Flooring question (installing Durock 1/2" concrete board)

[Richard]

Finishing out an upstairs bathroom. 2x10 floor joists and 3/4" subfloor.

I have a couple questions.

Room is roughly 6' 3" x (doesn't matter)

The Durrock is three feet wide. I understand I should leave a little gap between the two pieces and between the edge of the room to prevent crowding (or whatever the word is)

We will have a 1x6 as our baseboard so the baseboard will be 3/4" thick.

The tile she's planning on using is 24"x24"

Question #1: Can I leave say, a 1/4" gap between the two pieces of Durrock and have a 1 1/2" gap at the edge of the room? Normally I would not like this much of a gap but, 3/4" of that gap will be covered by the 1x6 and it will have a 24" piece of tile on it. I don't really see where the very edge of the tile is going to be needing that support (???)

Question #2 regarding installing the Durrock itself: I have read that I should fit the Durrock to the floor. Pull up one piece at a time and lay a bed of mortar down to adhere it to the 3/4" plywood and help even it out.

I have also been told that since it's going over 3/4" plywood that I do NOT need to mortar it down.

The floor doesn't have any appreciable bounce to it unless you maybe (literally) jump up/down.

We did the prior two bathrooms (in same house) and I did NOT lay any mortar down. So far, 14 years later, they seem to be doing fine.

I'm not against the mortar and I'm not 'for' it. I want to do it 'right' and I don't care about speed.

(I think the flooring guy who said I didn't have to use the mortar was saying that "HE" would not use it.....as it would presumably then allow him to get to the tile sooner and finish the job sooner which is something I'm not concerned with)


Thoughts?


If I DO use the mortar.... what would I use? I was at the box store today and to be frank, received little help.

 

[Richard]

(I have a box of screws so I can screw the Durrock down irrespective of using mortar or not)

 

[bamboozled]

Unless cost is a concern there are better systems. For example:

Schluter-DITRA - Schluter-Systems

https://www.youtube.com/watch?v=CdNkzhnfioA

 

[EddieWalker]

I prefer Hardie over Durrock for tile. They have a quarter inch thick product that is designed for floors that you just screw down to the wood. I'm not a fan at all of Schluter products. It's all plastic and styrofoam that is very expensive, overrated and getting more and more negative reviews from failure. None of the pros I know of use it, it seems to be more for the home handyman who watches a lot of HGTV.

 

[Barnbuilder]

I'd put the ditra down. That's how my tile guy does it. Backer board is crap. And you can add the heated floor to the ditra.

 

[jeff9366]

When I worked as a plumber's apprentice, we used 3/4" Durarock secured with 2" (sometimes 2-1/2") Phillpp's Head screws, screwed in til fraction below surface. No mortar. We did not leave a gap where the sheets meet, nor did we try to make the joints tight.

We laid tile over the Durarock, Mastic used to hold tile in place. Mastik varied as necessary to produce flat tile surface. It is difficult to get large tiles to lay flat but it can be done. Sanded grout was the final step.

 

[ch1ch2]

I have a pier and beam house and I had ceramic tile installed 15 years ago. It was explained to me that a concrete board, Hardy or Durarock had to be laid down first to prevent the tiles from cracking. We used Hardy. We screwed it down. I do not remember if we used mastic or mortar to attach the tiles. We have not had any problems.
As far as the edges...I do not see any reason you could not fill that 1.5 inches on the edges with mastic or mortar.

 

[downsizingnow48]

I recently used this backer board on a bathroom remodel. It is not as light as the foam boards, but is much lighter than the cement type boards and can be cut easily, like sheetrock, to fit your space. Comes in 1/4" and 1/2" sizes.

http://www.certainteed.com/resources/CTG-2506_Diamondback_DSS_Eng.pdf

 

[SJay]

Definelty put mortar under the backer board and screw it down. Also, mortar and tape your joints with fiberglass tape. Just replaced my son's bathroom tile because all the tiles where coming loose because of improper backer board installation. I wouldn't leave a gap of more than a 1/2" around the room. Remember to back butter the tiles, especially a tile 24x24

 

[FredH]

I am with Eddie . We used Hardie on both Bathroom floor's and on the floor and wall of Our Fireplace install . Also used it on the Wall's in My Mom's New Walk in tub install . There was No mortar under or Behind the Hardie , Joints were not tight , but no gaps either . Bathroom floor's have 12" tiles , Fireplace was 16" tiles on floor and wall and Mom's Tub walls are 6" tiles . Disdain the cement board stuff as if You have to cut it , the cut netting lets it chip and chunks fall out . If Floor is Sound to begin with without flex , The only issue's that may come up would be with Actual tile install , mortar used and Grout used .

The only tile jobs I have seen were there has been a issue is the Grout was not sealed after install . So many people bypass that step since it is so time consuming .

Fred H.

 

[Luke'sScreenName]

3/4" is too much at the perimeter. Do 1/2 at most. I agree to tape the seams. A few extra steps is easy compaired to ripping the whole thing out and re-laying it. 24x24 tiles can be a real pain to install if the room is not perfectly flat and square.

 

[KevT]

Is the sub floor flat? Mortar does not stick to plywood and depending on what mixture you use can cause premature rot ( hence why you use PT lumber on concrete) If you need a leveler use a vinyl.

What is the what ever size? The sheet are 3x5, turn the sheets 90 degrees and use a 15" ripper. I agree I like Hardee better but both also come in 4x8 sheets too.

Don't scrimp with the backer or it will show down the road when tiles crack or grout pops from movement. 40% waste is not waste for a job well done

 

[Richard]

Sub floor is flat (though it might have some small variations that I can't see)

The other size of the room is something like six/seven feet.

I've already got the 1/2" durrock laying by my door so that's the road I'm on. Getting ready to go measure the closet and start making some dust! (cutting to fit)

 

[JimRB]

Latex modified thin-set adheres well on plywood. I preferred using thin-set over mastic. It is easier to clean off clothes, hands and tile. It was also ready for grout the next day while mastic might be mushy for days. I sanded and vacuumed the plywood floors before spreading the thin-set. I never had any warranty issues back when I set tile. https://www.usg.com/content/dam/USG...ssets/durock-cement-board-submittal-CB399.pdf

 

[GPintheMitten]

I would never use mastic in a bathroom. Use a mortar mix to adhere tile. I bought.my tile at a tile store, not a big box store and received some good advice regarding the mortar product.
Don't try and get by with 6' in a 6' 3" room. Look at different ways to orient the backer board stock you have. Maybe a 5' and a 3' ; cut the 5' to 3' 3"?. Draw it out on paper if it helps.

Tape your seems with fiberglass and mortar.

Good luck.

 

[GLyford]

I believe the Hardi instructions says to use unmodified under it, then modified to lay the tile over it. If your floor is flat, the directions say you can use the 1/4" stuff under floor tile, but I used 1/2" so there'd be no chance of the screws hitting the under floor heat tubes, per my HVAC guy.

While it's true that people don't walk against the walls so you wouldn't need support for that, what about furniture? Chair or table feet or plywood cabinet sides may end up bearing weight in that space. Would that be enough to break a tile? Don't know. You could fill the space with thinset, I suppose. No idea if that would be enough to get away with or not. If the arrangement of the room is such that you will never have furniture against that wall, I'd be tempted to say go for it...but then, I'm a hack.

 

[Richard]

This is a bathroom so there won't be any furniture in there .....other than.... a chair of sorts...

That said, I might indeed change the rotation of the floor. Changing the rotation will allow for a better coverage of a specific seam (that otherwise falls pretty close to the edge if orientated the other direction)

 

[mecan]

Good luck, I used hardi and durarock when I did my bathroom and kitchen. Prefer the hardi, but had someone run out and grab a couple more sheets and they brought back durarock. Personally prefer the square head screws over phillips, and a driver over a drill. Make sure to sink the heads a little below the board. A 2nd person to back butter the big tiles and hand them to you helps alot. They become heavy fast.

 

[Steppenwolfe]

Do you want a professional opinion?

Thinset over the 3/4 " subfloor with 1/4" notched trowell
Install the 1/2" cement board onto the fresh Thinset and screw down with stainless steel 1 1/4" screws 6" spacing on edges and 8" in the field
Install all joints tight and leave 1/4" gap at walls
Next day, tape and float all joints with Thinset , let dry 24 hours
Now you are ready to lay your new ceramic flooring

 

[Pixguy]

Informative thread. Has anyone installed heated mesh from Warmly yours under your tile?