We've all seen it: that really ugly white powder that grows on cement grout and also tile, stone, brick and concrete, particularly when it's installed someplace with moisture (i.e., in a basement or outdoors). That white residue is called efflorescence.
This article goes into detail about efflorescence, including situations that readers have shared with us since the article originally published in September 2016.
What Causes Efflorescence?
Efflorescence for Inspectors explains that,
"Efflorescence (which means "to flower out" in French) is the dissolved salts deposited on the surface of a porous material (such as concrete or brick) that are visible after the evaporation of the water in which it was transported."
You might hear it referred to as "new building bloom" or even "whiskers."
According to the Portland Cement Association Trowel Tips information sheet of Efflorescence (downloadable PDF),
" A combination of three common circumstances causes efflorescence:
- soluble compounds (i.e., salts) in the masonry or adjoining materials
- moisture to pick up the compounds and carry them to the surface
- evaporation or hydrostatic pressure that causes the solution to move
If any one of these conditions is eliminated, efflorescence will not occur."
Efflorescence, then, happens. As a professional tile installer, your role is to anticipate such situations so as to prevent it from occurring.
Figuring Out Why Efflorescence Happens
Tile installers are often called on to look at challenging installation opportunities and also use their expertise to solve problems when they occur. Finding the solution can be difficult, and sometimes we scratch our heads and say, “Why is it doing that?”
Many times installers are asked to install exterior tile on a job that appears to be elementary. Unfortunately, some of them develop issues at a later date.
Take for instance a job calling for a natural stone to be installed on the exterior wall of a new retail store which has a roof above it.
The plans call for the stone tile to be installed over a waterproofing membrane coating the cementitious backer board on steel studs. It sounds routine and it should function well; which it did in this case, for about a year.
Sometimes Efflorescence Isn't the Fault of the Tile Installation
As time passed, the owner began to see a white powdery substance growing on the grout joints. Immediately the call goes out, “There is something wrong with the grout.”
Upon investigation, the grout had not failed, but a naturally occurring mineral salt which is present in all Portland cement products (thin set mortars and cement grouts) had found its way to the surface. This salt deposit is called efflorescence.
Normally, these residues can be washed away with a very mild acid solution and a bristle brush while being careful not to harm the stone (always test first to be certain the acid will not alter the existing finish). It this case it worked… for a little while. Continued scrubbing removed the salts, but it kept coming back. What was the cause?
For efflorescence to occur on the surface as seen in the photo above, water must be present to carry the minerals to the surface, evaporate and let the salts behind.
You may say, “It was the rain water going through the grout joints.”
The rain could have been the culprit, but not in this case. Remember, there was a roof over the tile.
The problem was actually caused by the roofer who failed to properly install the metal cap flashing on the parapet wall above the roof. The water went through the defective flashing, down through the thin set mortar to the lower portion of the wall and blossomed on the grout joints.
Once the tile installer (now a forensic specialist) found the problem, the roofer made the necessary repairs, the tile installer washed away the salt deposits and magically the efflorescence disappeared.
In this example, defective roof flashing led to excessive moisture, which in turn caused that ugly white powder on the grout joints and tile.
In another situation, the problem could be the result of moisture from the soil under a basement floor or wall and might require a vapor migration membrane instead.
The important point is to find the source of the problem and solve it so efflorescence doesn't reoccur. This is what identifies a true tile installation professional.
Troubleshooting Efflorescence Situations
Since publishing this article on 9/6/2016, we have received many questions about specific efflorescence scenarios.
One of the frustrations encountered when that ugly white powder occurs is that it takes detective work to determine the root cause. I have listed the situations readers have shared along with the questions to ask and/or potential solutions for each one.
New Pebble Shower Floor
"My wife and I had a new house built in Arizona and had a Pebble Shower Floor installed. The house is on a post tension concrete slab. The house was finished about the beginning of April 2016. We did not move in until October of 2016.
In January 2017, I noticed a dark jagged line about a 1/4-inch-wide on the pebble shower floor from the middle of the shower door opening at the top of the floor pan to the drain. A week later the line turned white. I am assuming that the white jagged line represents a crack in the grout, and the white is efflorescence.
The builder's tile subcontractor said he has never seen this before and needed to discuss this with others. The builder's subcontractor said that the rubber pan liner under the mortar bed had passed water testing and there is nothing to worry about. He said it also could be a low spot on the floor where water puddles. Sealing the grout will probably fix the problem.
When the white line gets wet it is somewhat fades but you can still see it. Low spot theory seems wrong since the rest of the floor is fine and puddles form in other areas of the floor with no white residue; in addition, the white line starts just where the pebble floor meets the perpendicular ceramic tile forming the door opening at the top of the floor pan. The rest of the floor dries fairly rapidly except for this line and at some of the junctions along the shower floor where the pebble floor meets the wall ceramic tiles."
Here are questions to ask about this situation:
- Was sloped fill (pre-slope) placed under the shower pan membrane?
- Are the weep holes in the drain body, which are an important part of this system, clogged or sealed shut?
- Was the mortar bed under the tile fractured (cracked) during the installation process?
- Does the jagged line in the pebble stone coincide with the mortar bed crack? (This can only be determined by dismantling the shower floor)
Spots of Efflorescence on Tile Floors
"I have a 46-year-old home with original tile floors. For some reason we are seeing spots of Efflorescence in different rooms. What do I need to do to fix this so it stops and does not recur?"
In this situation, more information would be needed to determine the cause.
However, moisture in the mortar bed or setting bed is bringing the naturally-occurring salts to the surface.
The question would be, what is the source of the moisture?
Dark Grey Grout Turns White
"I am having issues with my new grout turning white immediately after my remodel of the master bath. The dark grey is turning white and my contractor is ignoring my plea for help. I am now working with the manufacturer to come up with a solution. Their ads claim using this grout will not allow efflorescence to occur and can be used in showers. I have read many articles on this issue and have no idea what or who to believe ☹️.
What should have been a beautiful floor using light grey tile and dark grey grout is a major and expensive disappointment."
More information is needed to solve this issue, but here are a couple of questions to ask:
- Is this issue occurring in the bathroom floor, the stall shower floor, or both?
- What method was used to install the substrate (the surface just below the tile)?
One note: The grout most likely is not the source of the issue, but rather the residence of the efflorescence.
Efflorescence in a Shower Area
"We recently remodeled my parents’ bathroom to make a handicapped accessible shower for them.
Contractor prepared the floor of the 5x7 room so that it would drain towards the shower drain. Tile was installed on flooring two days later. Now it has hard white stuff in grout and on the tile and I don't know how to get rid of it. Painter says it's too hard to be texture or paint. Tiler is not answering phone calls or emails.
Do you think it is efflorescence? If so, it's a shower area and is going to stay wet a lot. I can send pictures."
This most likely is not efflorescence, but what is known as latex migration as shoown in the photo below. The key element here is that the residue is hard. Efflorescence is normally a soft powdery material that can be brushed away.
Latex migration, which occurs similarly due to excess water in the system, most times comes from the improper mixing or cleanup of the grout or excess moisture in the setting bed beneath the tile. The dried latex can be difficult to remove. Contact the grout manufacturer for their recommendations.
When using any chemical, always test first in an inconspicuous place to determine a satisfactory result will be achieved and use the weakest form of the product, then working up to a stronger proportion as directed by the instructions.
How to Solve an Efflorescence Problem?
"Our home builder had to replace all of the tile and carpet in our house due to a warranty issue. Well, the new tile and grout was put in and now we have an efflorescence problem.
The builder (still under the original warranty claim) wants to "Stain and Seal" the grout to solve the efflorescence problem.
- Is that the correct way to "solve" the problem?
- Or should I ask/force them to acid wash it?
- Isn't staining and sealing the grout just covering the issue and not solving it?
The builder also told us that we would not be able to steam clean the tile/grout anymore as it would break it down faster. We like to steam clean the floors to help disinfect it completely.
What is the best option: 1) Stain and Seal 2) Acid Wash"
Before doing anything, contact the grout manufacturer about having them physically inspect the issue and provide a recommended solution.
Only use an acid cleaner if the manufacturer makes that recommendation. The subsequent cleaning must be done by strictly following their recommendations.
An epoxy-based grout colorant MAY work, but the source of the efflorescence must be eliminated prior to applying the colorant.
A breathable sealer may slow down the moisture travel through the system, but it will not solve the issue.
The use of a steam cleaner may actually exacerbate the issue. Forcing more moisture into the floor system may bring the salts to the surface more quickly and in increased quantities. Additionally, the use of steam cleaning devices is not necessary for a ceramic or porcelain tile installation. Tile is the most hygienic and easily cleaned floor or wall product available in today’s market. Utilizing recommended cleaning procedures will yield a sanitary surface.
Leaking Washing Machine
"Thank you. I found this article very helpful. My washing machine had been leaking and going under all my cabinets. The salt powder was nowhere near the leak so now I am guessing that the water also was going under the floor.
Just confused why it's not everywhere though and just on a few tiles."
Most likely, the water was saturating the entire floor system which emulsified the naturally-occurring salts contained in the Portland cement. These salts (minerals) may not be equally distributed in the mortar or grout which would explain why the efflorescence is not occurring consistently.
Growing Area of White Powder
"15 years ago we had tile put down in our kitchen (wet bed) over a crawl space concrete floor. The tile was sealed after installation. All of a sudden 2wks ago, we began to see white powder in the grout only in a small area.
Thinking it was something just spilled I wiped it up with a wet paper towel. A few days later it was back & seemed like it was in a wider area than before. Again, I wiped it up and mopped the floor with Spic n' Span which I have used forever.
Now it is back again and seems to be in a larger area than ever!! We've had no water spills, etc. to cause any kind of flooding problem. It seems to have come out of "nowhere!" Please help! With any kind of solution!!!"
This was a real puzzle. The sudden appearance of efflorescence can’t occur after fifteen years of trouble-free service without a cause. There has to be a recent moisture intrusion into the wet bed (mortar or mud bed). The owner said that there have not been any water spills, but water is the culprit, but from where is it coming???
Here is the “rest of the story.” After many questions and inspections, the guilty party was determined. It was the water line to the ice maker in the refrigerator that developed a leak where the pipe went through the kitchen floor from the crawl space. This slow leak saturated the mortar bed, emulsified the salts and carried them to the surface.
The pipe was repaired. The floor dried out with the assistance of a dehumidifier, the floor was cleaned, and the efflorescence was gone.
Outdoor Patio Efflorescence
"We just installed new patio tile outdoors and are having only a part of it with this problem. It doesn't seem to get any more moisture than any other part however."
Here are questions to ask:
- Was the concrete slab poured directly on the ground (on the dirt)?
- Was a moisture barrier placed under the concrete?
- Was the moisture barrier compromised (holes penetrating the product) during the concrete installation?
- Is there a water line under the slab? Has it been pressure tested?
- Does the patio have consistent slope of ¼” per foot away from the house?
- Is there a low spot in the tile where the efflorescence is occurring?
Efflorescence in our Church
"We recently installed tile in our church (around 13k sq ft). Most of the grout has been affected by the white powder. We recently purchased large walk behind scrubber, is there a solution we could use in that, that would allow us to quickly handle the discoloration? Thanks!"
More information is needed to solve this issue, but here are a couple of questions to ask.
- Is this a new or remodeled installation?
- What is the substrate (surface beneath the tile)?
- Is the installation on ground (concrete on the dirt)?
- Was a vapor barrier placed under the concrete prior to the concrete placement?
- Does the scrubber also vacuum the water from the surface as it cleans?
What Have You Encountered and How Have You Addressed Efflorescence?
Have you encountered problematic efflorescence situations? How did you determine the source of the problem and how, then, did you address it in your installation? Let us know in the comments.
Additional Resources on Efflorescence:
Note: This article was orinally published on 9/6/2016 and has been significantly updated.