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Hardie Backer vs. Durock for bathroom floor backer

Hardie Backer vs. Durock for bathroom floor backer

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  #1  
Old 02-06-16, 12:10 PM
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Hardie Backer vs. Durock for bathroom floor backer

Hi,

I'm remodeling a bathroom. The tub is in, the tub surround is in (1/2" Durock) and we're now ready to prepare the floor for tile.

My questions:

Should I keep with Durock as the backerboard for the floor or should I switch over to Hardie backer?

The floor that came out was an old style mud / mesh and tile job that was about an inch or more thick. It was installed on top of 1/2 inch plywood which we left in. To keep the thickness of the new floor about the same as the old, I was thinking to go with a 1/2 inch backer.

We'll use thinset and screws to secure the backerboard to the plywood, then use thinset and tiles on top. The distance from the plywood to the bottom of the door casings is about 7/8 of an inch.

I'm leaning toward Hardie Backer (.42 inch) because appears to be a bit more water resistant than Durock. Is there any advantage / disadvantage to drop down to the 1/4 inch thick backers?

Any advice on this would be greatly appreciated.

Thanks
 
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  #2  
Old 02-06-16, 12:35 PM
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The cement board is not structural and therefore you need to beef up the floor first. I would add 3/4" Plywood or Advantech on top of the 1/2" then 1/4" hardi (is what I use almost exclusively) for the floor set in a bed of thinset. Your walls are fine. 1/2" hardi is a bear to cut unless you have diamond blade saws.
 
  #3  
Old 02-06-16, 12:50 PM
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Door casing can be under cut.
I 100% agree, 1/2" subfloor is what was used back in the 70's and not even close to being thick enough for tile.
No tile board is water proof, that's why the grout needs to be sealed.
 
  #4  
Old 02-07-16, 07:32 AM
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Thanks...

Thanks for the quick replies and I see your point about adding another layer of plywood and then going with thinner cement board.

Makes perfect sense but are you sure about the 3/4 inch thickness for the new plywood? Tile guy said to just use liquid nails and screws to install 1/2 inch Durock.

My concern is that we would end up with a big difference in floor heights from the hallway into the bathroom.

Could we go with 1/4 or 1/2 inch new plywood? The existing 1/2 inch floor is sound. I added screws between the original nails and there is no movement whatsoever.

If we add new plywood, would you still recommend applying thin set under the cement board or would liquid nails + screws be OK?

Thanks again for taking time to respond.
 
  #5  
Old 02-07-16, 07:42 AM
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forgot to ask...

Sorry, forgot to add this to the last post:

For the new plywood, should we screw it into the joists or can it get just screwed into the original plywood?
 
  #6  
Old 02-07-16, 07:50 AM
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That's not a real tile guy of he's making that kind of suggestions.
If I had someone make those suggestions I'd be showing him the door and find someone else!
1/4 plywood is never exceptable under tile.
Constrution adhesive or any form of glue is never used between the sub floor and plywood under layment.
A 1/2" subfloor is to thin for tiling and you'll just end up with cracked grout and tiles.
Another layer of 1/2 subfloor rated plywood over it will work.
You have to make sure the seams do not line up with the seams below, do not attach the second layer where the joist are.
NO screws, screws will leave raised dimples.
I use a narrow crown staple gun for underlayment.
It needs to be fastened every 4" on the edges and every 6 to 8" in the field.
The change in heights can be handled with a marble or wood threshold in the middle of the door way.
That's the way it's done all the time.
What since would it make to use a flexible material that's going to leave high and low areas between the layers.
There just is no reason to use 1/2 tile board on a floor, all it's going to do is raise the height.
 
  #7  
Old 02-07-16, 08:49 AM
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OK...excellent advice, thanks!

I'll go with the 1/2 inch plywood and will see about renting a stapler. I already have a compressor.

Will 3/4 inch staples do the job?
 
  #8  
Old 02-07-16, 10:33 AM
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Why would you rent one, there cheap to buy.
Need 1-1/4 staples.
 
  #9  
Old 02-07-16, 10:37 AM
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You only want to do this once, you need a sound sturdy floor. Again, I shoot for a minimum 1 1/4" thick subfloor (1/2" + 3/4"). The first is glued and screwed to the joists. The second is SCREWED to the first missing the joists. Use exterior deck screws NOT staples. You want the two floors to act as one for both expansion and contraction purposes. Tongue and groove make the floor even stronger. I have never used staples for anything other than floor prep for vinyl which doesn't apply here.

NO screws, screws will leave raised dimples.
Don't know what you are talking about Joe, you set the hardie backer in a troweled mortar bed, any dimples will be absorbed by the thinset. The mortar acts to fill any voids forming a bed that fully supports the hardie to there is zero movement.
 
  #10  
Old 02-07-16, 02:56 PM
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I've only done about 25 floors to get ready for tile.
I was told to use screws for the subfloor long ago and even went out and bought a stand up screw gun.
#1, cost 10 times as much, as the screw went in it lifted the underlayment before it grabbed.
Switched to the narrow crown gun and never went back.
Some of the floors are well over 10 years old and never had a call back.
Cost far less and took at least 1/2 the time.
I do not even use screws for the tile board, galv. roofing nails are faster, leaves a flat surface, and a whole lot cheaper.
 
  #11  
Old 02-07-16, 11:28 PM
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Sounds like conflicting advice from joecaption and czizzi. Both of them have individually done far more floors than I would ever even consider and I wonder whose advice is better or if it really doesn't matter?

I have asked these questions before and never received what I think is a satisfactory answer. I understand that a person needs to NOT lay additional plywood in a manner that allows the seams of the second layer to coincide with the seams of the first layer, that is just common sense to me. I DON'T understand the prohibition of any fasteners (screws or nails) holding the second layer from fastening into the joists where the first layer is fastened. The answer is always, "Because the second layer must be able to move independently of the first layer." Now that might make sense except a second layer that is fastened to the first layer every four inches along each edge and also every six inches throughout the field is NOT going to be moving independent of the first layer no matter what temperature and humidity changes take place, it is a physical impossibility unless most of the fasteners are allowed to break.

In my back bathroom (and I suspect the other areas of my house where there is ceramic tile) the construction is of 2x8 joists on 16 inch centers with a 3/4 inch plywood subfloor and a second layer of 3/8 inch plywood over the 3/4. The 3/8 is nailed through the 3/4 and although I haven't looked at it all carefully, I don't think any special care was used to miss the joists when this second layer was applied and I can see for certain that it was not fastened every six inches. Further, no tile backer board was used, the thinset was simply troweled over the plywood and the tiles set in place. EVERYTHING I read on this forum, as well as several other places, tell me this is wrong, wrong, wrong. Yet, the floor lasted without any problems whatsoever from the time it was built in 1987 until I tore off the tile and thinset in about 2000. I've only recently started to remove the 3/8 inch layer of plywood. I suspect that had I not removed the existing tile (I did it because I was installing a new whirlpool tub and also moving an interior wall about 14 inches outward) it would still be fine.

I understand why and how backer board is a better substrate for tile and thinset. I understand that laying the backer board into wet thinset and screwing (or nailing) the backer board in place is probably better than laying the backer board without thinset. However, without testable, scientific evidence I cannot see how fastening the second layer to the joists could possibly be detrimental. Nor can I see how or why a piece of 3/8 inch plywood fastened with umpteen thousand screws (every six inches) to the 3/4 inch subfloor won't increase the structural strength of the entire subfloor. Maybe, just MAYBE this is yet another case of, "This is the way it is done because this it the way it has ALWAYS been done." at work here. In my own field there is a lot of that kind of non-thinking that has persisted for over 100 years with absolutely NO scientific evidence that it is the best methods to use.

Maybe BOTH joecaption and czizzi are right, and wrong, at the same time. How many times have either of them (or anyone else that cares to comment) seen a floor that has failed in any manner due to the second layer of plywood having been fastened through the first layer and into the joists? What scientific evidence can be submitted that states two pieces of plywood will move independently even when screwed together at six inch intervals?
 
  #12  
Old 02-08-16, 02:56 AM
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I installed 3/8" plywood over a lot of my sub floor and nailed/screwed it thru the sub floor and into the joists. Most of that was done 20-25 yrs ago and all of my floors are solid with no creaks. I do understand the reasoning behind not attaching the 2nd layer to the sub floor but I had never heard that at that time.

20 yrs ago I did some work for a tile contractor. I wanted to tile the wood stove hearth [4'x6'] He supplied most of the materials including an additive for the thinset and directed me to apply the quarry tile directly to the plywood. There are no cracks in the tile or grout. Today I would use durock but either thru luck or maybe the additive in the thinset - the tile job has held up great.
 
  #13  
Old 02-08-16, 05:25 AM
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It has nothing to do with the the two layers expanding and contracting.
You miss the joist to hopefully draw the second layer down so it makes 100 % contact with the subfloor below.
Any tiny gap between the joist will cause flexing.
Same logic why you use thinset under the tile board.
 
  #14  
Old 02-08-16, 09:37 AM
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Anyone that has ever been in or lived in a home with wood floors has seen the seasonal expansion and contraction that happens to wood. Cracks open up and cracks close down. This despite the fact that the the floor is nailed every 6 to 8 inches along it's entire length. Engineered wood such as plywood has each subsequent layer at 90 degrees to the adjacent layer to provide some structural integrity to help minimize some of the movement. However, expansion and contraction is not thought of like a rubber band that stretches, but more like a balloon that will swell in all directions, albeit that is an exaggeration when talking about wood.

Another key point to floor systems is deflection. Most span tables talk of deflection of the floor joists. But there is also deflection between the joists. So a floor built to L/360 minimum standards may not necessarily be stiff enough for a tile installation. In order to make a floor suitable for tile you therefore need to beef up the thickness to 1 1/8" (either two layers of 5/8" or 1/2"+ 3/4"). This now eliminates deflection between the joists.

A third element in floor tile is slip, or providing a way to de-couple some of the elements so that the seasonal expansion and contraction of the lumber doesn't cause movement in the tile. There are specific membranes available that allow different surfaces to move under the tile. In older times, tile was set on top of a 1"+ cement mortar bed with lath embedded in it. On wood floor systems, this was installed on top of a layer of tar paper so that the wood subfloor could move all it wanted underneath while not disturbing the cement bed or the tile. Modern technologies have reduced the cement bed down to a more user friendly sheet good that can be installed by the average person.

So, how do you control all these different movements?

The first layer of plywood is glued and screwed to the floor joists. The second layer is then screwed to the first layer but missing the joists. Screws are used to close any gaps that may exist between the floor joists and to make the two layers act as one. This way, when the floor joists do their expansion and contraction things, both layers of the floor are not fighting this. The first layer absorbs and seasonal movement of the joists without stressing the second layer. Then to shield the tile from any wood based movement a layer of cement board is installed. This cement board is set in a troweled layer of thinset such that any and all voids, low spots, dips, irregularities or hollows are eliminated and the thinset supports the cement board 100% from underneath making a solid surface with no deflection from any voids. The cement board is also a superior bonding surface for the thinset to tile bond. Anyone who has ever demo'd a tile floor knows the happy feeling when the tile is only adhered to plywood and not to some cement based product.

Staples or nails will not close the gap between the two layers of plywood and may over time loosen up which may lead to either a floor that has some movement between the joists or to a noisy floor as nails rubbing on wood is the man cause of a squeaky floor. Screws will not work themselves loose over time.

Hopefully this explains my philosophy and the difference between my and Joe's installation methods. Again, the only time I use staples is when installing 1/4" underlayment for vinyl or sheet goods. I don't think they have the holding power. I also have pulled enough offending staples (large staples, no crown) from subfloor systems to eliminate squeaks to know that they don't have great holding power over time. As long as we are talking fasteners, the use of deck screw is that they are strong enough for flooring applications and won't corrode over time. I have also dug my share of drywall screws with broken heads on them from subfloors to see why the should not be used for that application.
 
  #15  
Old 02-08-16, 11:58 AM
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Joe and czizzi have given their OPINIONS but no testable scientific evidence to support their opinions. I have site-finished standard oak flooring in my kitchen, pantry and dining area and NONE of it has shown any signs of cracks opening and closing for any reason, let alone seasonal expansion and contraction. The house was built in 1987.

I also have the same oak flooring in my entryway with a ceramic tile inlay right in the center. Neither the tile (obviously NOT laid in a mud bed with reinforcement) nor the wood shows the slightest problem that could possibly be caused by not having a full inch (or more) of subfloor OR that various layers of subfloor need to be "decoupled" from each other.

I am NOT stating that the methods discussed by either joecaption or czizzi are wrong, far from it. What I AM stating is that it is NOT always necessary to go to the extremes both of these men (and a few others as well) state IS absolutely necessary. If the admittedly "light" construction techniques used in my home have stood in good stead for almost 30 years there is no reason for me to believe that they won't last another 30 years as well, at least in my climate area. Others may have different results.

Again I ask, where is the scientific evidence that supports your opinions that any method of construction that differs from what you espouse is wrong?
 
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Old 02-08-16, 02:03 PM
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Furd, I assume you have access to you own google search to do research to answer your questions instead of asking me to prove industry best practices. Tile Council of North America would be a place to start as they set the standards - Home - The Tile Council of North America. You can also research the thinset manufacturers to see what they will warranty, Latticrete and Mapei are two of the big ones. For wood subfloor specs, your look toward the National Wood Flooring Association - http://tinytimbers.com/pdf/nwfa-install-guidelines.pdf.

I'm really glad your house is rock solid. I on the other hand have been in many, many houses and seen issues with improper preparation, cracked tile, missing grout, loose tiles. My own kitchen has some pretty bad tile problems. I just don't have time to remodel my own house as I need to work on others to put food on the table. The tiles are original to the house and I have 12 cracked or loose tiles. They are set directly on plywood without any backer board.

I have always said that a tile installation should out last both the house and me. And I also state that I would hate to have to remove any installation I completed. So, again, if the topic interests you that much, there are lots of resources at your disposal for you come to your own conclusions rather than question my procedures. I follow best practices, I didn't write them.
 
  #17  
Old 02-08-16, 02:42 PM
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Thank you very much for those references! That is EXACTLY what I have been looking for without actually finding them.
 
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Old 02-08-16, 03:17 PM
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So if everyone is satisfied with the answers given, we will, now, give Wifiguy his thread back. I think we have hashed good, bad and ugly enough on this one, guys.
 
  #19  
Old 02-08-16, 03:27 PM
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Thumbs up

First off, I'd like to thank everyone who took the time to post answers to my questions. From what I have read, it appears that each of you have raised some very valid points with regard to the "best practices" for the job I am doing.

Here's my two cents with regard to two of the issues raised:

Staples vs. screws
In my opinion, screws provide great holding power, but they do tend to warp (dimple?) the materials they are driven into. When driving them in without pilot holes, they can't help but displace material. Since the upward direction offers the least resistance, that's where we generally see the "dimple" or protrusion around the screw head. This even occurs when you purposely drive screws below the surface of the material you are fastening. I saw this when I added screws to my existing 1/2 inch plywood subfloor.

Staples won't do this to the same degree as screws since they are thinner and have two "legs". That said, will they hold as well as screws? I'd say probably not, but I do think they will provide enough holding power for my needs.

Actually, I'm of the opinion that either will work. Since I believe the staples to be quicker to install, I'll probably go with them.

Tiling surface

Although my house's entire second level has but 1/2 inch of plywood under the carpet, I am going to lay down a new sheet of half inch CDX in the bathroom. Even though the old floor is beat up and showing its age, it is still (like me I hope) performing its intended purpose after being subjected to about 40 years of use.

The new plywood surface will be nice and clean, with as few surface irregularities as plywood will allow. This much improved surface should then work well with 1/4 inch thick Hardie backer and tile over thinset.
 
  #20  
Old 02-08-16, 04:02 PM
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In my opinion, screws provide great holding power, but they do tend to warp (dimple?) the materials they are driven into. When driving them in without pilot holes, they can't help but displace material. Since the upward direction offers the least resistance, that's where we generally see the "dimple" or protrusion around the screw head. This even occurs when you purposely drive screws below the surface of the material you are fastening. I saw this when I added screws to my existing 1/2 inch plywood subfloor.
To be honest, I have never had an issue with material displacement on a screw driven into wood. At least nothing that a quick pass of a stiff putty knife wouldn't knock off. What are the screws that you are using that are giving this issue?
 
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