Control joint installed through a tile installationThat title right there is absolutely ripe for me to go off on a sophomoric, mildly humorous rant about the viability of inferior illegal plant use. But I’m not gonna do that. (Okay, maybe later…)

A soft joint, or control joint,  is simply one grout line, all the way down the length of your installation, that is filled with colored silicone or caulk rather than grout. The purpose of a soft joint is to allow movement in your installation without cracking tiles or grout. When placed properly it will absorb any ‘normal’ seasonal and structural movements inherent in structures.

There are guidelines that need to be followed for a soft joint to be effective. The TCNA guidelines call for a control joint every 20′ – 25′ in each direction for interior installations and every 8′ – 12′ in each direction for exterior installations. Interior installations which are exposed to direct sunlight also need control joints every 8′ – 12′.

This simply means that if you install tile in your living room and it is larger than 25′ or 30′ you need a control joint – period. It is non-negotiable. If you do not have it chances are likely that your tile installation will fail. The number one reason for tile installation failure (on a floor) is lack of proper control joints. You need them! *It’s either lack of proper control joints or improper coverage, there are conflicting views. Both will lead to a failure and both are installer error – both need to be correct!

You need them on wood, you need them on concrete, you need them inside, you need them outside. And no, that is not the beginning of a Theodore Geisel book. I’m simply trying to illustrate the importance of a soft joint in a large tile installation. Because it is. Very important.

Along with these control joints you also need to ensure proper perimeter spacing. This simply means that your tile around the perimeter of your room is not butted against the wall or framing. You need room for stuff to expand.

You don’t realize it but there are a lot of things in a structure which move – constantly. With temperature changes, normal construction shifts (settling), even sunlight causes enough significant heat to expand and contract structural elements several times a day. You absolutely need to allow for this movement.

If you do not allow for this movement your tile installation will not last long-term. Your grout will crack. Your tile will crack. Your dog will burst into flames. Your tile may ‘tent’ which means that there is so much pressure pushing two adjacent tiles together that the bond from the mortar will eventually fail and the two tiles will pop – literally – off the floor and tent. They will sit there right in the middle of your room looking like a little teepee.  I tapped a tile once in an installation which did not have control nor perimeter joints and they literally popped – loudly – and tented.

Control joints also need to be installed above expansion joints in concrete – whether you use a membrane or not. A membrane will allow you to ‘shift’ the control joint in the tile over up to six inches (depending on which membrane you use) but it still needs to be there. If your concrete has a control joint it needs to follow all the way up and through your tile installation.

Most grout manufacturers make a matching caulk or silicone which can be used for these joints. When cured they match the color of the grout exactly or nearly so. You can tell it’s there – if you look for it. Don’t look for it. I understand that a control joint may change the look of your installation – you may not like it. I know. I get it. I don’t like them either. But you need them.

The photo at the top of this post shows a control joint through the middle of a tile installation. This is right after I finished installing it so the caulk has not yet cured – that’s why you can see it. Once cured it matched the grout color exactly. In my next post I will show you exactly how to prepare this grout line as a soft joint and install the caulk or silicone.

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  • Jared

    I am installing 8″x45.5″ wood plank rectified tile over a Gypcrete floor with pex radiant heat in it. I am running the tile lengthwise and will have to unfortunately stair step the expansion joint. Luckily most of it will be hidden under a couch but my question is in regards to the space of the movement joint. I am going with an 1/8″ grout joint but am unable to find any backer rod that comes in that width. I am considering cutting a 0.25″ backer rod in half with a utility knife to create 2 1/8″ strips to be used. Is that necessary or can I just use the color matched caulk to fill the grout joint?

    Is a 1/8″ enough of a movement joint to allow for expansion? Not sure how much my porcelain tiles will expand as they are heated up through the radiant floors. I couldn’t really find any information on that online.

    • Roger

      Hi Jared,

      With radiant I prefer 1/4″. I’ve done 1/8″ several times, though, and haven’t had issues. Yes, you can cut the 1/4″ in half, it’s only there to take up space. You can also just fill the entire joint – that IS a lot of silicone, though.

  • caroline

    we have a very large area of in total 100smq, made up of one large kitchen which is a square room of 7.5m x 7m, and then smaller rooms varying from 8sqm to 20 sqm going off this kitchen.
    The sub floor has underfloor heating and is part suspended floor and part new screed. we will use a ditra mat. is it enough to have an expansion joint going in the middle of both directions of the kitchen like a cross and then in the doorways connecting to the other rooms?

    also to install these expansion joints, should we use one of the schluter dilex products or just leave a gap (how big?) and fill with silicone. and the same for the perimeter, is it necessary to use the Dilex on the perimeter or can we simple leave a gap and caulk.

    Many thanks in advance. i was nearly put off tiling before reading your website!


    • Roger

      Hi Caroline,

      Yes, it should be enough to do the cross in the kitchen and at the doorways. You can use the Dilex, but it is not necessary. You can also just fill those joints with matching silicone (matched to your grout).

      You can leave a gap the size of your grout joints. Basically it’s just a grout joint without grout in it that gets filled with silicone. You do not fill the perimeter gap with anything (no dilex needed, either). Not sure if you have baseboards or mop boards over there (I’m a stupid American… :) ) but we normally use that to cover the gap around the perimeter. You CAN fill the perimeter with silicone, but that’s a LOT of silicone. It would be best simply to leave that space open and cover it with a trim of some sort.

  • Yul

    Hi, your website is really appreciated.

    I have a powder bathroom (no window, no sunlight). At the end of a short hallway, as you reach the garage doorway straight ahead, on the left is the powder room doorway. Facing toward the powder room doorway, the powder room is small but long and narrow at 86″ long by 38″ wide. I could describe the powder room as L shaped (with the short tail of the “L” on the left side immediately adjacent to the doorway), but with the 45″ custom vanity recently installed wall-to-wall in the 48″ space created by the tail of the “L”, the open floor space is mostly rectangular. As you enter the powder room and immediately turn left 90 degrees, you would be facing the sink and mirror. With the vanity installed, the tail of the “L” is now only 3″ before it hits the front edge of the countertop.

    Our contractors will install the 12″ x 24″ tiles with 1/8″ grout lines. A 1/8″ control joint will be left at the doorway as the tiles approach the engineered wood (full glue-down) that is throughout the hallway, kitchen, and great room.

    Question 1: Is backer rod necessary for the control joint? Or can I skip the backer rod and apply the silicone (Laticrete Latasil) all the way into the control joint?

    Question 2: After the baseboard is installed over the tiles, do the seams (where the baseboard meets the tiles) need to be sealed with caulk?

    Question 3: Would you position the 12″ x 24″ tiles long edge parallel or perpendicular to the 86″ wall? (I would like to use a 1/3 offset). Some websites suggest increasing the psychological width of long, narrow spaces by using a “perpendicular” placement. These websites say that a “parallel” orientation would create an even longer and narrower feel. First, in the small space of my powder room, I can’t even place 2 tiles in the perpendicular position, which might not look very good. Pictures from those websites indicate room for at least 2.5 tiles across. Second, the long axis of my powder room isn’t very long at 86″, and I noticed that with a max of only 3.75 tiles going parallel, the powder room didn’t really have a stretched-out feeling, probably because the ratio of the long wall to short wall is only about 2:1.

    • Roger

      Hi Yul,

      1. No, the backer rod is not required
      2. No, it does not need to be sealed
      3. I would run it in the same direction as the wood floor in the hallway.

      • Yul

        Thanks, Roger. We’ve already gone ahead with the parallel orientation, just as you recommend!

  • Paul S

    I have a 30 x 40 room with 6 x 36 porcelain tile I’m getting ready to install. I have 2 Windows to the east that are 7 foot by 5 foot. On the north and south I have the same plus a 6 foot patio door. So, that’s a lot of sun. 21 month old concrete substrate. How many and where do u suggest control joints? Should I quarter the room?

    • Roger

      Hi Paul,

      You need more than quarters. You need joints every 10-12 feet in both directions in installations exposed to direct sunlight – plus perimeter expansion space.

      And yes, I realize this reply is likely too late, but the info will be here for others in the future. Sorry for the delay.

  • Shawn

    How often do you replace a soft joint?(how long will the caulking last) If I were to tile a kitchen 16×12 is a soft joint around perimeter adequate or do I need one in the center?

    Also might tackle the bathroom with tile. If I do I’m going floor to ceiling with tile (60″x32″) and using the kerdi shower pan.

    Where would I put the control joint in this application? I’ll be using 12″x12″ square tile on the wall and 2″x2″ porcelain mosaic tile on the shower floor.

    • Roger

      Hi Shawn,

      In a kitchen that size you should not need more than expansion space around the perimeter. You don’t need to silicone it, just leave it open and cover it with base. 1/4″ around the perimeter is sufficient. You also do not need expansion joints in that shower.

  • Gary

    Can I make the expansion joint the same width as the grout lines? I’d rather have another soft joint or two, than make the grout line wider. Grout line might be 1/8″ or 3/16″, 13x13x3/8 tile, with a soft joint maybe every 6.5 feet.

    I’m planning an outdoor project — 3.66′ x 34′ cantilever deck, supported by floor joists (2×10, 16 O.C.) extending from the house. Plywood, ditra, with BARA-RAK edges sealed to ditra with kerdi band / kerdifix. The roof extends past the deck slightly, so it doesn’t get much rain. Doesn’t really freeze here. The previous tile deck had no waterproofing, tile attached directly to plywood with mastic. They were popping off along the edge pretty badly the past 3 years (rotted, been there ~45 years), but I am blessed that only the ply was rotted — not the joists.

    • Roger

      Hi Gary,

      Yes you can, That’s the way I do it anyway. No issues.

      • Gary

        Thanks. For my cantilever deck over plywood: do you see any advantage to putting down backer board before the Ditra, or should I just do the Ditra? Or should I skip the Ditra and cover backerboard with liquid membrane? It seems to me that Ditra might provide for more crack prevention than liquid membrane, but I have nothing upon which to base that.

        • Roger

          Hi Gary,

          I think ditra would be your best bet.

          • Gary

            Just the Ditra and no backer board? Apparently Schluter used to have an approved outdoor procedure (not over occupied space) for plywood/CBU/ditra/tile, but they removed it from the handbook. Supposedly problems came from installers not flashing adequately, not from it being a bad structure.

            For the decking, Advantech seems like it would be better than plywood (stiffer, less absorption) but Huber says not to use it. Again, maybe just a CYA, but I don’t have a valid opinion. Any experience there?

            • Roger

              I have built several decks with ditra directly over advantech. I waterproofed the ditra with kerdi-band and properly flashed everything. No issues at all.

              • Gary

                Thanks. Do you have a couple of specific recommendations for the thinsets? Either big box or tile supplier is okay. Whatever works best — I can’t imagine cost is much of a factor, at least compared to the amount I’m spending on BARA-RAK, ditra, kerdi band, kerdifix. All that Schluter stuff adds up to considerably more than the tile! If you could tell me how may sq ft per 50# bag, that would be helpful (13×13 tile).

                • Roger

                  My preferred in that situation is Laticrete 255 Multimax. It IS spendy, but it’s great stuff. They are 40lb. bags and I normally get around 80 sqft per bag with a 3/8″ trowel.

              • Gary

                What did you use for an edge? BARA-RAK? If so, did you stop the Ditra just short of the BARA-RAK, then bridge/seal that with Kerdi-band?

                If I use Kerdi band to flash up against my wood siding, can I just coat that kerdi with thinset and then paint it? Or is it another call for more Schluter profiles?

                • Roger

                  That is exactly what I did – bara-rak and kerdi-band. Yes, you can coat it with thinset and paint, or you can put up tile base.

                  • Gary

                    What trowel do you use for thinset between Kerdi-band and Ditra?

                    The wood wall to which I will be flashing is painted. Should I use modified on the painted wood under the Kerdi?

                    Readily available (stock) thinsets for the project include Ditra-Set (plus Bostik 425 additive where desired), Schluter Set and All Set, Laticrete 254 Platinum and 317 (with admix where desired), and whatever Big Box Blue and Orange have. With those choices, what works best?

                    At the KerdiBand – BARA-RAK interface, do you use KerdiFix underneath the Kerdi edge, or just run a bead after you thinset it?


                    • Roger

                      I use my kerdi trowel for kerdi-band (over anything). Yes, modified thinset over painted wood. My preference is 317. You can use it for everything and just add the admix where you need modified. I use kerdi-fix under the edge, then over the edge once it is finished as well.

  • Brian

    Should you caulk the gap you leave around perimeter that separates the wall and the tile? My project is in the basement. Also should you not install baseboards directly on the tile? Would installing directly on the tile restrict the tiles movement and eventually break the grout?

    • Roger

      Hi Brian,

      No, you do not need to caulk that. And no, putting the base directly on the tile does not cause any issues. The tile will expand horizontally, not vertically enough to cause any issues with the base at all.

  • Aaron

    I’m installing glass on a shower floor. It’s only a 4ft x 3 ft area. Tiles are pretty tight against the hardi backer walls. What is the best way to cut out an expansion, and how much should I cutout an 1/8th or more?

    • Roger

      Hi Aaron,

      Remove the perimeter tiles and cut them down. You should have at least 1/8″. For the record I REALLY wouldn’t recommend glass tile on a shower floor…

      • Aaron

        Thanks for the speedy response! Do you not recommend glass on floor because of being so slick?

        • Roger

          That’s part of it. The other part is the durability of it – it needs to be rated for floors. It’s a density of the glass thing, if it’s not dense enough simply stepping on it may crack it.

  • Mike

    I have a room 30′ x 30′
    12′ of this room is wood and the balance concrete.
    So I have an area 12 x 30 that is wood butting up to
    concrete. Could I use the schluter Dilex BWB between
    the two sub-floors. 6″ x 24″ tile is being used ?

    Thanks Mike

    • Roger

      Hi Mike,

      Yes you can! And it’s the perfect solution (I wish more people would…)

  • steve

    Thanks for the information.

  • Dustin

    Hey Roger,

    Thanks for all the great information… there are so many mistakes I would have made if I hadn’t read everything on your site.

    I have one big question which I don’t believe has been answered in any of the articles or comments (or maybe I missed it):

    How do you create a soft joint on wood look tile that is laid in a random stagger (or a stairstep) and the long / vertical sides crosses saw cut expansion joints on the slab?

    I know the easy solution is to lay my tile the other direction… but aesthetically we would not like it as much, and I might possibly run into the same situation if I run into a vertical expansion joint (I don’t recall right off hand if I will hit any of those or not).

    Here are some notes regarding my particular installation:
    – 1200 sq ft slab that was poured a 3 months ago and is currently in excellent condition.
    – Slab has saw cut expansion joints
    – Using 8″ x 48″ porcelain wood look tiles

    Please let me know if a picture would help… if so I can take one tonight. Thank you for your help!!!

    • Roger

      Hi Dustin,

      The technically correct answer is to cut your tile so the cut creates a line directly over those joints (yes, through the tile and pattern). You can zig-zag the soft joints through the pattern, which looks a hell of a lot better and has worked every time I’ve done it. You aren’t supposed to do it that way, and I’m not saying you won’t have issues with it, but I never have.

      • Dustin

        Thanks for the reply… Just bought all of your books this weekend. :) That’s great to know that you haven’t experienced issues with zig zagging the soft joint… That’s what I will be going with then. One last question for clarity: did you use any uncoupling / crack isolation membrane over the joints… Or did you just use a thinset like TEC Superflex which is supposed to allow for 1/8″ of movement (which is what I planned on doing)? Thanks again for your help… Excellent information with the perfect amount of humor!

        • Roger

          I installed over ditra.

  • Cosmo

    If putting in exspantion joints in after the fact should I cut through just the grout and then caulk or cut straight through everything including the hardibacker- then caulk?

    • Roger

      Hi Cosmo,

      Just through the grout.

  • Bruce

    June 30, 2015
    I have like ten questions in I don’t know how many parts of your blog I am sorry for asking so many questions. Here is my last one, I am trying to figure out how best to tile my walk In shower area where the open hallway meets the drywall In the bathroom. I was sold some schluter transitions or trim pieces that are finished on two sides according to the idiot sales lady and she said I butt them against my existing drywall, but my drywall isn’t perfect around the hallway it is cut flush with the trimmers but their will still be a gap so I asked her about trim and she said they don’t sell trim tile to cover the gap it’s just finished on both sides so it will look nice, I said Hugh? I don’t know how to add a picture.

    I wonder if this is not asking about the unfinished edge of wall tile when floating to make flat walls and there’s the edge full of mud.


    • Roger

      Hi Bruce,

      The number of questions is not a problem. The problem is I have no idea what you’re trying to describe here. You can upload a photo here.

  • John

    If using an antique pattern with Travertine tile. Is the soft joint still necessary?

    • Roger

      Yes. The type of tile makes no difference.

  • Shinto Vincent

    Dear Roger,

    Your article on the soft joints are such a helpful and i’m working on the shop drawings, but some questions are still unclear like; we are doing tiling on the walls and floors to the Back of House areas in a Hotel Room and our designer wants soft joint locations in our shop drawings.
    The back of house areas are vast and kind of difficult where i put the soft joints because all rooms are differences in sizes. Shall I go for soft joints in each rooms as per your design criteria or TCNA regulations?

    Please advise,

    Shinto Vincent

    • Roger

      Hi Shinto,

      The TCNA requirements are maximum widths, you can lay out your soft joints so they show less in particular rooms provided you do not go over the maximum spacing. They can always be closer.

  • John Fox

    I am about to tile a sunroom that is 12′ x 27′, built over an existing deck. Though it’s fully enclosed and insulated under the floor and in the ceiling (R-30), it will experience massive temperature swings as we will not heat/cool the room if we are not using it, and I am in NJ.

    The tiles are 6″ x 24″ and I plan to use a brick pattern, since the tiles are hardwood look.

    1. Should I have the stagger be 8″ or 6″? (in other words 25% or 33% stagger?)
    2. If I am understanding your answer to Johanne correctly, I need a control joint down the middle of the room. (In other words, the control joint is 12′ long and runs between center points of the two long walls, thus giving me two 12′ x 13.5′ sections.) If I got that right, how do I create a control joint with a brick pattern?



    • Roger

      Hi John,

      1. Either is fine, personal preference.
      2. You either turn the pattern the other way so you have a straight line down the middle, cut a straight line down the middle creating a grout line through the pattern, or run your soft joint along the pattern (so it won’t be a straight line, just a staggered, continuous soft joint).

  • Ro

    I have been watching videos and reading up on ceramic tiling since October of last year. Your post are by far the MOST clear and informative I have found and the humor was awesome. I am tiling my new bedroom and walk in closet for a total of 300 sq ft.using 17×17″ ceramic tiles. I’m popping my tile cherry with your ebook.
    I’m so terrified! !!!

    – Virgin Rose

    • Roger

      Hi Ro,

      Don’t be skeered! It’s fun. :D

  • Steve

    I have like ten questions in I don’t know how many parts of your blog I am sorry for asking so many questions. Here is my last one, I am trying to figure out how best to tile my walk In shower area where the open hallway meets the drywall In the bathroom. I was sold some schluter transitions or trim pieces that are finished on two sides according to the idiot sales lady and she said I butt them against my existing drywall, but my drywall isn’t perfect around the hallway it is cut flush with the trimmers but their will still be a gap so I asked her about trim and she said they don’t sell trim tile to cover the gap it’s just finished on both sides so it will look nice, I said Hugh? I don’t know how to add a picture

    • Roger

      Hi Steve,

      I have read this four times and still have no idea what you’re talking about. :D You can upload a pic here

  • Steve

    Question I see in a couple pictures you use white mortar to set your tiles I always use gray? What determines which color I should use? White tile white mortar?

    • Roger

      Hi Steve,

      The color and shade of tile. With lighter tiles you normally always want to use white. You can use white for everything.

  • Jared

    I’m finishing up a tiled tub surround and now noticed that I didn’t leave very much movement joint in one of the inside corners. Some of the tile are butted up to each other. This is a kerdi over top of dry wall construction. Is this a serious problem? Is there a repair short of destroying my work? Thank you!

    • Roger

      Hi Jared,

      Normally it’s just fine. Just silicone it. If it does end up with issues down the line you can always take a grinder and cut a gap in the corner, but that’s normally not needed. As long as you don’t have the entire wall butted against the other there is enough gap to compensate for residual expansion.

  • Rebecca

    Doesn’t the uncoupling feature of Schluter solve this problem?

    • Roger

      Hi Rebecca,

      Nope, you still need soft joints. With ditra you can move the joint six inches one way or the other when going over things like control joints in concrete, but you still need them.

  • Sissy

    First, thank you for all this information. I’m doing a small bathroom floor about 37 square feet. Is there somewhere to look up how many control joints I need and where to put them?

    • Roger

      Hi Sissy,

      If it’s that small you don’t need any. You only need them every 20-25 feet in an interior application unless exposed to direct sunlight, then it’s every 8-12 feet. Not square footage – straight runs that long.

  • Karen

    My grout started cracking at the doorway. We have faux wood flooring in the hall in front of the bathroom where the tile. We put down a wood piece between the wood and the tile. I took up that piece of wood. It has a piece screwed in to the floor where the piece of wood is. I have had 2 pieces of tile to come so loose they came right up. Help

    • Roger

      Hi Karen,

      Normally you want silicone between tile and any dissimilar material like wood. However, if your tile has come up that means there is a problem with the underlying substrate or bond of the tile. That causes the tile to move and any grout is going to crack. Do you know what your tile underlayment or substrate it? What is it bonded to?

  • Brandon

    I had to replace a very poorly installed shower pan in my shower and let some wet wood dry out which involved removing the bottom two feet of shower walls and tile. On my half wall between the tub and shower I removed all tile and the entire backerboard which is green sheetrock. I’m trying to avoid removing the entire walls up the ceiling on the remaining walls and replacing them with hardiboard though I know this would be the best and most long term fix. I couldn’t remove the tiles from the greenboard without tearing it up so I’m left with a butt joint of hardi and greenboard right at the bottom of a tile at what will be a grout line. The greenboard is a little thicker so I plan on using thinset to float the wall out and hopefully somewhat bond the greenboard to the hardi at the butt joint with the tiny gap that exists between them. Once I tile, is a soft joint a good solution along this line instead of grout?

    Thanks for all the information on your website!

    • Roger

      Hi Brandon,

      You can use a soft joint there if you want to, likely not really needed though, unless your shower is HUGE. :D My biggest concern is that you haven’t mentioned any waterproofing method at all. Neither greenboard or cement board are waterproof.

  • Johanne

    We are installing porcelain tiles in our kitchen and great room. It is 29′ x 13′. We are also using the Ditra Heat and membrane. Do we need a control joint with this system?

    • Roger

      Hi Johanne,

      Yes, you absolutely need a control joints. At least one down the middle of the 29′ section.

      Sorry for the delayed response, my spam filter went ape shit last week for some reason, I just found your comment in the spam folder, I hope the answer found you in time.