Effloresence mineral salt damp basement - Daniel Friedman 04-11-01Mineral Efflorescence - Water Deposit FAQs
Diagnostic Questions & Answers about the cause & cure of Salt Deposits, Brown & White Bubbly or Fluffy Crystalline Deposits on or in buildings

  • EFFLORESCENCE FAQs - CONTENTS: How to identify white stains, white fluffy material, white crystalline material on building walls & in basements and crawl spaces -mineral efflorescence is not mold.How to diagnose powdery white blotches on a painted stucco exterior wall - Stucco Bloom. How to identify signs of moisture or water entry in buildings & signs of high moisture. Although efflorescence and mineral salts left behind by water are not mold they mean that mold-friendly conditions are present in the building. How old is the efflorescence and how long does it take for efflorescence to form? Efflorescence = efflorescence = efforfescense = efflorescence if you're spelling efflorescence wrong.
  • POST a QUESTION or READ FAQs about white & brown building stains & deposits: efflorescence causes, significance, cures

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FAQs on efflorescence salts or stains on building surfaces:

Frequently asked questions & answers help diagnose the cause, cure, & effects of effloresence or salt deposits (white, brown, red, yellow) caused by moisture, rising damp, seepage causing white stains & deposits in buildings: white deposits on building surfaces.

This article series illustrates and explains white or sometimes reddish brown bubbly surfaces on walls and white powdery or crystalline deposits left on walls, especially masonry walls, by moisture - efflorescence.

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Efflorescence: white or coloured mineral salt deposits on or in buildings: FAQs

White fluffy effloresence on a concrete foundation (C) Daniel FriedmanReader Comments:

(Aug 18, 2011) Ken Quenzer said: I love this web sight. It has so much helpful information on all subjects. Thanks.

(Mar 1, 2013) Keith said: Finally, info that really applies. Thank you!

Question: Is this white fluffy stuff efflorescence? and If So how should I clean and Paint it?

JO said: I'm not sure if I have Efflorescence or not! There is a small wall inside my Kitchen that has flaking off paint and the paint that is still attached looks like chalk dust. Is this just damp? If so, what paint shall i use? Thanks for any help and advice!

Reply: Cures for Efflorescence or "white mineral salt stains and deposits"

Jo, I can't tell from your description if you have efflorescence or just peeling paint. Take a look at the photos on the page above where we show just what efflorescence looks like.

The "cure" for efflorescence involves:

1. Find and fix the leak or moisture source that is causing the problem

2. Vacuum and clean off the surface thoroughly

3. You can re-paint using a moisture tolerant paint (latex) or on foundations a moisture resistant paint such as those made by Thoro (TM) [Thoroseal].

But if you don't find and fix the moisture source, peeling or chalking or efflorescence are likely to recur. The lifting power of mineral salts forming on a masonry surface is quite strong and has no trouble pushing off paint.

Question: How do I stop Efflorescence from Growing or Forming

Lorraine said: hi Jim, did you find a way to stop the effloresences? from Lorraine

Jim said: I have the same fibrous growth in certain places on my basement concrete floor. I at first thought it was mold and used bleach to wash the area, but to my surprise it was back in less then a week and just as tall, 1/4-3/8" high. After some research online today I see it is the salts or effloresences leaching up. Under the right conditions it only needs a week or less to become visible and be 1/4" or more high.

Reply: Find and fix the moisture source or efflorescence will continue to appear

Lorraine, cleaning off the efflorescence is easy, using just about any household cleaner, even a damp sponge or vacuuming and washing the surface, then letting it dry. You can also try applying a sealer suitable for the particular surface material. But if we don't find and fix the moisture source the efflorescence will return.

Question: I think I have Efflorescence growing out of a bathroom floor - but it's growing really fast. Will it stop once the concrete has dried?

Jenn in So.Cal. said: I have this, at least I think it is, growing out of my bathroom floor. But the stuff I have grew/grows REALLY FAST. We repaired a plumbing leak in said bathroom this past Saturday. After which, we decided to remove the carpet was not only completely soaked, but old and worn out. (frankly I've never quite understood the idea of putting carpet in a bathroom. Gross!!)

Anyway- This left us with the bare concrete slab as a floor. Before midnight that night, 50% of this bathroom "floor" was covered with fluffy white "waves" of fine crystalline growth around 1/2 - thick. I vacuumed it up yesterday afternoon, and this morning it was back to where it was the night before!

Before I found this great site, and reading thru the info you provide here, we worried it could be some mutant miracle grow mold, waiting to attack my asthmatic lungs or my husbands allergy prone sinuses. Or maybe just a result of many years of "love my carpet" type powders and/or carpet shampoo, or something else entirely.

From what I've read so far, I think I've got mineral effloressence. If that is the case, will it stop once the concrete is dried out? I imagine we'll have to give it some time before laying tile. Which is fine, there's no rush. Are there any "prep" recommendations?? I thank you for your time. And for your wonderful and informative site. Very helpful indeed. I've already told a few friends about it! - Jenn in So Cal 7/19/2011


Jenn: Yes if you can dry out the area AND if you do not have an outside water source sending moisture up through the slab it may dry out enough that the efflorescence formation will stop or at least mostly stop; Efflorescence is a crystalline formation of mineral salts that can indeed appear rapidly on masonry surfaces when there is plenty of moisture present.

Question: I see white blotches where carpet squares were removed from the concrete floor. Is this a worry?

Half of my basement was completely finished 10 years ago and I have carpet squares with a rubberized backing over the concrete floor. I recently lifted up several squares and noticed small white blotches on many areas of the concrete floor. The carpet square backings are intact. Are the white blotches anything to worry about? They're not raised blotches -- they're pretty flush with the concrete. - Jim B.


Jim B: I can't know from so little info if the white blotches on the concrete floor under carpet squares are a real worry or not, but they do indeed sound like an indication of moisture in the basement;

SInce the rubber-backed carpet squares are pretty moisture resistant, moisture may have been trapped on the concrete floor below, forming mineral efflorescence If you remove the carpet squares and clean the floor and keep the humidity in the area low (target 40%) and if there is not an outside moisture source, you should be OK.

Comment: how long does it take for effloresence to form in a building?

This efflorescence can take as little as days to form. I was at work scraping paint chips from an outside wall. Came back 4 days later and noticed this stuff all over the wall. So it does not take years by any means. - Joe


We agree, Joe. Effloresence can appear in days - we see this after a single-event flood that has wet a building; it is also a process that can continue for years, even decades. The extent of damage depends on the building materials involved and the amount of moisture transmitted to the building interior. Lots of moisture indoors also invites mold problems, rot & insects.

Question: After a basement flooding we see this white efflorescence stuff - could it be from remaining floodwaters?

in february we had a very very bad flood in our basement due to a broken water line, we cleared out the basement and removed the carpet. within a few days and major rain we noticed puddles forming by the exterior wall. we had the old clay weeping tile removed and replaced and window wells installed. since then we have noticed efflorescence forming on the floor in front of that same exterior wall. there is no dampness on the floor, (that i can feel) i have cleaned (vacuumed) this efflorescence and it returns within days. now that it has been dryer because of the summer weather the formation has slowed down.

I would like to re-carpet the floor down there however i have to figure out what steps to take first to water proof this area. I have read many articles on the net but there is contradicting information. could the efflorescence be the remaining water from the flood and the pre-weeping tile? thanks - Teri. July 28, 2011


Teri, I've worked with efflorescence and building moisture and water entry problems since the 1970's. In all cases in my own experience as well as in what I've studied, you need the combination of moisture and a mineral-containing material like masonry, concrete, stone, cement, mortar, etc. to produce mineral-granule efflorescence Moisture wicks up through the masonry material from a water source, evaporates, and leaves dissolved salts behind on the material surface.

Efflorescence will pretty much stop appearing if you can dry out the area. Now I'd agree that following a cleanup it's possible for there to be some remaining moisture, say below a floor slab, or else an ongoing water problem that has not been cured. But if there were NO moisture, you'd not see efflorescence That's a sound conclusion.


thanks for your response dan, we just had a major rain and there is no evidence of water anywhere. we do have a sump pump in the basement as well, which does its job well. we also run a dehumidifier in the area. should i try to seal the floor with a concrete sealer before carpeting? and if so which one would you recommend? - Teri

Reply: A masonry sealer can slow down efflorescence formation

Teri if the floor surface is clean and dry a masonry sealer can help break the evaporation path that by capillary action pulls more moisture through masonry. There are two different approaches: silicone masonry treatments that mostly resist water entry into the masonry, and coatings such as portland cement based masonry sealer paints, or more extreme, epoxy paints.

No paint will withstand moisture pressure from beneath the paint surface for long, so paints don't absolutely stop moisture passage long term but they interrupt the evaporation-pull process.

But the masonry sealer paints I know about are not suitable for floors; you'd use an epoxy or other floor paint intended for concrete surfaces.

Frankly, all that said, if you've dried out the water source painting should not be necessary, but finally, in a basement, I would never put down wall to wall carpeting in any event. You're asking for an intermediate or long term mold and allergen problem. I prefer an epoxy painted finish floor, ceramic tile, or vinyl tile glued to the concrete floor surface. Over that if you want a few cleanable area rugs, that's fine. - Dan

Question: I bleached the efflorescence spots but it returned, Why?

I cleaned what seemed to be mineral efflorescence with bleach diluted in water, and the next day it appeared again in the same spot. Is it mineral efflorescence, then? Thanks. - Elena

Reply: Efflorescence is not a biological product; it reappears due to moisture or water leaks. Bleach won't "kill" mineral deposits nor stop their reformation

Elena, because mineral efflorescence is a mineral, not a biological product, cleaning with bleach is only of cosmetic use and may not really be necessary at all. You could use any household cleaner. But unless the moisture source is also found and stopped, the efflorescence will indeed return.

Just how fast efflorescence salts reappear (in your case the next day) depends on building variables such as the amount of water outside the wall, the rate of moisture movement through the wall, the mineral content of water when it reaches the inner wall surface, and the evaporation rate from that surface (in turn a function of indoor humidity). In other words, bleach won't stop efflorescence formation on a wall surface. - Dan

Question: Is the white fluffy stuff that appeared after Hurricane Irene efflorescence or mold?

After the water from hurricane Irene dried out of our basement, we have noticed some white fuzzy stuff that I believe is efflorescence. The floor where it is coming in is slightly pocked, as though the white stuff grew out of the floor. Does this sound like mold? - Slothburger

Reply: How to distinguish efflorescence from mold

Slothburger, there is white stuff that is efflorescence (crystalline mineral salts), and there is white stuff that is mold. If the white stuff looks crystalline under a magnifying glass, and if it's being produced on a masonry surface, it's probably efflorescence


for WHITE MOLD PHOTOS - take a look and you'll see the difference between what mold looks like and what efflorescence (this page above) looks like. - Dan

Question: what is the best way to remove the white mineral salts stains on outside rendered and painted walls

Thanks - Marg

Reply: Look at our stucco paint failure information, clean, seal, and repaint + find and fix the leak

Marg you might search InspectAPedia for stucco paint failures for examples of white salts showing up in exterior paint on a masonry type wall surface.

Ordinary cleaning with any household cleaner, followed by thorough drying, followed by application of a sealer to reduce future moisture up-take, then re-painting will clean up the issue.

But you want to perform some diagnostic detective work to be sure you understand where the moisture came from in the first place; if, for example, moisture is entering a wall from a building leak, the efflorescence (white mineral stains and salts) will return unless the leak is fixed.

Question: White crystallized material in the shower drain - could this be effloresence and is it a health risk to someone suffering from pseudomonas-related illness

My husband remodeled our bathroom. It has plenty of sunlight coming in. My problem is there is this "white crystallized material" that is collecting in the shower drain. My husband tends to think that because the shower is Travertine that it is run off from the stones, although he did put a sealer on them.

I have extreme lung problems and I am currently being treated for pseudomonas. I constantly worry about this stuff in the shower drain. I did not read anything on your website about efflorescence collecting in the drains only on buildings. Is it possible that this is what is in my drain and it's due to the regular moisture associated with shower water?

I appreciate any help you can give me. Thank you. Sincerely, H.G.

Reply: Effloresences in shower drain? Unlikely & in any case it's too small a particle reservoir to explain an indoor air quality health concern - but here are some things to watch out for

H.G., of course I'm sorry to read about your pseudomonas health worries.

If there is an effloresence problem on a building surface it is generally a salt crystalline material deposited on an above-ground above-water-level surface - because effloresence is a mineral salt left behind on a surface by the process of evaporation. It is very unlikely that the material in your shower darin falls under that definition - it's a wet area with little evaporation, and since the drain materials will be plastic or metal they won't be a source of mineral salts.

I agree that runoff or mineral deposits from tile could possibly collect in a drain, but I'm unsure what mechanism would leave that material specifically in a drain.

If you would be kind enough to send me some sharp photos of the drain and material in question as well as details about the tiles that you installed there I would be glad to comment further. If you like you can also send a physical sample of the material to our forensic lab where I may learn something further by direct examination.

Use the CONTACT link found on any of our web pages to find an email and mailing address. [Note to other readers: please do not send us anything by mail without prior agreement by email. Unsolicited samples of any kind will have to be discarded. - Ed.]

Very small areas of just about anything are unlikely to themselves explain an indoor air quality problem

But more importantly, the total area and quantity of a deposit in a drain (surely no more than a 1-3 square inches) would not itself be a plausible source of high levels of a problematic indoor air particle.

Further investigation of your building for IAQ concerns

However building leaks, drain problems, or use of certain building materials in the construction of your home could be potential sources of irritating or otherwise problematic particles. A competent onsite inspection by an expert usually finds additional clues that help accurately diagnose a problem with building moisture, or that might point to a material that is shedding or contributing to an indoor air quality problem.

While I argue that "tests" for indoor air quality alone, without taking a case history, building history, and without making a thorough expert building inspection would be unreliable, it might be appropriate to screen your home by some additional testing beyond just an inspection. Because a competent useful inspection and testing are costly, I do not recommend that step without some justification. See MOLD / ENVIRONMENTAL EXPERT, HIRE ? for help in deciding if such an inspection and testing are warranted.

As you probably know from your doctor and your reading, pseudomonas is a bacterium that is widespread in the human environment, and commonly found in both homes and hospitals. This bacterium lives in water. It does not spread through your home in air. As this bacterium can also be found in healthy people, more often people suffering from pseudomonas-related illness often have a compromised immune system.

In my OPINION, anyone suffering from a compromised immune system would want to take care to avoid living in an environment that might have high levels of contaminants or particles that are likely to exacerbate their health concerns.

One group of such indoor contaminants often found in homes include various molds, some of which are often present in a home that has suffered leaks or moisture problems but that nevertheless can be hard to spot, such as some members of the Aspergillus and Penicillium families. A building screen for problem particles should thus include indoor mold contamination.

Check with your doctor

If you haven't already done so, you should ask your physician what sorts of environmental materials or exposures would be most likely to cause or exacerbate your own health problems. Those are materials for which we should first screen your home or other places where you spend most of your time.

Question: I cleaned off effloresence but it came back, what do I do now?

I cleaned what seemed to be mineral efflorescence with bleach diluted in water, and the next day it appeared again in the same spot. Is it mineral efflorescence, then?
Thanks. - Elena 9/2/11



because mineral effloresence is a mineral, not a biological product, cleaning with bleach is only of cosmetic use and may not really be necessary at all. You could use any household cleaner.

But unless the moisture source is also found and stopped, the effloresence will indeed return. Just how fast it reappears (in your case the next day) depends on building variables such as the amount of water outside the wall, the rate of moisture movement through the wall, the mineral content of water when it reaches the inner wall surface, and the evaporation rate from that surface (in turn a function of indoor humidity).

In other words, bleach won't stop effloresence formation on a wall surface.

Question: effloresence keeps growing back on our walls, effloresence seems to be spreading - how do we stop it?

We have efflorescence in a wall in our apartment. It will grow back within two or three days, even after being treated with a water-stop kind of "paint" -- we had a painter treat our wall and then he painted it, and after just a few days, the paint had already bubbled up again. It's going to be my one-year-old son's bedroom, and I really don't want bubbly paint in there... I don't know what to do to fix this... If it was just a basement, I wouldn't care. The wall appears to be dry. The plumber checked all the pipes. WHAT CAN WE DO??? - Teri 9/6/11

We expanded our living room 8 inches to meet the foundation blocks and new concrete was poured. Tile was placed ontop of the concrete and efflorescence began to form along the grout lines.

It appears that our contractor did not do a vapor barrier under the newly poured concrete and this efflorescence is slowly spreading. Short of digging up the concrete (and the tile) is there anything we can do to remove & seal it from the top down? We live in Florida on a slab house, so we have a very wet rainy season, but even in the dry season we still are getting efflorescence in the tile (just not as fast). - Candy 9/28/11

How do you stop reoccuring effloresence on a concrete basement floor. I live near the water and keep two dehumidifiers running 24/7. The floor is not damp, but despite using muriatic acid and drylock powder several times, I still get reoccuring crystals. Some stopped, but there is still a great deal. - Kathy 9./29/11


Kathy et als:

Recurring effloresence on concrete floors or other masonry surfaces is indeed annoying, and hard to stop. The bottom line is that unless we can find and stop the water source on the other side of the masonry surface, the effloresence will return.

On some surfaces such as concrete block foundation walls, you can slow down the formation of effloresent salts by painting the cleaned surface with a masonry sealer, but don't expect that to be a permanent repair. On floors it's more difficult as you'd need to use a harder-surfaced floor paint that, while it's impervious to moisture, will still be pushed up off of the floor by moisture and salt formation below.

Candy: I'm guessing that effloresence forms on the grout lines because being cementious they are more porous than the floor tiles themselves. Unfortunately the "fix" is as I stated just above. If you can't dry out the soil below the floor it will be very difficult to stop the salt formation inside. You might slow down that process by sealing your grout lines with a grout sealer. Clean the surface, let it dry, then apply grout sealer.

Question: what might be causing effloresence on various surfaces?

We seem to have effloresence in our kitchen but don't know if we have a leak. It's an external wall (plastered some 5/6 years ago) that seems to have a pipe running up it (it gets hot if heating or hot water are on). This leaves the rest of the wall feeling damp and cold. Could it be the existence of the pipe in the wall that is causing the effloresence or is it more likely to be a leak? Had damp specialist out who seems to think the wall is not too damp and more likely to be condensation causing effloresence. So confused!! - Rachel 10/19/11

A Few years ago I noticed that the gybroc wall in the basement was peeling off and getting black, mainly in the bottom where the foor and the wall meet.

I removed all the gybrock and and I found that all the wood underneath was rotten and there was a lot humitity in that area which worried me a lot. I did not know what was going on with the foundation.

Next day i got a foundation expert to take a look. He told me that we didn't need a French drain, but a membrane on the foundation would solve the problem. The problem is, that still after paying alot of money to replace the cement and place a membrane along the entire foundation, we are still getting efflorence along the inside wall. The company that we dealt with guaranteed 10 years without water infiltration. What do you think we can do? Thank you in advance, for your assistance. Regards, Hanoi - Hanoi 10/24/11

We are looking to buy a home and I see what seems to be efflorecence. It is in a small area of the basement. It is near the hose faucet. Also, we have had record rainfall in Maryland. Should I worry about this? Thank you in advance - Tim 11/1/11

i have recently been seeing the white patchs on my concrete walls in the basement. my neighbor had months of work done in their basement as they had been flooded. could whatever repairs they had done be redirected towards my property and that is why I am getting the efflorescence. My yard has always flooded in a big rain. - Diane 11/6/11

We recently saw a long line of red granular substance between the junction of the fire place brick wall and regular wall, was able to scrape it out, also saw it growing independently on the brick surface adjacent to the fire place, can't figure out what it is, can you please help. Thanks - Dipa P 5/23/12


Dipa: perhaps you can send us some sharp photos and we can make a more helpful guess - else we're flying blind except to suggest checking for water leaks, effloresence etc.

Drew: thanks for the nice comment.

Question: how to clean off or remove effloresence

Hello, I read most of your info about cleaning but I am a contractor who has used white vineger in a spray bottle. Just spray on heavy and the white stuff desolves and runs off the wall. However it is not a permanent fix it will grow back in its natural time span as before. I have never had any good luck with any latex sealers or paint in this situation. My next test will be using epoxy paint or resin. - Cleaning 7/9/2012


Cleaning effloresence: thanks for your comment. I agree completely that vinegar, being acidic, works very well at dissolving mineral salts such as may be deposited on a masonry wall by moisture moving through and evaporating off of the surface of the wall.

But because cleaning alone is pretty much irrelevant to fixing the leak and moisture problem that is causing the mineral salts effloresence deposit in the first place, in our article above we seek to accomplish two things: 1. show what effloresence looks like so that people don't mistake it for mold - it's not, and 2. explain that to fix the problem you need to find and fix the moisture at its source.

I also agree that surface sealers, being a last minute band-aid, are not effective if painted onto a wall surface or floor surface subjected to actual water pressure. The lifting power of water and effloresence salts is tremendous and can push such coatings right off.

What a wall sealant can accomplish, however, is interrupting the evaporation off of the surface of a masonry wall that sprouts effloresence because of a dampness problem rather than an actual water pressure or leak problem. And then such coatings work best if applied to a very clean surface.

Questions & Reader Comments: about effloresence in or on buildings

Wow this is by far the most informative and easily understood site on the subject of mould/effloresences, Thank you sooo much! - Erika 7/13/12

I have just built a new house with a concrete swimming pool, one side of the swimming pool is exposed on the outer wall, a couple of brown stains have appeared, as if the wall is seeping, the paint has also peeled, however when you touch the stain it seems to be dry, this has happened on 3 or 4 places along the outer pool wall which is approx 8 meters long, is this normall, pool is only 2 months old. - Tim Baldwin 8/24/12

Excellent site. Your photos are pretty good and I am fairly sure that I have effovescence 'growing' out of my concrete floor (This is after the area was jam packed with stuff for 4 months, no air circulation). My suggestion is to have pictures using more pixels so that one can zoom in on it to see a bit better the crystalline growth. - Jan Luthe 11/5/2012


Jan, thanks for the suggestion, I'll consider how we might follow it.

Meanwhile, in the article above I already include photos of effloresence at various magnifications ranging from the naked eye to stereo microscope to high power microscopic examination - but they are individual images.

I've kept all InspectAPedia images as small files so that the web pages load rapidly. I would welcome your opinion about how to balance these objectives.

Tim Baldwin:

Perhaps you can use the CONTACT US link to send me some photos? I'm not sure what's going on.


Thanks so much for the nice note; we work hard to make our information accurate, unbiased, and useful - and are thrilled when a reader has found it so.

Question: I've identified effloresence - it's not mold - the realtors were wrong; but how do I stop effloresence problems on a brick building?

Hi, After finding your very helpful site I've finally been able to determine that the white fluffy material and paint bubbling on several of our internal walls, is this efforvescence and not surface mould as the estate agents keep saying. However this confirmation in turn presents another problem. I have had to pull off and completely re-plaster and paint one of the walls already - when I did I found the walls were wet through behind the plaster, so I suspected rising damp or something anyway.

However now this stuff [effloresence] just keeps coming back. The house is rented and having told the estate agents (about what I thought was mold coming from the damp) I was told it was impossible since the house has had damp coursing.

This is an old house though and it was done after, with method of injecting some kind of sealant through drilled holes in the brickwork (i can see the drillmarks on the outside).

As I understand this isnt failsafe though and this efforvescence is coming up even on an internal wall (but mostly on the insides of the outer walls, but we do have a cellar under the house which gets damp - could this be the problem? I'm not sure how or what we can do to find or remedy the cause since I don't own the house and they will not listen, they just keep saying it's surface mould and to open the windows more!

I know it's not because the walls were so wet behind the plaster. I'm sick of living in a damp house and cannot afford to move, fix the problem myself or keep plastering the walls just for it to keep coming back seemingly with a vengeance! :( I've wondered if using dehumidifiers could help at all? Not sure what else I can do. - Hazel Leigh 12/10/2012



Yes you've correctly pointed out the underlying problem with effloresence. Unless we can interrupt or stop the moisture source the effloresence problems will continue.

Brick walls on older homes were often originally built with an air gap between the wythes in an effort to let moisture that (nearly always) penetrates the wall exterior run down the wall interior space to drain out at weep holes at wall bottom. It is very difficult to completely seal a brick wall exterior against moisture, so the old timers didn't try. Instead they provided a way for moisture to escape without entering the building interior. If you have this type of wall and there are no weep holes or they are blocked that couldbe part of the problem.

Search InspectApedia for (or use this link) BRICK WALL DRAINAGE WEEP HOLES to read our article that explains the cause & cure. \

Damp crawl spaces often are traced to improper handling of gutters & leaders or surface runoff.

Search InspectApedia for (or use this link) CRAWL SPACE DRYOUT PROCEDURES for some suggestions.

I agree that just plastering the interior won't cure the problem; the lifting-pressure of mineral salts and effloresence is very strong. Sealing an interior surface can slow the process by stopping the evaporation process on the wall interior that pulls moisture into the wall, but in my experience that won't be enough if there is a significant outside moisture source.

Send us photos if you can and keep us posted

Question: white fluffy moldy stuff growing in the shower

White fluffy effloresence mistaken for mold in a new bathroom floor (C) InspectAPedia MO'BWe just had our bathroom remodeled and we are finding white/fluffy moldy stuff growing in the shower.

Does anyone know what this is? We are using the other shower since we are afraid that this could be something dangerous. As anyone had this experience?

Any insight is greatly appreciated. - M. O'B 3/8/2013



Your photo (included here) looks like effloresence - described in the article above. An interesting question is why the mineral salts are growing just around a single stone in your new bathroom shower floor. When we see just a single very limited effloresence formation such as in your photo I speculate that it's due to an installation anamoly, perhaps a contaminated stone or a poor seal around this individual stone.

If the stone didn't seal properly in a shower floor, when the shower is used water penetrates around the stone, wets the area below, and leaves mineral deposits as water evaporates back up through the same passages.

On the other hand if you begin to see more of this white crystalline "growth" forming on your floor I'd be looking for a leak or moisture problem below the floor. You will want to discuss that with your contractor. Normally we can't fix effloresence by sealing the in-room surface, but in this case, and if the water is coming from the shower above the floor, it's worth a try. Let the floor dry thoroughly then try a small amount of sealer recommended by the installer.

Question: builder didn't want to vibrate concrete during wall pour

(Dec 28, 2012) Banda said:

I live in a new construction in Indiana - basement poured in May 2012 and moved in Aug 2012. I wanted the basement walls to be vibrated at the time of building, but the builder was quite surprised at the request - however did comply after requesting more money $$$. I have now noticed hairline cracks appear on all the walls - mostly vertical, but some diagonal as well.

One crack from the egress window resulted in a damp patch about the size of my hand and the concrete guys are to take a look at fix if need be. I also have the brownish dust (effloresence) on the walls which the warranty guy from the builder dismissed as "nothing to worry of". I have a dehumidifier running 24/7 at a setting of 45%).

Any tips on how I could convince the warranty guy and the concrete guy that the basement walls are more porous that they ought to be and that it needs to be addressed? Since the vibrartion of the concrete was not per the text book (the dip and pull was a lot quicker than it should) I have quite a bit of "pock marks" or honey combs where I think the air bubbles simply moved to the exterior and not bubble up to the surface - which I think is another reason for the moist walls (I get moisture readings from 0% to 100%). Thanks.


Banda I think vibration of concrete during a pour is intended to remove excess air and help avoid cold pour joints. IF you see leaks occurring at a cold pour joint or similar artifact it's reasonable to ask that the wall be repaired so as not to leak.

Other cracks in new concrete such as settlement (more serious) or shrinkage (usually not structurally serious) may also need to be patched to stop basement leaks.

Question: Effloresence on concrete walls in Northern Iraq

(Feb 4, 2013) Chrstine Goodman said:

Not sure how to approve my question below, but consider it approved :-). I'm quite eager to know what this stuff is, so appreciate your input. Thanks

(Feb 4, 2013) Christine Goodman said:

Here in N. Iraq we have stone tiles everywhere in the house. Only in the bedroom, however, are we finding this weird pure white, fluffy, cotton-like stuff a few inches from the concrete walls, parallel to the grout lines - not on top of the grout. It's a bit sticky. it has been quite rainy and we rarely heat the bedroom, so it stays at ca. 10deg.C I vacuum it up, and it returns the next day. I'm wondering if it's a health hazard, and what I can do to get rid of it permanently. Thanks for your help.


Christine it sounds as if you are describing effloresence. The two approaches are to fix the water source and to lower the indoor humidity. Lowering humidity alone may not stop the problem since moisture will still move through the wall.

Question: Builder omitted end of fascia, leaks into walls

(Feb 11, 2013) eddie said:

i recently had a new facier board fitted to the front of my house but the bulider forgot to put an end piece on it, shortly after fitting the facier we had very heavy rain for over a week and now my bedroom wall is full of white stains which i think is as a result of rain getting into the facier before the builder was called back to fit an end stop to the facier. Could this be efflorescence stains i'm now getting on the wall. the wall in question is not an outside wass but the adjoining wall to the house next door as i live in a mid terrace


I agree that water leaks at a fascia MIGHT pass across a soffit and into the building walls. It's worth a small test cut to inspect the wall cavity to have a more clear diagnosis.

Question: effloresence on stone fireplace

(Feb 27, 2013) Dick Jacobson said:

I have a rock fireplace and efflorescence is coming through the mortar. Will the white floffy stuff damage the integrity of the concrete?


Small amounts of effloresence are not likely to damage the concrete in mortar joints and might be a temporary artifact if the fireplace is new.

Watch out: inspect for chimney leaks or a missing or damaged chimney cap or crown: water leaking into the chimney can damage it and could make it unsafe.

Question: strange white powdery dust along edge of concrete repair

(Mar 31, 2014) Violet Adlam said:

Filled cracks in garage floor , several months ago ,noticed while sweeping today a white powdery dust along the edge of the repair ,what can this be .?


Can't say from just your note; concrete patch over-spread dust, effloresence, something else.

Question: how best to fix air & water leaks in an old stone foundation

(July 11, 2014) mainer said:

Please Comment My Older Stone Foundation.125 years old…..

This foundation has air leaks, efflorescence, and water leaks.

To energy retrofit I have been advised to apply spray foam on the granite and stone to two feet below the frost line on the interior foundation.

Some has been painted with stucco type waterproofing long ago, and some with a "blue paint" (why blue?).
There is old effervescence from the poor drainage (and no gutters) on the stucco type stone covering. And I cannot be sure that there will be more water pressure in the future. I need to apply the foam now before the winter.

What is best wall preparation for these stones?
Will future water behind the foam cause any problems?

I will have some exterior excavation and I am having the exterior stones re mortared( roof runoff caused them to frost and break away) and will re-slope the soil.

The uphill side of the house under the front porch I cannot access at this time .

I have been repeatedly advised NOT to put up gutters as most likely they will fail, I see around town evidence that people have lost their gutters due to snow, etc.

This site that you all have compiled is very useful,
Thank you.



Some buildings such as metal roofed barns can be difficult to keep gutters-on unless the gutters are installed below the fall line of the roof and snow guards (in snow country) are installed on the roof.

But if I inspect 100 buildings that have no gutters installed and that have basements or crawl spaces and that are in climates where there is much rain and snow, I will find water entry problems in 99 of them.

Start outside directing roof runoff away from the building. If you're not going to install gutters you'll need waterproof geotextiles below ground and surface grading to direct runoff away from the building - a much more costly approach than gutters but necessary in some situations.

I'd defer digging and installing a waterproof membrane and drainage system around the whole building outside unlness it were absolutely necessary or until other site work justified the cost and disruption of the excavation.

Inside you can't do a decent job of sealing the walls without removing soft friable stuff that may have coated them previously, though you could install a hard plastic barrier over the whole wall surface, directed to an interior perimeter drain.

(July 15, 2014) mainer said:

thank you Dan
for your prompt response,

I will regrade the exterior,
I will remove the effervescence before applying the foam,
apply the plastic barrier only where there is potential moisture problems to interior drain.
much appreciated.



Thanks for the follow-up. Keep us posted.

Before the actual re-grading, think about whether it's necessary (and cost justified) to cut away soil, grade the remaining surface to drain away from the building, then install a geotextile drainage system that will catch roof spillage below the eaves and absolutely keep it out of a basement or crawl space, directing that water to daylight well away from the building.

Question: Philadelphia row home stone foundation leaks & effloresence

9/1/2014 Matt said:


I recently purchased a ROW-HOME in the city of Philadelphia. The home was built in 1850 and has a stone foundation, stone 16" walls. I do not have access to dig around any par of the home. I am experiencing efflorescence in much of the basement, which does not bother me. I am assuming this is groundwater.

One corner of my house on the first floor has bloomed twice. Once last July (soon after i bought the house) and then again this July. I repaired a leak on the roof above the affected area and I also fixed a leak in my bathroom, also above the affected area. I thought I found the source of waterflow and repainted only to have the same issue occur a year later. The affected area is the original back wall of the home, a kitchen addition was added in the 50's.

My questions.

How far will a stone and mortar wall soak water up from the ground? (my issue is up to 4 ft high)

How far will water intrude from the roof, and not show up on the third and 2nd floor, only to affect the first floor?

I am currently running a dehumidifier in the basement 24/7. This is probably making my problem worse? since I am helping the water wick into my basement by lowering the humidity in that room. Correct?

I believe I have rising damp in this wall. Should I run for the hills? (I do not plan on spending thousands and thousands to fix this.)




I only run for the hills if threatened by earthquake, fire, mudslide, hurricane, flooding, or gunplay. Most building problems can be addressed, and often if we make a careful diagnostic inspection we can find inexpensive steps that can avoid a costly repair.

Although some basement de-watering companies and other folks refer often to "high ground water", few builders, including those building in Philadelphia 125 years ago, were foolish enough to knowingly build a basement or crawl area below the local high water table. Much more often, I'd estimate more than 90% of the time, if we see damp or wet basements or crawl spaces the water therein is coming from roof spillage or surface runoff.

Often a close look at the moisture or leak stain locations and patterns will show leak stains high on the wall, confirming that diagnosis and even pointing to a principal water source such as a downspout by a building corner or a gutter spilling along the building wall.

"Rising Damp" is a legitimate concern in some structures. Rising damp is a term that describes the migration of moisture by capillary action (water molecules) upwards from damp soils even where there is no significant actual water in the soil. Rising damp can indeed migrate up several feet above the surface of the soil.

In the UK and some other locations foundation builders include an impermeable or low-permeable barrier low in the foundation wall to impede this moisture movement. But for an existing foundation wall such a move is impractical and costly unless for other reasons a foundation needs to be rebuilt.

For the home you describe, Matt, I would first make a very careful outdoor inspection of the roof drainage and surface grading conditions around the home. No dehumidifier can keep up with actual water entry from exterior water leaks.

When you are certain that there is no actual roof spillage etc. around the foundation, you may sill want to keep a dehumidifier going in the basement. I prefer dehumidifer models that can be set up to drain by gravity to an acceptable disposal source or if necessary I install a simple condensate pump to keep the dehumidifier emptied.

You are quite correct that when you dry the basement area you increase the molecular-level movement of water molecules through a damp foundation wall: in effect we're pumping moisture into the building. That's why I want to focus first on outside water leak prevention.

In the most extreme cases of very leaky stone foundations where outside access to repair the foundation leakage is too costly or infeasible, I've seen successful indoor repairs made by pouring a new high-portland cement wall against the old stone foundation, possibly also including an interior trench and drain system as well. But in my opinion that's a last resort.


(Sept 5, 2015) how old is the efflorescence? said:
OPINION - how old is the efflorescence?:

We had a leak in the toilet above a basement floor water level was about 1/4 of an inch that had exposed concrete in about three places. Water sat for about 12 hours. We wiped it up and using a dehumidifier dropped the humidity to 50% (from 70%) in the basement and had a "white growth" just like your picture above. Notice this about 5 days latter. white cotton-like substance on the foundation wall or on a plaster wall

Yelp, that is what I have. Thank you so much for your artical, now that I understand it I don't have to worry about it. What a relief. Thank you again. Donna R


(Sept 9, 2015) Martha said:
We have 3 rooms in one corner of our home that have a musty odor, dampness inside the ac duct registers and, most recently, efflorescence and other discoloration around the edges of the duct register. We have a new, powerful, AC unit installed within the past 2 years when the musty odor started. Last summer we removed the carpet from the entire house and replaced with hardwood. we also replaced all the windows with highly efficient models. No other rooms of the house have this problem. My husband went into the attic and found nothing unusual with the vent "boots." We have called our AC installation and service company who will be out this week to evaluate. Do you have any thoughts about cause?


Look for condensation accumulating in or on the ductwork; lost duct insulation.

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