cement backer board on floors

[chip]

John,

Here we go!!!

I understand to a point, your contention about deflection.

Util-A-Crete cement backer board is manufactured be Fin-Pan.

Bonsal markets this product and does not manufacture it. I sometimes talk possesevily, when it comes to products that we market for various manufacturers and I appologize for the confusion.

Fin-Pan was the original manufacturer of Wonder Board. Those of you who have been around in the trade since the '70's & '80's may recall that Wonder Board used to be a very hard board with a tighter mesh.

That is what Util-A-Crete is today.

Fin-Pan had instances in the early '90's of fractures to tile and stone, and found that when the board is adhered to the substrate with latex or multi-purpose thin set, expansion and or contraction of the substrate can and will, cause a crack in the thin set leveling coat to carry up through the board and thin set and tile. The crack is very fine, due the mesh pulling it back together.

So they did field tests and with the assistance of the Tile Council of America, changed the specification for the installtion of cement backer board to be installed with a dry set mortar as a leveling coat, and dry set or latex/polymer modified thin set under the tile.

Just like in your mud jobs John, when you put a cleavage membrane between you lath and the substate you have isolated your installation from the substrate. When you do put a cleavage membrane in place, are you concerned about deflection?

I know that I will never make all of you believe that this is the way to go, but I can assure you if you use this method with our (sorry, Fin-Pans) backer board, you will save money (dry set thin set is inexpensive!!) and you will never have a failure. And if you use Bonsal, we won't make as much money sellin you dry set mortar. We aren't as dumb as I look, some people would tell you that would be impossible any way (but they know me better than you). We just want to make you succesfull.

Art Phenis

[Sponsored Links]

[kalford]

There is a perfect example of what I said in the previous topic.The TCA says;"Dryset OR Latex Modified Thinset"

Obviously stradling the fence and leaving the ultimate choice and responsibility squarely on the shoulders of the installer!!

You will NEVER catch me using regular Dryset to install tile and not even my beloved TEC.

Set your tile with it and I can pop it up with only a pointer and minimum effort....I've done it!!!

I know someone who installs that way and I can name failures....BIG failures as a result of using Dryset to set the tile.

Keith Alford
"Install it Right or Stay Home"

[chip]

I'm with you on the latex/polymer modified thin set issue.

But honestly the vast majority of clay bodied tile set in the state of Florida, is set with dry set mortar.

The state of Floridas consumption of Ceramic tile is in the top 3 nationally. So that means alot of tile installations are succesfull using dry set mortar.

We will always reccomend using the best thin set you can as cheap insurance for a successful installation.

But as we detailed in previous discussions, dry set mortar will absorb into properly prepared cement and tile and harden around the sand/aggegate and create a mechanical bond.

If it didn't work, how many floors could contractors, builders and manufacturers eat and stay in business.

Do I reccomend floor thin set/dry set mortar? Yes, but would I suggest you use a better product? Absolutely!!!!!!!

Please understand that I believe you are doing the right thing. But before latex/polymer additives were available, did all tile installations fail? The majority? 1/2? 1/10? No because cement will mechanically bond to cement and clay.

Art

[Edited by flatile on 06-09-2001 at 11:09 AM]

[LDavis]

Flatile, nice review of TCA recommendations. Kalford, slow down on the read. TCA says dry-set only as the leveling bed mortar between the CBU and the plywood. Latex/polymer modified thinset for adhering tiles to CBU. The nails/screws adhere the CBU to the subfloor, not the thinset. Thinset is STRICTLY a leveling bed to function as additional support to the CBU and help even out irregularities in the existing subfloor.

Unless 1/2" CBU will help even out a transition height difference, I always use 1/4" for floor applications. If the subfloor is not "beefy" enough to support a tile installation, the extra 1/4" of CBU won't make the "saving" difference.

A CBU is not a mud job, but it does seem to be the majortiy of the future at this time. Do it like the manufacturers say and you are CYA!

[chip]

Thanks for your input!!

1/4" backer board is ok, but you probably have noticed the cost differential is minimal.

The additional 1/4", if clearance is available, is reccomended for additonal strength.

1/4" was brought to market for light traffic areas with transition issues and for counter top application.

Will 1/4" work? Yes.

Should you use 1/2" when you can? Absolutely

I still can't believe I found someone out there who agrees with me!!!!!!!!

Thanks again,

Art Phenis

[kalford]

Hey John,
Maybe you're onto something "sticking" to mud.LOL

LDavis,I too use 1/4" cement board on floors in alot of cases.I do alot of remodels and height is almost always an issue.1/2" on open wall-studs, 1/4" over drywall/greenboard.I try to steer the customer away from installing tile on greenboard around a tub/shower.It'll last for years but the backer will last for even more years.

O.K. I finally see your point about the support on the floor for the backer.My wife has the same problem with me.I'm not easy to convince.One question.Is shrinkage not an issue with the dryset?

Keith Alford
"I know everythang...I just can't remember all of it"

[LDavis]

Flatile, you are right, the cost difference between 1/4 and 1/2 CBU is minimal. Depending on the manufacturer, weight difference is significant. Especially when it comes to hauling those "bad boys" upstairs. (Wheres my backbelt and truss!)

Now your gonna open up that "can of worms" about the structural support a CBU does or doesn't offer in a floor installation application. I'm with you technically, if a 1/4" is good, surely 1/2" is better. (Wall applications anything less than 1/2" is out of the question) Does any manufacturer actually endorse 1/2" as structurally superior for floor applications?

Always willing to learn something new and helpful.

[chip]

Shrinkage is not an issue in this application.

You will still have a good layer of mortar between the substrate and the board.

If you are using Full Flex, at about $17.00+ a bag compared to $4.00 to $5.00 a bag, you will be more competitive and be able to put a little more jingle in your pocket at the end of the week. Month. Year.

Obviouvly you guys can't pull yourselfs away from the computer today either? I'm addicted, any body have a # for the local chapter of CAA. I just gotta have my fix!!!!!

Have a great week-end, my wife is due home any minute and is going to make me go to the beach. What a drag, 90% naked woman all around, taking there clothes off. It's like a curse, it happens to me all the time. H E L P !!!!!!!!!!!

TALK TO YOU SOON,

Art

[LDavis]

Kalford, unless the shrinkage is "south of the belt buckle", I don't think its a consideration here. Like John has said (I think it was John), functions as a sort of slip sheet or dare I say "uncoupling" device.

I know, if its nailed/screwed, what uncoupling? Thats why I'm here too, gimme some more EDUMACATION please....somebody.

[kalford]

Yeah,I just don't get it.
Latex thinset holds it's integrity even under adverse conditions.Ever tried to clean it off of a tool after it has set? Let me tell you...it don't "crack" like dryset will! That's why I have a hard time picturing it cracking under backer and that crack carrying through to the tile.I won't buy that unless I see it myself.

Art,my wife is yellin at me to get off the internet.Yes,I have fond memories of the scantily clad ladies of the deep south........did I mention that I'll be making that trip alone?

[chip]

I know, I know. I said good bye already, but my wife isn't home yet.

So I'm glad you haven't experienced what I am talking about and do it our way and you never will.

Unless you are opposed to saving money?

I understand they have some great beaches in Jacksonville.

Oh,Oh my wife just got home.

I'm in trouble big time.

see ya.

Art

[kalford]

The beaches from Mayport Naval Base(Hanna-Park) through jax beach south to just above st. augustine are really nice.
Hanna Park was built after a huricane destroyed that area in the early 70's.They made a nice park out of it.In the late 60's to about 1973 you could drive right out on the beaches at jax but it was destroying the dunes so they stopped it.

Keith Alford
"Hire some help.............go to the beach"

[John Bridge]

Well you guys have all confused me on one minor point. Back when I was writing my book, I had a guy who was very familiar with industry terms review the manuscript. One of the things he corrected me on was the use of the term "thin set." Thin set is the method of installation, as opposed to thick set, which is a mud bed.

Dry set mortar, he told me, is what I really meant when I referred to the concrete adhesive material (yes, dry set/thin set is concrete).

Nowadays, everybody uses the term thin set to describe an adhesive, but now you guys are differentiating between "dry set" and "thin set." It seems to me this is still incorrect. All of the concrete adhesives are "dry set mortar," whether they contain polymers or not. And "thin set" is still a technical term for a method of installation.

Unless I'm wrong. It's happened before.

In any case, around here the tile supplies just sell "thin set." It's either modified or it's not. If you go in and order "dry set," you'll get a vague look. Of course, you get that a lot around tile supplies anyway.

[kalford]

You're right John. It's just easier to say "dryset" to refer to non-modified thinset and "thinset" to refer to modified dryset instead of typing "latex modified" each time.......................I think.

I still have a problem with NOT wanting to bond the backer to the floor.What about Ditra or the like? A layer of Ditra and thinset is about 1/4" thick...maybe 3/8". There is no way that would be "stiff" enough to support a tile floor without being "bonded" to the floor.Right?Wrong?

[John Bridge]

Oh, and on the subject of whether backer board adds structural value to the subfloor.

I've been involved in several discussions on this issue, with engineers and others, including "industry" people. Engineers seem to agree that if something is bonded to the floor, and that something has mass, it increses the stiffness of the floor. Gluing and screwing two sheets of plywood together, for example, makes a pretty stiff arrangement.

I can also understand why people don't want to bond CBUs to the floor as Art mentioned. But the hot/cold cycle in a house doesn't affect the plywood as much as it does the immediate substrate, be it mortar or backer board. I think that cracking in the past was more a result of wet plywood and substandard carpentry. We can argue that further.

Here's the deal, though. Comparing the rigidity of reinforced mortar to that of cement backer board is useless. The former is extremely rigid and does not fully depend on what's under it for its stiffness. The latter is only as good as what's under it -- if you subscribe to the school that says the backer adds nothing to the structure.

I'll tell you, folks, I can build a reinforced mud bed that can support itself with nothing under it. It'll never happen with backer boards unless they are vastly improved.

[kalford]

AMEN!! Backer board will never be the substrate that a quality mudbed is.Like you said John,a mudbed isn't dependent on the floor under it like backer is which only goes to reenforce what we've said about bonding backer.By itself it is not rigid enough to fall within the deflection guidelines necessary to support a tile floor.If this were not true there would be no problem going over particle board.Backer boards are not self supporting.That's why I did my bathroom like I did.Had I chosen to use a mudbed the first sheet of plywood could have even been thinner and there wouldn't be a second layer.

Hey John,two houses side by side.One has mudbed system one has ply and backer........FLOOD!! Which one will need the most repair?

[Edited by kalford on 06-09-2001 at 04:40 PM]

[Bud Cline]

I think the myriad of ideas that may or may not substantiate an idea as to the benefits of one system (mudbed) as opposed to another system (CBU's) cames from the fact that so many installation practices can be regional.

Mudbed when I was living in Texas was the "cats meow" but it was also all there was for a long time. I don't argue that it is still the best system depending on who does it and the practices they follow and the materials they use. I agree with John that a mud bed is stronger structurally. I also think a mudbed can be more suseptible to cracking under the right conditions, but I can't really prove it.

CBU's are prevelant in this part of the country. In Texas I participated in many redo's that were originally mudbed. Here a lot of the redos are found to be on plywood. This area must have subscribed to "plywood only" for a long time because I'm just not seeing the old mudbeds.

I don't know if the talent just wasn't here or what. Unfortunately I am still seeing a lot of failures originally installed on particle board also. So that method must have been very popular for a long time also. You know it took particleboard many years to prove its uselessness as a subflooring in many cases.

In this town of 25K there were for many years only two full-blown tileguys and they had most of the work for a long time. One was an independent that sold tile out of his garage and the other was an installer for what has been the only real flooring installer in town for 30+ years.

When I arrived eight years ago tile was booming, there was a shortage of qualified tile installers, it was a gold mine. They were at that time using CBU's but I don't think anyone knew why. My mention of TCA or ANSI brought questionmarks to most faces. Now that I have been here eight years and torn out a lot of work I can see that someone must have really been cleaning up as far as shortcuts.

My mention that I attempt to subscribe to a particular philosophy of installation governed by organizations such as TCA and ANSI generally brings the response; "sure, doesn't everybody"? Well I can tell you "NO" they don't and haven't.

I think I would rather carry cut and fit CBU's than mix, carry and finish mud these days. Just seems easier getting everything to the job and all. I also firmly believe that 1/2" CBU's DO IN FACT OFFER ADDITIONAL STRUCTURAL BENEFIT to a floor when set in thinset. I'm not so sure about 1/4", I think 1/4" creates problems of its own.

[chip]

I don't know who started all this talk, but he should have his head examined. Oh wait a minute it was me, and they did that and said there was nothing to be found.

I have said it before and will say it again, the traditional mud bed method is the "best" way to set tile and or stone.

CBU is the 2nd.

With the lack of tradesman who are capable of mudding a job, at least they have a product that has qualities similar to the mud method.

No it is not designed to add to the structural integrity of the dwelling.

But it is concrete, not plywood, osb, particle, luan, gypsum etc.

One more time "mud bed is the best way to tile"!!!!!!!!!!!

take good care,

Art Phenis

[John Bridge]

Uh, how was the beach, Art?

[chip]

I couldn't have planned it better.

As soon as she got home, it started to rain.

So I had to stay in and watch the college World series and then of course got some shut eye in as well.

Any body know who won, USC was ahead 6-3 the last I knew.

Tommorow another day in the mines. Bonnie Tile my largest customer is having their annual golf outing.

Work, Work, Work.

good night,

Art

[Tom]

Hi, everybody,
John, in response to your question, I have a small handyman business in Long Island, NY. I used to give tile work to a tilesetter who I sometimes worked with, and I've been doing some tile work on my own for a few years (I first used mud after reading your book). I don't have the same level of experience as the professionals here, but when I use cbu I use Hardibacker, which according to the manufacturer has the same strength in 1/4" or 1/2". The 1/2" size is used only to make the transition to sheetrock. This could be different with other brands.

[kalford]

According to the Hardibacker website:Hardibacker(1/4") and Hardibacker 500(1/2")exhibit typical "flexural" strengths of 2100 and 1700 psi so whoever said that 1/4" was as strong as 1/2" just flat out lied.The "compressive" strengths are close at 7000 and 6500 psi but so what.A sheet of paper has some pretty impresive compressive strength too but I don't want to set tile on it.

Now for installation.On the Spec/Data sheet under Hardibacker Installation Instructions titled:Floor Installation paragraph 3: Attach sheets to subfloor:
Apply minimum of 3/32" thick
Dry-set mortar OR MODIFIED
THINSET to subfloor.

under,Finishing with Natural Stone:
In ADDITION to fasteners,ADHERE sheets to the subfloor with a MODIFIED THINSET MORTAR.

But that can't be! A leading underlayment manufacturer and MEMBER of TCA advocating a BOND be made between the backer board and the subfloor!?!?!?!?! Not only that but indicating that it will be STRONGER and help PREVENT cracks!!! So according to Hardibacker, Bonding is better!

[chip]

Yes it's true, Hardie backer does recomend either.

Why? Sitting on the fence?

Any one had any problems with this product?

Art

[John Bridge]

Hi again, Tom.

Your input is as welcome as anyone's. As you can see, there is confussion on this issue. I hope that in some small way this forum enables us to arrive at some conclusions.

Okay, we have two guys from Lon Giland, NY, now. Jim "flatfloor" is also from there. Y'all don't be gangin' up on us, hear?

I've always liked the looks of the Hardie product myself. Recently, though, I ran across a piece of the stuff made by USG -- Perma Base. It looks pretty consistent throughout, which cannot be said of some of the other cement backers. What do you guys think?

[chip]

It's made by National Gypsum.
USG makes Durock.
Permabase was formerly made in Canada, by the company that makes Ski doo's. I can't remember what it was called then.

Unifix, I think.

The styrene pellets are the tell tale recognition factor.

All I know is the product when introduced by it's former owner, reaked havoc on the margins all manufacturers were able to maintain. Something about the US $ going back to Canada,These ecomomic things have always confused me.

Art

[Tom]

http://www.hardibacker.com/
If I choose a product and then click on product specs, the flexural strengths for hardbacker(1/4") and hardibacker500(1/2") are both given at 2100 psi. There could even be confusion on this from the horse's mouth

[Tom]

In the previous post I hadn't seen the PDF ten point spec sheet from the hardibacker web site. Here it does show the 1/4" as being stronger than the 1/2" board in flexural and compressive strength. Click on technical information.http://www.hardibacker.com/

[LDavis]

I'm getting a headache. Interesting how an "apparently" simple question/discussion can lead down such a "winding" path. The simple explanation I've received from CBU manufacturers in the past has been, 1/4" on floors and countertops, 1/2" for wall applications.

In this area, I've seen CBU's applied to floors with everything from construction adhesive and fasteners to just fasteners. Lay the CBU on the floor and nail it. Nothing between the CBU and existing subfloor.

For me, the "bottom-line" remains, follow each manufacturers instructions to the letter. There are differences. Wonderboard says you don't fill/tape CBU joints for floor applications.(Fill joints as you set tile, but no mesh tape) Hardibacker says fill/tape CBU joints for floor applications. Use modified thinset, use non-modified thinset.

At some point, it will all come out in the wash. Until then I'll follow specific instructions for each and keep THEM covering my ass! Now, let's go do some mud work!

[kalford]

On USG's site under; Underlayment;Installation......PDF
1. Lamination

Laminate 5/16" DUROCK brand underlayment
to minimum 5/8" thick exterior grade plywood
using ADHESIVE or mortar suitable for BONDING cement backer board to plywood.Apply adhesive with 5/8" V-notched trowel,mortar with 1/4" square-notched trowel.

There you have it guys.The top two manufacturers of cementious backers advocating BONDING the backer to the plywood and one of those suggesting the use of adhesive,such as MASTIC,is a suitable alternative to mortar when installing their product to floors.

I've beat this Horse all I'm going to.Let's talk about something else.

[LDavis]

John, it appears you are venturing into the world of CBU's as a possibility for some of your future jobs? Anyway, here is my 2 cents. I've used some of just about everything out there at one time or another. However, I've used tons (literally) of the Hardibacker product. Primarily the 1/4" for floor applications.

I don't know whether or not its any "BETTER" than some of the other brands available, but I know for a fact it is lighter and easier to cut/handle than most of the others I've dealt with.

I work alone 95% of the time. The largest floor installation I've done invloving CBU was 1250sf in a condo in Aransas Pass. (Upstairs) I was very glad to be carrying Hardibacker and not one of the other heavier products up those stairs. This particular condo is 20+ years old and the subfloor was "suspect" in terms of existing support.

To make a long story short, this installation has been down for 2 1/2 years now and "holding toghether". I do have some faith in the "Hardi" product.

[LDavis]

Kalford, point taken. If I can remember back to the start of this "monster", my response related to TCA recommendation to use nonmodified (dryset, their words, not mine} as a "supporting plane".

I know there are manufacturer recommendations that are "at odds" with this.

I'm going with "up-to-date" manufacturing instructions.
My "southpole" is going to keep a nice, warm cover on it!

[John Bridge]

Thanks for the correction, Art.

Latney,

Actually, I used Durock on a couple upstairs bath floors several years ago. I did not use thin set under it, and I nailed it down with drywall nails. Didn't even bother to read any specs.

Naturally, I had severe problems with the job, so I avoided using the stuff. Now that I'm getting some sound advice, confused though it may be, I may consider using a CBU for retrofit bath floors. As you know, I do mostly remodeling, and it's a real pain doing a second story mud job, tracking over carpet, etc. -- plus is raises the floor too much. Most all of our ground floors here are concrete slab.

I've narrowed my choice (with everyone's help) to either Hardibacker or Perma Base (which I know nothing about -- yet). Durock and Wonderboard and the like are just too messy. This is not a product endorcement; it's just a personal choice.

Upstairs baths tend to be small, and the framing is usually adequate. If I were doing a larger floor (greater span), however, I would still insist on mud.

[chip]

Please, by all means always follow manufacturers instructions. By all means if that south end isn't covered you aren't covered.

But let me just say, that the 2 manufacturers refferenced have between them the following:

One company has an interest in the ceramic tile industry that stops, with 3 walls and some flooring. Gypsum isn't approved.

The other is owned by a setting products manufacturer and their margins & profits are higher with latex or multi-purpose thin sets.

Does this help anyone other than them?

I won't kick this horse any longer, thanks for your input and lets move on.

Art Phenis

[Bud Cline]

John,

Here's some "For What It's Worth".

I almost always use either Durock or Wonderboard. I see no real difference in the two. One exception though; when I have purchased Durock from the local Big Box more than a few times I have gotten what I think is "seconds". Of course the Big Box denies they buy or sell seconds but there is something wrong whether anyone will admit it or not.

The problem is the backside sometimes has an irregular abundace of cement material along the dressed edges. When you look at it closely it is easy to see something in the manufacturing process has gone awry, this causes the board "not to lay flat". So I must stone the product which of course is messy and time consuming.

I know what you mean when you say the stuff (CBU's)is messy. To eliminate most of the shedding of cement crumbs I "saw" every piece. I think this is the carpenter in me coming out. Others say I'm nuts for not doing the usual "score and pop" method with a utility knife but that method is where the crumbs originate from. I don't think my way is any slower than cleaning up the mess ahead of each board constantly.

The other product I use when I have control over procurement is the Perma-Base product. I believe Perma-Base is the more installer friendly of the three products. It is a little lighter, it cuts very clean, but most of all it will allow you to set a screw or nail head without effort and without "shiners". Perma-Base is also a little smoother and therefore is easier on your hands and knee gear. I have no fears of the bonding properties or surface because it is smoother.

OK now here is where I am going to catch a little hell from some of you guys. After years of screwing and nailing I finally rented a roofing nailer to install some CBU floor. I just had to try it. Wow, what a mess. None of the nail heads would set. I tried everything. So we had to go back and pound every damned one of them nails. Never again! So then I bought a stapler. A 1/2 crown made by Senco. I did a little research and Senco was the only people that seemed to know about CBU's and the stapling of them. I was told the gun (stapler) I purchased was designed for CBU's.

This is by far and without doubt the cleanest, safest, fastest means of mechanically fastening CBU's as far as I'm concerned. And the staples "always set" without fail. I don't know if anyone recommends this procedure or not. A couple of good size jobs will pay for the stapler pretty quick. I might say walls are always screwed using the CBU screws. (Pierce point, double threaded, self setting, coated, square drive.) Try them, you'll love 'em.

[kalford]

Bud,
I use a roofing nailer with great success.I turned the pressure to 100psi and Press down firmly on the back of the gun instead of "banging" it.It does leave a nail proud occasionally but it is still way faster than the ol claw-hammer and nail apron.

A crown stapler huh? Sounds interesting.Maybe I'll give it a try.I'm up for whatever works best.

[Bud Cline]

Keith,

As a testimony to my personal experience with the rented roofing nailer I took over a job where a previous installer had used a roofing nailer to install several hundred feet of Wonderboard. Upon our arrival we found about 95% shiners, now that will excercise your wrist for a while.

In my experience, I tried air adjustments and gun adjustments and everything I could think of. When nothing worked and then I came across this other job with the same problem I simply gave up on the nailer idea. That's when I bought the stapler. In fact the Senco Dealer allowed me to use the stapler free for one job and he provided the staples at no charge, I guess he was confident he would have a sale if the stapler outperformed the nailer which it did.

[kalford]

I'll see if I can get me a free tial on one.Anything is better than crawling around swinging a hammer...........of course there is always...Ditra.

Keith Alford
"Install It Right...but don't KILL yourself doing it"

[John Bridge]

And there is still mud, but that's pretty labor-intensive, too. I know, I know. Don't say anything.

[kalford]

Well John,
My next two jobs are mud jobs.Both remodeling.One has an old mudbed that cracked up when they had the house releveled.The other is a 1920's 3-story house that they have added a shower to.

Oh...I ordered your book today...I'll be expecting a $1.20 rebate.