Sub Floor Thickness for Tile

Reply

  #1  
Old 04-20-15, 02:42 PM
J
Member
Thread Starter
Join Date: Apr 2015
Location: United States
Posts: 4
Received 0 Votes on 0 Posts
Sub Floor Thickness for Tile

Hello Everyone,

thank you for reading/helping me out on this project. I am remodeling my bathroom. I ripped up the old floor tile and down to my sub-floor.

My sub floor is 5/8.
Floor Joists are 2x8 , 16 on center.

I plan on laying long tiles - 6" x 24"

I am trying to determine the thickness of plywood I should add to my existing sub floor, I plan on adding 1/4 backer board to the floor as well.

Any advise would be great, Thank you
 
Sponsored Links
  #2  
Old 04-20-15, 03:32 PM
J
Member
Join Date: May 2007
Location: USA
Posts: 1,607
Received 0 Votes on 0 Posts
Hi Jimmy,

You left out the other important info about the framing. We also need the unsupported span of the joists. Measure accurately. Is the longest 10'10" or 11'9" or? Our answer will also be more accurate if we knew the species and grade along with age and condition. Is there a basement or crawl under there? Where are you roughly?

On the subfloor; ⅝" meets min. standards in most states, but is kinda, well, kinda bad. Is the subfloor the same throughout the house or was something removed from this room? What kind of floor do/did you have before?

Have you checked how flat the floor is now? It needs to be very flat for long tiles like that. Decided on the backer yet? What specific type of thinset, etc?

Jaz
 
  #3  
Old 04-23-15, 04:13 PM
J
Member
Thread Starter
Join Date: Apr 2015
Location: United States
Posts: 4
Received 0 Votes on 0 Posts
Hello Jaz

Thank you for replying. I apologize about the delay. I was checking my email account looking for a update email when someone responded to my post. Might have to set that up .

I m working now but will be home later to answer your questions

Thank you
 
  #4  
Old 04-24-15, 09:29 AM
J
Member
Thread Starter
Join Date: Apr 2015
Location: United States
Posts: 4
Received 0 Votes on 0 Posts
Hello Jaz

-The support span is 12ft 4in
-I'm not sure about the species and grade
-The joists age - 55 years
-Condition is good,
-Bathroom is above basement with open ceiling
-5/8 subfloor is thoughout the house. One level house.
-Bathroom had 1 1/2 plaster on top of 5/8 subfloor then tile. I'm down to 5/8 subfloor
-The floor is level / pretty flat.
I have not decided on thin set.
I was told to use Hardie backer board.

Really Appreciate the advise - thank you
 
  #5  
Old 04-24-15, 11:30 AM
J
Member
Join Date: May 2007
Location: USA
Posts: 1,607
Received 0 Votes on 0 Posts
Jimmy,

Since those joists are from '59- '60, I need you to measure to see what they actually measure. Current 2x8's are 1.5 x 7.25", I'm sure yours are bigger, but how much?

Jaz
 
  #6  
Old 04-25-15, 08:13 PM
J
Member
Thread Starter
Join Date: Apr 2015
Location: United States
Posts: 4
Received 0 Votes on 0 Posts
Hello Jaz

My joist are 1.5 x 7.5.

Thank you
 
  #7  
Old 04-26-15, 04:36 PM
J
Member
Join Date: May 2007
Location: USA
Posts: 1,607
Received 0 Votes on 0 Posts
As you've already learned, (at the other forum), your joists are over spanned. The best case scenario for you is a max span of 10'11" if everything is perfect, and the joists are #2 Southern Pine. And that gets you to L360 deflection which is the worst they can be. So, you need to stiffen those joists up a bit.

I know you have doubts that you may not have measured the span correctly. Did you ever re measure? You do NOT measure the whole length of the joist, just the span, the portion that only has air under it. I looked at my chart again and I think you actually did it right. The difference is that when your house was built they used a load factor of 40/10 live/dead instead of what I'm using which is 50/20.

Why did I do that? Believe me, your plywood, and everything fastened to it will weigh way more than that. (10 lb. sq. ft.). I figure 20 lbs. which is also much less than you'l have. So, 50/20 is my min.

So, go ahead and sister all the joists to stiffen them, and/or shorten the span by building a support (wall/beam) under there.

Jaz
 
  #8  
Old 04-27-15, 08:05 PM
J
Member
Join Date: May 2007
Location: USA
Posts: 1,607
Received 0 Votes on 0 Posts
Jimmy,

A little birdie told me your span is not 148" but it's really 139". That's a big difference. Although some of the joists spacing are under 16" oc, you can not consider it since they are not all less than 16" oc. You are still over spanned.

Doesn't mean it'll fail for that reason, but I wouldn't tell you to go ahead.

Jaz
 
Reply
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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: