How Long Should Concrete Cure before Installing Tile?


We are being asked to set porcelain tile over a concrete slab that will be less than 60 days old when we get onsite. The slab is not under roof yet. Is this cause for concern? In general what are the guidelines for MVER or in-situ for ceramic tile? We get conflicting info on this all the time. Thanks!


ANSWER - Generally speaking allowing the concrete to cure for 28 days allows it to achieve 90% cure and there is no significant shrinkage in the concrete after that in terms of installing ceramic tile over it.

You need to rely on the manufacturers' data sheet recommendations for the thin-set dry set mortar you are using to adhere to the concrete.  Most manufacturer's for regular polymer modified thin-set mortars say that the slab needs to cure a minimum of 28 days.   Premium thin-sets have more polymers in them and will even perform better than regular polymer modified thin-sets in terms of bond strength and being more resistant to movement.

Regarding Moisture Vapor Emission Rate (MVER) and Relative Humidity testing the ceramic tile industry is not consistent with this.  The Calcium Chloride ASTM C1869 that measures vapor emissions is referred by some tile installation product manufacturers.  Some say for interior applications, particularly when installing a membrane over the slab, as low as 3 lbs/1000sf/24hours maximum is required, which is probably too conservative, and others will go as high as 12 or more.  They normally don't have requirements for exterior applications as there limited controls. This test isn't considered reliable as it can't be calibrated and the surrounding environment can create variables that make the results not reliable.

The in-situ ASTM F2170 relative humidity probe is more meaningful in terms of measure the moisture the slab at that time.  Generally speaking for interior applications, particularly when installing a membrane over the slab, manufacturers require a 75% to 80% maximum RH.  They normally don't have requirements for exterior applications as there limited controls.

Make sure the slab has a broom finish and that water readily absorbs in it.  If not then you need to tell your client to scarify the concrete to open up the pores and give it texture of at least CSP 3 or greater.

Make sure the slab is flat and not out of plane more than 1/4" in 10 feet or 1/16" in 12" or for tiles with any edge larger than 15" it needs to be nor more out of plane than 1/8" in 10' or 1/16" in 24".  If it is an exterior or interior wet area then you have to have a slope of 1/4" per foot towards the drain.

If there are any shrinkage cracks in the slab then you need to isolate them per TCNA F125 Partial or full crack isolation coverage. Structural cracks can't be isolated they must be repaired per project engineer.

Be sure to install movement joints at all perimeters, transitions and within the field of tile per TCNA EJ171.

77 thoughts on “How Long Should Concrete Cure before Installing Tile?

  1. Tania says:

    Hi – we are doing the entry of our home with a marble/granite mosaic and travertino tile surround. This weekend we are going to remove the current mess, and lay a 2 inch concrete foundation. Noting that this is a small layer of concrete, how long should be leave the foundation before laying the tiles and mosaic. Thanks in advance for your help.

  2. Donato Pompo says:

    Assuming you are installing 2 inches of mortar, not concrete, over an existing concrete slab or wood sub-floor, you can adhere the tile to it after curing it overnight. Assuming it has the right ratio of sand to cement to water.

    If the 2 inch mortar bed is being bonded to the concrete slab then it should be bonded with a thin-set mortar as a slurry bond coat over the properly prepared concrete prior to applying the mortar.

    If the 2 inch mortar is being installed over a wood sub-floor then the wood sub-floor must be sturdy and not have significant deflection, there should be asphalt impregnated paper or polyethylene put over the wood sub-floor first, and the mortar bed must have wire reinforcement embedded within the middle of the mortar.

    If you mean you are installing 2 inches of concrete over ground, that is not considered thick enough for a foundation. Plus the concrete should have rebar embedded within it to stabilize it to prevent cracking.

    • Richard Sherry says:

      Hi Donato, hope all is well with you. My plumber is filling in a hole in the corner of the floor after installing the pipe etc for the slate shower tray with cement. The plan is to install the shower tray the next day, will the cement have hardened enough?

      Many thanks

      • Donato Pompo says:

        I assume what you mean by a shower tray is a prefabricated shower pan. Concrete on average takes about 28 days to cure but that varies depending on the thickness and the environmental temperature and relative humility. Since you are putting a prefabricated shower pan over the concrete it should not be a problem to install it the next day.

  3. Derick Wallace says:

    I am having to replace a section of my main drain that runs through my kitchen slab. Which means I will have to cut out a section of my kitchen slab and then re-pour the concrete. How long will I need to wait for that concrete to dry before doing a floor float, then tiling?

  4. Donato Pompo says:

    The general rule is to wait 28 days for concrete to cure before installing tile over it. There are rapid curing versions that can be used to speed it up.

    The concern is shrinkage in the concrete as it cures in its early stages.

    The thickness of the pour makes a difference in how fast it will cure. One manufacturer says that for every 18 degrees F over 70 degrees F that a concrete cures it will reduce the cure time by half.

    There are also special uncoupling membranes and flexible thin-set mortars that will allow you to install over the concrete sooner. Check with the various manufacturers as listed in our Resource section of our website at

  5. Kim says:

    I’ve got my townhouse flooded due to Harvey. Found out that I had loose sandy mortar underneath my old tiles so I had to remove all of them – leaving 2 1/2″ between my foundation and finished flooring level. Hired contractor place 2″ concrete on top of existing foundation to install tiling at the same finished level. Contractor used some bonding liquid before placing concrete over. How long does my contractor need to wait before he install tiling on top of the new concrete layer?

  6. Donato Pompo says:

    Kim, if the underlying concrete had time to dry, and if the installer installed 2 inches of a dry-pack mortar over the concrete, you should be able to install the tile the next day. This is assuming you do not have any moisture issues such as a high water table causing continued moisture. You might want to apply a waterproof membrane over the mortar bed that is appropriate for your situation.

  7. Jenny says:

    HI, My guest room has a step down of about 1.5″ to a sitting room which leads into a bathroom. The sitting room and bathroom have Saltillo tile. I’m going to get quick set concrete poured over the tile, to bring them up to the same floor level as the bedroom. How long until I can lay tile and any thoughts about putting how long until I can put a new vanity cabinet down on it and wood flooring (in the bedroom). thanks so much

    • Donato Pompo says:

      First of all you have to make sure the Saltillo tiles are attached well to the substrate because if they come lose so does everything on top of it.

      Next you have scarify and clean the Saltillo tiles prior to pouring the concrete.
      Just prior to pouring the concrete apply a slurry bond coat of a polymer modified thin-set so the new concrete will bond well to the scarified Saltillo tiles.

      You should wait at least two weeks if not more for the concrete to cure, so that most of the shrinkage has occurred and most of the moisture has evaporated. If you are going to put a real wood floor or something other than porcelain tile, then you have to test the concrete to make sure it meets the requirements of the manufacturer of the flooring material. Otherwise you can have moisture problems with the flooring material. If you install a porcelain tile then it isn’t so sensitive to moisture.

  8. Derix says:

    I have a 9’x8′ room with an existing concrete in place and wanted to create a T&B room for this space, will be pouring 6″ concrete once I’ve laid all the plumbing. Should I wait for 28 days before I lay the tiles or should 7 days be enough for me to start?

  9. Donato Pompo says:

    It is best to wait 28 days for curing the concrete so that most of the shrinkage has occurred and most of the moisture has evaporated. There are products that you can use that will allow you to install sooner such as uncoupling membranes that allow you to go over the slab within 7 days or some adhesives that claim to allow you to install as soon as 14 days.

    Hopefully you have installed a vapor retarder over the ground before you pour the concrete and run it up the sides of the slab and footings to prevent moisture migration into the tile concrete slab.

    • architect ahmed says:

      dear sir I read ur comments and I want to get suggestion from you,the matter is that I am fixing floor tiles with mortar (Portland cement and sand) ,so I want to know after fixing for how much time(days)I will need to cure tile(water curing ,to give water to tile after fixing and before grouting.

      • Donato Pompo says:

        Cure time depends on the type of adhesive you are using, how absorbing the tiles and their substrate are, and what are the climatic conditions.

        Check the directions of the manufacturer for their recommendations. If you are not using a manufactured mortar or adhesive but are mixing sand and cement yourself then you have to guess. Generally speaking you can bond to a mortar bed 72 hours after installation if the temperature is 70 degrees F and 50% humidity. You can normally grout the tile the next day after adhering the tile. But you have to consider all of the variables before proceeding.

  10. Daniel H. Shin says:

    Hello, I’m having Saltillo tile installed over an outdoor concrete patio. It’s currently covered in paint that was peeling in a few areas.

    Do I need to fully remove this paint before installing the Saltillo tile? The peeling area came off easily with a putty knife, but most of the paint is solidly on the concrete.

    If I do remove all the paint (not sure how I’ll do this), should I use a waterproofing Hydroflex before the thinset? I live in Los Angeles so not too much rain for most of the year.

    Thanks so much for your advice!

  11. Donato Pompo says:

    If there is paint on the concrete it will need to be removed whether it is pealing or not. To get a long lasting attachment to the concrete you need to bond directly to it.

    There are paint strippers that you can use to remove paint, which can get a little messy. After removing the paint you need to make sure there are not residuals left on the concrete.

    You can also grind the paint off with a grinding disk. This will also scarify the concrete to open the pores so that the thin-set adhesive or the membrane will bond to it well. Make sure that once you are done that the concrete is clean and readily absorbs water.

    If there are shrinkage cracks in the concrete then you should put a crack isolation membrane over them or the entire slab to prevent them from telegraphing through the tile. These membranes are normally also waterproof membranes, which can help limit efflorescence staining from water migrating up through the slab, grout, and Saltillo tiles. Although make sure the membrane you use is approved for exterior application and doesn’t have limitations for moisture content in relative humidity. Some slabs might not have a vapor retarder under them as they should and the concrete can be subjected to too much moisture periodically when it rains or otherwise.

    • James Maina says:

      Hello Donato! I’m putting travertine tiles on an exterior patio that is painted. The contractor is telling me it is not necessary to remove the paint on top of the concrete because he is using a good thin set mortar. He tried to remove the paint but he was not able to. How long would the travertine tiles last if Installed on top of painted concrete? Should I take a chance?

      • Donato Pompo says:

        Considering the cost of the travertine tiles and labor for installing them I would not bond to paint. The installation won’t be any better than the paint’s attachment to the concrete.

        You then have to find an adhesive that will bond to the paint depending what type of paint it is. Exterior deck paint is normally an epoxy based paint so you need to use an expensive epoxy adhesive.

        I have never seen paint of any type last for many years. The all eventually will degrade. Once you cover the paint with the tile assembly then it might be attacked by the alkalinity of the damp concrete.

        I would scarify off the paint. It isn’t that much work with the right tools. Then bond to the concrete with the appropriate modified thin-set mortar.

  12. David says:

    I’m having a wood burning stove fitted in the corner of our salon in France. The walls are stone and the floor is oak boards on oak beams. The boards are 300 mm thick. I have laid a concrete hearth 40 mm thick (aggregate, sand and cement) onto the boards, with a membrane beneath. I have two questions, please ~ how long should I wait for the slab to cure before laying slate tiles; and, as this is a base for a stove the tile mortar/adhesive I propose to use is heat resistant (up to 900C). Is that O.T.T. or would it be safe/best to use a flexible adhesive. Thanks in anticipation.

  13. Donato Pompo says:

    As stated above it is always best to wait 28 days for curing as a general rule. You want most the shrinkage to occur and the moisture to evaporate before installing. There are a number of factors that determine how long it takes for this curing to occur. It depends on how thick the concrete is, and what the humidity and temperature it is subjected to during the curing process. Some manufacturers say that for every 18 degrees Fahrenheit over 70 degrees Fahrenheit that cementitious materials will cure in half the time.

    Any cementitious thin-set adhesive should be resistant to heat. I don’t think there is any value in using a flexible thin-set for a surface that won’t have traffic on it.

  14. Donato Pompo says:

    Generally speaking after you put up the brick and mortar you need to grind down high spots and fill in low spots with a mortar in order get a plumb and flat surface for the tile installation. I would wait at least 7 days after putting up the brick before you prep the brick wall surface; that is assuming it isn’t real cold or damp or humid. If it is then wait an extra week.

    After preparing the brick wall surface then wait at least 72 hours or longer for it to set up. If you want protection against efflorescence staining and crack isolation protection, then install a liquid applied waterproof/crack isolation membrane over the prepared surface. Then follow the membrane directions for curing before you adhere your tile to the membrane.

  15. Kathy says:

    Thanks for all these replies! We flooded during Harvey. We had a concrete slab and a wood subfloor over it. The subfloor has been pulled out. Part of the house was cemented over the slab some years ago and tiled. So where there is subfloor being pulled, the level is lower than the rooms with tile. A helper has filled that gap with cement with the plan to then place tile on top. Best guess is the cement is one to two inches deep. How long do you suggest waiting before 1: putting tile on the floor. and 2: fully utilizing the room and putting heavy bookcases, desk, etc back into the room? Thanks!

    • Donato Pompo says:

      For that thin of an application of mortar, you normally want to wait at least 7 days if the temperatures are averaging 70 F and not a high relative humidity.

      Make sure there are no cracks in the mortar before you install over it. If there are cracks then you need to isolate them with a crack isolation membrane then bond the tile to the membrane.

      Once you install the tile, you can normally walk on it after 24 hours and then you want to wait at least 72 hours to subject it to heavier traffic; that is assuming you are using a good polymer modified thin-set mortar adhesive.

  16. Eric Nelson says:

    Hello. We’re planning to use a dry-pack mud mix to raise the level of two concrete slab sub-floors to match the height of a third concrete subfloor. One area is 8’x10′ x 2.5″ thick. adjacent to that is the second area, 8’x14′ x 1″ thick. The first area is very rough concrete surface, so no need to scarify. The thinner area is fairly smooth so I plan to chisel the surface every few inches. Both surfaces will receive a slurry coat prior to installing the mud-mix. 12×12 porcelain tile will be installed.
    My mud mix will be 4:1 sand/Portland, with just enough water so that I can form a snowball.
    It seems I have read conflicting times between laying mud-mix and installing my porcelain tile.
    Question (finally!). What is the min/max times to wait between installing mud-mix and the tile? I’ve read “lay tile within 16 hours, or else you must wait 28 days”.
    Being a diy’er with not much diy time, I was hoping to be able to do the mud one weekend, and lay the tile the following weekend.
    What is best wait time?
    Why is the cure time different (if it is) between concrete (sand/aggregate/Portland cement) vs mortar (sand/Portland cement)?
    Much thanks!

    • Donato Pompo says:

      Installing a 4:1 sand/cement mortar in a dry-pack consistency as you described is the best method of installation for floors. If you are doing a bonded mortar bed to an existing slab, then scarifying the slab and using a slurry bond coat is correct.
      You need to fully compact the mortar to get the appropriate compressive strength and to help prevent shrinkage cracks. Assuming you have no cracks to remediate and you will have adequate movement joints installed within the mortar bed application and at perimeters, you can install right over the fresh mortar bed with a thin-set mortar bonding the tile to it. You don’t have to wait unless you want to install a crack isolation membrane over the mortar bed; then you have to wait at least 72 hours under good climatic conditions. Fresh setting tile gives you a good tenacious bond and allows you to embed into the mortar if you are trying to compensate for any variations in the tile. You can also wait 24 hours or later to install it. If you are installing a moisture sensitive stone, then I would pre-float and wait at least 72 hours to let it cure and then use a rapid setting thin-set adhesive.

      • Kathy Gillis says:

        Donato! Hello. I have a clarifying question for you. I see the 28 day cure time for concrete before laying tile. So for my 60″x30″ shower, using a 4:1 sand mix used as a dry pack pre-slope deck (~1/2″-1 1/2″, applied over 1 1/2″ plywood, roofing paper and lath) followed by PVC lining and a 2nd dry pack deck (~1″)- it seems like I should be able to lay my tile the next day because I’m using a sand mix rather than concrete (if I’m interpreting what you are saying correctly).

        • Donato Pompo says:

          If you are installing a 1″ thick dry-pack mortar bed over a membrane, based on a 4:1 sand to cement mix, you should be able to install the tile the next day assuming it isn’t excessively cold.

  17. Erica says:

    Hello, like the person above, I am having a drain pipe removed and replaced in my kitchen, dining and entryway. The cut in the slab will be about seven feet long. The plumbers will re-pour the concrete. We are removing the flooring currently in the area (a mixture of carpet, tile and laminate) and replacing it all with a vinyl plank floating floor. Is it still recommended that the concrete cure for 28 days with a floating floor? We really need to list the house to sell in five weeks. Is there an additive I can ask the plumbers to add to their concrete to make it cure faster? Anything else we can do? How will we know when it is ready for flooring?

    • Donato Pompo says:

      How soon concrete cures depends on several factors. 1. how thick the concrete is. 2. How wet the concrete is applied. 3. How absorbing is the substrate that it is applied over. 4. What the climatic conditions are in terms of temperature and humidity.

      The only way to quantitatively determine how much it has cured is to core and install Relative Humidity probes. Depending on what kind of product you are installing over it, will depend on what that Relative Humidity (RH) of the concrete should be. Generally speaking it is desirable to be at 75% to 80% RH.

      Since you are installing vinyl planking floated floor it is even more critical that the concrete is adequately dry or the planking can have problems.

      You have a relatively small area so I would expect it to cure a lot sooner than 28 days, but you should review the data sheet of the vinyl product you are going to install to see what their moisture requirements are for the floor.

      • Erica says:

        Thank you for your reply. I’m using Cali Bamboo Vinyl Plank floors. The spec sheet doesn’t seem to say anything about moisture but they have an underlayment product (Cali Complete) that says Moisture: 12lbs/24h/1000sf or 12% MC. Unfortunately, I really don’t know what to do that with info. I also don’t see us coring into the cement. The flooring is currently scheduled to be installed two weeks after the plumbers pour the cement. The flooring installer seemed to think that was ok but I just wanted to find any additional ways I could increase the likelihood of a good outcome. Is there something I can tell the plumbers to ensure the cement is less wet? Is there a cement additive?

        • Donato Pompo says:

          MC probably stands for moisture content meaning Relative Humidity. If your flooring installer is a professional installer he should be aware of moisture concerns with vinyl products. He should do his due diligence to make sure there isn’t excessive moisture.

          You could take a liquid applied waterproof membrane and paint over the cured concrete to help minimize moisture vapor transmission.

  18. Victor Harker says:

    Great article on installing tile. I just want to know that how long is the ideal concrete cure to foundation laying tile and mosaic. Thank you advance for your helping answer.

    • Donato Pompo says:

      As stated above it is always best to wait 28 days for curing concrete slabs as a general rule. You want most the shrinkage to occur and the moisture to evaporate before installing the tile.

      There are a number of factors that determine how long it takes for this curing to occur. It depends on how thick the concrete is, and what the humidity and temperature it is subjected to during the curing process. Some manufacturers say that for every 18 degrees Fahrenheit over 70 degrees Fahrenheit that cementitious materials will cure in half the time. On the other hand, if it is very cold or wet it will take a lot longer.

  19. Marcus Coons says:

    Thanks for mentioning how you should consider the amount of humidity that the concrete has before installing tile on it. It is important to understand that doing some research can help you find the best way to use the type of concrete you need. A friend of mine was talking about how he needed to get some concrete, so I’ll share this article with him.

  20. john says:

    I have poured a 60mm concrete hearth of 1 Metre x1 Metre on top of my slab to raise my hearth. My question is, as it is a small area how long does it need to cure before laying tiles?

  21. Donato Pompo says:

    The rule to be safe is 28 days. If you are using a good quality thin-set mortar to adhere the tile to it, it might allow 14 days of curing. Curing has to do with thickness of the mortar, whether it is going over a absorbing surface, and what are the climatic conditions. If it is well over 24 C e.g. 32 C with low Humidity, you might be able to cut the cure time in half. The point is you want to minimize shrinkage that might lead to cracking in the concrete that then could telegraph up through the tile.

  22. Brian says:

    I am installing a shower in my basement. When I removed the old shower stall their is a square cutout of the floor where the drain is located approximated 2 ft in length/width. I plan on installing a KBRS pre-sloped shower base over the concrete. I plan on installing a new drain and then encasing the drain in concrete. Is this correct? Do I need to wait 28 days for the concrete to cure before using thinset to attach my shower base to the concrete?

    • Donato Pompo says:

      If you don’t need to move the drain location in the concrete slab, then all you have to do is use the KBRS prefab foam shower pan drain kit. Either the standard type drain or a trench drain.

      If you need to move the location of the drain in the concrete slab, you will have to chisel out the old one and open up the path to the new location. In that case you will have to fill and patch the concrete. Because you are putting a prefabricated foam shower pan base down, you only need to allow maybe 72 hours of curing at 70 degree F and not more than 70% relative humidity. The foam shower pan shouldn’t be affected by any shrinkage in the concrete patch.

  23. Reggie says:

    I am in the process of a bathroom addition. I poured the slab around 8 months ago and I am going to float approximately 2″ of mortar and then thin set 4×18 marble. It is approximately 220sf. Do I need to use a crack suppressant? If so should it go on the existing slab or the mortar float?

    • Donato Pompo says:

      In theory, if the slab doesn’t have any cracks, and you don’t expect it to develop cracks over time, then you don’t need a crack isolation membrane.

      On the other hand if you do have cracks or get cracks in the slab later on, or if the 2″ mortar bed develops shrinkage cracks, then those cracks can continue up through the marble.

      A crack isolation membrane is safe insurance. It not only will protect against shrinkage cracks, not structural cracks, but it provides a moisture barrier if you have moisture vapor transmitting through the slab.

      Whether you are doing a bonded mortar bed by bonding the 2″ thick mortar bed to the slab, or if you are doing a 2″ thick non-bonded mortar bed over a cleavage membrane with wire reinforcement suspended within the mortar, the crack isolation membrane should go on top of the mortar bed. It is best to use a liquid applied crack isolation membrane when installing marble over it as it has more tensile strength.

      • Reggie says:

        I do have some cracks in the slab where I left a couple plumbing block outs. I was going to go non bonded, non reinforced mortar over the slab. Would you advise against this? Also, if I use a liquid applied crak isolation membrane, how soon can I put it on? Any product reommendations?

        • Donato Pompo says:

          If you go non-bonded mortar bed you have to 2×2 inch 16/16 wire mesh suspended in the middle of the mortar to control shrinkage and cracking.

          Depending on the membrane, you can apply it within 72 hours after floating a dry-pack mortar bed. Read the instructions. Laticrete Hydro Ban or Custom’s Redgard, or Mapei’s Mapelastic are common liquid applied crack isolation/waterproof membranes.

  24. Emma says:

    There are things we should know about concrete and paving the road. From the place where I lived, there are collapsed and broken roads. It takes more time to fix it. Your blog, reminds me of what to do when it happens.

  25. Alex Lee says:

    I am planning to have wet underfloor heating for my kitchen. This will then be covered by cement before laying the porcelain tiles over the cement. How long will the cement need to cure or solidify before laying the porcelain tiles? I was told that the estimation is 1 day for every 1mm of cement – is this correct?

    • Donato Pompo says:

      I assume when you say having a wet underfloor heating that you mean there will be hydronic radiant heating tubing. Be sure to follow the manufacturer’s directions for the installation . Normally you have to have at least 3/4″ concrete or mortar over the tubing. Then you should have a crack isolation membrane on it.

      The general rule for concrete to cure before installing tile over it is wait 28 days to allow the concrete to cure and to finish shrinking. If you use certain polymer modified adhesives you can maybe set tiles after 14 days of curing. There are crack isolation uncoupling systems that will allow you to install the tile a lot sooner. You can’t judge it by the thickness of the mortar although that is a factor in its curing. It also has to do with humidity, temperature, underlying substrate, and environment.

  26. Carmen says:

    After removing the old tiles in a deck, my installer grinded some high spots, filled some holes, then applied a thin coat of platinum laticrete thinset on of the existing mortar bed. Then he used quickcrete mortar mix for a 1“ to 2” mortar bed, applied a thin layer of platinum Laticrete thinset and the next day he painted the floor with a crack isolation membrane (hydroban). I’m concern about curing times and proper use of materials. He is starting the tile installation next week. Could you please give some guidance?

    • Donato Pompo says:

      It sounds like your installer knows what he is doing. Grinding and filling the concrete substrate is proper. Using the platinum thin-set as a slurry bond coat to then immediately apply the mortar mix for a bonded mortar bed in order to properly slope the surface 1/4″ per foot is proper. Skim coating the mortar bed with the thin-set to achieve a smooth surface and strengthen the mortar bed surface is smart and proper.

      The critical part is how soon you apply the Hydro Ban membrane over the surface. Normally you want to wait about 72 hours, but it depends on how much moisture content is in the mortar bed, how thick they applied the membrane, and what is the atmospheric temperature and humidity. Hydro Ban can be moisture sensitive if it is applied too thick and the temperature is low and the humidity is high. If you see light green colors in the membrane then it isn’t fully dry to a dark green color. By waiting to let it cure is good, but make sure there are not blisters or emulsified spots or any dirt. If there are they can normally be easily repaired and patched and clean.

      You can’t leave the membrane exposed the ultra light and other environmental conditions for too look or it can degrade. Check Laticrete’s data sheet to be sure. The data sheet says you can flood test the membrane within 2 hours for ideal conditions, but I have never seen it dry enough to be able to do that. You normally have to wait at least overnight depending on the temperature and humidity.

      • Carmen says:

        Thank you Donato! I have one more question about expansion joints. Here in Hawaii nobody uses them, but in a second floor deck I believe we need them. The deck is 40’ by 24. Where should we install them? Any recommendations on the type of silicone? And do we do it just in the tile layer or also in the mortar bed?
        Thanks again

        • Donato Pompo says:

          They do use movement joints/expansion joints in Hawaii as we do work there. Of course not everybody, but those who know it is mandatory in the standards do or should.

          Movement joints (expansion joints is a type of movement joint) should be installed at the wall to floor transitions, and every 8 to 12 feet in each direction. Standards say to have a 1/2″ wide movement joint, but if you install them more frequent you can narrow it to match up with the width of your grout joint so it doesn’t standout.

          If there are pre-existing control joints in the concrete slab then you are suppose to honor them and continue them up through the tile assembly. Otherwise on a bonded mortar bed you should continue the movement joints within them.

          The standards for some reason say not to saw cut the movement joints in the mortar bed after it is installed. From my experience, as long as the mortar bed is properly installed it isn’t a problem to saw cut them. Plus with all of the variables in laying out the tile it gives you more control to saw cut them in after the mortar bed is down.

          The standards say to use an ASTM C920 sealant that is either a 100% silicone or polyurethane sealant. If it is on a walking surface then the sealant needs to be a traffic grade sealant that will wear well. Make sure you follow the manufacturer’s directions that include using a closed cell polyethylene foam back up strip or bond breaker tape.

  27. Rebecca Gardner says:

    It was helpful when you explained that concrete slabs need a texture of at least CSP 3 or greater. I just learned that my parents want to find a concrete pumping specialist to put in a walkway in their large backyard. This info should help them find a reliable and knowledgeable concrete service to hire, so I’ll have to share it with them later today!

  28. Anna says:

    Screeds should be firm enough to walk on, usually at least 3 days after application, before tiling can be started. The concrete should be at least 7 days old. All substrates to be tiled must be clean and surface dry.

    • Donato Pompo says:

      It is true mortar bed screeds should be firm enough before you walk on them. Depending on the weather it can be the next day. We normally want it cure for at least 72 hours before we apply a liquid applied waterproof membrane. In colder weather the curing is retarded so you have to wait longer. Before installing the tile the substrate surface must be clean, saturated dry, and should readily absorb moisture to ensure a good bond with a polymer modified thin-set mortar.

  29. retaining walls says:

    Truly I tell you allowing the concrete to cure for twenty-eight days allows it to achieve 90% to 93 % cure and there is no significant shrinkage in the concrete after that in terms of installing ceramic tile over it.

    • Donato Pompo says:

      Generally speaking it is true that concrete is mostly cure at 28 days. Although that is based on 70 degrees F and 50% RH. If it is cold it will retard the curing. If it is hot weather it speeds it up.

      There adhesives for tile and stone where you can adhere as soon as after 14 days. There are uncoupling membranes that allow you to over concrete sooner.

  30. Jeff McNiece says:

    I think you’ve answered some of this, but I’m trying to put down a custom interior shower pan using Portland cement and sand mix . How long do I need to let it cure before I can walk on it (to start hanging the backer boards), and also start to lay down the tile? Also, should I coat the entire pan floor with a waterproof membrane, and if so how long should I wait? I assume I can start to tile immediately after the last membrane coat dries? Thanks in advance for all of your insights!

    • Donato Pompo says:

      The factors in drying a mortar bed is based on how thick it is, what type of mortar you use and how you mix and apply it, and what is the Relative Humidity and temperature in the room. Normally over night if it feels solid you can walk on it, but put down a piece of plywood first. I would have hung the backer board first.

      Depending on what type of waterproofing you are using determines how soon you can apply it. I assume you didn’t use a sheet membrane under it. So I am assuming you are applying a liquid applied membrane over the mortar bed. The mortar bed should dry for at least 72 hours before applying the membrane, but at least per the membrane manufacturer’s directions.

      The membrane should be flood tested as required by the plumbing code. To flood test you need the membrane to dry at least per the manufacturer’s directions, but at least a day or two; even if the manufacturer says it dries in 2 hours, but everything has to be perfect for that to work.

      Once the membrane has been successfully flood tested then you can dry the surface and start installing.

  31. andy says:

    Hi Donato Pompo, thanks for this article. Amazing how much time you have spent replying to everybody. Read a lot of the comments and after pouring my own little slab of concrete for tiling I am sure that I am doing the right thing (first time trying!). Thanks again for all the advise you have given.

  32. brian petty says:


    • Donato Pompo says:

      It depends on what type of membrane you are installing on how soon you can put a shower pan liner over it. There are different types. Also it depends how fast the mortar bed cures. The thicker it is and depending what the temperature and relative humidity is will affect how fast the mortar cures.

      Normally a shower pan liner is a sheet membrane. If you are going to use the sheet membrane and then put a mortar bed on top of it, you can probably do that after a week of adequate curing. Some of the liquid membranes require a certain relative humidity value of 90% or less in the mortar bed before covering it. The uncoupling membranes that are waterproof can be applied right away.

      Bottom line is follow the membrane manufacturer’s directions on when to apply and how to install it.

  33. Paul says:

    Hi Donato, great article. I need to install porcelain tile (600mm x 600mm x 10mm) on 100mm concrete pad out side the patio. The size of the concrete pad is 1.8m x 10m. The outside temperature is around 30 deg C. I read, its required 28 days to cure the concrete. I need to complete the work soon. So can I install the tiles 7 days after the concrete pouring ? Will it create aby problem like tile cracking or etc ? Please advise.

    • Donato Pompo says:

      There are uncoupling membranes that can be applied over concrete slabs that are not fully cured. Such as Custom RedGard® Uncoupling Mat. You bond the mat to the concrete and then immediately you can bond the tile to the mat.

  34. Scott says:

    Outside my front door I have an 11 inch step down to a concrete pad (30 years old) I want to ad a 4.5 inch pad on top of the existing slab and then top that with 1 inch slate tiles. Multiple questions…

    Do I need to do anything special to bond the new concrete pad to the old?

    Do I need to wait for the new pad to cure so certain period befor I tile with stone?

    What is recommended to adhere the stone. Modified thinset?


    • Donato Pompo says:

      Keep in mind that the building code for stair risers is to be no more than 7.5″ tall and no smaller than 4″ tall. It can be uncomfortable for the people if the riser is too short or too long, which can lead to tripping under the wrong conditions.

      Yes whenever you bond new concrete to old concrete, you should first scarify the old concrete surface and then vacuum and power wash it clean. Once the surface is not wet, but can be damp, you can apply the new concrete.

      You need to add a slurry bond coat to the old clean and scarified concrete surface just before you apply the new concrete. This can be concrete plaster adhesive glue or it can be a thinset mortar adhesive applied very loose.

      Since the concrete is so small it should dry fast if you have warm and dry weather. I would wait at least 1 week and then tile over it.

      Slate is very dense so you do need to use a polymer modified thinset mortar that meets either ANSI A118.4 or the improved formula that meets ANSI A118.15.

  35. Lee Hansen says:

    I’m in Palm Springs where the high temps are 90′ to 100′ now in May. I’m wanting to remove a 6′ border of pavers that are next to my 25 yr old existing concrete and pour new concrete before I tile the entire area with a porcelain tile. My questions are can I pour concrete in this high temperature? Also assuming I have to wait the 28 days before I lay tile? Lastly, how should I treat the 25 yr old existing bare concrete or do I need to do anything other than pressure wash?
    Thanks for any advice.

    • Donato Pompo says:

      Not sure if you mean 6′ or 6″ border of pavers. I assume the pavers are installed over sand or dirt if you are going to pour new concrete.

      Generally speaking you want the surface temperature and the concrete product to not be more than 90 degrees F. You can put up a canopy to create shade that will generally drop the temperature down 15 degrees or so. You can also install a misting line that will cool things down too with fans. You can also pour the concrete in the early morning or at night as we have done on other jobs in the Palm Desert area. You can cover the fresh concrete with burlap bags and wet them down several times during the day to keep it wet so it doesn’t dry too fast.

      The area where the new concrete goes has to be compacted. A vapor barrier should be placed over the compacted dirt. You should drill holes on the side of the existing concrete and epoxy rebar so the rebar extends into the new concrete area. Once you are ready to pour the concrete you need to coat the edge of the old concrete with a fresh tacky coat of a polymer modified thinset mortar so it bonds the new concrete to the old concrete.

      That little concrete probably will cure enough within 14 days. You should scarify the old concrete to open up the pores so it readily absorbs water. I would recommend a liquid applied waterproof/crack isolation membrane over the properly prepared concrete and pretreat the new concrete area where it transitions to the old concrete.

      You need to control the temperate of the tile, concrete and installation materials when you do install the porcelain tile so you don’t exceed 90 degrees F.

  36. Richard Spaulding says:

    Hi, we removed some old tile along with what looked like gypsum concrete to get down to the concrete slab. The contractor is now laying “ready to use concrete” Quikrete to bring the floor height back up (average of about 1.5 – 2 inches). How long should we wait before placing 16×16 and 16×24 porcelain tiles? Thank you!

    • Donato Pompo says:

      To be safe I would wait 72 hours to make sure you don’t have any shrinkage cracks on your concrete. If you do then you need to isolate them with a crack isolation membrane.

      Make sure you score in some control joints in the concrete while it is still fresh and stiff enough to help prevent cracks, but layout it out so it lines up with a grout joint in your tile installation so it can be filled with an ASTM C920 sealant e.g. silicone or polyurethane caulking.

        • Donato Pompo says:

          The 28 day curing of concrete is what is considered mostly cured when a thick (over 4″) application of concrete for a concrete slab over a vapor retarder. Today some manufacturers of polymer modified thinset mortars are recommended on new concrete slabs that has cured 14 days. On a mortar bed it isn’t uncommon to come back and install after 24 hours. So the thickness of the mortar and the climatic conditions will indicate how long you should wait before installing the tile.

  37. Susan says:

    Hi, our outdoor porcelain tile (2’x4′ with thin ~1/8″ grout) was installed at our new home, on top of a concrete slab that had just been poured ~ 2 weeks prior. Initial grout crusted up, so they regrouted. Happened again. They regrouted a 2nd time with an epoxy grout – better, but still lots of bubbling/crusting/raising and grout failure. I assume it’s because the underlying patio never cured, the tiles are large and don’t breathe and the joints are thin and don’t help to cure below. Any suggestions? The grout looks terrible. Should we just remove it and live with no grout for a few years? Or a different grout? Will that help it cure underneath? Thx for any help.

    • Donato Pompo says:

      Normally it is not recommended to install over a poured concrete slab for at least 28 days to allow it to cure adequately unless you use special installation products.

      The other possibility that could be causing or contributing to the problem is if they did not install a vapor retarder membrane under the concrete slab and up the sides of the slab to prevent water from migrating to the slab. Depending on the soil conditions under the slab you could have a high water table or other conditions subjecting the slab to moisture.

      I would remove the grout and let it cure for awhile. The epoxy grout should have prevented moisture from coming through so I don’t know why that isn’t working unless it wasn’t installed correctly.

  38. Susan Vinci-Lucero says:

    Thank you so much for your quick response. They were in a rush to complete construction and put the tile over the slab about 23 days after pour (better than 2 wks I thought, after checking pics). It’s doubtful they used any special product beforehand to address curing, but we live in the high desert, so very dry normally, but unusually wet that summer (just a few weeks after tile install in 2018). Not sure about vapor barrier. Anyway, you think that even with 1/8″ grout line and such large tiles, it still might cure after 5 years if we remove all grout? How long do you recommend leaving grout out? And do you think regrout again with epoxy next time (hopefully doing it correctly!) ? Thanks for all your help.

    • Donato Pompo says:

      I think it is unlikely that your problem is due to the concrete slab not fully curing and having impervious tiles. Concrete will cure underwater through hydration. The concern about going over concrete to soon is that there could be excessive shrinkage in the concrete that could cause a problem. Not that it will subject the tile to excessive moisture.

      The concern would be if you have an outdoor moisture issue such as a high watertable and don’t have a vapor retarder to prevent moisture from migrating into the concrete slab.

      If you don’t have an outdoor source of moisture subjecting the concrete slab to moisture then using an epoxy grout should not be a problem.

  39. Susan Vinci-Lucero says:

    Thank you Donato. We will have it all thoroughly removed, wait a bit, and then try again with the epoxy grout. There’s no obvious moisture source, it’s a covered patio, and we’re in a very low rainfall and humidity area. Perplexing!

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