Cement Backerboard & Mortar

Reply

  #1  
Old 01-04-07, 10:24 AM
B
Member
Thread Starter
Join Date: Oct 2006
Posts: 42
Received 0 Votes on 0 Posts
Cement Backerboard & Mortar

I'm laying tile over a plywood floor on a second story. When looking at backerboard there were two thicknesses, 1/4 and 1/2". What thickness should I use?

They had the traditional backerboard there and then something called "Hardi Board", which was beige and seemed to be made of a different material. Which one is considered the best?

Finally, for the mortar to lay down on the plywood and the backerboard to go over, I got "Fortified Thin-Set Mortar". Am I good or is there a better choice?

Thanks a million guys.

Bill W.
 
  #2  
Old 01-04-07, 11:04 AM
S
Member
Join Date: Nov 2006
Location: USA
Posts: 1,342
Received 0 Votes on 0 Posts
I use 1/4 0n floors so it will transition better to other floorings, such as carpet.
You need to use unmodified under the board and latex modified with the tile. My own preference is for concrete board, be it Wonderboard or Durock, but, if properly installed, Hardi or Ditra membrane are both supposed to be recommended systems that work. I've just never used either because I like the concrete board. As to which system is "best", that's a toss up and you'll get lots of varying opinions. I have my reasons for the choice I prefer and others have theirs. Bottom line, they're all three officially recognized methods.
 
  #3  
Old 01-04-07, 11:42 AM
H
Member
Join Date: Jan 2006
Location: USA
Posts: 3,525
Received 8 Votes on 8 Posts
1/4" cement board is made for floors and is all thats really needed. The 1/2" board really doesnt add any additional structural integrity to the floor. What is more important though is what you'll be putting the cement board over. The structure needs to be solid with little to no movement for a successful tile installation. What do you currently have for a subfloor. What is the size of your floor joists, their on center spacing and their unsupported span from below? What is the subfloor comprised of - plywood, osb - how thick and how many layers? Will you be using ceramic tile or natural stone on the floor?

As to type of backer board and thinset I think Smokey covered that.

Hey Smokey good to see you are a little gentler when it comes to the Hardi and Ditra these days.
 

Last edited by HeresJohnny; 01-04-07 at 12:00 PM.
  #4  
Old 01-04-07, 12:20 PM
S
Member
Join Date: Nov 2006
Location: USA
Posts: 1,342
Received 0 Votes on 0 Posts
Hey, old dogs can learn new tricks, it just takes a little longer.
 
  #5  
Old 01-04-07, 12:49 PM
B
Member
Thread Starter
Join Date: Oct 2006
Posts: 42
Received 0 Votes on 0 Posts
Cement Backerboard & Mortar

The subfloor is plywood, and I'll be using ceramic tile. As for your other questions regarding layers and size of floor joists, I have to admit I don't know. I was going to do the demo and then check the subfloor for condition and stability. What should I be looking for?

Bill W.
 
  #6  
Old 01-04-07, 01:51 PM
H
Member
Join Date: Jan 2006
Location: USA
Posts: 3,525
Received 8 Votes on 8 Posts
Check to see what size floor joists you have, what the joists unsupported span from below is and what the on center spacing of the joists is. Report that info back here. This will determine if your floor structure will support a ceramic tile installation or you need to do anything to strengthen what you have. Also report back with the thickness of the plywood subfloor and how many layers of plywood you currently have.
 
  #7  
Old 01-04-07, 08:43 PM
B
Member
Thread Starter
Join Date: Oct 2006
Posts: 42
Received 0 Votes on 0 Posts
Cement Backerboard & Mortar

I'll apologize in advance for asking this question, but how do I determine the size of the floor joists, the unsupported span from below, the on center spacing, and the thickness of the plywood? Thanks.

Bill W.
 
  #8  
Old 01-05-07, 07:28 AM
H
Member
Join Date: Jan 2006
Location: USA
Posts: 3,525
Received 8 Votes on 8 Posts
As to the size of the joists, you can drill a test hole in the subfloor and see how deep the cavity is. Stick something long enough to reach the sheetrock ceiling below and measure to the top of the subfloor. Subtract the thickness of the subfloor and you'll have your joist height. Make your test hole close enough to a joist so that you can determine if the joists are 2x material, trusses or ijoists. As to on center spacing, measure the distance between the rows of nails securing the subfloor to the joists. As to unsupported span, measure from the floor below the distance between the walls supporting the room above. Measure in the same direction of the joists.
 
  #9  
Old 01-05-07, 09:18 AM
B
Member
Thread Starter
Join Date: Oct 2006
Posts: 42
Received 0 Votes on 0 Posts
Cement Backerboard & Mortar

Very clear explanation. I'll get those details this weekend and post my findings. Thanks.

Bill W.
 
  #10  
Old 01-05-07, 11:41 AM
B
Member
Thread Starter
Join Date: Oct 2006
Posts: 42
Received 0 Votes on 0 Posts
Cement Backerboard & Mortar

OK. Got those figures.

Joist height is 15 inches. Floor thickness is 1 inch. The joists are wooden beams, not sure what the proper term for them would be. The unsupported span from the floor below is 12 feet. The on center spacing is 16 inches. Thanks.

Bill W.
 
  #11  
Old 01-05-07, 12:42 PM
H
Member
Join Date: Jan 2006
Location: USA
Posts: 3,525
Received 8 Votes on 8 Posts
Bill

You are good to go with what you have. Make sure the plywood subfloor is well secured to the floor joists. If you have any creaks in the floor use some deck screws to fix the problem. Use an unmodified thinset under the cement board. Use a 1/4" notched trowel for this. Screw the cbu every 8" in the field and 6" around the edges. Some cbu's have a screw pattern right on the board. If thats the case you can use their screw pattern. Use the cbu screws that have the square drive heads. You can find these in Lowes or HD in the general area where they have the cbu. These screws are easier to set the heads flush with the top of the cbu. They supply the square drive bit in the box of screws.
 
  #12  
Old 01-05-07, 01:10 PM
B
Member
Thread Starter
Join Date: Oct 2006
Posts: 42
Received 0 Votes on 0 Posts
Cement Backerboard & Mortar

Thanks so much for your help. I'm sure I'll be back soon with more questions.

Bill W.
 
 

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