# glue down durock? do i have to?



## john orrico

hey all,
i am actually doing my own kitchen and am installing 5/8 durock directly to my floor boards. I am using the correct screws and spacing them 6 - 8" apart. the home depot guy didn't mention anything about gluing down the durock. i have about 60% of it already screwed down. am i screwed??


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## Michaeljp86

Id glue it


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## jproffer

The good news is: If you've only screwed it down...you only have to take the screws out to get it back up.

You don't glue it down. But you DO have to put thinset under it to fill in the voids and keep it rigid. Without it, the tile WILL eventually crack.


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## A.W.Davis

Just take out the screws pull up the hardibacker and thinset it to the floor accordingly.

edit, jproffer beat me to the punch.


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## Michaeljp86

I know a guy who just lays thinset down on the wood and lays the tile in it. We were in a house where the tile was done right and he sees the cement board and goes why the heck would they do that. He did a house with a old pine floor that had a big hump in it. He just poured on the thinset and stuck the tile in it.


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## john orrico

*so i'd better do it right*

i guess i'll be getting some thinset tomorrow and taking out a whole lot of screws. thanks guys.. last chance to stop me..... can i just put way more screws???


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## kevjob

read the instructions for floors and it clearly states thinset under board. The reason is screws hold it down the thinset fills all the voids by supporting the entire board and stagger all corners.


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## TNGHomes

What do you mean by "floor boards". You should be mortoring the backerboard to a solid clean substrate of 3/4 plywood. If you are looking to install the backerboard over say pine boards (subfloor in old homes) then you are going to have substaintial problems. If you are going over hardwood then rip it up first then install the backer to the plywood subfloor benieth. If I misunderstood then my apologies however backer is to go over soild plywood substrate only. P.S. HD knows almost nothing about what they are selling.


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## BACKWOODS

Just make sure the screws you are using are alkaline / corrosive resistant. Otherwise the thinset will rust them out. Regular drywall screws cannot be used. Spend a few extra bucks and get a good flex type thinset. I use Ultraflex2 from Lowes. I am sure HD has an equivalent. 
Check out www.johnbridge.com for some tips. I am not much of a tile guy but I learned a lot from reading. Read before you do it, kinda like measure twice, cut once.
:thumbup:


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## Mike Finley

TNGHomes said:


> What do you mean by "floor boards". You should be mortoring the backerboard to a solid clean substrate of 3/4 plywood. If you are looking to install the backerboard over say pine boards (subfloor in old homes) then you are going to have substaintial problems. If you are going over hardwood then rip it up first then install the backer to the plywood subfloor benieth. If I misunderstood then my apologies however backer is to go over soild plywood substrate only. P.S. HD knows almost nothing about what they are selling.


:thumbsup: These were my thoughts exactly when I read "*Floor Boards*" too, you don't want to be installing CBU directly to a sub-floor that is made up of dimensional lumber. Follow TNG's advice if this is the case.


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## reveivl

You really do want to start at the beginning, here. What are you putting down, stone or tile? Are your joists suitably stiff for this? (dimension, span). How far apart are they? What is the existing subfloor? 

Most issues are relatively easy to deal with now, before you tile it, and a disaster after you do so.


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## PrecisionFloors

Michaeljp86 said:


> I know a guy who just lays thinset down on the wood and lays the tile in it. We were in a house where the tile was done right and he sees the cement board and goes why the heck would they do that. He did a house with a old pine floor that had a big hump in it. He just poured on the thinset and stuck the tile in it.


That guy you know does it wrong (I'm sure you know that).....It amazes me the wrong stuff we see on a daily basis though. Oh well, more work for those of us that do it right when it fails I suppose.


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## Floordude

That guy, learned from that guy, that learned from that guy, that learned from that guy...

1 week experience, repeated fro 30 years. There needs to be formal training and skills testing, for all trades making a living and calling themselves, professional.


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## Bill_Vincent

BACKWOODS said:


> Spend a few extra bucks and get a good flex type thinset. I use Ultraflex2 from Lowes.


This is a point of contention in the industry. Most CBU manufacturers tell you to use modified thinset, while TCNA recommends UNmodified. The reason being that you're not trying to glue the CBU down with the thinset. That's what the screws are for. You actually DON"T want the layers to bond together, because that basically eliminates the whole idea of multi-layering the subfloor, and makes it one layer. Also the biggest reason why it's so wrong to use Liquid Nailz, PL400, or any of the other construction adhesives.

I know it's the manufacturers warrantying the product, but the way I see it, I think of the TCNA kinda like the Conumer Reports of the tile industry, and I'll take their word over any others, basically because the only "horse" they have in the race is the betterment of the industry. I'll use Kerabond and water, thank you very much!!


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## Michaeljp86

PrecisionFloors said:


> That guy you know does it wrong (I'm sure you know that).....It amazes me the wrong stuff we see on a daily basis though. Oh well, more work for those of us that do it right when it fails I suppose.


 
Thats my problem, this guy takes my work all the time because hes been doing it for years. I see him do alot wrong but hes smarter then me because he knows how to do everything so he gets the job. :furious:


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## Bill_Vincent

Michaeljp86 said:


> I see him do alot wrong but hes smarter then me because...


What's wrong with this picture???

I'm going to copy and paste a post I just submitted in a thread at John BRidge's pros forum:



> While there is some truth to making a good first impression, more than anything, three words I keep repeating in here, and will continue to repeat:
> 
> SELL YOUR QUALITY!!
> 
> People don't mind paying more, if they know they're getting their money's worth. Especially those who are into their second or third home, and have had occasion to deal with some schmoe who owned a wetsaw and promised them the world for next to nothing.* I keep a copy of the TCNA Handbook with me at all times. More than once I've had to back up what I was telling a potential customer, or even talking to a customer in the middle of a job. It's funny to watch their face when you show it to them in writing. "Yeah, he really DOES know what he's doing! I'm in good hands!" Also, just about everyone I give my card to, I'll write the url to the shallow end*[the tileadvice forum at John's]* on the back of the card, so they can verify anything I tell them independently.* Little things like this, will sell the job, and it'll do it for a price where you can afford not to cut any corners, and give your customer an installation that'll last longer than they do.


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## Tileguytodd

> I know it's the manufacturers warrantying the product


Yea and we know how that works dont we.

Remember that Pool I redid last year that was Under Warranty Bill??

They Never Paid The Bill!!!
Thats why I dont trust manufacturers claims.............(like SLC over single layer plywood for example)

So, where were we..Oh yes...Cement Board/Thinset question again.

How large is the area?? If its not too large, I'd add plenty mo screws and Risk it myself............Let me tell you why and remember, this is NOT by the Book and Not the way I would normally set tile.

Commercial contractors can be a funny lot...most of them know everything there is to know (of course)
One of these guys uses mechanical fastners for cement board only.. They refuse to pay our Exhobinant price just to put in Underlayment (cement or not)
So, they get thier tile work but they also OWN the floor.......they are fine with that.
Most of these floors are in the 80 - 140 s/f area (public restrooms in commercial buildings etc)
They have not had any failures in My time ive been dealing with these folks.(9 years)
In fact, i just recently did 3 more for them (about 240 s/f total)

(of course if i did 3 floors this way on my own name, 2 of them would probobly fail in the first 6 months...go figure!!!)

So........Is it worth the risk?? Probobly not if it is a large floor.
small bathroom or entryway...........I'd probobly add some screws making sure I had 1 every 3" at edges and 6" aprox through the field and call it good.......WERE I YOU!!! Remember, it is a gamble so If it does fail, DONT CALL ME!!!
Being a PRO however....I get PAID to make sure its done BY THE BOOK so If i put it in, its getting thinset under it!!:thumbsup:


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## Bill_Vincent

Tileguytodd said:


> Yea and we know how that works dont we.
> 
> Remember that Pool I redid last year that was Under Warranty Bill??
> 
> They Never Paid The Bill!!!


Yeahhhhhh, I don't think I'd be holding my breath.


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## Jerry T

There is no work around for this other than taking the lazy way out. 

Pull that CBU up and do it right using thinset underneath. Make sure to tape the seams.

You do need to come back first and clarify what your substrate is.


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## 415moto

Michaeljp86 said:


> Thats my problem, this guy takes my work all the time because hes been doing it for years. I see him do alot wrong but hes smarter then me because he knows how to do everything so he gets the job. :furious:


No offense guy, but you just posted this in response to using glue under CBU




Michaeljp86 said:


> Id glue it


Based on that, Id say you shouldnt be laying tile either.


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## Bill_Vincent

You're talking about either the 200 or 300 (it should say which yours is on the side of the gun), and I've got both of them. If you look at the bottom of that page, you'll see the extension that goes with those guns. As for the screws, where I got started with the Sencos was from my local Daltile Warehouse. They sell both the 1000 count cans of screws, as well as the 4000 count boxes. What got me to go to this site is that Dal no longer carries the 1" screws for when I'm going over hydronic radiant heat. Now that I've been to Juldan's site, they're actually cheaper than any place else I know of that carries the Duraspin screws, even WITH the shipping!


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## PrecisionFloors

Bill_Vincent said:


> Floordude-- I agree with Jerry. Are you sure it's the 18 volt? A friend of mine bought the 14 voilt from HD, and that thing won't hold a charge for even an hour of constant use. My 18 will go atleast a couple of hours, and by that time, the second battery is fully charged.
> 
> 
> 
> This is why I leave people shaking their heads sometimes. When deciding who I should listen to, there are three sources I check. First, is the manufacturer's instructions. Second, is TCNA recommendations, and third is my own field experience. There are many times where I don't agree with a manufacturer about their own product, and this is one of them. *Another good example would be Schluter saying you can go over sheetrock with Kerdi.* But in the case of the fiberock, that void still exists, and for that reason, I'll listen to TCNA's recommendations. Who knows-- they might be right, and for some reason, thinset isn't needed. I'm not about to put my reputation on the line to find out, though.


I have been leery of this as well, but I do it (everybody over at JB's seems to subscribe to it). Why do you think its not a good idea Bill? My thoughts are, what happens to the "sweat" on the other side. Or do the Schluter folks think that it will only sweat on the hot side? Maybe I am way off base but I still feel weird about drywall in a shower.


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## Bill_Vincent

PrecisionFloors said:


> My thoughts are, what happens to the "sweat" on the other side.


That's exactly my thought. I know it won't do anything immediately, or even with in 5-6 years. But over time, I'm afraid that the condensation will deteriorate the gypsum in the sheetrock, and make it rot. I'm not about to find out the hard way.


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## Michaeljp86

Bill_Vincent said:


> That's exactly my thought. I know it won't do anything immediately, or even with in 5-6 years. But over time, I'm afraid that the condensation will deteriorate the gypsum in the sheetrock, and make it rot. I'm not about to find out the hard way.


 
I dont like sheetrock in a shower either but my grandpa put it in this house in '60 or '61 and so far its fine. If it were my house I wouldnt use it.


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## Bill_Vincent

I also know of people who've put their shower pan tile down with mastic and it hasn't come up yet. Doesn't make it right, nor does it mean it works. It means those are the exceptions to the rule. The majority of showers and tubs where the tile was installed over sheetrock, have failed.


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## PrecisionFloors

At least I ain't the only one lol. Bill, are you using cbu and Kerdi?


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## Bill_Vincent

Yep-- Durock.


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## MattCoops

Jerry T said:


> Bill, I love ya like a brother :notworthyand I am not being argumentative... it's more like butting heads here :wallbash:. The sole point I was attempting to get across is that Fiberock is not a "CBU" backer board. It's a backer board for sure, but it is classified as a "Fiber-Reinforced Water restistant Gypsum backer Board Underlayment" type of backer board.
> 
> Hardi, on the other hand, is classified as a "Fiber-Cement Underlayment" type of backer board. To make this more confusing, James C Hardi claims hardibacker falls under both the "Cementitous Backer Unit (CBU) type of backer board along with the "Fiber-Cement" type of backer board.
> 
> This article explains the differences in backer boards far better than I can...
> http://www.tileletter.com/Sept06/TCNAtileBackers.htm
> 
> But forget all that and I will use jerry speak to make this point .
> 
> Say one of us was hired to go to install tile over CBU backer board... if I put down Fiberock , I would be using a product that was not within those specifications. This maybe a small issue but it has the potential to be a huge issue. Imbedding it in thinset is a whole nother issue... and USG is the one saying we don't need it, not me. That's one of many reasons I don't use Fiberock.
> 
> I check in on several tile forums and i have noted many times posters saying.... "I use Fiberock CBU under my tile jobs". Can you see my point?
> 
> Just trying to get all installers to know what they are putting down before they do it.


Great article. 
Informative post.

I prefer the Coated glass mat water-resistant gypsum board as a backerboard choice on floors, walls, countertops, and shower walls. 
DensShield rocks :clap:


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## ApgarNJ

i only use hardie on most of my bathroom jobs. and most pans are all mud/tile. vinyl pans just scare me though, just always in the back of my mind thinking it might leak someday no matter how much you plan to make it last forever, nothing is forever.

i got sick of durock. just easier to work with hardie.

i really am not sure about putting that denshield on the floors, but they say it's ok for flooring, wouldn't you think it would crush down over time with traffic? being that it's almost like gyp board under that rough paper.

anyone here use that on a floor yet?


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## Bill_Vincent

Everyone has their own preferences. I'll work with Hardi if and only if it's necessary, and I'll walk away from a job before I'll use Denshield.


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## 415moto

Michaeljp86 said:


> This is how I would have done it because thats how I read to do it. I feel less stupid now :clap:.


Where did you read that a CBU mnfctr say to use adhesive?


Teetorbilt didnt read about that method anywhere, he is saying he knowingly doesnt use the mnfctr recommended and approved method of CBU installation, because he thinks his way is better.


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## Michaeljp86

415moto said:


> Where did you read that a CBU mnfctr say to use adhesive?


Im not sure where I read it at but I'll go dig around and see if I can find it.


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