angles along the bottom plate of the wall and tie it into the subfloor. This arrangement will support whatever slight sag the wall might have over time. If you are going to put backer board on the floor then use a router or a chisel to plow out a space for the bottom part of the angle. If going with a mud floor you don't have to worry about it.

If you can get some framing under this wall , by all means do it. But if it seems extremely difficult, post some pictures and we might be ab le to think of some options.
  Reply With Quote
Old 06-12-2007, 08:41 PM   #8
jerseyreef
Registered User
 
Join Date: Mar 2007
Posts: 102
Aaron,

I've been doing this in my house for the past year and let me impart some advice and similar to what Rob was saying.

After much trial and error, what I found worked best is to locate the nearest parallel joist to the interior/exterior you’re working with and only cut the existing sub-floor to that joist. You can either split the difference along the center line of the joist or sister a new along side it and attach the new sub-floor the either method. The reasoning for this is two fold
  1. Providing proper support - If you cut out the sub-floor where an interior wall lays parallel between two parallel joists, the now unsupported sub-floor will now sag and you'll have to support it which may involve jacking up the interior wall a bit, just to slip in the new joist materials. If the interior wall is load bearing or supporting some decent load, it will sag. Way too much effort and complex.
  2. Defined square - It's by far easier to work in a known defined square area, then trying to match up uneven dimensions. Trust me, you'll need these pieces to go in seamlessly.

In the image below, you can see how I cut out the existing T&G sub-floor. The old existing floor remained on the left side of the room and I installed a sistered joist to make the new sub-floor install easier. I'll also tack down the old T&G with 8d ring sank nails to secure them.

Also, you'll need to note that 3/4" from 40 years ago isn't the same as it today, you'll be 1/32" higher on the old floor than the new floor. Nothing but a belt sander can't take of in a few seconds

__________________
Thanks,

Mike - JerseyReef
jerseyreef is offline   Reply With Quote
Old 06-15-2007, 02:41 PM   #9
AaronB
Registered User
 
Join Date: Apr 2007
Location: Kitchener, ON Canada
Posts: 10
Mike - you're the man! That's an awesome idea, and I will certainly be using that approach. Makes a lot more sense, looks easier, and looks like it will do a better job of supporting the walls (no need for the blocking now).

Thanks a million for the idea!
AaronB is offline   Reply With Quote
Old 02-21-2008, 04:37 PM   #10
poolmaninct
steel mud pipes tiles ....underground
 
Join Date: Jan 2008
Posts: 121
mike does the sister member on the left run the whole span? or are you bolted where access was available?

ray
__________________
less with the jaw .....more with the paw

Ray in Connecticut
poolmaninct is offline   Reply With Quote
Reply

Buy John's New Book!   Tile Your World Online Store   Contractors Direct Tile Tool Store   Stonetooling.com   Tile-Assn.com


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


All times are GMT -6. The time now is 05:06 PM.


Sponsors

Powered by vBulletin® Version 3.7.4
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright 2014 John Bridge & Associates, LLC