Replies

1. 
   Patrick_OSullivan | Oct 03, 2023 03:45pm | #1

   > My upstairs floor uses 2×12 joists and is 2 foot on center with 7/8 osb

   What is the span of the joists?

   > One thing that helps is there’s a wall on the first floor almost directly under the center of the shower I’m not sure if that makes a difference or not

   Do you know if it's a load bearing wall?

1. 
   derekr | Oct 03, 2023 03:49pm | #2

   The span isn’t very far because I have 3 walls below it

   From the side wall to the next wall under the shower is like 10 feet, then from the wall under the shower to the next wall is 7 feet, then from that wall to the next is 4 feet

   I’m not sure If it’s load bearing wall or not but it has a double 2x4 on top, would that mean it’s load bearing?

1. 
   andy_ | Oct 03, 2023 09:06pm | #3

   "I’m not sure If it’s load bearing wall or not but it has a double 2x4 on top, would that mean it’s load bearing?"
   Double top plate is not an indicator of bearing.

   For the tile, are you concerned about weight? or tile cracking from deflection? Either way, someone else can chime in on the math for deflection and span loads, but tile weight shouldn't be an issue especially for a bathroom with a shower and not a tub. If you have concerns about cracking tile, use a good decoupling membrane under your tile.

1. 
   Patrick_OSullivan | Oct 03, 2023 10:39pm | #4

   > but tile weight shouldn't be an issue especially for a bathroom with a shower and not a tub. If you have concerns about cracking tile, use a good decoupling membrane under your tile.

   Decoupling membrane will help prevent subfloor expansion/contraction from cracking tile, but deflection, particularly live load deflection, could cause tile issues.

   Without specifics, it's hard to know if these are 2x12 ceiling joists stretched to their limit to support drywall, or if they're sturdy assembly to support loads from above.

   Is this an attic being converted? A non-bathroom, but finished space being converted? We need more info.

1. 
   derekr | Oct 04, 2023 12:04am | #8

   It’s not an attic it’s just the 2nd floor

2. 
   derekr | Oct 03, 2023 11:23pm | #6

   Yea I guess the tile cracking was concern

2. 
   Patrick_OSullivan | Oct 03, 2023 10:40pm | #5

   A non-load bearing wall could very well have a double top plate.

   Are you trying to do work yourself, with a contractor, a design professional, etc.? These details would be helpful.

1. 
   derekr | Oct 03, 2023 11:24pm | #7

   I’m tiling the shower myself I didn’t frame it though

   Just wasn’t sure if there were any rules for this type of stuff, tile shower in 2nd floor

2. 
   derekr | Oct 04, 2023 12:31am | #9

   The wall on the first floor under the shower is perpendicular to the first floor joists, this makes it load bearing right?

   All 3 walls are perpendicular on the first floor joists actually

1. 
   Patrick_OSullivan | Oct 04, 2023 08:02am | #12

   > The wall on the first floor under the shower is perpendicular to the first floor joists, this makes it load bearing right?

   No, not necessarily.

   What's under the wall (e.g. in the basement if you have one)?

   > All 3 walls are perpendicular on the first floor joists actually

   Are the other two walls exterior walls?

1. 
   derekr | Oct 04, 2023 10:07am | #13

   2 exterior walls 2 inside walls, all perpendicular to my first floor joists

   With one of those inside walls being only 4 inches from the center of the shower

   Under the first floor is just a crawl space with pillars and joists

3. 
   gusfhb | Oct 04, 2023 06:57am | #10

   Load bearing means that no one is going to yank it out in the future.
   The 'load' is not a problem unless the floor is somehow under built
   The local stiffness of the floor itself will affect the tile cracking.
   An extra layer of plywood underlayment ought to stiffen the floor locally enough to prevent tile cracking. Then best practices in building the shower stall

1. 
   derekr | Oct 04, 2023 07:24am | #11

   Yes I put another layer of plywood on top of the 7/8 osb

   The tile on the walls is not a concern? Just the floor?

4. 
   dan_saa | Oct 04, 2023 12:06pm | #14

   John Bridge tile forum is the best resource where tile pros will help DIY and tell you flat out when you are making a mistake. They also have a joist span deflection calculator, google John Bridge deflecto. Check the forums for how to use.

1. Expert Member
   MALCOLM TAYLOR | Oct 04, 2023 01:04pm | #15

   dan_saa,

   +1 for John Bridges.

2. 
   derekr | Oct 04, 2023 01:12pm | #16

   I made an account it says I’m in moderation Que before I can use it though