Remove 1/4" plywood or not for porcelain tile


  #1  
Old 03-30-06, 06:18 PM
L
Member
Thread Starter
Join Date: Mar 2006
Posts: 7
Upvotes: 0
Received 0 Upvotes on 0 Posts
Question Remove 1/4" plywood or not for porcelain tile

I'm planning (trying) to put new flooring in our kitchen/dinning room. The kitchen has Vinyl Flooring with 1/4" plywood sub floor. The dinning room has carpet without the 1/4" plywood. I'm planning on putting heating cable in thin set and then porcelain tile for the new floor. The existing floor in the dinning room has 3/4" particle-board or chip-board.

My question is, should I remove the 1/4" (have to remove all the base cabinets in the kitchen) and put 1/2" fiberock board over the entire entire floor? OR just add 1/4" plywood to the dinning room and then the 1/2' fiberock? I've heard that the 1/4" plywood may swell and buckle and cause the tiles to crack.

Any advice would be helpful!
Thanks
 
  #2  
Old 03-31-06, 11:24 AM
T
Member
Join Date: Oct 2004
Location: New Jersey
Posts: 1,078
Upvotes: 0
Received 0 Upvotes on 0 Posts
First, the 1/4" ply needs to go. There are no 1/4" plywood products that should ever be under a ceramic installation. Next, please post the unsupported span of the 2x10's and lastly, you say particle board or chip board is the subfloor. More often, people who claim that as their subfloor actually have osb (oriented stran board) which is shavings of wood, ranging from about 1/2" to 1 1/2" wide by as much as about 2 1/2" long, pressed together in a resin. Also, are the subfloor panels tongue and groove?

By the way, you can remove the underlayment from around the cabinet bases by renting a toe kick saw. It's like a circular saw with a small shaft mounted blade that allows you to cut along the cabs under the toe kicks. but...

given the amount of height you will add to the floor 1/2" cement board, 3/8" thinse or slc over the wires, then the tile thickness, removing and reinstalling the base cabs might not be a bad idea. You could have appliance fitting issues later.

Kitchens and dining rooms are not light traffic areas and dining room floors experience a lot of point loading as well. This is hell on the between the joist deflection, which is probably the biggest floor killer. Though your plan meets the scraping the bottom minimum for a tile installation, in all honesty, I'd reserve that sort of floor for a bathroom without infloor heating. Backers give you no added strength to the floor. They only offer a more suitable bonding surface for the thinset.

How I would spec it out, add 3/8" (1/2") if you can spare it "bc exterior" plywood over your subfloor. Plywood long edge crosses the joist, short edge lands about 2" past the joist, not on it. Screw it down every 6" around the perimeter and every 8" in the field. Use 1 1/4" deck screws and fasten it only to the subfloor. This will make the strength of the floor between the joists MUCH greater. 1/4" perimeter gap, 1/8" gap between panels. Then lay out your heat mats. Dam the perimeter of the area and pour self leveling cement (slc) over top to bury it all quickly. Then use either Noble CIS or Schluter Ditra thinsetted over top of the slc layer. Being Ditra is orange, I'd use that (I'll explain later). CIS is 1/16" thick installed, Ditra is 1/8" thick installed. Then set your tile to the membrane. That will isolate your tile from the rapid expansion/contraction effects of the heat mats.

Should a tile need replacing later, the orang color of the Ditra lets you know where to stop digging so you don't damage the heating system below. The above make the strongest installation and the safest for future repair maintenance needs. Your plan might only last as long as the shortest warranty period of the materials you select and does not lend itself to safe repairs later on.
 
  #3  
Old 03-31-06, 11:45 AM
B
Member
Join Date: May 2005
Location: usa
Posts: 209
Upvotes: 0
Received 0 Upvotes on 0 Posts
By the way, you can remove the underlayment from around the cabinet bases by renting a toe kick saw. It's like a circular saw with a small shaft mounted blade that allows you to cut along the cabs under the toe kicks. but...
I just wanted to add...
If you happen to use a toekick saw, be advised they are extremely unforgiving, one wrong move and you can easily be missing a few fingers or open up huge lacerations on various parts of your anatomy. Very dangerous tool, make sure you read and follow the directions to the letter.
 
  #4  
Old 03-31-06, 03:33 PM
L
Member
Thread Starter
Join Date: Mar 2006
Posts: 7
Upvotes: 0
Received 0 Upvotes on 0 Posts
Hey Tilebri,

The spans of the 2x10 are 10' and spaced 16" on center. It's not tongue and groove from what I can see. I checked out the osb borad and that is what the existing floor is. Thanks so much for the info.

Guess I'll start taking out those cabinets
 
  #5  
Old 04-01-06, 04:45 AM
T
Member
Join Date: Oct 2004
Location: New Jersey
Posts: 1,078
Upvotes: 0
Received 0 Upvotes on 0 Posts
t-g is part of the minimum requirement. If it's not t-g, then the additional layer of ply is not optional, it's required. Are you using a cable only type system or mats that have the cable running through it?
 
  #6  
Old 04-02-06, 05:32 AM
L
Member
Thread Starter
Join Date: Mar 2006
Posts: 7
Upvotes: 0
Received 0 Upvotes on 0 Posts
It's only the cable not the mats. I have to run the line of cable myself.

Oh, just for an update the cabinets are out and with little trouble I might add. One thing that was a pain was cutting one of the cabinets where the water line ran up.

so I'm saying bye bye to the 1/4" plywood today, hopefully.

Another question if you don't mind . Should I screw down the OSB floor before putting down the new plywood? It's nailed down right now and the nails are about 4 -5" apart

Thanks for all the help.
 
  #7  
Old 04-04-06, 07:15 AM
T
Member
Join Date: Oct 2004
Location: New Jersey
Posts: 1,078
Upvotes: 0
Received 0 Upvotes on 0 Posts
Rescrewing is up to you. At 4-5" apart, it sure sounds pretty well fastened as it is. Pouring slc requires lath in the pour. There are plastic laths on the market and I would suggest one of them in your pour instead of metal lath. Had you been using mats with cables run through them, the issue would not have even come up.
 
  #8  
Old 04-04-06, 09:59 AM
L
Member
Thread Starter
Join Date: Mar 2006
Posts: 7
Upvotes: 0
Received 0 Upvotes on 0 Posts
I went to home depot last night to check the plywood. They carry STD spruce and CSP sheathing.

One of the guys said the CSP is exterior grade and that should be used for the subfloor.

I just wanted to check here first before buying as I have to strap the plywood onto the roof of my jeep to get it home. Good thing home depot is only 2 mins away!

If you want I can post some pics as I do this project (the girlfriend loves taking pictures, might keep her happy as her kitchen is torn to bits right now ) and then post this as a how or something.

Thanks again for all this info.
 
  #9  
Old 04-04-06, 10:32 AM
T
Member
Join Date: Oct 2004
Location: New Jersey
Posts: 1,078
Upvotes: 0
Received 0 Upvotes on 0 Posts
First it's heat cables, not mats, then you turn out to be Canadian! Nothing wrong with being a Northern neighbor I've never met a Canadian I didn't like, but just like you guys need to do things in kilometers and liters and such, you also have your own grading system for plywood up there. Now I'm not familiar with Canadian rating systems for plywood, but universally, sheathing rated plywood is for sheathing, that is, exterior walls and roofs. The veneers hold unknown amounts of voids that can be disasterous for a tile installation. They must have underlayment rated panels.

Seems they have ratings:
http://www.canply.org/english/produc...rlaid_mdo1.htm

You would want ac sanded or bc unsanded. at least 3/8" thick, no 1/4" plys. If you can't get the info you need from the store, lumber yards have folks who actually know their products. There are no underlayment panels in a 1/4" thickness approved for use under ceramic. "Multiply" and U-Lay brands sell 1/4" plywood underlayment panels which they claim as acceptable under ceramic, but they did not pass industry testing as part of a flooring system. Not that much help this time but you don't want the wrong stuff.

At least you folks drive on the right. Europeans have the metric system and drive on the wrong side ofthe road. Thanks for your beer too.
 
  #10  
Old 04-05-06, 12:26 PM
Bud Cline's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Nov 2001
Location: Central Nebraska
Posts: 1,245
Upvotes: 0
Received 0 Upvotes on 0 Posts
The heating cables aren't a major challenge but they do require some fore-thought.

I have learned that the cables must be glued to the surface about every 6 to 8 inches or they can get screwy and out of control.

I personally wouldn't trowel the thinset over the cables. I know the cable manufacturers suggest this method but to tell you the truth it is problematic to say the least. I always bury the cables in SLC and this is why they must be glued so closely because if you don't the stinking cables will float to and above the surface of the SLC and I can promise you, you don't want that to happen.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: