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Old 12-10-2014, 10:13 PM   #1
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1x12 plank subfloor, question about tiling


I am in the process of renovating an entryway. I removed the carpet to expose some 1/4" fiber board(beaverboard maybe) over top of 1x12 planks ran diagonally on 16" center floor joists. This was an addition, and the wood floors adjacent to this are 1/4 higher than the planks.

My question is I have read not to use cement board on top of plank floors, but usually this is in reference to smaller planks. Can I cement board directly on these planks? They are quite even as is. Should I install another subfloor over the planks, then cement board, then tile. I am afraid this is going to be over an inch taller if I do this! I can handle a little bump up to the entryway, but 1" seems extreme.

Beverboard?


1x12 Planks
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Old 12-10-2014, 10:30 PM   #2
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Quote:
Originally Posted by ryanl View Post
I am in the process of renovating an entryway. I removed the carpet to expose some 1/4" fiber board(beaverboard maybe) over top of 1x12 planks ran diagonally on 16" center floor joists. This was an addition, and the wood floors adjacent to this are 1/4 higher than the planks.

My question is I have read not to use cement board on top of plank floors, but usually this is in reference to smaller planks. Can I cement board directly on these planks? They are quite even as is. Should I install another subfloor over the planks, then cement board, then tile. I am afraid this is going to be over an inch taller if I do this! I can handle a little bump up to the entryway, but 1" seems extreme.

Beverboard?


1x12 Planks
Can not install any cement board over that subfloor without first adding plywood. Not OSB, plywood. A minimum of 3/8" plywood, thicker would be better. Then you can install the cement board on top of the plywood.
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Old 12-10-2014, 10:38 PM   #3
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Thicker would be the only way to go. If allowable 5/8 min.
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Old 12-10-2014, 10:47 PM   #4
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Thats what I was afraid of. I need to stay as low profile as possible. I know thicker is better, but I have to go thin on one. Would it be better to lay 3/8ply with a thicker cement board, or 5/8 ply with a thinner cement board?
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Old 12-11-2014, 05:43 AM   #5
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why cement board. why not just plywood, bc or ac. properly spaced and screwed down. I know its old school, but those jobs are still strong 20-25 yrs later. then you can use the thickness you need for the strength you need
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Old 12-11-2014, 06:21 AM   #6
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why cement board. why not just plywood, bc or ac. properly spaced and screwed down. I know its old school, but those jobs are still strong 20-25 yrs later. then you can use the thickness you need for the strength you need
No longer being considered an acceptable method (tile directly on plywood). There are a few Model-T's still around too but that doesn't mean they are the thing to buy today.

Could use 5/8" ply and DITRA (1/8").
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Old 12-11-2014, 07:03 AM   #7
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And no, using a thicker tile board will do nothing to add strength.
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Old 12-11-2014, 08:53 AM   #8
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to bud cline. fair enough point taken. and yes I forgot ditra. the sluter products are very good.
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Old 12-11-2014, 10:01 AM   #9
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Ryan I'll offer a crash course in installing ceramic tile for what it may be worth to you.

First of all if by "Beaverboard" you are referring to "particleboard" then yes...what you have there appears to be particleboard. Get rid of it of course as you are doing.

Your 1X12 subfloor is typical of the vintage of the structure. You may think the floor is stable but it in fact is not. That type of lumber moves with seasonal changes. The splits and separations shown in the photo are testimony to this fact. The boards cup and crown and split and curl seasonally.

The subfloor would be a little stronger if the boards had been installed perpendicular to the floor joists, but as they are their deflection is slightly greater because of the unsupported board lengths between the floor joists. What you have is however typical.

The plywood is needed to tame-down the movement of these boards because plywood is more tolerant to seasonal changes than dimensional lumber. The plywood does not get adhered to the boards, only screwed down to what's below.

Cement board offers no structural value what-so-ever. It is nothing more than an excellent "tooth" for the tile thinset to hang onto. Therefore the additional thickness should be in the plywood, not the cement board. The thicker the plywood the better. A thickness of 3/8" is the absolute minimum thickness allowed by the rule book if you care to comply with the rules. Remember I said "minimum".

You may have to live with a small change-up in elevation between differing flooring finishes and components.

When you install cement board it must be placed in a fresh bed of thinset and immediately mechanically fastened to the substrate. The thinset is to fill any voids that may exist and is not a means of gluing the cement board to the plywood.

We also haven't addressed the potential "span deflection". Too much deflection will kill a tile installation in a short time. So...What is the size of the floor joists and what is the unsupported span of the floor joists? If you also knew the wood species that would be helpful. I wouldn't spend another dime until the deflection can be determined. Not all structures are suitable for a ceramic tile installation.

Your deal! Ante up!
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Last edited by Bud Cline; 12-11-2014 at 10:04 AM.
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Old 12-11-2014, 01:13 PM   #10
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You can add a layer plywood then...
Or.
Remove the planks and add the amount of plywood then.....
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Old 12-11-2014, 01:19 PM   #11
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I do not recommend ⅜" ply over any plank floor. My min. recommendation is " if the planks are about 4" +- and in good condition. But when the planks are wider like yours, you should go thicker. Wider planks require thicker ply cuz they will distort more and the distance from high points is further. Go as thick as possible as already mentioned.

So after repairing the subfloor, install ⅝" or " underlayment and consider Ditra instead of concrete backer. You'll save at least 3/16" over the " CBU.

Let us know the joists' info Bud asked.

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Old 12-11-2014, 06:15 PM   #12
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Quote:
Originally Posted by Bud Cline View Post
Ryan I'll offer a crash course in installing ceramic tile for what it may be worth to you.

First of all if by "Beaverboard" you are referring to "particleboard" then yes...what you have there appears to be particleboard. Get rid of it of course as you are doing.

Your 1X12 subfloor is typical of the vintage of the structure. You may think the floor is stable but it in fact is not. That type of lumber moves with seasonal changes. The splits and separations shown in the photo are testimony to this fact. The boards cup and crown and split and curl seasonally.

The subfloor would be a little stronger if the boards had been installed perpendicular to the floor joists, but as they are their deflection is slightly greater because of the unsupported board lengths between the floor joists. What you have is however typical.

The plywood is needed to tame-down the movement of these boards because plywood is more tolerant to seasonal changes than dimensional lumber. The plywood does not get adhered to the boards, only screwed down to what's below.

Cement board offers no structural value what-so-ever. It is nothing more than an excellent "tooth" for the tile thinset to hang onto. Therefore the additional thickness should be in the plywood, not the cement board. The thicker the plywood the better. A thickness of 3/8" is the absolute minimum thickness allowed by the rule book if you care to comply with the rules. Remember I said "minimum".

You may have to live with a small change-up in elevation between differing flooring finishes and components.

When you install cement board it must be placed in a fresh bed of thinset and immediately mechanically fastened to the substrate. The thinset is to fill any voids that may exist and is not a means of gluing the cement board to the plywood.

We also haven't addressed the potential "span deflection". Too much deflection will kill a tile installation in a short time. So...What is the size of the floor joists and what is the unsupported span of the floor joists? If you also knew the wood species that would be helpful. I wouldn't spend another dime until the deflection can be determined. Not all structures are suitable for a ceramic tile installation.

Your deal! Ante up!

Bud, Thanks for all your help. Ok let me answer some questions...and ask some more!

I am in cable engineering, so forgive me if my structural lingo isn't exactly correct!

My joists are 2x8, 16oc with a span of 10'. Type of wood I am not sure (I am still trying to figure out what type of wood floors I am looking at in my living room!), The front entryway is 10x7, joists are anchored to a what I believe is a solid block foundation. Sitting about 4' above ground level. The only time the entryway even is used, is when some door to door person comes a knocking. Everyone else uses the side door. So there will be little traffic if that helps any.

My next question. Would it be better to just remove the plank flooring altogether and replace with 3/4" ply? My only problem would be that the walls are knotty pine and go down about 1/8th" from the floor so getting to the edges if nailed there (most likely?) might be difficult without removed the Pine panels.

Ohh and that 1/2" particle board is like no particle board I have ever seen if that is in deed what it is. It was more like what I see in old attics on the ceiling.

Last edited by ryanl; 12-11-2014 at 06:17 PM.
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Old 12-11-2014, 06:26 PM   #13
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Quote:
Originally Posted by ryanl View Post
Bud, Thanks for all your help. Ok let me answer some questions...and ask some more!

I am in cable engineering, so forgive me if my structural lingo isn't exactly correct!

My joists are 2x8, 16oc with a span of 10'. Type of wood I am not sure (I am still trying to figure out what type of wood floors I am looking at in my living room!), The front entryway is 10x7, joists are anchored to a what I believe is a solid block foundation. Sitting about 4' above ground level. The only time the entryway even is used, is when some door to door person comes a knocking. Everyone else uses the side door. So there will be little traffic if that helps any.

My next question. Would it be better to just remove the plank flooring altogether and replace with 3/4" ply? My only problem would be that the walls are knotty pine and go down about 1/8th" from the floor so getting to the edges if nailed there (most likely?) might be difficult without removed the Pine panels.

Ohh and that 1/2" particle board is like no particle board I have ever seen if that is in deed what it is. It was more like what I see in old attics on the ceiling.
I haven't looked it up but am satisfied your floor structure criteria will meet the required minimums for what you want to do.

Removing the planks??? Don't even go there. In my opinion that is not the thing to do. Your walls are likely built on top of those boards. To remove them would be opening the biggest can of worms you have ever seen. Add the plywood on top of them.

The particleboard has proven to be a bad deal over the years, get rid of all of that crap.
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Old 12-11-2014, 06:34 PM   #14
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The particleboard has proven to be a bad deal over the years, get rid of all of that crap.
That was the first to go, the entire first floor was covered in mastic and the particle board was no exception. I had to remove that before I knew what the subfloor even looked like. I started with a hammer and prybar thinking I could just pull it up. Then found it was nailed every 6" with twist shank nails. I went out and bought a shingle shovel after 10 minutes of trying. Using the shingle shovel made the work so much easier. Probably 2 hours and it was done.
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Old 12-11-2014, 06:39 PM   #15
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Also there was tar paper on top of the planks I assume as a vapor barrier, that I removed. Do I need to add anything before the plywood?
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