Glue Down Durock? Do I Have To?

MattCoops

This has been quite an awful long discussion when there should have just been a response of:

TROWEL SOME THINSET UNDER THAT CBU BEFORE YOU SCREW IT DOWN AND TAPE THE JOINTS

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Matt with Cupan Custom Tile & Paint of Lowell, Massachusetts
Design and installation of ceramic tile and natural stone for floor, wall, and countertops
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Jerry T

Not so partner , I think you would be surprised.

The handbook says all backerboards should be imbedded in thinset.... that was not my point.

You keep bringing up hardi.... which implies to me that you think Hardibacker and Fiberock both fall in the same category of backer boards. That is simply inaccurate and could possibly get an installer in a heap of trouble if he/she were to mis-spec one for the other.

Bill_Vincent

Okay, I'll bite. Tell me-- what's the difference?

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Bill_Vincent

But you DID make that point, and the reason I said something about it is that it's misinformation, because as you just said, all BACKERBOARDS should be bedded in thinset.

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ApgarNJ

I've seen that backboard called fiberock and to me, it looks identical to hardi tile backer. unless there is something that I don't know about. I have used thinset( unmodified) under hardibacker. i don't use durrock anymore, but when I did use it a few times, i didn't use thinset under it, because I didn't know any better. If the subfloor is in bad shape, then i can see the need but if you are going over a nice smooth surface and put enough screws, i don't see where putting no thinset under it, would cause the tile to fail. if there are big knot holes or other spots of the plywood subfloor, then by all means, put thinset under it. they tell you to do that because they can't see everyone's subfloor and if they say just put it down with screws and that's it, theyll have morons trying to span large divits or gaps in the subfloor with the backerboard.
i was on a job where we were installing doors and trim, and the funeral home hired someone to do the tile in their foyer. the guy came in, used large caulk tubes of construction adhesive, under the hardibacker, and then used a (get this) roofing nailer! with just normal galv roof nails in it. it went down really fast, he got paid, years later the floor still looks great. i'm sure it might fail at some point, but i guess the way he looks at it, he got paid, and saved so much time over the guy who was going to use hardiebacker screws.

this is a good discussion to have because so many people don't know, as was the case with me years ago, it wasn't that i wanted to do it wrong, it was that i didn't know. i just got the tile backer and figured it would go down and didn't need anything under it.

MattCoops

You should always set your backerboard in a troweled bed of unmodified thinset.

It's ok to use a roof nailer and galvys.
But I stick with specialty screws made for backerboard installation.

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Matt with Cupan Custom Tile & Paint of Lowell, Massachusetts
Design and installation of ceramic tile and natural stone for floor, wall, and countertops
(978) 601-8774 | cupantile@gmail.com | view tile pictures and more

Bill_Vincent

The problem is even if the two surfaces are completely flat to each other, there's going to be a paper thin void between the two, which will cause a minimal vibration between the two surfaces. Over time, that vibration will kill a floor. It doesn't seem like much, and sometimes, it's not enough to do anything. But most times, it is. It'll drastically reduce the life of the floor.

Back last year about this time, I had a job where the homeowner was a GC from Mass., who was building a summer home up here. When I got there, he'd already screwed down all the Hardiboard, and it was obvious that there wasn't a drop of thinset underneath. I went through this same spiel with him, and his response was why bother? It's just going to crack in a couple of years, anyway, that tile doesn't last in woodframe houses!!

Well, YEAH!! If you don't install em right!!

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Mike Finley

Glavanized nails are acceptable. Thinset under your hardi or not is a dubious issue in my opinion.

This isn't a black magic or mystery of the Incas situation.

Not installing thinset will not guarantee you a floor failure. Thinset has been determinded by the manufacturer as the best process to apply to all cases. I believe the manufacturer knows there are plenty of situations that you could not do it with no dire consequences what so ever. However since they are warantying the installation of their product if there is a failure they must have an established process that you must conform to in order to give them a base line of quality.

Not thinsetting your hardi is no differnet then not flashing every window on a house, there are some windows that will leak, some that might now and then and some that never will, all depending because all of the cirucmstances acting on them are all a little different.

MattCoops

Never mind that the TCA is telling you to trowel thinset underneath backerboard.

The CBU manufacture is warrantying the product for life if you do so. So isn't that reason enough to mix up a little thinset.
The thinset is nothing, it's the screwing it down that is the time killer.

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Matt with Cupan Custom Tile & Paint of Lowell, Massachusetts
Design and installation of ceramic tile and natural stone for floor, wall, and countertops
(978) 601-8774 | cupantile@gmail.com | view tile pictures and more

Bill_Vincent

Not with this, it isn't:

http://www.juldan.com/store.html?specials.html
Click on the Duraspin Screwguns on the left side of the page. I've got 2 of the DS200AC's, 1 of the DS 300AC's, and one of the DS275-18v's.

Every last one of them great guns. It takes me all of about 3 minutes per sheet of Durock. The three AC guns come with extensions so you don't even have to get on your knees to screw the sheets down. Two bathrooms, a front entry, a kitchen, and a mudroom-- average about 5-600 feet-- the Durock cut in, thinsetted down, and screwed in in about 4 hours, between me and Adam, and that's not even our best. That's average.

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Floordude

I got one of those in a give away over at TFP, thanks to Jerry.

I got a chance to use it, and charged both batteries. Got two clips through it and the battery died. Put the other battery in and it did the same thing. Had to get out the DeWalt and the Phillips head.

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ApgarNJ

what screws are you using with the ds200ac. i have that gun but only really use it for when i have to hang some sheets of drywall on smaller jobs where a rock guys won't get there.
HD has the drywall screws, green deckings screws, and subfloor screws but i can't find the screws they are selling there on that site though. glad to see they do have them not sure why HD or lowes doesn't sell them. since hardie backer is sold there.

by the looks of that page, the floor attachments come on the other models
the ds300s2 and ds300s4 models which are a little bit more money but still a time saver.

Teetorbilt

I'd bed the entire substrate in an epoxy like Plexus and forget any screws except for top levelers in the beams. Expensive but perfectly flat floors.

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PrecisionFloors

Can't do that Teetor. The purpose of the thinset is to act as support for the cbu, not as a bonding agent. If you were to epoxy it down it would defeat one of the main purposes which is to isolate from the substrate.

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Teetorbilt

I've been using my system for 20 yrs. on yachts and mega-yachts without any complaints. I've never had a recall on a home either.

I'm also willing to stick my neck out, embrace new technology and forgo the tried and true. So far, I'm winning, This is not to say that I haven't had some setbacks and lost my A on a few jobs but it's all part of being on the top of the heap.

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Jerry T

Bill, I love ya like a brother and I am not being argumentative... it's more like butting heads here . 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.

Jerry T

If i remember right the instructions tell you how to initialy charge the batteries so they will hold a charge. I have never had a problem with that, go back and read the charging instructions

Michaeljp86

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

Bill_Vincent

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.

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ApgarNJ

Bill, the screw gun you have, is it the one that loads from the top or from the bottom in front of the trigger?
i have the one shown towards the top and i don't know if it has an extension for it . mine isn't cordless though. do the screws on that page work with all the duraspin guns?
i am happy to find the screws for it, that is a good site you posted, not sure about the prices for normal drywall 1 1/4"s but at least they have the backerboard ones and stainless.