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??

Michaeljp86

Id glue it

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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Jim P.

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.

john orrico

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???

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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Kevin
Basement Finishing Highlands Ranch Colorado
Littleton Colorado, Basement Remodeling
Kitchen Remodeling Denver

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.

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.

Mike Finley

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.

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

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

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

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.

Bill_Vincent

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:

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Tileguytodd

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!!

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Tilewerks
Tile and Stone Contracting
Warba,MN 55793

Bill_Vincent

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.

415moto

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


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