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Old 02-24-2014, 06:32 AM   #16
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getting it right


In my op I stated in step 2 that I would screw down ply into subfloor and not joists. I said that because I read it somewhere (probably here). I would just like to verify that is correct as it is kind of counter intuitive. I would imagine added strength if its all tied together.

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Old 02-24-2014, 06:37 AM   #17
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Yep---screw the top layer to the subfloor--not to the floor joists---
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Old 02-24-2014, 07:00 AM   #18
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OK I believe you but I'm wondering the reason for that
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Old 02-24-2014, 07:13 AM   #19
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Let's let Jaz answer that----I read it somewhere long ago and have always done it that way-----sounds like it's time to get the technical answer from Jaz---(or another member with a good answer---)
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Old 02-24-2014, 01:16 PM   #20
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The reason that it's recommended we not fasten any underlayment to the joists is to help isolate it from the framing. The joists deflect a bit under normal traffic and loads which can cause fasteners to pop up in time and also cause squeaks. The bridging (X) and the subfloor help prevent too much horizontal movement twisting of the joists, so there not need to also attach the underlayment.

I've been guilty of doing exactly what I just said we should not do, in the past. I recall back in the late '80's fastening 1/2" Durock and going out of my way to hit the joists when possible. Now I know it's not best practice to do that. Will there be a failure if this step is done wrong? Probably not by itself, but there's no way to know.

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Old 03-07-2014, 10:04 AM   #21
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Went to the tile store and now I'm getting info overload.

To recap:

12 feet span, 2x8 joists on 5/8 osb.

My plan was :
1/2 ply over osb, thinset, ditra heat, thinset, tile.

This brings the floor higher then I'd like and the tile guys said the 1/2 is not necessary with the ditra. I get the feeling you guys would disagree?? Keep in mind that I'd like to use the ditra..

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Old 03-07-2014, 11:13 AM   #22
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Quote:
Originally Posted by creeper
Went to the tile store and now I'm getting info overload.

To recap:

12 feet span, 2x8 joists on 5/8 osb.
You forgot to mention the 12" o.c. spacing. It matters to people who don't go back and read the entire thread again.

Quote:
My plan was :
1/2 ply over osb, thinset, ditra heat, thinset, tile.
Note you're using DitraHeat. It's a new product and you don't mean heat and then Ditra.

As for the total height. I don't get it, although the new methods results in thinner buildup, people want it even thinner. In the old days you had 3/4 - 1" of mortar plus the tiles. This method calls for Ditra, which is much thinner. The only reason you're using 1/2" ply is because the sub is only 5/8" and you said the floor was bouncy.

Is there a way to make it thinner? Sure, go 3/8" underlayment instead of 1/2". Or eliminate the underlayment altogether. But if the floor is bouncy, guess what will happen?

What's on the floor of the adjoining room? Raise that floor, or if it's carpet, shim it near the transition. Or, do what most of the rest of the world does. Install the same flooring in all the rooms.

Jaz
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Old 03-07-2014, 11:52 AM   #23
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[QUOTE=JazMan;1318171]You forgot to mention the 12" o.c. spacing. It matters to people who don't go back and read the entire thread again.

Yes, sorry about that omission

Note you're using DitraHeat. It's a new product and you don't mean heat and then Ditra.

Correct again


As for the total height. I don't get it, although the new methods results in thinner buildup, people want it even thinner. In the old days you had 3/4 - 1" of mortar plus the tiles. This method calls for Ditra, which is much thinner. The only reason you're using 1/2" ply is because the sub is only 5/8" and you said the floor was bouncy.


Is there a way to make it thinner? Sure, go 3/8" underlayment instead of 1/2". Or eliminate the underlayment altogether. But if the floor is bouncy, guess what will happen?

What's on the floor of the adjoining room? Raise that floor, or if it's carpet, shim it near the transition. Or, do what most of the rest of the world does. Install the same flooring in all the rooms.

Just as the rest of the world does, the current floor is the same as the other rooms...hardwood.
At least on this level anyway, as it is a split level. Ceramics in the bathrooms and lower level (not basement) hallway. Thick mortar bed on top of a thin underlayment of some sort.

The difficulty I'm having with the height difference in this application is the adjoining living and dining rms have 3/8 hardwood on top of the subfloor.

The subject floor (kitchen) currently has 5/8 of various things on top of the subfloor.
If I install 1/2 ply + 3/8 tile + DitraHeat + thinset I am raising the kitchen floor even higher then it is now, which will be quite significant.

Sidenote( The preferred tile choice is 12x24x 3/8. However my choice is available in 12x12x 2/8. Which Im being informed, may be easier for a newb like me to manage.

So I think what you have said is if I choose to go a little thinner with the plywood it will likely fail ??
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Old 03-07-2014, 12:30 PM   #24
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Quote:
Originally Posted by creeper
So I think what you have said is if I choose to go a little thinner with the plywood it will likely fail ??
Nobody knows that. It's impossible to know. All we know is from experience it's safe to do "X" and if you do "Y" there's a better chance of failure.

Quote:
The difficulty I'm having with the height difference in this application is the adjoining living and dining rms have 3/8 hardwood on top of the subfloor.
Well there you go. I would not have done that. If I had to have a thin wood floor, I would have installed 3/8 or 1/2" ply under it to keep the floor at a reasonable level. To me a 'reasonable height' is 3/4" minimum above the subfloor. That way you have many choices for the adjoining rooms and stay close to the same height. But elevations of even 1" or more are workable with a beveled transition at the doorways.

This is done all the time in residential. Commercial could be a problem cuz you have mostly strangers who may trip not knowing the layout.

The 12 x 12 will be easier, but the floor still has to be flat like your kitchen table...almost.

Jaz
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Old 03-12-2014, 10:00 AM   #25
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Still gathering info before I begin the big job ( and time).

A neighbour said my floor has vibration and not bounce. Is there a difference??

Anyway, I had the small ones run around and jump on the floor while I viewed it from underneath and I can definitely see some movement in some areas....like where some cross-bridges were removed to accommodate the quagmire of pipes and wires.

Reinforce with more cross bracing is not an option for me, but I can add more blocking if deemed necessary. Where and in what fashion would I do this??

Also, is it possible to just lay boards across the joists for strapping instead?? Would the desired strengthening and stiffening be achieved? I have lots of deck boards and 2x4 spruce. Here are some pictures:

Thanks again,
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getting it right-joists.jpg   getting it right-joists1.jpg   getting it right-joists2.jpg   getting it right-joists3a.jpg  
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Old 03-12-2014, 10:02 AM   #26
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thanks
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Old 03-12-2014, 07:41 PM   #27
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In the joist pocket that are missing the blocking---a 2x4 block can be nailed in between the joists at the very bottom--rather like the blocks inder the metal air duct in the picture----

a 2x4 could even be nailed below the joists--but that looks rather amateurish--

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