The days of grabbing a three dollar bag of “thinset” and sticking floor tile right to the plywood in a bathroom are long gone (for professionals, anyway). For a proper tile installation you need a proper substrate. One of the most readily available are cement backerboards. These include products such as Hardiebacker, Durock, Fiberboard, wonderboard and a host of others.
When properly installed on your floor it is an ideal tile substrate for a quality and lasting installation. Notice I said typed “properly installed”? Laying them down on the floor and shooting drywall screws through them does not constitute proper installation.
Choose your weapon. I prefer Hardiebacker or Fiberboard. Whichever you choose make sure you get the proper thickness. With rare exception the 1/2″ variety would be the best choice simply because I like to overbuild stuff. With proper floor framing and deflection ratios, though, you can use 1/4″ to minimize height differences. This is not to say that 1/2″ adds significant sturdiness to your floor – it does not.
Dry fitting Backerboard on floor
You need to realize that cement backerboards, or just about any tile flooring substrate, does not add deflection stability to your floor. That is the up and down movement in your floor when you walk, jump, or use a pogo stick on your floor. The backerboards will not significantly diminish that movement. This needs to be addressed by adjusting your floor joists and framing – not by adding stuff on top of them. If your floor is bouncy without the backerboards it will still be bouncy with them.
Bouncy is not good for tile. (There’s a sentence I never thought I would say type.) I will, however, address deflection ratio in another post.
Start by ‘dry fitting’ all your pieces. This simply means cut and lay your pieces into the room without attaching them. Get all your pieces cut, holes cut out, and doorways undercut to fit and lay everything in there just like it will be when installed. This saves a load of time, mess, and headaches.
Backerboards dry fitted - notice gaps in seams
The joints in backerboards should be staggered. that just means that none of the seams should line up across the room and no four corners should be placed together. By staggering the seams you add strength to the installation simply by not having a significant weak point in the substrate.
You also want to leave 1/16 to 1/8 inch gap between each sheet – do not butt them together, and around the perimeter. If you butt them together you leave no room for expansion. The backerboard will not expand, but your walls will. If everything is butted tight and your wall expands into the room guess what happens. That’s right, your dog may burst into flames and no one wants that! It will also cause your floor to pop loose and possibly ‘tent’ or peak at the seams.
Beneath the backerboards you need thinset. Just about any thinset will work but you need to have it there. skipping this step virtually eliminates the purpose of preparing your substrate for tile – you may as well go grab that three dollar bag and start setting tile now. You need it – really.
Installing thinset beneath backerboards
Now that you have them all laid in there properly pick one side of the room to start on and pull a row out. You should only pull out one row at a time to place thinset beneath. That way you can replace them easier and in the proper position. If you pull out the entire room you may get to the last piece and discover everything has shifted 1/2″ and the last piece needs to be cut again. Not really a big deal but you won’t realize it until the backside of it is covered with thinset and you now need to pull it up, wipe the thinset off the wall from pulling it up, cut it, clean the thinset off your saw, snuff out the flames engulfing your dog (again), and replace it. It’s a bit easier just to pull one row at a time.
You need to trowel thinset onto your floor. I cannot overemphasize this (well, I could but you’d get sick of hearing it). This step is imperative for a proper tile installation. The thinset is not meant to ‘stick down’, adhere, or otherwise attach your backerboard to your subfloor. It is simply put in place to eliminate voids beneath your backerboard. Once laid into the thinset bed the floor becomes a solid, fully supported substrate for your tile – that’s what you want.
If you have an air pocket or some certain spot in your floor that is not level or flat with the surrounding area and you simply screw your backerboard onto it this will create a weak spot in your floor. Constantly stepping on that spot will, over time, loosen the screw and your floor will move.
When your floor moves your grout cracks. When your grout cracks your tile may become loose. When your tile becomes loose your tile may crack. When your tile cracks your dog will burst into flames – again. Put thinset beneath your backerboard. And put your dog out.
Installing thinset beneath backerboards
Once you have the area fully covered with thinset you can lay your backerboards into the bed of thinset and screw it down. DO NOT use drywall screws! Let me repeat that – THAT! Drywall screws are not made, nor are they sturdy enough for your flooring. You will either bust the heads of the screws off or be unable to countersink them into the backerboard. Hard to get a tile to lay flat over the head of a screw.
There are screws made specifically for cement backerboards. You should be able to find them at any hardware or big box store. They have grooves on the underside of the head which will dig into the backerboard and create its own ‘hole’ in which to countersink the head as it is screwed in. How cool is that? If you look closely at the photo you can see the ‘grooves’ beneath the head. They are more expensive than drywall screws – just so you know. But you need to use them.
Each manufacturer has their own specific spacing instructions for screwing down the backerboards – follow them – really. Some say every 12″ and some want every 6 – 8 inches. The board you use will determine the spacing. (And its right there on the sticker so don’t tell me you couldn’t find it.)
Start your screws in the center of the board and work out. This eliminates undue stresses on the boards. If you screw all the way around the outside and it is not perfectly flat you are going to have to release that pressure somewhere and it
Backerboard screw
won’t happen until you have all that pretty tile on top of it. Working from the center out eliminates that. It would probably never, ever be a problem but if you’re anything like me your installation would be the millionth one for that one in a million occurrence.
Backerboard placed into thinset and screwed down
Your floor is probably too thick (should be) for the backer screw to actually penetrate into the floor joist. If not, or just to be safe, do not place screws into the area above the floor joists. The plywood or chipboard which makes up your floor will expand and contract at a different rate and, more than likely, in different directions than your joists. If you screw your backer into the ply and into the joist six inches over it will cause inconsistent movement – no good. Do not screw your backerboard into your joists.
After I have all my floor down I will go back and double the screws around every seam. Just put another screw between every screw along the seams. It helps me sleep better at night.
The last thing you need to do is tape your seams. Get an ‘alkali resistant’ mesh tape – similar to drywall tape – and place it over all your seams in your floor. Then mix up some thinset and trowel it over the tape with the flat side of your trowel. Just like taping and mudding drywall. This will make your floor one large monolithic structure and lock it all together. You want alkali resistant tape so it will not break down due to chemicals present in most thinsets. I do not have photos of this because I do it as I set tile.
That’s it! Congratulations, you now have a perfect floor for your perfect tile installation. When installing floor tile – or any tile for that matter – the most important aspect of the installation is always the preparation. Everything beneath your tile is important, if any one aspect is done incorrectly it may compromise the integrity of your installation. Take your time and do it correctly, you will be much happier for it.
Now go put your dog out.
Roger,
I am getting ready to do my first tile job. A kitchen and adjoining dining room. Nothing like learning on the small stuff. I have a 1/2″ plywood sub-floor beneath rolled linoleum. The linoleum will not come up. It is glued down like crazy. The largest piece I can get up at a time is about a 1/2″ diameter. The linoleum has a slight texture, but is not bumpy. It is actually in good shape. Can I just put thin-set over the linoleum and then screw down my backerboard? Is 1/4 backerboard think enough?
Thanks
Erik
Hi Erik,
Standards dictate a minimum of 1 1/4″ substrate beneath your tile. If you currently have only 1/2″ over your joists beneath the linoleum you’ll need to add 3/4″ of plywood, then 1/4″ backer. That said, I know I’m too far away to stop you. So foregoing the minimum thickness requirement – yes, you can put down thinset then screw down your backerboard. 1/4″ or 1/2″, whichever, neither one adds dimensional stability. It is only there as a proper substrate to adhere tile.
Roger,
Could you clear up some confusion I have regarding troweling thin set into the gap between the backerboards prior to applying the mesh tape? After reading your detailed instructions about the importance of leaving the gap-and preventing my dog from combusting- you later answered a question by saying to fill in the gap then tape then smooth over more thin set just like drywalling. what gives?
Sorry Jeff, I’ve been meaning to rewrite that to clarify.
The seams on the same wall, in the same plane, need to be filled with thinset, then taped, then smoothed over with thinset to create a monolithic wall. It is important to leave the gap so it can be filled with thinset rather than just a little bit getting in there when you tape it.
In the CORNERS, you only want to tape and skim over – that is where you compensate for the movement.
ah shit, Jeff, you were talking about floors.
The gaps between the sheets get filled, taped and skimmed. The perimeter of the room does not – that is where the movement is compensated for. The gaps of the plywood beneath the backerboard should be left unfilled to compensate for movement.
How much working time do you have with thinset before it becomes unusable?
Hi Kevin,
It depends on the thinset. The laticrete I use is good for a little over two hours. It will tell you on the bag how long you have. It’s called the ‘pot life’ of the product.
Thanks. I had a friend help me with my bathroom project, and he put drywall compound on an area which will be tiled (not in a shower or wet area). Will thinset bond to this or will I have to scrape/sand it off.
Thinset will bond to it and it will be fine provided it doesn’t get wet.
Thanks….I thought the moisture from the thinset would ‘mushify’ the drywall compound.
Nope, the hydration in the cement of the thinset happens too quickly. To turn drywall or patching compound to mush it takes repeated exposure over a couple of weeks (depending on the amount of water, of course).
Thanks for all of your help….Merry Christmas from your friends up in Canada!!!!!
Roger.
I am installing 12×12 tiles in our lake home kitchen. When I took up the old 1/2″ subfloor I noticed that underneath was angled 1×8 pine boards with gaps between them.(similar to another post by someone) Would it be okay to remove the 1×8’s, install 1/2″ plywood and then 1/2″ cement board? I would rather not raise the floor any higher then it was. Since the 1×8’s are 3/4″ thick I would still be 1/4″ below the original height (1/2 plus 1/2) of 1 1/4″.
Thank you,
Bill
Hi Bill,
You can install 1/2″ ply and 1/2″ backer if you leave the pine in place. If you remove them you need a minimum 1 1/4″ subfloor beneath your tile – that includes a double layer of plywood. If you choose to remove them you can install a 3/4″ and 1/2″ layer of plywood and 1/4″ backer, then your tile. Right now, over the boards, you can install 1/2″ of plywood and 1/4″ of backerboard, then your tile.
The minimum substrate beneath your tile is 1 1/4″ of double-layer plywood (or wood, the pine + plywood). This is necessary to allow your floor to be strong enough to support tile with minimal movement, which can crack grout and tile. Your backerboard does not need to be 1/2″, it is only there for a proper substrate to which your tile is adhered. You can use 1/4″. If you are adamant about the height you can use ditra rather than backer, which will only add just over 1/8″.
Roger,
Great article. I’m currently redoing my guest bathroom. We had the old small ceramic tiles. Under it was a mortar bed. After ripping out the mortar bed, we found the joists and plywood cut to fit between the joists but not in a continuous sheet. Here’s a picture:
http://a4.sphotos.ak.fbcdn.net/hphotos-ak-ash4/392771_10150460799094383_557379382_8503778_1077279628_n.jpg
Although too late, should we have ripped out the mortar bed or kept it and tried to level it (it was structurally should with a few cracks)?
Going forward, do we need to lay new plywood over what we have and level it and then lay thinset and the CBU? If so, what thickness plywood?
Thanks,
Cuong
Hi Cuong,
As long as the mud bed was in good shape you could have left it. The plywood supported between the joists is a proper and acceptable method used to keep floor height down when using a mud bed as your tile substrate. It allowed the proper thickness of mud and still let you make a proper or acceptable transition at the doorways.
I would put a layer of 3/4″ plywood over that then 1/2 CBU. You’ll have a nice solid floor doing that.
Roger,
Thanks for the quick reply. One of the home improvement store reps said that OSB would work. What do you recommend?
Back to the mortar bed. How would you remove the few millimeters thick layer of thin set left on top of the mortar bed? It’s uneven with ridges left from the backs of the ceramic tiles. How would you level and smooth the bed once the thin set is removed? Any other advice on the mortar bed? I can supply a picture if needed.
Thanks,
Cuong
As long as you are installing backer over the osb it will be fine (be sure to place thinset beneath the backerboard). I have a grinding cup for my grinder which makes quick work of any cured stripes of thinset remaining on a substrate. You can try to use a razor scraper, but it’s tedious work.
Roger,
Thanks for all great info on your site. Very useful!!!!
The house was build in 1972. I am remodeling my master bathroom, wanted to install new tile on the floor. I removed old tile and noticed all joists are not leveled. I can see the subfloor is sagging about 1/4 of an inch and in some areas more. I read some articles on how to level subfloor using roof shingles.
Is it ok if I will do the following preparation of the subfloor?
1) Place roof shingles on top of existing subfloor where needed to eliminate sagging
2) Add new 3/8 plywood on top of the roof shingles and screw it
3) Apply thinset
4) Place 1/4 backer board, screw it and tape it
If these are correct steps, should I screw new 3/8 plywood in to the joists or not?
Hi Mark,
I’ve honestly never heard of that method, very interesting.
First let me say that no, that is not the proper way to level your floor. You would be better off with either a self-leveling cement, which can be a bit expensive, or simply adding your layer of plywood, then installing thinset on top of that, lay your backerboards flat and level over that – adding thinset where needed to get it flat – letting it cure, then screwing down your backer. Roofing shingles will still leave open spaces, albeit minor, beneath your second layer of plywood. The second layer of plywood should not be screwed into the joists, only into the first layer.
With all that said, there’s no way I’m gonna be able to stop you from here, eh?
Sorry, I misread the article, they used roof shingles to level prior installing hardwood floor.
I did some more research on what you suggested. And I found self leveling compound (SLC) sold by http://www.tileshop.com/installationproducts/adhesives/thinset/Pro-Level/774.aspx
Since I have to apply SLC on top of the plywood they also recommend to apply a primer that will create a better bonding.
Do you think it will be ok if I will do the following:
1) Apply special SLC Primer to existing plywood floor
2) Apply SLC only where it is needed. I only want to apply SLC where it is needed because I can’t raise the floor too much it will not meet with other room. Do you know what is the minimum required thickness for SLC?
3) Apply thinset
4) Place 1/4 backer board, screw it and tape it
Also, I was doing the walls using James Hardiebacker 1/2 inch using Backerboard screws, I was having problems screwing them in all the way. Some of them sticking out between 1/32 to 1/16 of an inch. Is this ok, or I will have problems tiling over the screws?
Thanks You for sharing your knowledge with dyi world.
Hi Mark,
I do not like ‘superior’ brand products – they are anything but. Superior brand is the tile shop’s specific brand they have made for their stores. There is no in-depth technical support for the products and if you do manage to get a specific answer from them about an aspect of their product you will not get it in writing – if something goes wrong, good luck. The specific question I would have about that particular product is this: Can it be poured to a feathered edge?
Every brand is different, so the minimum thickness would be dependent on the product. If you only want to use it in some areas it will need to be a brand that can be poured to a feathered edge. I’ve searched their website as well as everywhere online and there are no existing spec sheets for any of their products – it’s a crapshoot. It is my opinion that if you call and ask they will tell you ‘yeah, absolutely…’ – they wanna make a sale. So in short – I would not, ever, purchase that product.
If you have 1/4″ height to match up to the existing floor you would be best pouring slc to that height. This will give you the proper height as well as a substrate to which your tile can be directly adhered. You CAN NOT drive screws through slc. I don’t mean it isn’t possible, it is, I mean it will crack the slc and negate any support you have beneath your backer. If you want to use an slc in in only certain areas you’ll need to install a substrate above it which does not require mechanical fasteners, like ditra.
Not sure why you had trouble with the screws – is your drill a sissy?
Provided you use a large enough trowel (5/16″ or bigger) the screw heads won’t interfere with your tile. You may have a bit of trouble with the trowel ‘skipping’ over the heads of the screws, but your tile will be fine.
HOW IMPORTANT IS THE MESH TAPE ON THE SEAMS OF THE BACKER BOARD ? THANK YOU
Hi John,
It is very important. It creates one monolithic structure for your tile installation and locks all the individual sheets together. If you don’t have it your sheets may move in different directions which will lead to cracked grout at the least and cracked tile is a possibility.
Roger, appreciate your excellent articles about flooring and protecting dogs. I am about to lay backer board for a tile bathroom floor. Odd dimensions create a 2 inch gap along one side. I have laid this out so that it is on a non-traffic side (behind the toilet and under the vanity). Is a 2″ strip of backer board worth the effort? should I cut the board so that the strip is wider, essentially moving the seam a bit further into the room, but wider giving it more strength? thanks
Hey Lance,
I wouldn’t even bother with it. Just leave the gaps along those sides where no one is going to walk on them and call it good.
Hey Roger – with respect to mortar for use with tile on concrete backer board, any particular brand that you are fond of over the others?
Thanks much,
Dale
Hi Dale,
I am a Laticrete whore.
I use the 253 gold for most of my installations, but I haven’t yet met a Laticrete thinset I don’t like.
Hi Roger – one follow-up question…at least for today. Any brand of Silicone caulk you are particularly fond of?
Regards,
Dale
Well Laticrete, of course.
Seriously, I use it on 95% of the jobs I do – great stuff.
Hi Roger,
I’m remodeling our kitchen. Tile floor is “REQUIRED” if you know what I mean.
I removed 1/2″ laminate hardwood glued over linoleum glued over 3/4 ply.
I can’t get all of the glue off……my question is….can I use 1/2 ” backerboard over thin set
and achieve a flat enough surface to tile ? or do I need to ” float ” a mortar bed before tile ?……also I might have a deflection issue as well…….any advise would be appreciated
Thanks, Chris
Hey Chris,
Provided your floor is sturdy enough (no deflection issue) you can go right over that with thinset and backerboard flat enough without a problem. You *can* float a mortar bed over it, but it will add more than an inch to your floor. If your floor is bouncy you’ll need to beef it up before adding the backerboard or tile substrate.
Roger,
Am I correct that I can apply the thinset, fasten the hardie backer and apply the tape on the seams as I come to them when setting the tile from start to finish in the same day?
Hi Dave,
Yup, as long as your fast enough to do it all in a day.
There is no problem with that whatsoever.
Roger – A couple of questions. I’m tiling a bathroom floor. The bath has a water closet (shower / toilet) where most of the water will be contained. The old tile has been removed and the subfloor is in very good condition (1/2″ plywood over 3/4″ tongue and groove plywood). So back to those questions. First, is it absolutely necessary to remove the 1/2 layer of plywood or could I simply remove the plywood in the area of the water closer (shower) and replace it with cement backer board. That is the lazy I mean easy option. If the answer to that is no, would it be appropriate to simply install 1/4″ cement board over both layers of plywood? I said I had a couple of questions but I lied…there is a third. I ran across a Durock product that is a rolled on membrane that is “supposed” to be a base layer for tile on various surfaces including wood. It looks easy which makes me suspicious. Any thoughts?
Thanks a bunch for the information. Finally a place to go the get the truth!!
Dale
Hey Dale,
You will need an appropriate membrane to which your tile is adhered – plywood isn’t it. So the answer to your first question would be no, that won’t work. The difference in the expansion properties of cement board (essentially none) and the wood (essentially a shit-load) is going to create considerable stress on the tile installation above the two. You can install 1/4″ backer over the entire floor provided you place thinset beneath it to fully support is, that’s no problem. Durock, to my knowledge, does not have roll-on membrane. They do have a membrane on a roll – which works very well, and would work for your installation. But I know of no roll-on membrane. Have a link? Unless you were referring to the membrane on a roll, of course.
Hi Roger – So my lesson for the day is that adult beverages and email can make one dyslexic. You are absolutely correct in translating what I was trying to say. I ran across a Durock product that is a membrane on a roll, not a rolled on membrane (ie some liquid product that is rolled on with a paint roller). Although rather expensive, the membrane will save considerable time and mess. Again, I appreciate your insight.
Thanks a bunch,
Dale
Great info…..when leaving a gap between backerboards, does that remain empty always, or does it get filled with thinset when placing the mesh/thinset application….
Hey Kevin,
You fill it up with thinset before placing your tape over it, then float over the top of the tape with more thinset. That locks it all together.
I am installing tile in my 1955 kitchen. I have removed all the old flooring cover and now have the original subfloor which are planks with 1/8″ – 1/4″ gaps between them with some knot holes etc. Am I able to apply thinset directly to these planks before install the 1/4″ backerboard?
Hey John,
You’ll need to install an additional layer of plywood over that before installing thinset and backer. You can not place thinset over those planks, it won’t work.
redoing shower with tile on cement slab. can we tile right to the slab? and what do we use to waterproof the corners of the floor?. is the grout the protection? we’re using 6mil plastic first and then hardiebacker second on the walls. what specific screws do you use for walls? just put mortar on after that for our black onyx tiles?
Hey Jon,
A cement slab is not the proper substrate for a shower floor. There must be a sloped, properly waterproofed substrate created for your shower. Read through my five part series on how to create a shower floor starting here: Creating a shower floor part 1.
You listing is very helpful. I have two questions:
1) How long should I let the thinset under the backerboard cure before I lay the tile or is no delay required?
2) Can I walk on the after lay it, to reach corners or should I avoid walking on it all together? A lot of websites suggesting starting at the middle and working to the edges, but then I don’t see how to avoid having to walk on laid tiles.
Hey Sean,
You can lay the tile immediately after installing the backerboard. You can walk all over it too.
I am tiling a floor that spans across a concrete slab and new OSB floor (in a addition onto the house). At the transition between the house and addition the floor surfaces goes from concrete slab to exposed brick (from the top of the foundation wall) and then to the new OSB flooring of the addition. I am concerned about the seams between the slab / brick and the brick / OSB resulting in the tiles cracking. I had thought about using a floor leveler to smooth over the transition at top of the brick and then covering the entire seam / concrete / OSB with backer board that is mortared to the OSB and concrete flooring. I plan on using Schluter-DITRA over the entire floor. Your thoughts would be greatly appreciated.
Hey Paul,
I would forego the backer. Just use slc on that transition then install your ditra. It should compensate for any movement just fine since it also acts as a crack-suppression membrane. Trying to adhere backerboard to concrete creates more problems than it ever solves.
Roger,
Thanks for your advice. So after I install the Ditra over the OSB / transition / slab that has been leveled with slc can I use additional slc along the edge of the ditra to transition the tiles from the Ditra to the concrete slab?
Thanks again.
Yes, no problem with that at all.
About 15 years ago. I put down 1/4″ plywood and then sheet vinyl tile. Do I need to remove the 1/4″ plywood and vinyl before i install the cement board for the Porcelain tiles, or can I install the cement board right over the 1/4″ plywood and tile?
Thanks,
Mike
Hey Mike,
It would be best to remove it, but you can put backerboard over it as long as you use thinset beneath it and screw it down well. With 1/4″ it isn’t too much of an issue, with luan (the 1/8″ ‘doorskin’) it creates problems.
Now that I think about it, I think it was 1/4″ luan, Would the 1/4″ luan be ok?
Thanks, again
Mike
Never heard of 1/4 luan. Doesn’t mean it doesn’t exist, though.
If it’s actually luan it needs to be removed. Luan has no structural stability at all and should not be below a tile installation.
Thanks, Roger.
Really appreciate the help. I was right the first time . I pealed up some vinyl and it is 1/4″ plywood.
Thanks again,
Mike
Roger,
My fiancee and I are installing a tile floor for the first time in our guest bathroom (the house was build in 94 in Austin, Texas) – when we pulled up the carpet we noticed that there is 2 pieces of plywood with a plank between them, the plank seems to be slightly bowed and causes a lip of about 1/4″ meaning the surface is a bit out of flat. Should we use thinset under the CBU to make this more flat? I’m a bit hesitatnt using something like a self leveler because I’m worried it may drip down in cracks (second story floor)
Pictures are at:
http://photobucket.com/firstfimefloor
Hey Brian,
You should always use thinset beneath backerboard, but you already knew that.
The thinset beneath the CBU can level it out but it would be better to take a belt sander to the plank first and knock it down a bit. 1/4″ is little higher than comfortable.
Thanks Rogers,
I read some more last night, and we have 23/32 OBC throughout the house, in the master bathroom there is definitely another layer of plywood or OBC on top beneath our existing tile. The reason we know this is we have a section of the ceiling cut out due to some other work, we don’t really have a good way to see what is under the bathroom the pictures were taken of. We bought this house a few months ago so we still don’t know everything about it yet.
I have no idea about this bathroom, the plywood feels a TINY bit bouncy when I bounce up and down on it but doesn’t when my fiancee does. But I do weigh around 290 lbs.
We looked a bit more at that “plank” we think that is the top of the wall that is between the garage and the living room. But we aren’t experts and could easily be wrong. What does it look like to you?
If we decide to add an extra 1/2″ plywood to be safe would it hurt to lay the plywood over that beam? We would just get the plywood to fit and run it over the beam. The seams would be perpendicular to the other seems already there. We are also using 6×6 porcelain tile if that changes anything as well.
Also, I added a picture of the joists between the first and second floor. This is considered an engineered truss right?
http://i814.photobucket.com/albums/zz66/grakk_egg/floor/20111105_0752421.jpg
The measurements are
24″ apart
16″ high
On the diagnol from the center of the metal piece to the next is 20″
No idea on the length.
I think if you run a layer of plywood over everything, including that beam, you’ll be just fine. The top of that wall shouldn’t create any problems for you.
Run the plywood directly over it? don’t worry about trying to level out the subfloor under it? Also which direction should the grain of the plywood go, and where should the seam in the two pieces of plywood be? Sorry if this is a dumb newbie question
If you need to level the subfloor out to get the ply to lay flat then yes, do it. Run the plywood perpendicular to the grain of the subfloor layer, perpendicular to the joists. Overlap the seams below by at least 1/4 of the length of the sheet. More importantly, overlap the top of that wall by at least 1/4″ of the sheet length if possible. Offset all your seams so none of them match up with four corners.
Hi,
I would like to if I have to first level out the wooden sub-floor, with self-leveling compound, or can I just go ahead? and what to do if the floor squeaks?
Thank you
Joseph
Hey Joseph,
If I am understanding your question correctly you are planning on installing the tile directly to the plywood? If that’s the case then no, you shouldn’t just go ahead. You need a proper substrate to install the tile to, the plywood on your floor is not it. Depending on which substrate you choose dictates how you go about leveling the floor if needed. If the floor squeaks put some screws through it into the floor joists to tighten it down.
I am trying to redo my kitchen floor, it is a concrete slab that had asbestos tile and then linoleum. I have taken up the linoleum and the asbestos but can not get the black nasty glue up even though I went through about 100 straight razor blades. I would like to put down backer board 1/4 and need to know what type of screw anchors to use. It is a very old house 1964 and there is one crack in the concrete. I really want to use the 1/4 backer and don’t mind drilling holes for the anchors but need to know the proper
size. Can you help me?
Hi Patricia,
Attaching cement board to concrete IS NOT an approved installation method. It will not last over the long-term. You would be better off either using a highly modified thinset which is approved for use over cutback (the black stuff) or chemically or mechanically scarifying the surface of the concrete.
That said, if you are set on using it there is no requirement for the anchors – any size will work. Make sure you place thinset beneath the backer to ensure full support.
Hi Roger,
I’m also interested in applying backer board to my concrete floors. I live in a 100+ year loft and part of my concrete floor is patched with plywood in one area and a black resin type material in other areas. I’d like to lay down the backer board to make the surface even and ready to tile. I’ve had difficulty driving anchors into concrete before. Is it necessary to use thinset and screw to the floor? Or can I just install using thinset alone?
Hi Sarah,
The thinset alone likely won’t last unless you use a highly, highly modified thinset. And if you’re gonna spend the money for that, just forego the backerboard and tile directly to the concrete. Better yet, spend the money on a proper membrane such as ditra and do it properly. Cement backerboard IS NOT approved for tile installation over concrete. There are membranes made for such an installation.
Hi Roger,
I have a problem with my tile floor. It was installed last November and I also have warm wire installed under the tile. Everything was fine until September when some parts of the tile floor would make a popping sound when walking on it. Then the grout started to crack in those spots. The tile man came back and re-grouted those spots. It was still popping after that. Last weekend i turned the floor heat on and now the floor is doing fine. My question to you is what happens in the spring when we turn off the floor heat will this problem happen all over again?
Thanks for any info that you could advise.
Thanks
Robert White
Hi Robert,
The popping is likely due to expansion. The cracking grout is due to movement in your substrate or incomplete coverage of thinset (VERY common with in-floor heating) in those areas. You may or may not hear the popping again – probably not – but the fact that it did pop indicates that something likely became debonded. Knock on the tiles in those areas and see if they sound hollow. If so you will probably have the cracking grout issue again. Simply regrouting areas where grout has cracked never solves the underlying issue that caused it to begin with.
Hi Roger,
This may be a silly question but here goes.. If it takes me all weekend to put the backerboard down, can it be walked on for a week so I can tile the next weekend?
Hi Lisa,
Not silly at all if you don’t do this everyday.
Yes, you can walk on it as long as you need to.
Jim,
I am remodeling a bathroom. The door meets up to the hallway with carpet. Should the backerboard and therefore the tile only be installed to halfway through the threshold where the doorstop would be on the jamb?
Also, is there a minimum width that the backerboard should not be cut smaller than? I ask because I have a relatively small floor space (66″x82″), which means I could have 6 or 10-inch strips. Is this acceptable, or should I cut-down the full sheet to allow for wider pieces?
Thanks
Louie
Hey George, (I’m Roger, not Jim, but I’ve been called much worse.
No worries)
I normally stop the tile edge halfway under the closed door. Backerboards can be cut down to about four inches wide or so. Smaller than that and the screw will usually snap it in half when you screw it down. Six or ten inches is fine.
I am preparing to install a tile floor in a small half bath and have found a lot of good info here. I have two doorways to contend with that have c1920’s Victorian style oak trim and jambs that will need to be undercut (too difficult to remove without splitting…ask me how I know). I am thinking that it is more complicated to determine the amount of undercutting required than to just add the thickness of the backerboard and tile due to the 2 layers of thinset. Am I correct and if so, what is the best method to determine the height of undercut required? On another note, this bath is only a little over 3 ft. wide (did I mention it was small?) and I am still trying to decide on what size floor tiles would look the best. Is there a rule-of-thumb on the minimum number of grout lines (rows) one should have in a floor for visual aesthetics? TIA
Hey Jim,
I’ll usually get all the materials (the tile and backerboard) and add two or three layers of cardboard to it, depending on what size trowel you’re using for the tile. If you are using a 3/16″ or larger use three layers, smaller use two.
There is no rule for minimum grout lines, tile size, or really much else when it comes to aesthetics. It’s a matter of what looks good to you. And by ‘you’ – I mean your wife or significant other.
Roger,
When you say “cardboard”, do you mean something like the thickness of the cardboard on the back of a legal pad? (For 3/8 x 1/4 trowel)
Thanks again,
Jim
I mean cardboard like the boxes the tile comes in. It’s a bit over 1/16″.