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snowchild 12-02-2012 12:02 AM

ceramic tile over OSB
 
2 Attachment(s)
Hi,

We are building a new construction 2 story home over an existing walkout basement.

The main level subfloor joists are older 2x10 solid lumber @ 16"oc with new 3/4 T&G OSB cover. The span is 14ft each side of the supported centerline. On this floor we want to put ceramic tile in the kitchen area. Do we put the tile directly over the OSB subfloor? The floor is very noisy to walk on, should we be adding some kind of noise dampening? Will Ceramic tile crack with floor movement? Any considerations we need to be aware of?

I should mention the house will be heated with hydronic radiant flooring. Any concerns there ?

The upper floor uses Solidstart 20 Plus engineered LPI's 16"oc with a depth of 11-7/8" . The cover on that is 1/2" osb that will have 3/4" pine T&G over it. There will be a master bathroom that I want to put ceramic tile down. Should that area get 3/4" plywood or OSB on it before adding tile?

Noise level from foot traffic is a concern also. What do you recommend to deaden sound between floors?

joecaption 12-02-2012 08:46 AM

Anyone else seeing anything interesting about the way this was framed?

I would never use 1/2" for a subfloor, at least 3/4" T&G plywood or better yet a product like Advantec.
Engineered floor joist tend to bounce, there a ton of old post on that one subject.
While it's open I would add 3/4 plywood on both sides that glued and nailed or screwed at least in the area that going to get tiled.

snowchild 12-02-2012 11:07 AM

4 Attachment(s)
Joe

If you are referring to the header over the window, it's 2x10's boxed with 2x6's top and bottom. The opening was originally designed for a wider window and was later changed to a smaller window and moved to one side.

The 1/2" osb was originally laid down to facilitate the building of the shed dormer walls and to get the roof on. The framing was done late in the year last year and we were concerned primarily with getting the roof on and closing it in since this is in the NW and could get hit with early snowfall. The floor was originally designed to be 2x6 T&G but it was not delivered on time so the framing sub contractor decided to use what he had on hand. The next concern was that the radient floor heating would not be efficient under a 2x6 solid wood floor and so it was decided to add 3/4" T&G pine flooring to the existing 1/2" osb. That has not been done yet.

It should also bo noted that the 2nd level floor is only open span in the front area of the house. Originally that area was not going to get a 2nd floor. We added it to reclaim the space. In the rest of the house, the 2nd floor has many supporting walls under it. See the picture below looking toward the rear two thirds of the house. Therefore, in the area where the tile will be added, the engineered floor joists are supported from underneath by walls.

Just for further information, the exterior framing is 2x6. That is covered with 1/2" OSB and the siding is solid log 2" x 9" screwed to the outside walls. The roof is supported through to the basement floor (9" concrete) with those 2 huge logs that run the full length. They are keyed into horizontal log beams under the ridgeline with a gluelam on top of it that support the engineered roof beams.

rusty baker 12-02-2012 11:17 AM

I personally would not put ceramic on that floor, but maybe "Jaz" and/or "Oh' Mike" will come along. They are the tile experts.

funfool 12-02-2012 11:21 AM

Yeah joe, you got me curious now. What I can see looks fine, insulation is covering some key points. I was concerned if the logs were structural or decorative, I see the ridge board in second set of photos.
I find it very interesting and like the design, not finding a problem with it though.

joecaption 12-02-2012 11:44 AM

I've never seen engineered floor joist hung that way. Keep in ming I'm not a framer, but any of the jobs I've worked on of my framer have done where not done that way. Not saying it's wrong, just differant then I've seen.
Any I've seen where sitting on the top plates with a special thicker rim joist made just for this style rafter.
Seem like the hanger would act like a pivit point and may have more deflection.

http://www.woodbywy.com/literature/TJ-9001.pdf

snowchild 12-02-2012 12:01 PM

Quote:

Originally Posted by joecaption (Post 1064987)
I've never seen engineered floor joist hung that way. Keep in ming I'm not a framer, but any of the jobs I've worked on of my framer have done where not done that way. Not saying it's wrong, just differant then I've seen.
Any I've seen where sitting on the top plates with a special thicker rim joist made just for this style rafter.
Seem like the hanger would act like a pivit point and may have more deflection.

http://www.woodbywy.com/literature/TJ-9001.pdf


Yes Joe you are correct. Only the front area was done that way, the back area was supported onto the top of the walls with a rim joist, sort of an after thought. That area was originally designed to be open to the cathedral roof. We reclaimed the area because we needed more space than the structure allowed. The house is not huge, its 28 ft wide by a bit over 50ft long. The hangers are simpson top mounts. The bottom of those joists will be covered with drywall.

Correction: There are hangers on the centerline 2x6 glulams in the rest of the house but the exterior walls are not hangered in those areas.
Should we cover the bottom with osb prior to drywall to add stiffness? Will the 3/4" t&G on top be sufficient to add stiffness? Perhaps we should do a 3/4" t&g ceiling underneath and forego the drywall?

hammerlane 12-02-2012 12:19 PM

Quote:

Originally Posted by snowchild (Post 1064765)
Hi,

On this floor we want to put ceramic tile in the kitchen area. Do we put the tile directly over the OSB subfloor? The floor is very noisy to walk on, should we be adding some kind of noise dampening? Will Ceramic tile crack with floor movement? Any considerations we need to be aware of?

If you put that tile directly on the subfloor the grout will eventually crack and possibly the tile. You need to lay down cement board on a bed of mortar. Also screw down the cement board. Then on the cement board yopu spread the thinset for the tile and then lay the tile. At least thats how our tile was laid and we have had no cracks in 18 months.

hammerlane 12-02-2012 12:34 PM

I had this article in my files...it is courtesy of John Bridge.

• Ceramic Tile Floors

- John P. Bridge ( May, 2005 )
“Ceramic tile floors. Sounds simple, doesn’t it? Pull up the rug and “put down” tiles. Smear grout in the joints, clean it up and move back in. If you have vinyl on the floor you can go right over it with the new tiles, as vinyl makes a wonderful uncoupling membrane. Tile mastic works better for tile floors than thin set mortar does, especially when using large tiles. If the floor structure seems a little spongy, you can correct it by nailing down cement backer board before installing the tiles themselves.”

You have just been presented with a paragraph-size synopsis of the type of tile misinformation you might receive on the Internet, in tile and flooring outlets, at big box stores and in certain printed publications, not to mention home improvement shows on radio and TV. Yes, there are thousands of “experts” out there poised and eager to set you straight and get you on your way to tile flooring bliss. Don’t buy into it for a minute.
In the next few paragraphs I intend to give you a very brief overview of the correct ways that ceramic tile flooring should be installed. I’ll list sources of further reading at the end.

First of all, ceramic tiles (to include porcelain tiles, quarry tiles, various paver tiles and others) are hard, brittle and breakable. For them to be installed successfully on floors they must be well bonded and well supported underneath. If your floor is the least bit springy or “mushy” when you walk on it, it will be necessary to do some serious shoring up before tile setting begins. I cannot over-emphasize this. For our purposes, the tiles themselves have no structural value of their own. The use of cement backer boards or various membranes will not ameliorate an unsound floor structure.
• Cement Backer Boards
Cement backer boards, such as PermaBase, Wonder Board, Durock, Hardi-backer, and others are used to “uncouple” a tile installation from the subfloor below. Before they are fastened, CBUs, as they are called, are bedded in thin set mortar, which is the usual adhesive used in setting floor tiles. The panels are then nailed or screwed to the subfloor following manufacturers’ specific directions. CBUs do NOT improve the stiffness or structural value of the floor.
• Anti-fracture Membranes
There are various membranes on the market that accomplish the same uncoupling effect that CBUs provide. Two of the biggest names are Nobleseal and Ditra. I happen to be in cahoots with Schluter Systems, makers of Ditra, and I consider it among the best products on the market. But membranes will NOT rectify an insufficient floor structure. Vinyl linoleum and tar paper certainly won’t do it either.

• Adhesives
“Thin set mortar” is a portland cement product that is used to adhere ceramic and stone tiles to a “substrate.” The substrate is the layer directly under the tiles, i.e., cement backer board, Ditra membrane, etc. Thin set comes in a powder form that must be mixed with water just prior to use. Thin set cannot be pre-mixed before it is needed. It will “set-up” and become hard just like any other cement product. It does not need air to do this, and you can’t keep thin set in a can or plastic tub on a store shelf.
Therefore, any product you see on the shelf purported to be “pre-mixed thin set” is not thin set and cannot be used to install floor tiles. It is instead some sort of mastic, which is an organic glue that might be used to install certain very small tiles on a kitchen back splash, for instance. The same goes for “pre-mixed grout.” Real tile grout is made from portland cement also, and in my opinion, pre-mixed grout should not be used for anything at all.
Remember that thin sets and grouts will ALWAYS come dry in a sack or box, and remember that it is impossible to pre-mix them and keep them from setting up hard as a rock.
Tile mastic, the organic glue, can be used only on small tiles and in areas that don’t get wet. It should not be used on stone tiles at all as it can be absorbed into the stone where it can cause stains. And tile mastic should not be used for ceramic tile floors.

JazMan 12-02-2012 12:59 PM

A single 1/2" OSB or plywood does not make a subfloor. Years ago when 1/2" ply was used as the subfloor, ("the" subfloor is the layer attached to the joists), a second sheet of 5/8" was always added. You can not install tile directly on any subfloor regardless of how thick it is.

So, for the tiled area you should add 5/8" B/C exterior glue underlayment, then either 1/4" concrete board set into thinset and fastened per directions, taped etc., or install Ditra. Then the tiles.

Jaz

snowchild 12-02-2012 02:55 PM

Quote:

Originally Posted by JazMan (Post 1065027)
A single 1/2" OSB or plywood does not make a subfloor.

So, for the tiled area you should add 5/8" B/C exterior glue underlayment, then either 1/4" concrete board set into thinset and fastened per directions, taped etc., or install Ditra. Then the tiles.

Jaz

Thanks for your expert advice.

We covered the 2nd floor 1/2" osb (and why it was done) above. It is not meant to be the finished subfloor and will be added to.

The main area where ceramic tile will go is the main floor kitchen, a large area 19ft by 13ft which has 3/4" T&G OSB as its subfloor. This is the area of concern for me. I have no problem adding ditra (if I can find it locally), but since the subfloor in this area is already 3/4" do I really need to add any more thickness to it before the ditra+thinset+tile?

And what about the hydronic heat? Does ditra work with that? Will the uncoupling effect cause the radient floor to be non effective? Any knowledge in this area?

JazMan 12-02-2012 06:16 PM

OK, go it. To sum up, you have 2x10 joists, 16" o.c. that span 14' 0" and the subfloor is 3/4" t&g OSB. Am I correct that the OSB is "subfloor" grade t&g and not just plain 3/4" OSB?

If it is t&g, and properly installed, (glued, screwed, 1/8" gaps bet. sheets etc.), you can install 1/4" CBU or Ditra over it. But that only takes care of the deflection between the joists. The other deflection criteria is for the joists themselves.

2x10" spanning 14' is bare minimum at best. It was probably built to meet minimum code. Can you tell me the species and the grade of those joists? Also re-measure the span to see if it's really 14' 0" or a few inches less.

As for the hydronic heat. I don't know much about that, but is it the system that is installed under the subfloor between the joists or?

Jaz

snowchild 12-02-2012 08:29 PM

It is actually a 12ft 9" span wall edge to wall edge, and the joists are actually 1.5" x 9.25" and the species is fir in reasonable condition with no grade marks but very old and very hard, and the 3/4" OSB is floor grade and it is glued with sublfloor adhesive, and nailed with 6d ring shanks from a hitachi nail gun with 80lbs of pressure by a hulking great guy that stands 6' 6" and weighs 280lb in his bare stocking feet, and that's before breakfast! :)

The issue is the floor thickness. The radient heat is 1/2" pex with 2 runs per joist bay under the subfloor with aluminum conductor plates. The thicker the floor gets, the less heat will get transferred through it, or that is what I am told. Thats why we were told not to use 2x6 finished plank flooring and we opted instead for the 3/4" t&g. We don't want wood flooring in the kitchen and bathrooms so we decided to go with ceramic tile, but we have no experience with laying ceramic tile.

This project is very rural. There are no inspections, and very little code although we have tried our best to adhere to code or better. We are told that we have actually built it stronger than it needed to be. We do want to do it right, it is afterall our house, not someone else's We hired a contractor to oversee the project but not to build it. We wanted to build it ourselves and we have done 90% of the work ourselves. Now we are coming down to the finishing, the devil is in the details as they say. The photo's I have supplied are fairly old right now, the house logging has been compleated and I chinked the entire house myself this summer which although it wasn't necessary, has added a lot of charachter. It is a very striking house, built on 5 acres of Montana Prairie, quite different to anything around here and it gets a lot of compliments from the locals.

From what I see on this forum, you are the expert when it comes to ceramic floor tile. We very much appreciate any advice you care to give even if the advice is to not put down the ceramic tile.

oh'mike 12-03-2012 05:16 AM

Jazman is an expert--respected by all who know his work and teaching---

I ran a deflection chart for you---you are good for tile---458----minimum for tile? 360----- for natural stone ? 720.

As to the under floor heating? Wood is an insulator --and cement board or Ditra and tile are a heat sink---
You will be fine----The heated floors are very comfortable---I have a heated basement slab and am considering adding it to my hall bath when that day comes.

Hammer450R 12-03-2012 06:42 AM

Geez where do i start...did you pass framing inspection yet?


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