Two by Six floor joists

busyguy · 01-23-2011, 05:08 PM

Hi,
Informative and helpfull information on here.

Please elaborate on Two by six floor joists ,
I have a 50 year old house with true Two by six floor joists , 16.5 spacing
10 feet span, do not know the species.
3/4 grove and tongue Pine nailed right on that.

The floor is solid does not bounce.

Whe installed 3/4 hardie over thinset and the floor is now rock hard.

Would 18 inch Porcelain tile be too much , or should i go with ceramic.

It is the kitchen so tiling is prefered

Any suggestions are appreciated

Thank you

JazMan · 01-23-2011, 05:23 PM

On the joists. I don't see how 2x6's spanning 10 ft. can be solid.

However, depending on the species and grade, it's possible your true 2x6's will be OK for ceramic & porcelain.

Quote:

Whe installed 3/4 hardie over thinset and the floor is now rock hard.

I guess you meant to say 1/4" Hardie. But, Hardie should NOT be installed over any plank sub-flooring. You need plywood first.

If the floor met specs, 18" tiles would have been fine IF the floor was flat enough.

Jaz

busyguy · 01-24-2011, 05:11 AM

Jazzman,
Thank you for your replay, i am sure its 3/4 hardiebacker, was told hardiebacker is a good underlay for tile.
However , should i take it back up and just install the tile over the tongue and groove floor, or just proceed.
Mind you we put like five pounds of srews down.

Thanks again

JazMan · 01-24-2011, 11:09 AM

If Hardie now makes 3/4" tile backer they must have started last week. Measure it again. You'll find Hardie 500 measures less than 1/2". This one is for walls or floors. The 1/4" Hardie is best for floors.

BUT..................................... You didn't understand what I said above.

Quote:

But, Hardie should NOT be installed over any plank sub-flooring. You need plywood first.

How large an area is this? If you had hired someone to do the work I would say to make them remove it. Since you did it, I might not. It's still wrong though, so don't be surprised if you see grout cracks (or worse), if you continue.

Quote:

Mind you we put like five pounds of srews down.

Is that a lot of screws? Depends whether it's a bathroom or a kitchen, but screws will not correct what was done wrong.

Jaz

busyguy · 01-24-2011, 02:42 PM

You are right its 1/2 inch thick.
Its in the Kitchen , almost 160 square feet.
Did read somwhere else that hardiebacker is ok on tongue and grove .

Is there a diffrence between plank and tongue and groove?
supposetly i had 3/4 play tongue and groove as sub , that would be alright then?

Mine is Pine.
I do not understand the Playwood installation first.
We used screws every 8 inches and i can not see it moving anywhere.
Maybee i am missing something, so please let me know before i proceed.

Ripping the hardie out, installing 1/2 inch play and then 1/4 hardie makes the floor extra high , is it not also over kill ?

Sorry for so many questions, just trying to understand

Thank you

JazMan · 01-24-2011, 05:44 PM

When you said:

Quote:

Please elaborate on Two by six floor joists ,
I have a 50 year old house with true Two by six floor joists , 16.5 spacing
10 feet span, do not know the species.
3/4 grove and tongue Pine nailed right on that.

That to me means your subfloor are planks. Plywood subfloor is always tongue & groove, so that goes without saying. So.....are you saying your subfloor is 3/4" plywood?

When you say :

Quote:

Did read somwhere else that hardiebacker is ok on tongue and grove .

We still don't know what you've got there.

Quote:

We used screws every 8 inches and i can not see it moving anywhere.

You're not actually thinking you will see it move do you?

Let us know if it's plywood or planks.

Jaz

busyguy · 01-24-2011, 05:59 PM

Hello, and thanks for your help
It is 3/4 grove and tongue Pine

Got my info from ehow.
i do have the link but do not know if i am allowed to link to anything in this forum
thank you

JazMan · 01-24-2011, 07:59 PM

We still don't know what you mean by:

Quote:

It is 3/4 grove and tongue Pine

Inserting links is fine with me. I'm not sure the owners of this site will like it, but it's done all the time. It's actually a good way to double check what people read elsewhere. You should NOT trust everything you read....and that goes for this site too.

I've read some of the tile installation steps at EHow, and I'm not very impressed actually. Especially the one I just looked at about how to install ceramic tile on a kitchen floor. The person who wrote it doesn't know how to do it. I think he/she read it online somewhere.

Jaz

cep89 · 01-24-2011, 08:15 PM

You need 1 1/4 of subfloor. If your wood is 3/4 and 1/2 of hardibacker, you should be good. If you can jump up & down on the floor and someone near you can't feel it you should be ok. If they can feel the floor flex it will fail and you have rip it all out down to the joists and replace it with 3/4 inch t&g plywood and then 1/2 hardibacker. This of course is assuming that your structure is correct and undamaged.

JazMan · 01-24-2011, 11:26 PM

Quote:

You need 1 1/4 of subfloor.

Sorry neighbor, that is not correct. The only time you need that much plywood is when installing natural stone tiles. And BTW, Hardie does not qualify as part of the subfloor system. Neither Hardie, nor any CBU adds structural strength, just a tile-friendly surface to tile onto.

Although I wouldn't recommend it, 5/8" ply subfloor is acceptable when installing most concrete backers or Ditra.

I wouldn't guarantee anything under 3/4", but those are the specs.

Jaz

busyguy · 01-25-2011, 04:57 AM

Hello

The link to my installation is

http://www.ehow.com/how_4840067_tile...ove-floor.html

Its exactly my scenerio, just that i used 1/2 inch hardie because i needed the hight.

Thanks again, you been verry helpfull

cep89 · 01-25-2011, 07:28 PM

I have heard that 5/8 is ok too, but I have also heard that 3/4 is better. And given he said his joists are 2 x 6 I would go with 3/4 to reduce chances of it flexing. I have a hard time seeing the logic that cement board attached properly to plywood does not add any structual support than just the plywood. I don't have any testing to back this up, but it just seems much more solid after installing CBU.

JazMan · 01-25-2011, 07:55 PM

Busyguy,

Thanks for posting that link. I was afraid it might contain some goofy instructions that the writer pulled from his a**. What he suggests is NOT recognized as an approved method of installing tiles. He just heard about it someplace, it's definitely not in any reputable manual.

He also has no clue on how to mix thin set mortar.

You follow his directions and you'll never want to tile again.

Isn't the internet a wonderful thing?

Jaz

JazMan · 01-25-2011, 08:11 PM

Quote:

I have heard that 5/8 is ok too, but I have also heard that 3/4 is better.

Well...................of course!

Quote:

I have a hard time seeing the logic that cement board attached properly to plywood does not add any structual support than just the plywood. I don't have any testing to back this up, but it just seems much more solid after installing CBU.

I know, I thought the same thing for years too. It actually does make the floor feel stiffer, but it's a false stiffness..... kinda. I thought I proved it to myself by tapping on the floor the day after installing Durock. (But I was mistaken on what I witnessed.) What I mean is that if the floor is subjected to its limits, the bond between the CBU and the ply will break then it's toast. Plus some manufacturers want you to use unmodified mortar which of course doesn't bond well to plywood.

Also the floor's weight limit is reduced by the added weight of the CBU. This has been tested many times by engineer types and by the people at the TCNA and others.

The term is "structural" strength. No CBU has structural strength. They have no grain to support anything. Try spanning your favorite CBU over two supports, then stand on it. You will hit the ground in a mili-second.

Jaz

Daniel Holzman · 01-25-2011, 11:14 PM

You state that you have true 2x6 joists, spanning 10 feet. I assume this means that the actual dimensions of the lumber are 2 inches x 6 inches, meaning the joists predate modern dressed lumber. Assuming a modulus of 1.7 million, reasonable for your age lumber, and an allowable stress of 1700 psi, your joists have an L/D of more than 400, meaning they are stiff enough for standard tile (12 inch or smaller).

However, you want to go with 18 inch tile, which is large format, and you might need L/D of 480 or even 720. I suggest you check the Schluter website (they make Ditramat) for recommendations on minimum floor stiffness. By the way, you note that you were thinking of porcelain, but were also considering ceramic. Porcelain is a type of ceramic tile, and I believe the stiffness requirements are the same whether it is ceramic or porcelain.