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Mold/Mold or efflorescence?


QUESTION: Hello, I have spent most of the past 10 years living in a small bedroom (10ft x 10ft), with little ventilation as I kept the windows and doors closed. There has been a white chalky bloom on my walls for as long as I remember. It has never got any worse than you can see in the attached pictures. Cleaning it is quite difficult, I used hot soapy water with a little bleach and wiped with a towel and gave it some elbow grease. 3 of the walls are plaster on brick, the 4th is just a thin partition wall after an extension, and the plaster is painted directly (no paper). All walls are affected by the bloom. Is this mold, or just a stain of some kind? I am a non-smoker. Thanks!

ANSWER: Barry,

Hard to tell the problem from these photos.  If the brick walls are even slightly moist during some seasons or after rain, then this could be efflorescence.  It does not look like mold.  If the room smells musty, then it could be mold.  If not, then it is probably caused from moisture in the plaster.  Have you considered allowing more ventilation?  That may help.  

Many factors may com into play here: type of heating system, is there central A/C, are the walls interior or exterior facing, are you above grade or below grade (in a basement), etc.

Feel free to ask additional questions and/or provide more information.


---------- FOLLOW-UP ----------

QUESTION: Hi, thanks very much for the reply! I live in the uk, so it's a bit of a colder climate here and I don't have an air conditioning unit. The heating system is gas central heating, and the room is located upstairs above ground level. I never thought the room smelled bad. The bloom was on all 4 walls. One of the walls is plasterboard to separate another bedroom and there is nothing on those walls. That room is a spare room though and not really lived in, also that side of the wall is papered.

The reason I'm asking is I've just finished gutting the room, replaced all the furniture, cleaned down all the walls thoroughly and put up new wallpaper with an anti-mold paste. I'll also be using a dehumidifier and a humidity monitor, and trying to maintain good air circulation. I'm a bit paranoid though that if its mold it will be in the walls and I'm just covering up its visibility.


If you are able to maintain the moisture content of the walls below 12-15%, and the relative humidity in the room below 50%, then even if there are dormant mold structures in the wall they should not be able to live or grow.   

Again, judging from your photos this does not appear to be mold, but instead some kind of leaching of minerals for some undetermined reason.  Hopefully your wallpaper will be an adequate cover-up.


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Steve Major (Principal -- Lakeland Environmental)


I can answer questions on indoor mold (fungal) infestations, indoor air quality, and indoor moisture problems. This includes mold testing, investigation, and remediation. PLEASE indicate your state or region, so I can provide the best possible answer.


I have extensive experience in the investigation, testing, and remediation of indoor fungal (mold) infestations, including the design and oversight of remediation projects, hands-on cleaning and removal, and safe work practices. I developed a successful mold remediator training and certification program, and have trained many mold workers and remediation supervisors in proper techniques. I have a strong knowledge of the ways in which moisture and airlow patterns in buildings can affect fungal growth and air quality.

BS Cornell University. IAQA Certified Mold Remediator. 40-hour HAZWOPER certification. NYS Department of Health Certified Training Director.

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