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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  • Mark

    Hi Roger, I’m considering if I can repair a shower pan and the bottom 12″ of tile on the shower walls (rather than replace the entire wall).

    Would installing an expansion joint on the wall in between the old tile and the new tile make any sense?

    • Roger

      Hey Mark,

      It would make sense, if it was a HUGE shower. Or if you have a lot of movement in the structure. It’s normally not needed, though, you can just set the new stuff and grout between them.

      • Mark

        thanks for responding Roger.

        During demo the situation has since resolved itself…. we’re re-tiling the while dang thing!

  • adrian

    Hi roger, very informative site. I have a 7m2 bathroom floor which tented about 3 months ago. Do I need expansion joints, and if so were about. Will these joints prevent further tenting.

    • Roger

      Hi Adrian,

      With a bathroom that size there should be expansion joints running in both directions every 3-5M. My bet, however, would be that there is no perimeter joint and the tile is either butted directly against the perimeter, or the perimeter is grouted. If it’s grouted you’ll likely be fine simply removing that grout. If not then placing a control joint in both directions at 3M should fix it (ideally placing them in the center, or close to the center, of the room).

  • Byron

    I’m installing 12″x24″ porcelain tiles stacked vertically over RedGard on HardiBacker on the shower walls of our remodeled bathroom. The 46 1/2″ x 96″ back wall is where I started and I have only set four tiles so far centering the middle grout line and cutting the outer two tiles with about 1/8″ gap to the adjacent walls. Now I am worrying about the perimeter joint being wide enough. Should I remove the outer two tiles and trim them for a 1/4″ joint or leave it. The back wall is 46 1/2″, so I have centered the middle grout line and trimmed the outer two tiles

    • Roger

      Hi Byron,

      Leave it. 1/8″ is plenty. You normally don’t need regular control joints in shower walls unless they are over 15 feet long, regular 1/8″ perimeter joints in the corners is fine.

      • Byron

        Thx. I went back and looked. The joints were less than 1/8″ and was even grout filled on the left side. I used a Dremel grinder with a diamond blade and cut a bit of a gap. Maybe overkill but at least I don’t have to worry about tenting.

  • Eric


    I get the importance of expansion joints, I have seen many large fields of tile with tented tiles myself. However, how do you install one when using patterned tile, such as Versailles or Pinwheel? Do you just zig-zag the joint, following a straight line as close as possible? Thanks for your help.

    • Roger

      Hi Eric,

      Just follow the grout lines with whatever pattern you have. Provided you have a soft joint from one side all the way to the other continuously then it’s a good soft joint.

  • jamie

    ok, so, tiling the floor w/ 1″ (flat, historic style) hex and also a subway tile wainscot. hardiebacker on floor, wet-area (green) drywall on walls. it’s a bathroom w/ clawfoot tub in the middle with 360-degree curtain (no shower water will hit walls except perhaps occasionally by accident, and i got a good panasonic 130 CFM ventilation fan, so moisture on the walls isn’t a big concern). but i’m concerned about how to simultaneously ensure proper expansion at the floor/wall seam and also prevent water infiltration there (i left a tiny gap between the drywall and hardiebacker). i’m using a chair rail tile turned upside down (instead of a cove molding tile) as the bottom-most row of wall tiles, for that full wainscot effect. if i fill the gap between the 1″ hex floor tiles (applying those first to hide the imperfect edges i’ll end up with) and the upside-down chair rail tile with a color-matched caulk, which you say isn’t a permanent material anyhow, isn’t that making the corners of the room the most vulnerable to water infiltration? sometimes you accidentally get water on the floor, and it seems like the perimeter of the room is where it’ll end up, and that it’ll just seep right into that little gap, negating the benefits of having used water-resistant materials on the floor and walls to begin with, since there’s nothing at all there but a little air gap. is there some sort of waterproof sealant i should put into that space before i apply any of the tile to the floor or wall? it’s a 90-yr-old house and the new materials will appear identical to what would have been used in the original house (tub, toilet, sink, wall heater, etc., are all actually original antiques), and i’d like everything in the new remodel to be as durable as the original materials would have been (that is, to last another 90 years), and to fully masquerade as being original to the house. and water damage to a historic home with old-growth 2″ by 4″ 2x4s is obviously a much bigger travesty than the same thing happening in a home of modern construction where everything can be replaced from the store with the very same materials. i’m not ripping out a 90-yr-old bathroom; i’m ripping out a couple-decades-old remodel (rife with particle board, including under the toilet flange! :wtf: ) to bring the bathroom back to its former glory like the rest of the house which was (thankfully) left alone to age gracefully like old houses generally do. i want the bathroom to do the same.

    • Roger

      Hi Jamie,

      I would use 100% color-matched silicone. It’s not permanent, it’s made to be replace, but in that application that may be every 10-15 years.

  • Dan Taylor

    Is their a typo? The directions for soft control joints say 20′ to 25′, do you mean 20 to 25 feet or inches? Thanks, Dan

    • Roger

      Hi Dan,

      Why would you think that’s a typo? It’s 20-25 feet in each direction on interior applications, 10-15 feet in each direction on exterior and/or interior installations with direct sunlight. Those are in addition to perimeter joints.

      • Dan Taylor

        Just to be clear, we are doing shower walls that are 3’x8′ and 5’x8′.

        • Roger

          Oh. :D On walls that size you only need soft joints in the corners, they serve as expansion joints.

  • Mark

    I am installing a 16×16 ceramic tile with thin-set over a 22 year old slab on grade in central Florida. The shape is irregular but its longest measurements are 40×25 feet. Since it doesn’t get very hot or cold here and I am installing in the spring, do I need a control joint in either direction? Thanks

    • Roger

      Hi Mark,

      You need at least one across the 40 foot run.

  • Doug G


    I am attempting to install 16″x16″ tiles on a diagonal, with 2″x2″ metal (copper?) inserts. We’d like to cut the corners off the 16″ tile, and place the inserts in that gap, square with the room. …if that makes sense.

    Any advice on how to snap out guide lines for this type of install?
    Also, any tips would be greatly appreciated.
    (my dog looks VERY nervous, and is not straying far from any water sources)

  • jim

    Should the soft joint be as wide as the cut in the floor or do you keep it the same size as your grout lines and also what if you got a
    Slot of cuts in the floor

    • Roger

      Hey Jim,

      Same size as the grout lines for both.

  • rita

    Hello.I was trying really hard to find info regarding thickness of thin set under ditra xl and above ditra for porcelain tile 9mm thick( something in between 5/16″ and 3/8″) just trying to understand what will be final thickness for my floor with underpayment.I want to level it with 3/4″ hardwood.On Ditra site they are showing details with tile 5/16″ thick,so I don’t know.Please help.Thank you.

    • Roger

      Hi Rita,

      Ditra XL will give you a height around 3/8″ with the thinset beneath it. The height of thinset above it will be determined by the size of trowel you use to set your tile.

  • Bob

    Excellent site. I am tackling my largest job yet, tiling a basement floor just over 1000 square feet. I have 3 LARGE control joints with minor cracks. I also have 2 settlement cracks (minor). Should I fill the joints with caulk level with the floor and then match up a control joint in the tile? What type of caulk or other compound would I fill the joints with? What should I do with the settlement cracks? Would you recommend putting down Ditra over the entire job? Finally, what should the spacing be for the tile control joints?

    Thanks for sharing your know-how.

    • Roger

      Hi Bob,

      I would recommend ditra if given the choice. You can fill those joints with caulk or silicone or just leave them open, makes no difference really. If you use ditra you don’t need to do anything with the cracks. If not you need to use some sort of crack suppression membrane over them. Redgard is a good one and readily available. Spacing for control joints in your tile installation are every 15-20 feet in each direction.

  • Robert

    Roger, I do have a sawed cut on an interior bathroom slab and I’d love to know how to best deal with it.

    I need to pour a self-leveling compound to make the slab nice and flat. Can this SLC fill the cut groove or do I need to keep it empty? Then, would Ditra work over it? And finally, do I align the grout line with this cut and use caulking instead of grout? Many thanks for your time.

    • Roger

      Hey Robert,

      Unfortunately the saw cut needs to be honored all the way through the installation. So you need to leave it open. You also need to install a soft joint above it, but if you’re using ditra you have the ability to move that joint three inches in either direction from the cut.

      • Robert

        Thanks for the quick reply, Roger. If I’m to keep the saw cut open but still need to use the self-leveling compound … would you caulk the groove so the slc does not settle in there?

        • Roger


  • Michael

    Hello Elf;

    Just read your bit about control joints. Hadn’t known of these. Does my 13×13 ft kitchen project need such a joint?


    Michael :dance:

    • Roger

      Hey Michael,

      Likely not unless you have a southern facing kitchen with a very large window which will cause extreme temperature differences over the course of a day. You do still need expansion around the perimeter.

      • Michael

        Thanks Roger;

        As I say, have not heard of control joints before. Their function is the same as the perimeter expansion gap, or, dare I say joint, would I be correct in that conclusion? Did someone mention a joint? Don’t be stingy …


        • Roger

          Yup, they serve the same purpose – to allow expansion in your installation without undue pressure.

          PASS IT DAMNIT! :D

          • Lory

            Geez I’m getting old. Had to read that twice. :bonk:

  • Michelle

    Hi Roger,
    the bathroom floor that Im doing is 5 feet by 8 feet does that need a control joint and if so where? All the way across the floor?
    and also you said when there is a change of plane you always use the silicone… might be a silly question but I want to do it right… In the corners of the shower wall you put silicone only or you put it over the grout?
    thank you again for all your help!

    • Roger

      No control joint in a room that size, but you do need to leave space around the perimeter. Silicone only, no grout.

  • Jennifer


    Freakin awesome site. One question that I can’t really find a direct answer to is what to do where the CBU meets drywall. I have had every type of advice you could imagine.
    We are tiling a shower/tub and the CBU will come out past the tub about a foot (to hit a stud) and we are leaving about 3inches of drywall at the top edge over the shower (hubby was worried about messing up the ceiling). My plan is to use the hydrobarrier or redgard over the CBU once we have taped and thinset the joints.
    Do I just tape and thinset the joint onto the drywall and then paint on the membrane over the joint and onto the drywall?
    Our house is only 6 years old and poor construction is why we are in this mess in the first place….I want to make sure that this bathroom, at minimal, doesn’t give us any further problems. We are Airforce and are prob going to have to rent this house in the near future when we move so it needs to be pretty bulletproof.

    • Roger

      Hi Jennifer,

      You mean advice like this: Drywall to backerboard transition? You can paint the membrane out as far as you need it, the remainder of the backer can be finished just like regular drywall. If you will have any seams between the two inside the wet area it needs to be taped with alkali-resistant mesh tape and thinset. Outside the shower can have regular mesh tape and joint compound.

      If the walls in your rental need to be bulletproof you may want to add a ‘no drive-by’ clause in the rental contract. Just sayin’. :D

  • Jack

    Do I need to caulk all joints in my stand up shower tile installation (i.e., the corners/90 degree angles where the tile meets tile as well as where the tile meets the ceiling)?

    • Roger

      Hey Jack,

      Yes, any change of plane needs caulk or silicone.

  • Jane

    Hey Roger:

    One last question for tonight. In laying floor tile up to the tub, would we want there be a control joint in between the tub and the tile? In my last house, I installed a granite floor (slippery as $hit), and it cracked. You could hear it cracking when the tub was filled with water. My current tub and old tub were/are cast iron. Not that I think the tub expanded, but possibly shifted downward with the weight of water in it. Should the wainscot tiles surrounding the tub also be control joints and not grouted? 

    • Roger

      Any change of plane, or any spot that tile meets a different material (like cast iron or acrylic) needs to have a 1/16″ to 1/8″ gap and that should be filled with silicone. The tub did shift downward with the weight of water, they always do. That’s why the joint between the tub and wall tile should be siliconed as well.

      • Jane

        My head is spinning from everything I’ve read on your site today – going thru all the conversations to get educated and get my questions answered. Although still in the demo phase, your site and your answers to my questions have saved me having to deal with unqualified help at the big box stores. It’s also helped us with more efficient shopping, although I’m the one with the credit card, so my husband can’t spend anything without me! (Actually, it’s my mom’s card and she offered to pay for some of this remodel). As cheaply as we’ve wanted to go, this full bath is probably going to exceed my budget of $1500.

        • Roger

          Glad I could help Jane, if there’s anything you get stuck on just let me know.

          • Jane

            My husband is handy and does everything; electrical, plumbing and he will even do the tiling and finish the walls. I will learn to lay tile and always do the priming and painting. The tile is the cheap part, it’s everything you don’t see that costs so much! Fifteen years ago we laid tile on concrete here at the house and we haven’t had one problem with any cracking. My tile setter at the time said that the Ultraflex II I bought was the best mortar he’s ever experienced. We always use modified thinset. Difference now is my husband learned how to lay tile beautifully.

  • Matt Spry

    Roger- in a previous post you are talking about there are VERY exact procedures that must take place when tiling over plywood subfloor, what exactly are those procedures. I under stand you don’t recommend tiling over plywood but can it be done?

    • Roger

      Hey Matt,

      Bill Vincent has the short version for you here. And he’s very serious: do any one of them incorrectly and you’re screwed.

  • Manny


    I’m installing a commercial job and they are asking me to have a control joint every 12 ft.  Its a rather large open area, rougly 40 x 80.  Should the control joints end up like squares throughout every 12 ft or just one direction the length of the floor.  Thanks

    • Roger

      Hey Manny,

      Every 12 feet (if that’s what’s spec’d) in both directions. So yes, you’ll have 12 foot squares. It absolutely amazes me that someone actually put that in the specifications! :D It’s normally on us to know better and, of course, take the heat if it fails. Good to see.

  • Terry

    I am installing tile in a 14 x 24 ft room and the tile is on the diagonal. I was wondering if it is acceptable to have a zig-zag control joint instead of a perfectly straight line. My thoughts are that a zig-zag control joint won’t be so noticeable. Of course if it also not so effective then I will go – straight.
    Thanks in advance for your advice,

    • Roger

      Hey Terry,

      The zig-zag control joint will work just fine.

  • Gary

    Hi Roger, great site!!!,
    I was wondering, can caulk be used entirely not just in control joints instead of grout?

    • Roger

      Hey Gary,

      Nope. Using caulk as grout will eventually lead to one hell of a mess. Caulk is not meant to be a permanent product, it is designed to be periodically change out. Eventually the bead will become loose from the sides of the tile. Once that happens that small space will become filled with dirt and all kinds of nasty stuff.

  • Skip

    I am using ceramic tile in my hall way,I didn’t want any grout line, do I need anything to keep the the 12×24 tiles from doing bad things, like rubbing together.Would this be a place for a soft joint? I was going to use plywood but that doesn’ t sound like a good idea, what about duroc ?

  • Morgan Kouba

    Hi Roger. I’m putting 18″ tile on a concrete slab. The slab was poured 4 months ago and now has a diagonal crack less that 1/16″ wide running through the room. About 12 feet long. I planned on using Aquadefense (waterproof and crack isolation membrane) on the slab. Do you have any recommendations? Porky

    • Roger

      The Aquadefense will work fine. Just make sure you paint it a minimum of six inches wide – at least three inches on each side of the crack.

      • Porky

        Sounds good. Actually I was thinking about using the aquadefense on the entire floor just in case a crack decides to form else where later. Porky

  • ron

    When installing tile over 3/4″ plywood, do you need to tape the butt joints to prevent possible telegraphing of the same to the tile ?
    Thanks, Ron

    • Roger

      Hi Ron,

      No, it won’t do any good. And you really shouldn’t be tiling directly to plywood, if that is what you’re doing. Installing a proper substrate for tile adhesion – even 1/4″ backerboard – is much easier, quicker, and leaves room for error to an extent. While tiling over plywood is an accepted method, that method involves VERY exacting procedures, products, and steps in order to achieve a lasting installation.

  • Yogi

    Roger, I am tape & thinsetting the CBU joints in an all tile, ceiling too, shower. The ceiling wher I used Hardi is underneath a God awful hot attic. Should I caulk the wall to ceiling joint? I’m worried about ceiling expansion. I already did tape the two pieces of Hardi overhead but not yet the CBU wall to ceiling joint. I left a 3/16″ space on all joints. Thanks, Yogi

    • Roger

      Hey Yogi,

      You can tape and thinset that joint as well. When cured the thermal expansion will be evenly distributed along the ceiling and down onto the walls if necessary. Just make sure you caulk the joint in the tile installation or that may cause problems. While the backers will distribute it, they may move more than the tile at the change of plane.

      • Yogi

        Thanks, This is my first ground up shower project. I’ve only been working off and on it for a year. The Mrs. Started griping about it and I told her whats the rush we got another bathroom? I :bonk: gotta get this done. I hate sleeping on the couch. “Respect the Elf!”. Yogi