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Interior Mold: Causes,Prevention, and Remediation

-Charles Graves Painting

Best remediation company VA.webp

A somewhat common scenario that we see with new customers who call us for mold remediation, basement finishing, or bath remodels: They have mold growing on some of their interior surfaces (most commonly basements, crawlspaces, bathrooms, or attics), and this is virtually always accompanied by elevated moisture levels originating from somewhere in, on, or around the home. Remediating interior mold starts with identifying and eliminating the source of the water/moisture intrusion, then drying out the home. Once that is accomplished, the next step is remediation (this involves a long process- see bottom of page for full remediation process.) 


What are our mold/mildew qualifications?

As a certified mold remediator and inspector with PMII and OSHA, I (Charles) have received both private and government training on mold remediation, prevention, and inspection. This covers mold, mildew, fruiting bodies, and all types of microbial growth.  Our company has specific staff members who's sole job is to remediate mold and mitigate water damage- often these are very serious situations. (Our painters and project manager are also trained on the proper steps to avoiding mold on exterior paint projects as well.)

In addition, we are also a Class "A" Licensed Contractor in both PTC (Painting Specialty), and HIC (Home Improvement). Our combination of mold remediation and Home Improvement proficiencies are important for us to not only remediate the mold, but fix the structure so as to eliminate the cause of moisture and bring everything back up to code. 

What is mold? How does mold work?

Mold and mildew are both small, multi-celled microorganisms in the "fungus" category. Fungi are eukaryotic organisms; i.e., their cells contain membrane-bound organelles and clearly defined nuclei. Mold and mildew spores are between 2 to 100 microns, and colonies can grow significantly larger. Mold and mildew are both spread through spores, which are non-living reproductive cells. Living mold and mildew give off spores into the air, which are carried by wind and land onto surfaces. (Some mold releases mycotoxins, see next paragraph for more information.) From there, if a surface is suitable for mold or mildew growth, the mold or mildew spores will germinate into mold colonies. Mold then generally eats into the surface, whereas mildew (thankfully) tends to remain on the surface in a powdery form. Mildew is more likely to impact plants; mold is more likely to impact non-living carbon-based food sources, like wood, paper, paint, etc. Most types on paint tend to be mold, not mildew; but are often misclassified as mildew. Mold tends to eat currently non-living substances with carbon-based organic compounds (things which certain elements of it were once alive but are now non-living), such as drywall, wood, paper, cellulose, insulation, paint, carpet, etc; Mildew tends to eat and colonize on currently living plants. All types of fungus are heterotrophs; they feed off of absorbing dissolved molecules. All mold and mildew needs 4 things to grow and reproduce- air, water, a food source, and a suitable environment for mold/mildew.


Why is mold a problem/risk?


Mold affects everyone differently, but in general, mold causes health problems in people for 2 main reasons: 1) Allergies, due to the immune response to mold spores. This occurs whether or not the mold is releasing mycotoxins, and allergic sensitivity to mold varies between people. Mold allergies can cause, among other symptoms: runny nose, sinus congestion, itchy skin or throat, hives, wheezing, irritated or itchy eyes, lung irritation, coughing, etc. The symptoms for this are similar to allergic rhinitis. 

2) ​When mold releases mycotoxins, it can cause more serious issues in people over long periods of time. (Note: not all strains of mold release mycotoxins, and contrary to an unfortunately popular myth, A) black mold is not the only types of mold which release mycotoxins, and B) not all black mold releases mycotoxins. This myth was started because what's known as the worst mold strain, Stachybotrys Chartarum, releases very harmful mycotoxins. However, on average, black mold is more cause for concern because of the potential of it being Stachybotrys.) Lab tests can confirm the mold strain; however, the wisest and most straightforward course of action is simply eliminating the underlying causes of the mold, then remediating the mold, following our mold remediation process (see bottom of page). The other flaw with mold testing is that air is constantly circulating; and if you have issues which are causing mold to grow, harmful mold strains that *do* release mycotoxins could simply colonize and grow later. It could be as soon as a couple weeks after you do testing. This is why mold testing, or even remediation, without first eliminating the underlying causes of mold, is simply a fool's errand; it's a momentary false feeling of security, without actually solving the cause of the mold. 

What causes interior mold?

Mold colonizes when mold spores are present in the air, and when 4 other factors are present: There is air, water, a food source, and an environment suitable for mold, within any cubic area.


Since air always contains varying small levels of mold (known as EAL, or environmentally acceptable levels) which could colonize under the right conditions; and since homes will always have air, and always have some carbon-based pre-organic building materials; the correct method to eliminating mold is to first eliminate any sources of moisture where moisture shouldn't be present. Then, after, to remediate.

What causes moisture where it shouldn't be present? Here are the top 5 likely causes, from most to least common. Note: There are many, many more potential causes of moisture intrusion, so don't feel stuck if none of these apply to you. If we are hired, we do a comprehensive mold and moisture inspection, and our mold inspection checklist has over a hundred things we look for. 

-Hydrostatic pressure from wet soil, in an improperly waterproofed basement. This is because a large majority of homes currently in existence were not waterproofed when first built by the builder; and because Northern VA is in the Piedmont region, with very wet soil; and because it isn't an inexpensive endeavor; a large amount of basements have been neglected. This results in moisture (water) seeping through the foundation walls and concrete slab, to equalize the moisture content between the 2 mediums. And often this moisture remains trapped inside the basement walls, allowing mold to colonize and impact the IAQ (indoor air quality) in the process. 

-A plumbing leak- whether large, or a steady drip- in plumbing pipes or plumbing items. Broken seals, clogged pipes,  corrosion, electrolysis (from copper pipes being directly connected to zinc pipes, which shouldn't happen and causes a chemical exchange of electrons that corrodes the copper), accidental nail shot through the wall, an improperly waterproofed shower, improperly primed and glued plumbing joints, old or leaking toilets or sinks, only re-doing the shower pan but not the rest of the floor (resulting in a leak at the connecting point of main floor tile to shower curb), chemical drain cleaners, and high-velocity water, are a few causes of plumbing-based leaks. 

-Leaking roof. Poor installation; lack of, or improperly installed, waterproofing; lack of, or improperly installed, or damaged, flashing; lack of sealant used where needed; puncture; general age of roof; incorrectly installed skylights; etc are all things which tend to preclude a roof leaking. 

-Leaking HVAC unit. Clogged condensate drain, clogged pipe, condensate pump is damaged or malfunctioning, evaporator coil is damaged or malfunctioning, damaged drip pan, damaged/open duct, etc. 

-Exterior water run-off issues. There are many potential causes for this- a few include clogged or damaged gutters or downspouts, not having downspout extensions and underground extensions where needed, grading issues, etc. 

There are many more causes- our goal on every single inspection is to identify all of them. 

There are also causes of higher-than-normal outdoor mold growth on both your home and your surrounding environment/yard, which can in turn impact IAQ, so we also will give recommendations on this as well. 

What is our mold remediation process?

Prior to sending you a proposal/contract or doing the process, we do a FULL MOLD AND MOISTURE INSPECTION to inspect the interior and exterior of home, including grounds, attic, foundation, gutters, inside walls, surfaces, etc for moisture issues that may cause mold or microbial growth in the future. If any are discovered, we will assess the scope of mold remediation needed to eliminate the mold. We will determine whether it is a condition I, condition II or condition III. It is important that all moisture problems be identified and eliminated prior to or during the remediation process.  


The remediation process can vary in whether or not we use a biocide, (although we usually do, with few notable exceptions), and a few other minor ways, but generally our process is as follows: 

1) Completely turn of all A/C units, and plastic off all vents, and the return system. Create a double-entry zipper containment chamber for entry into mold contaminated area, and seal off the mold remediation area completely with 6mm plastic sheeting.

2) create negative air pressure through the use of an industrial fan and ventilation system bringing air out of the building. This is necessary to prevent mold spores from getting into the vent system or redistributed throughout the building.

3) As the process is going on, we will be using a HEPA VACUUM (throughout), DEHUMIDIFIERS, and AIR SCRUBBERS (throughout). Our company currently owns 3 Force Air 2000 high volume air scrubbers, 3 Vantage commercial-grade 1500 dehumidifiers, 4 Dri-Eaz commercial-grade compact dehumidifiers, and all of the other equipment necessary to professionally complete your mold remediation project safely, completely, and efficiently. The air scrubbers clean the air, trapping mold spores. The HEPA air purifiers further help eliminate any mold spores at the end of the project. The HEPA vacuum allows our crew to vacuum up mold spores, and other materials, without blowing dirty air out. (The HEPA vacuum blows out cleaned filtered air, and doesn't allow mold spores to exit the vacuum. HEPA vacuums are specially made to target contaminants between 1 and 5 microns, which includes mold. NIOSH recommends HEPA filters and air scrubbers during the mold remediation process.).

4) The next thing that we need to do is spray down all mold-infected surfaces, immediately prior to removal. (When mold is wet, it cannot spread its spores through the air.)

5) Then, tear out all old drywall, and all old insulation, all old carpeting, padding and tack strips, and any other mold-infected porous items or surfaces, double-bag in sealed bags, and dispose of it outside. We take the bags outside through the nearest exit to avoid potential spores exiting the bags and contaminating other parts of the home. If it is a basement, we take out a basement door or window. If it is an upstairs bedroom, we take bag through window, unless it is not feasible to do so. 

6) Examine the wood framing. Any rotten or moldy wood should be replaced. For moldy framing that cannot be replaced without incurring significant cost (such as load-bearing framing), it should be scrubbed and cleaned with a biocide/moldicide/mildewcide, then encapsulated. Compromised joists that have been damaged from mold enough to hinder their load-bearing capacity must be doubled-up or reinforced to ensure the structural integrity of that joist.

7) Cleaning all hard, nonporous surfaces with an EPA-approved biocide or antimicrobial, if necessary (sometimes bleach and water, but never a mixture of bleach and ammonia). Sometimes, water may need to be removed from cinderblock or brick with a wetvac, depending on the site conditions.


8) During this entire process, dehumidifiers and air scrubbers will be cleaning and eliminating any excess moisture. We will do a surface check before proceeding to step 9.

9) Encapsulate all of the framing and wood in the infected area, to prevent future mold growth and to encapsulate against future moisture penetration.


10) Then, we install new drywall (and cornerpieces), tape the drywall, apply 3 layers of joint compound, then sand, prime and paint 2 full coats. We use a moldicide additive in the new paint, also, to help prevent against mold growth in the future. That way, any few and far between spores, or new spores in the future, would not be able to take hold of those surfaces.

11) Vent cleaning is very important part of mold remediation. Vent cleaning should be done both prior to and after mold remediation. 

Mold remediation technology continues to evolve and improve, and research continues to be conducted, so these steps may be updated in future. However, no amendments to existing contracts will be made without customer written approval. These steps are subject to variance, and are not to take the place of a written contract. Every specific job has its own site conditions. 

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