Line for the control joint

Photo 1

In my previous post I beat you to death with the reasons why you absolutely need a soft joint (control joint) in certain tile installations. Sorry about that, I have a hard time expressing how important they are without being a dick. They”re important – really. So now that I’ve properly reprimanded you it’s time to show you how to do it. :D

Cleaning out the line for the control joint

Photo 2

You need to figure out where your control joints will be located before you grout. I will sometimes take pieces of blue tape and mark that line every few feet or so ’cause I get dizzy easily. The less grout you get in it the better. You will need to clean out any grout that ends up in there so try not to let it end up in there.

Cleaned out line for the control joint

Photo 3

Once you have your floor grouted and before the grout is cured (do this right after you grout) you need to clean out the control joint. I use a ‘hook knife’ which is just a curved blade that I can run down the joint to loosen all the grout (that’s what that funny looking tool is in the picture).

After you do that you can take your shop-vac and suck all the grout out of that line. Be careful not to remove grout in the adjacent lines! Keep your hose an inch or so away from the tile. (Wow, that sentence is ripe for a very bad joke) In photo 1 you can see the grout in the lines crossing the control joint – you want to simply cut straight down the control joint across these lines. When you vacuum out the grout be careful not to remove grout from those lines also. (If you click on photo 2 you can see what I mean)

Photo 3 shows the control joint all scraped out. Again, you can click on it (it’s huge) and see where I’ve cut across the other grout lines. Then just vacuum it all out. Photo 4 shows the line ready for caulk. Most manufacturers have a matching grout or silicone for whatever color grout you choose. If not, Laticrete has a large number of colored silicones called Latasil and color charts to see which would best match your grout.

Control joint ready for caulk or silicone

Photo 4

Once you have your control joint all cleaned out just fill it up to the top with matching caulk or silicone. Make sure you get the line full – you don’t want any hollow spots in the line which will eventually end up cracking or disappearing. You can run a damp sponge down the line once you get it full to smooth out the top.

You may need to do this more than once depending on the width of your grout lines. After the caulk or silicone has cured it may shrink a bit too much to look acceptable. If that is the case then go ahead and run another bead down the line to fill it back in.

That’s it. Photo 5 shows the completed control joint. I used a matching caulk on this installation which will darken as it cures. Once cured the color will match the grout exactly.

Completed control joint in tile installation

Photo 5

And there you go. Now you can go out and be a tile ninja and berate people because they have no idea what a control joint is in relation to a tile installation. You can look like a superstar because you can explain to people why their tile looks like a teepee (Read my last post) or why their floor sounded like a gunshot last night. That’ll scare the hell out of you – believe me.

If you have any questions at all about whether your installation needs a control joint or not – just ask me in the comments below! I’ll answer you when I get home from work – really – read around. I’m fairly personable. :D

And don’t forget to sign up for TileTips!

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  • John

    Hi Roger,

    I appreciate all of your info. I have a room that is a out 12×29. The concrete floor has joints in them. 2 joints in the 12 foot direction, and one long joint running in the 29 foot direction. I may be misunderstanding, but I believe I’m supposed to follow place a soft joint above these lines in the tile job…is that correct? If so, this would mean I need a soft joint running in multiple directions. I’m laying wood look planks 6×24, running with the length of the long room. The concrete joints are not straight at all, and wave several inches in either direction along the room, so it would be impossible to run the soft joints directly above them even if I tried. I’m trying to figure out the best way to go about this. I am tiling directly onto the concrete, as I do not have anywhere near the budget for ditra or something like that. I do know I need to purchase some sort of membrane to at least go over those joints, which I I haven’t figured out which to use yet.

    I’m looking for any input you have on a membrane for the concrete joints, as well as your suggestion placing soft joints in the tile. Thank you again for your time.

    • Roger

      Hi John,

      If you use kerdi-band (or an equivelent, I know customs makes one for redgard) that would work, you can also use mesh tape and hydroban or redgard over it for the joints.

      Regarding placement, you can place the soft-joint a few inches on either side if you need to, that is normally sufficient. You can also zig-zag a soft joint back and forth following the pattern of your tile, that also is normally sufficient.

      • John

        Roger, thank you for your reply. So, as far as the joints in the concrete, you’d be comfortable just using a schlueter band across them? I was under the impression that I’d need some sort of uncoupling type membrane to go over those joints in order to prevent cracks in the tile job. Thank you for your time once again.

        • Roger

          Kerdi-band is just fine. What you’re looking for is a monolith, of sorts. A manner in which to separate the bond from one side of the joint to the other if it moves. Having the kerdi-band straddle the joint allows this as the tile is bonded to the band, which will allow differential movement (on a scale small enough) to accomplish this. If there is more movement than that – you have a bigger problem than cracked grout. :)

          • John Watson

            Thanks again Roger. If I’m using the kerdi band to cross the gaps on the concrete, what would be a good way to stick it down? It calls for thinset to go down, then the band on the thinset. However, that is for applications on ditra or other floor types. Since this is concrete, I’m assuming I dont want thinset filling these expansion gaps. Is there another recommended way to put this band down over the gaps without thinset? Or would you still go with thinset and not feel concerned about the expansion gaps?

            • Roger

              Hi John,

              I normally stuff backer rod down in the expansion gaps, then you can go over it all with thinset and the kerdi-band without compromising the expansion gap.

  • Al

    Do soft joints need to be full zig zag across or just short sides of tile with wood planks? Also backer rod or bond breaker tape?

    • Roger

      Hi Al,

      It needs to be zig-zag. The short ends would work for that direction, but in moving toward one another it would grind away the joints between the short ones, on the long side of the tile. Backer rod if needed.

  • donald l brown

    We have not grouted a zig zag controlled/expansion joint on the floor. The title are porcelain. We used schluter membrane heated floor system. the title are 48” long by 8”, some are 24” by 6”. (large title) My question is do I install a backer rod (round polyurethane) into the joint prior to placing the silicone caulk, or do I just install the caulking with no backing rod? The joints are 1/4” wide. what would you suggest? Thanks

    • Roger

      Hi Donald,

      With 1/4″ wide I would absolutely install backer rod. If you don’t it’s gonna take a 55 gallon drum of caulk to fill them. :D

  • greg

    thanks for making your knowledge fun to read. quick question:
    is a soft joint the same thing as an expansion joint and also the same thing as a control joint? 3 terms? same meaning?

    i watched a crazy video on youtube about an expansion joint, where they actually cut into the concrete sub floor, then fill it with a few different things after the tile is laid, of course the tile isn’t laid covering the expansion joint in the concrete, speaking of laying things, brb my girl is upstairs waiting for me.

    • Roger

      Hi Greg,

      Yes, as far as tile installations they are all essentially the same. As far as concrete an expansion joint is built in when the concrete is poured, a control joint is cut in the cured concrete (what you’ve described). There is nothing called a soft joint in the concrete itself, control and expansion joints are treated the same way in the tile installation – with a soft joint.

  • Tracey

    We used tile as baseboard in my new masterbath and the groutline between the floor tile and the baseboard/perpendicular tile has cracked. Do I need a soft/control joint there? My bathroom is 7’x13′ with an adjacent WC that’s 3’x5′. Do I need another one? There is tile running up the side of my soaker tub — do I need one at the joint where the tile starts to go up? And do I need this in my shower, where floor tile meets wall tile or in the corners? I think they grouted and then caulked over. Please advise!

    • Roger

      Hi Tracey,

      Not a soft joint, but basically the same principle. You need silicone (or caulk) at any change of plane. That is a change of plane, it should not be grouted.

  • DaveB

    Thanks for all the great articles! I’ve referred to them on multiple occasions as I am doing a lot of tiling in my home. I used a soft joint every 8-9ft in my electric heated floor living room. It was an 18×18 brick pattern so the soft joints were easily run straight across. Now I’m doing a 6×36 wood look porcelain tile running with the length of the room (@50ft long down through three rooms). (5/8″ ply + 3/4″ ply + RPM mats + Nuheat wire + 5/16 – 1/2″ of SLU + thinset + tile just like my living room). But with the randomized wood look tile pattern my soft joints will have to zigzag across the tile, is this OK?

    FYI I will also be doing either 3/32″ or 1/8″ grout joints if that matters.

    • Roger

      Hi Dave,

      It’s not ideal, but it will work. Technically you should cut a straight line through the installation for your soft joint. And yes, I know that sounds like it’ll look like crap – and it does. :D

  • Mike

    Installing a wood grain tile floor overtop of butted uncoupling membranes throughout a basement. Most of the working area has OSB subfloor. movement joints in doorways, perimeter, etc. There is a long room (15′ by 30′) where continuous floor will be layed and I was hoping to place a staggered movement joint at the halfway point of the room (dividing the floor into roughly two 15′ by 15′ segments). The staggered joint would be near the butted areas of two 15′ by 15′ the uncoupling membranes but obviously not following the seam directly. Is this going to be a problem?
    Do i even need the uncoupling membranes on top of a subfloor?

  • Brian

    Hi Roger,

    Whats the best way to run a soft joint in a large room with a randomized offset/brick pattern? The room is oddly shaped, but is longer than wide, and the tiles are wooden plank style 8×36

  • Brian

    Hi Roger,

    Whats the best way to run a soft joint in a large room with a randomized offset/brick pattern?

    • Roger

      Hi Brian,

      The best (and proper) way to run a soft joint is to cut the tile so you have a straight line for the joint. But you can follow the pattern through from one side to the other as long as it’s a continuous bead.

  • Brian

    Hi Roger,

    Whats the best way to provide this soft joint in a large room (about 350sqft) with a randomized 10-30% overlap? The room is longer than wider, and the direction of the tile was going to be run with the length of the room for aesthetics.

    • Roger

      Hi Brian,

      Technically you should cut a straight line through your pattern. You can zig-zag it back and forth following the grout line if you want, just make sure it’s a continuous bead.

  • Sunny

    Hi Roger, thanks for your sharing, I saw you used a “hook knife” to clean the joint, so I think you might be interested in our new tool for that job. It is a hand tool with a carbide tip in 1-4mm sizes. Designed specifically for grout joint 1-4mm. So it can better fit into the seams between tile, easily run down the joint, remove the thin-set mortar out and with little danger of chipping or scratching your tile. It is light weight, safe, green and also very cheap. :dance:

    • Roger

      Hi Sunny,

      I know, it’s commonly called a grout saw. :D

  • debra

    reading blogs and questions and coming up with my own…doing research…house currently has tile laid directly on cement, of course cracked and broken. Will be replacing and I understand the need for backerboard; but something in one of the above questions has me asking: can I use redgard throughout the house instead of backerboard?

    • Roger

      Hi Debra,

      You don’t use backerboard over concrete. You can use a membrane like ditra, or yes, you can use redgard. Believe it or not the ditra would actually be the cheaper option. :D

  • mike

    Hi Roger, new to your site – incredible stuff…

    I’m going to install 1/2″ travertine in a ‘french pattern’ over Ditra using the Ditra-set mortar above and below, in a rectangular room that’s about 27′ square, with a central floor-to-ceiling fireplace. Clearly, expansion control joints are required. I was planning on using one of Schluter’s expansion joint products – probably the one with the replaceable membrane – and break the room up into four quadrants. However, after reading this thread, maybe I’d be better off just using silicone, following the tile pattern, so I wouldn’t have the obvious straight seams (and more tile cutting) using the Schluter expansion control joint product. What’s your thoughts on using the Schluter expansion product? Would you use it, or go with silicone? If I did use it, what installation tips would you give me?

    Thanks in advance for your time…

    • Roger

      Hi Mike,

      The schluter expansion profiles work well with straight installations, on your patterned one I would use silicone.

  • Mary

    Hey Roger,

    Is there any reason to install the soft joint after grouting a tile installation, or could you do the caulk first and then the grout? Are there pros/cons for either order, or does it not matter?


    • Roger

      Hi Mary,

      Doesn’t matter. Time is the only factor. I don’t have time to silicone first, wait a day for it to cure before I can grout.

  • Paul

    OK. After reading your replies. I think you already answered my question. Zig zag soft joint from wall to wall at transition areas. Check.

    • Becky

      A couple of questions re: soft control joints. We are installing wood plank porcelain tile (6” x 24”), over cement board, on the main floor of a house with a crawl space. The dimensions (across 3 contiguous rooms) are approximately 40 feet long and 15 feet wide (although the last 5 feet of one end is 22 feet wide). B/c of angled walls/other issues, we are installing the tile horizontally, so that it is possible to install joints/breaks across the 40 feet down a straight line (if that is correct). Based on this post and your preceding one, I think I need 1 or 2 control joints through the length. My questions are: (1) whether those joints can properly be one straight line, along one side of an entire “row” of tile, or do I need to zig-zag back and forth, so that the joint goes down one side of one tile, across its bottom, then continues down the other side of the next tile in the same “row? (2) do I also need to leave a control/expansion joint in the mortar, along the same line? (3) should I use 1 joint or 2 across the 40 feet? (4) do I need to add a control joint in the 22-foot end section and, if so, (5) should I run that through the entire length of the room, even though the rest of it is significantly narrower? Thank you in advance! Becky

      • Roger

        Hi Becky,

        1. Straight
        2. No, the mortar will compensate by cracking if need be, it won’t affect the tile above it.
        3. Two.
        4. Yes
        5. Entire length.
        6. There is no number six, just wanted to see if you were paying attention…

        • Becky

          Thank you so much! We have had some tile adherence issues due to cold weather and the lower temperature under the crawl space, but will finish our project up as soon as it warms up. Thank you for the help!

  • Paul

    I am putting down 9″ x 36″ porcelain planks on slab ( 4 rooms open floor plan no doorways ~ 1300 sq ft. ). I have 130 sq ft of Ditra XL left over from bathroom job. Any value in XL over concrete vs 1/8″ standard? Also wrt a control joint with staggered planks, can the joint be staggered as well or is it best to have a straight line? If that makes sense. Thanks ever so much.

    • Roger

      Hi Paul,

      XL is simply thicker for most purposes. While it does lend more uncoupling than regular ditra, it’s not necessarily needed for an installation over normal concrete. Yes, you can stagger the control joint.

  • Ray Stark

    I have a large rectangular workshop. I am throwing down 12×24 porcelain tiles because PAINT IS FOR SISSIES WHO WEAR SLIPPERS IN THEIR GARAGE!!!!! THERE! I SAID IT!!!

    OK, per you eloquent but practical butt chew above, for the lateral and vertical expansion joints ( as viewed from above) the concrete dudes installed with a crack tool, I plan to apply 24″ wide sticky-back fabric crack isolation material over these joints, lay my tile using Megalite and then use a sanded caulk to Z-pattern back and forth down the fabric membrane both horizontal and vertical (as viewed from above!!). Once the caulk sets up, I’ll go back with regular 1/8″ sanded grout. Will that give the panels enough wiggly-jiggly room with 1/8 joints? The floor is 24 years old and only has cracks down in the crack joint and they are 1/8 or less. Very stable.

    Befre I found your blog, I was pondering saw-cutting the tile over the tile joint but your suggestions above got me wondering if just running a soft joint down the isolation membrane would do the job. I await your answer.

    Bonus question: Should I fill the crack joint with a soft goo like caulk or foam rope and RTV before laying down the isolation membrane???

    Thanks in advance for the answers…

    • Ray Stark

      Change of plans…

      I am going to use Custom Megalite (recommended by Custom for medium bed installations of porcelain) and coat only the hairline crack areas with a coat of Red Guard -per Custom’s suggestion.

      As for the crack joints, I am going to fill them in with 50-year caulking and then install the tile right up to the joint, expanding the crack joint from 1/8″ to 1/4″ over these joint areas. I’ll wipe the joints clean of any mortar down to the caulk with a tuck-pointing tool or piece of 1/4″ Masonite as I install the tiles. Once the mortar sets up and I can walk on the tiles, I’ll go back and fill in all the joint cracks with matching sanded caulk. Once that hardens up, I’ll hit it with regular grout everywhere else. Hopefully, that will allow any movement to occur. The slabs (all the pieces bisected by the crack joints) are good and solid so I will just use mortar to bond the tile on them. Supposedly, the Megalite has a tolerance of up to 1/8″ of movement. Must be full of stryofoam chunkules as its also much lighter than standard mortar.

      As for the tile baseboards, I am going to suspend those so the mortar doesn’t fill the gap between the floor tile and the wall. I’ll caulk the gap after set-up with grout caulk too and then use regular grout on the top edge.

      Thanks for giving me time to work this out in my mind for a better solution. You must be busy and that is a good thing. Or, on a week-long bender. Hope its the former. :whistle:


      PS Loved the work on your REAL work site. No wonder you are busy.

      • Roger

        I am SUPER busy, no week-long bender (that’s in two weeks when I go on vacation :D ).

        Sounds like a great solution.

    • Roger

      Hi Ray,

      That will work just fine. And yes, I would fill the crack joint with silicone or foam before installing the membrane – it keeps thinset out of it. Unless your membrane isn’t installed with thinset, in that case don’t worry about it.

      • Ray Stark

        The Custom call center recommended solution is merely Red Guard over cracks 1/8 and smaller -which is everything but the man-made crack joints. I will use no membrane as the Red Guard serves as a membrane. (Using Red Guard and Custom mortar satisfies the lifetime warranty requirements issued by Custom. I am good with a warranty! It includes labor for the repair! Yeah! Like THAT is ever gonna happen! :) )

        The crack joints have been caulked with a 50-year caulk with silicone about half way up the joint and, thanks to your suggestions, the man-made crack joints will travel up through that caulk to the sanded caulk. Each “panel” of concrete will be mortared as usual using MegaLite to the concrete except for the small areas coated with Red Guard, which the mortar “floats on.”

        To isolate the two adjacent mortar bases at the crack joint, I am going to try and use a 1/4″ piece of Masonite to slide down the crack to stop mortar from oozing into the joint. I’ll make sure it is clean as possible before moving off the joint area. By the time I get working on the adjacent tiles, the first side of the joint should be pretty well set up. When I am done, there should be a nice 1/4″ clear path to the caulking with mortar on both sides. I am taking pictures an will upload these to a garage building site. I’ll come back here and post the link when I get it done.

        Thanks for taking time out of your busy schedule to help know-nothings like me.

        (Catch-up for newbies like I was a few weeks back:

        I am using all Custom products from Homie ‘Po.

        I am laying 12 x 24 porcelain tiles in a garage/workshop. Porcelain doesn’t work as well with standard thin-set mortars because it is almost completely impervious to moisture absorption. So, they put some extra-sticky bonder into porcelain mortar.

        The Custom guys consider any tile larger than 18″ to be a “big” tile requiring a thicker mortar bed. Thinset is for 1/4″ notch trowel or smaller. I am using a medium bed mortar, ($40 per bag) that also has the ability to “wiggle” a little without breaking the tile. Porcelain is harder than ceramic tile and I want to isolate the tile as much as possible to prevent any cracks. I will install that with a 1/2″ notched trowel.)

  • chris z

    Yet another question for you. I would like to lay my nice big 20″ porcelain tiles on a diagonal over a control joint. Of course i will need something like redguard over it. This would make the soft joint in the tile zig-zag up to a maximum of about 6 1/2″ from the joint in the concrete. Is tbere better way to do this?
    No ditra in the budget. Bostick porcelain-mate thinset unless you tell me it is crap and to return it.

    Thanks for all your help man. Or Elf.

    Whatever, just thanks


    • Roger

      Hi Chris,

      Yes, that is the best way to do it. The bostik thinset is a very good one.

  • shaunae

    Awesome info! Thanks! I have an area that I am trying to figure out the best placement for the soft joints. It’s a 30x 30 large room separated into 4 smaller rooms by load bearing walls. So essentially it’s 4 different rooms but all connecting and open besides the two load bearing walls. This makes up the kitchen, family room, living room, and formal dining room. Each little room is 15×15 about but I am wanting to do a continuous flow of tile between all. Distance across the two rooms is 30 feet from wall. Then there is a 25 foot hall that connects to the 30×30 area described above. The hall is 5 feet wide. I am using 12×24 tile and laying it in 1/3 running bond pattern such that I will not have a continuous line along the 25 foot hall because of the staggering. I will have a continuous line across the 30 foot wall to wall section. What would you suggest for soft joints? Also, are soft joints only effective when the run the entire length of the line from wall to wall? Thanks for any tips and hopefully any of that made sense.

    • Roger

      Hi Shaunae,

      I would have a soft joint in all doorway or room transitions and at each end of the hallway (if it does not end at a wall). Soft joints need to extend wall to wall, but they don’t need to be a straight line, just a continuous line, KnowWhatIMean? You can jog the soft joint in the z pattern of your staggered layout as long as it is one continuous line.

  • mike

    I am tiling over the original t&g wood floor. Is this a suitable substrate for schluter ditra?

    • Roger

      Hi Mike,

      Nope, you need to go over that with plywood first.