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Old 03-12-2009, 01:50 AM   #1
JimmyD
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Jimmy's Upstairs Bath Remodel

I need help with the deflecto calculation

Bathroom upstairs is 5 feet wide
Floor joists are 2 x 10 x 14 feet (bedroom downstairs is 14 feet wide between walls).
One wall of the bathroom is directly over one wall of the bedroom

For the span, do I enter the width of the bathroom (5 feet), or the actual span of the joists (14 feet)?

Current floor is vinyl over 3/4 plywood, we want to put 12 x 12 limestone down.

Thanks
Jim
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Old 03-12-2009, 03:11 AM   #2
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You would enter the unsupported span of the joists. If I understand your post, the joists span 14' with no support anywhere underneath them. That's L/380, which is okay for ceramic tile, but not for stone.
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Old 03-12-2009, 05:12 AM   #3
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I agree with Kevin about the joists. Also, your subfloor would need another layer of at least 3/8" thickness plywood or OSB if you wanted stone.
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Old 07-12-2009, 02:44 PM   #4
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Jimmy's upstairs bathroom remodel

I have started a 2nd floor bathroom remodel.

1. Existing subfloor is 5/8 plywood, with a 2 ft x 3 ft section replaced due to water damage. Subfloor has black mastic from old sheet vinyl. I plan on putting 5/8 plywood underlayment down. Should I put some sort of building paper between layers of plywood, so the plywood underlayment does not stick to the subfloor?

2. Bathroom is 9 feet deep (door at near side, toilet at far side), and plywood is 8 feet long. Should I put the 1 foot piece under the toilet at far side, or at the entrance to the bathroom, or does it matter? joint in underlayment would run parallel to toilet, almost under the toilet -- centerline of toilet is 15 inchces from far wall

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Jimmy
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Old 07-12-2009, 03:26 PM   #5
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Welcome, Jimmy.

I've combined your earlier thread on the project here. Can't tell if you ever saw the responses to that one at all. If you'll bookmark this thread in your Favorites and use it for all the project questions it'll help us keep up with what you're working on and what's been previously asked and answered.

You don't want anything between the layers of subflooring and you really want to scrape all the old "cutback" from the surface of the first layer. Best if you can get it down to more of a stain, eh?

You want to install your second layer of subflooring perpendicular to the joists and overlap the joints in the first layer as far as possible; by half a sheet if you can do that.

Then you'll need to add an underlayment of some kind for your tile installation.

Are you still contemplating natural stone tiles?

My opinion; worth price charged.
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Old 07-12-2009, 03:48 PM   #6
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I wasn't sure if the 2nd layer of plywood is part of the subfloor or the underlayment. I am planning on 2 layers of plywood plus either Ditra or hardibacker.

2nd layer of plywood will be perpendicular to the first, edges will be 4 inches from floor joists.

Deflecto said no to natural stone (not close). It is also marginal for tile, but I may take my chances with porcelain tile. Will Ditra provide some decoupling and help here?

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Old 07-12-2009, 04:13 PM   #7
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Frequently a little confusion about that, Jimmy. For mine own part, an underlayment is the material to which one attaches his floor covering. On a wood-framed floor, everything under that is subflooring to my mind.

You want all layers of subflooring to be oriented with the face grain perpendicular to the joists. No matter how many layers.

Ditra is helpful in uncoupling your tile installation from subfloor movement, but you've still gotta have the proper structure providing the appropriate limits to deflection. Your subflooring will be very good; your joists will just not be adequate for natural stone.

You could double up the joists if that's feasible for you, but absent that you gotta use a good ceramic.

My opinion; worth price charged.
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Old 07-12-2009, 04:42 PM   #8
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"You want all layers of subflooring to be oriented with the face grain perpendicular to the joists. No matter how many layers."

Thanks Cx. That is an eye-opener. I wonder how many people have missed this? So I keep both layers of plywood perpendicular to the joists, with the top layer offset from the lower layer in both directions (no ends or sides of top plywood over an end or side of lower plywood), with no gaps at the ends or sides (plywood butted up against one another, and the ends over floor joists? Is this all correct?

Then i am good to go with Ditra?

What is good ceramic tile? Porcelain is what I was thinking. Any brands better than the next (or any to avoid)?

Jimmy
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Old 07-12-2009, 04:46 PM   #9
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One more question: What are the guidelines for screwing both layers of sub floor together?

Any bonding (liquid nails, etc)? what type should I use?

Thanks again; good thing I didn't cut the plywood yet.
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Old 07-12-2009, 05:16 PM   #10
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Jimmy,

Read this article cover to cover. It will answer most if not all of your questions...may even a few you didn't think to ask. I do not glue the two layers together. CX does. If you decide to glue them you need a spreadable glue like Titebond II. It has to be fully spread over the entire surface. Do not use anything out of a tube...too many voids will be created.

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Old 07-12-2009, 05:30 PM   #11
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Thanks Brian; I have seen the article, but was confused about the top layer. Until I saw Cx's reponse, I was going to add the 2nd layer as it shows in the article.

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Old 07-12-2009, 05:31 PM   #12
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Look at the article more closely, Jimmy. At a glance it does appear to show the incorrect orientation, but if you study it a little it's clear that all the panels are perpendicular to the joists.

Yep, really they are.
Quote:
Originally Posted by Jimmy
with no gaps at the ends or sides (plywood butted up against one another, and the ends over floor joists? Is this all correct?
Always gapped. 1/8th" is the usual recommendation.

My opinion; worth price charged.
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Old 07-12-2009, 06:06 PM   #13
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So do I put the end (short edge) of the plywood over a floor joist, or 1/4 the distance between floor joists? Article addresses underlayment, not a second layer of subfloor.

I plan on using 1.625 inch deck screws, 6 inches on center on the edges and in the field. (5/8 inch plywood subfloor, top layer).

Thanks,
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Old 07-12-2009, 06:58 PM   #14
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Quote:
Originally Posted by Jimmy
Article addresses underlayment, not a second layer of subfloor.
Yeah, and I wish they wouldn't do that. If you were fixin' to tile directly onto that second layer of subflooring, you could call it an underlayment, I suppose, but it's really still another layer of subflooring.

One of the guys who authored that article is in the bidness of manufacturing tile installation underlayments. And they don't look like pywood, eh?

In any case, I recommend you try to comply with the methods in that article to the extent feasible, but in a small room like you've got you just lay the sheets in the correct orientation and in a layout that works while ensuring as much joint overlap as you can get. In some bathrooms the sheet is gonna hafta be cut to fit wall to wall and you ain't gonna worry about where the end joints are, eh?

My opinion; worth price charged.
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Old 08-01-2009, 12:54 AM   #15
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Toilet flange question

Current toilet plumbing looks like an elbow with a closet flange glued to the outside of the elbow as it exits the floor. Measuring ABS pipe at the flange: inside diameter is 4 inches, OD is 4.5 inches. ID of flange is 4.5 inches, pipe is cut off more or less flush with the top of the flange. Flange is currently unsupported by subfloor (hole in subfloor is slightly larger than 7 inch OD of flange), but must be braced well because it feels solid, with no flex. There is approx 15 inches of ABS pipe in the floor before an elbow & pipe in the wall. There is enough space that I can cut off the lip of the old flange & cut away most of the flange where it is glued to the pipe, but this will not likely leave the pipe smooth.

1. Can I get a street closet flange (?) that is glued to the inside of the existing pipe? What exactly do I ask for at the plumbing store?

Other options include:
2. Cutting the subfloor and replacing the elbow & flange from above
3. Cutting the drywall ceiling on first floor & replacing the elbow & flange from below (but I worry the bracing may get in the way, and am not keen on cutting into the ceiling drywall)
4. Use flange extenders to make up the expected 1 + 1/8 inch gap after I add 5/8 plywood, ditra, tile, thinset.

What do you recommend? (I'd rather do #1, but really want it done right -- No leaks)

Question 2: does anyone seal the flange to the tile to reduce the likelihood of leaks ruining the subfloor/framing? I am thinking of silicon caulk between the flange and tile, where the flange sitting on top of the tile.

Thanks
Jimmy
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