Dealing with Water Intrusion and Mold Problems in Houses

Mold problems are more common, but can be easily managed if done so properly.    Decker Home Services

By William Decker, CMI, Illinois State Licensed Inspector


Mold problems (uncontrolled fungal growth) are increasing in houses.  National TV programs have covered this issues in great detail, although they usually get many of the details wrong (TV reporters get it wrong?  Go figure!).  This problem is, mostly, the result of "tighter" buildings (better insulated and sealed), increased efficiency heating systems, newer and less expensive building materials and recent design trends like finished basements and attic areas that are not properly constructed to properly manage water and moisture.  With new building materials and construction techniques, there are always going to be unintended consequences.


While mold can be a serious problem, it is easily manageable and avoidable.


What is Mold:

Mold is an organism that is kind of a mix between being a plant and bacteria.  Mold "spores" are always in the air, just like pollen from weeds and flowers.  Normally, this causes no problem, except for those few people who have allergies and get runny noses and sneezing during allergy season.  It's not the mold spores in the air so much as the concentration of these spores that cause the grief.  Spring and fall are the prime mold count seasons, at least in this area (greater Chicagoland area), but that can change based upon rain patterns and temperature differential.


These mold spores, which are in the air both inside and outside your house, can find areas where there is warmth, water and food.  When this happens, the mold starts to grow.  The more mold growth, the more spores are produced and the increased concentration of these spores cause problems.  When this happens in a house, the mold spores multiply and cause the irritation.


First Things to Remember:

What you have to understand:  Mold is NOT the problem, mold is a SYMPTOM of a problem.  The actual problem that causes the mold growth in a house is water intrusion of some kind.  This intrusion can be in the form of liquid water (like from a roof or pipe leak) or from excessive water vapor (excessive humidity in an attic area or a poorly ventilated bathroom or crawlspace).  If you remediate the mold, but do not fix the CAUSE of the mold growth the mold will grow back and you will have wasted a lot of time and money.  Hiring a professional Home Inspector who is specifically trained in thermal imaging and has experience with water intrusion and mold problems and will help to solve the actual causes of the problem and not just gloss over the results.  Too often, my clients are overly focused on the mold and not on the cause of the mold.


When dealing with mold, the simple equation to remember is WATER + FOOD + TIME = MOLD GROWTH.  Fix the cause of the water problems and eliminate any one of these factors and the mold growth problem is solved.  To understand this, let's look at each one of these variables.



Water can enter a house in many ways, and it will do so in all possible ways.  People are mainly concerned with water entering their house through a leaking roof.  While this does happen, it is much more common to have ceiling water leaks caused by bad attic ventilation, condensation problems and improper attic insulation and ventilation or un-vented bathroom exhaust fans.  Water can also enter a house through badly installed windows and doors, plumbing leaks and badly flashed masonry copings.  Remember that water has three forms, liquid, solid and vapor.  Ice dams caused by non-professional attic insulation and poor ventilation will cause water problems when they melt.  Snow can blow into an attic through roof and gable vents that are not professionally installed.  High indoor humidity levels, and the commonly seen the 90+ % humidity levels in our area (Chicago), is usually enough, in itself, to promote mold growth.


The most common concern is water intrusion into basements.  Remember, basements are really just big holes in the ground.  All basements are moist and with the modern trend towards having a "finished" basement, using paper backed drywall, mold has more food (the paper covering the gypsum core) and more places it can grow (behind the basement walls) than ever before.


All basements should be equipped with de-humidifier units and these should be run constantly during the warm months (April through October, in the Chicago area) to keep basement humidity levels low.  It does not take a couple of feet of standing water in a basement to cause a mold problem.  Most basements do not "flood" but only have minor seepage problems, as in small amounts of water dripping through minor foundation cracks and wall penetrations.  I have seen many new, but foreclosed, houses that have no plumbing leaks or roof problems that turn into "mold farms" simply because the outdoor humidity changes and the lack of "conditioning" of the inside air.


Mold Food:

Like all living things, mold needs food to grow.  The most common food for mold is cellulose, most often seen as paper.  Wood is also made of cellulose, but paper is a kind of "pre-digested" cellulose.  Wood develops mold problems, but usually in the form of wood rot which is harmless to humans.  Paper, on the other hand, is easy for less hardy and faster growing mold genus to grow on.  While it may take wood months to rot, paper faced drywall can be mold infested in as little as 48 hours.


Most of the new building materials are made of cellulose.  Wood is just densely packed cellulose.  Drywall is covered with paper which is made from recycled newspaper which is just ground up cellulose.  Even the now preferred, "green" blown-in insulation is just ground up cellulose, but I call it "mold food".  One of the largest sources of indoor cellulose is the lint that comes out of your clothes dryer if it is not properly vented and regularly cleaned.  We rarely see mold problems in older houses with plaster walls because plaster is not made of cellulose and does not provide food for the mold.  Many times, older houses that have never had any problems with mold, when they undergo remodeling, develop mold issues because the older plaster has been replaced with cellulose faced drywall.  It seems like mold had sources of food everywhere in your house.


If you are finishing your basement, instead of using drywall use wooden paneling.  DO NOT use "green board".  Many people, including most contractors, assume that since green board is a "water proof" (actually, only somewhat water resistant) form of drywall, that mold won't eat it.  This is not true.  Green board is still paper and the mold doesn't care if the paper is green or gray, it's still mold food.


Another solution is to use fiberglass faced drywall for the first wall course, closest to the floor.  If these products get wet they will not promote mold growth because the mold will have no food and the fiberglass will not wick the water upward.  When I was a kid, everyone finished their basement with wooden paneling.  It was cheap, easy to use and inexpensive to replace.  Even just putting paneling, like beadboard, for the first 4 feet at the bottom of the wall, maybe with a chair rail finish on top, would go a long way towards preventing mold growth.



Put water and cellulose together and add some mold spores (the "seeds" that mold grows from) and give it some time, and you will have mold growth.  Mold spores are everywhere because mold is a natural part of the environment.  The key is to not give the mold spores time to grow and rise to harmful levels.  If you experience a water problem in your house, the likelihood of developing a mold problem is directly related to how quickly you dry out the affected building materials.  If you get basement water, run a de-humidifier as quickly as you can.  You want to dry out the area fast (within 8 - 12 hours).  Fans DO NOT dry, they only move the wet air around.  You want to close the windows and run de-humidifiers.  Use a shop vac to remove as much water as you can, especially from carpets (and don't forget that under those carpets are carpet pads which are really just big, fat sponges).


Mold Types:

There are thousands of types of mold.  Mushrooms are fungi, just like mold.  Cheese is formed through mold growth on milk.  Buying fresh, "organic" vegetables and bring them into the house without cleaning them first will introduce foreign and exotic mold spores into your house.  If you have a lot of house plants, the number of mold spores in the air of your house is greatly increased because many molds grow on plants.  Additionally, when you have a lot of plants, you usually have higher humidity levels in the house air.  And remember that the spring and fall seasons bring a great deal of mold spores into the air when the windows are open.


Most types of mold are harmless to humans and cause no problems.  One commonly seen mold genus is common mildew, which we all see if we don't regularly clean our shower tiles.  Cladosporium is another common, but harmless, mold that causes wood to rot and is necessary (otherwise all dead trees would just sit around taking up space).  All these molds are usually harmless and occur naturally in outside air.

But is your house has moist cellulose sitting around some uncommon mold types will start growing to greater than normal levels.  Penicillium, the mold from which we get the antibiotic Penicillin, is a commonly seen household mold whose spores can cause allergic reactions in some people.  Aspergillus Niger is another commonly seen household mold that also affects some people, causing symptoms similar to the flu.  Because Aspergillus sometimes appears black in color, it is commonly mistaken for the "Toxic Black Mold" which is, in itself, a misnomer.  There are many molds that are black (like mildew) and are totally harmless.  The type of mold can only be determined by professional laboratory sampling and testing.  Just because you have some black stuff growing on your walls does NOT mean that you have "toxic mold".


The real "Toxic Black Mold" (I hate that label.  I causes so much unnecessary panic) is called Stachybotrys Chartarum.  Stachybotrys is especially dangerous not because of allergic reactions.  It produces mycotoxins, which many people react to as they would to nerve gas.  While very harmful, and even deadly, Stachybotrys is not common and is usually seen only in houses that have experienced long term water damage.  The trick is to not completely freak out and think that every little black spot is "Killer Mold".


How do you know you have excessive mold?

If you see discoloration on walls or baseboard near the floor, especially in basement areas or in the corners of exterior wall closets, this could be mold.  Look for areas of discoloration starting in circular forms (mold colonies) what spread outward and appear to wick up the walls, following the water.  If you see surface mold, there is no real reason to have the mold tested.  Regardless of the type or genus of the mold, the steps needed to remediate it are the same.  All harmful home mold growth should be professionally remediated regardless of the type.  If you are experiencing flu or cold like symptoms (runny nose, persistent cough, watery eyes, asthma like symptoms, etc) but do not see any signs of surface mold, there could be mold growing, unseen, behind your walls or in unseen attic and basement areas.  If no visible mold is seen, mold testing using air sampling can be done.  This testing will determine if the mold spore levels in the air is excessive and the type of mold that exists in the air.  It will also determine of any high mold counts are the result of an infestation or just caused because it is mold season.  Hire a certified (specially trained and equipped) mold sampling professional like a Home Inspector or an Industrial Hygienist.  Many mold remediation companies also offer to test for mold, but this is considered a conflict of interest and is unethical.


SPECIAL NOTE: Many people are under the misconception that mold can be washed away and killed using household bleach or other chemicals.  BLEACH IS COMPLETELY CONTRAINDICATED FOR MOLD REMEDIATION!  While commonly used for non-porous materials, like tile, using common household bleach to clean mold off of porous materials (drywall, wood, paint, etc) will only make the mold growth worse.  When the bleach breaks down the remaining chemicals actually serve as a sort of fertilizer for mold, making the growth come back faster and larger.  The type of chlorine based mold remediation products are only used for large scale, industrial, mold remediation have a much higher concentration of chlorine than is available for safe use by the general public and will cause lung damage (chlorine gas is dangerous!  Think World War I gas attacks)!   Mold remediation is a process that should only be done by licensed, certified, specially trained and insured mold remediation professionals based upon your specific conditions and level of infestation!  If you do only have a small amount to surface mold, try using hydrogen peroxide rather than bleach.  There are also mold cleaning products available in the big box stores, like Mold Control.  But "cleaning" mold with these products should only be done if the mold growth is very small and isolated.


As a general rule of thumb, you do not "clean" or "kill" mold.  You REMOVE mold.  This means REMOVING all removable building material that is infested.  Those building materials that cannot be removed (structural wood, etc) must be properly and professionally treated and encapsulated before putting the drywall back.  This can only be done after special training and with special equipment.  Don't try to save money by doing it yourself or hiring a fly-by-night company or your local general contractor or handyman.  Hire a professional.  If you don't, I can assure you that your mold problem will return and you will have to pay to have it done right anyway.  Trust me.  I see it all the time.


What to do if you have mold problems:

Regardless of the type of mold, the process of mold remediation is the same.  As previously stated, mold remediation is something that should that should only be done by specially trained professionals.  I have seen many instances where people with mold problems try to remediate "on the cheap", with very bad results.  Non-professional "mold contractors" wash the mold with a bleach solution but do not remove the affected building materials. In a matter of weeks the mold is back, and with a vengeance!  Remember, you can spend the necessary money doing the remediation professionally up front, or YOU WILL be paying for it in the end, on a much bigger and more expensive scale.

Interior wall corner.  No visible problems.

Thermal imaging reveals water condensation behind wall.

Mold revealed behind wallpaper.

Remember, before the mold is remediated, the SOURCE of the water infiltration should be determined and repaired.  If this is not done, the mold will return.  A professional home inspector with specific experience in solving water intrusion problems should be consulted.  Thermal imaging is an essential part of finding the cause of the water problem and fixing it before dealing with the mold.


Professional mold remediation involves multiple stages:

1) The affected parts of the house should be isolated.  This involves using plastic partitions and negative air pressure filtering machines to exhaust the spores outside the house.  This also involves closing off all HVAC ductwork that serve these areas with all ducts, furnace and air conditioning machinery properly cleaned.  Remediation workers will wear isolation suits and wear specially rated respiration devices.


2) Remove all the affected building materials.  The key to proper mold remediation is not to "clean" or "kill" the mold, it is to completely remove the affected building materials.  All drywall, non-structural wood members and insulation must be isolated (double plastic bagging) and removed from the house to be safely disposed.  Additionally, all clothing, furniture, carpeting and other household items should be removed and professionally cleaned by mold professionals.


3) Any non-removable building materials should be cleaned using specially designed vacuums and cleaning machines.  All affected  areas should be remediated using one or more of the approved mold killing processes:


Dry ice blasting




Ozone cleaning


Hydrogen peroxide


5) Once treated, all affected areas should be encapsulated to prevent further spore release of any mold that has survived (and some ALWAYS does).  This involves covering these areas with specially designed encapsulation paints which include fungicide chemicals.  Encapsulating the mold will stop its growth and seal it from moisture and the release of more spores.


6) The affected areas should be rebuilt, replacing the removed building materials with new wood, drywall and paint.


7) After the mold is professionally remediated, the affected areas should be re-tested, called clearance testing, using air sampling.  This testing should be done by an independent mold testing professional or home inspector specifically experienced with mold clearance testing.  The mold remediation company should not do the initial or clearance sample testing.  This is a conflict of interest and unethical.  If the clearance testing reveals that there are still excessive mold spore counts, the remediation contractor should be called back and further remediation done (at no additional cost!  Make sure that's in the contract.)  A professional mold remediation contract will include this condition.  Make sure that any remediation contractor agreement includes further work if clearance testing shows more mold.

Mold can be a problem, but if properly addressed, both in the mold problem aftermath and in the initial cause, it is a very manageable problem.  Above all. do-it-yourself fixes or trying to find the least expensive fix will only make the problem worse.  Remember, you will never get more than you pay for and your house is an investment worth preserving.