Mold Remediation - Best Practices
Mold remediation is a unique industry. Not only is the sector almost entirely unregulated, it also contains many divergent opinions on the very basics of methodology. Ask three mold remediation contractors for their opinion on a technique and you'll hear at least four different opinions. Our hope is to address this problem and provide a clear outline of the current best practices utilized by the premier mold remediation firms.
This document is not intended to provide a guideline for DIY mold remediation. Unless the area of mold growth is small and the cause of the moisture very obvious, professional cleanup is recommended. The EPA uses 10 sq.ft as the cutoff point, however in practice, the severity of the mold damage is a bigger determinant than the extent of the effected area. At a minimum, hire a local mold inspector to identify thoroughly inspect the issue.
ADDRESS THE SOURCE OF THE PROBLEM
Mold removal is a complete waste of money if the contractor doesn't first address the conditions that caused mold in the first place. As obvious as this sounds, many mold remediators don't feel this is an important part of the project. This is especially true among companies touting 'fogging' techniques. Beware of any mold removal contractor who doesn't insist on addressing the moisture problem first!
The source of the problem is often addressed by a different company than the mold remediator. A plumber, roofer or HVAC contractor is often involved in this step. You don't need necessarily need a mold remediation contractor who will actually address the underlying problem, you just need one who will request that it is completed prior beginning their work.
Common sources of mold remediation problems include:
Undetected plumbing leak
Bathrooms, kitchens and crawlspaces are most likely to suffer from hidden plumbing leaks. Plumbing failures can lead to both mold growth and wood decay (dry rot); the latter occurring much more often with slow leaks. If wood decay is present, framing and structural repair may be necessary.
Excessive indoor humidity
Elevated humidity levels will often manifest in mold growth on the interior facing surface of the exterior walls. The actual source of the humidity can range from inadequate ventilation or air conditioning, crawlspace flooding, vapor emissions or unusual occupant activity.
This one is pretty obvious. If groundwater enters a home, mold growth is a common result. As a general rule of thumb, if materials remain damp for more than 72 hours, mold growth is possible. With each additional day, the likelihood of mold growth increases significantly.
Air conditioning malfunction
A/C units can lead to mold growth through two avenues: condensation on surrounding surfaces, and clogged condensate lines. The former occurs when the temperature of the adjacent materials drop below the dew point, creating condensation. The latter occurs when the condensate/drip lines become clogged with debris and overflow. Both issues tend to cause localized, rather than systemic mold problems.
Siding / window failure
Though less common than many people imagine, windows and siding materials do fail occasionally. Thankfully, these issues rarely require large scale mold remediation. Most projects are limited to one or two windows, or one area of failed siding. When large scale siding failures
PREPARE SITE & ESTABLISH CONTAINMENT
Readying your home for a mold remediation is a straightforward task, with much overlap from traditional construction projects (remove pets, keep children away, etc). The most common question we hear is whether the homeowner must leave the site during the remediation project. Of course, much depends on the individual project, but in most cases there is no need to vacate the site. Remaining on site allows you to keep a close eye on the technicians, and also makes you available for any questions that may arise. This is especially true for projects where the mold remediation techs must decide whether an item should be salvaged or disposed.
Containment is primarily used in mold remediation to limit the movement of mold spores. However, dust and debris from other demolition activities such as sheet rock removal are also important to isolate and remove. Containment is constructed with a combination of existing structures (walls, ceiling, etc.) and temporary materials (poly sheeting, adjustable poles, etc.) Without proper containment, you'll likely cause more harm to your building and your health.
Exceptions - when containment isn't necessary:
- The area of mold growth is less than 5 sq ft.
- The entire building is contaminated and requires equal remediation throughout. This does not apply if the area of contamination is more severe in one area of the building. For example if the air quality testing indicates a wide dispersion of mold spores throughout a home, but the actual source of mold is a single wall, it is still important to setup containment in the area.
- Remediation is planned for only the attic space.
- Crawlspace remediation with an exterior entrance. If the access is within the home, construct a containment chamber from the hatch to the exterior.
Key equipment used in containment for mold remediation:
- 6 mil poly sheeting for walls
- Painters tape at all wall / ceiling junctions
- Zippered doors
- Negative air pressure (achieved with a HEPA air scrubber ducted to the outside)
Steps in the mold remediation preparation process
Step 1: Identify unique concerns:
- Vaulted ceilings. If you home contains vaulted ceilings, ensure your remediation contractor has a plan for containing the high ceilings.
- Drop ceilings. Primarily a concern for commercial buildings, drop ceilings present unique challenges because of the additional airspace above. Typically the best solution is to simply increase the CFM of the negative air machines to compensate for the air flow.
- Client access? Will the containment zone block access to critical facilities, such as the kitchen or only bathroom?
- Damage to existing materials. If the area undergoing containment was recently painted, damage may occur from the adhesive in the tape.
- Expanding work area. If additional damage is discovered, is the containment designed for easy expansion?
- Sound sensitivity. Will the sound of air movers and power tools disrupt adjacent occupants?
- Combustion safety. Are there any combustion appliances in the containment zone? If so, the negative pressure machines can back draft the exhaust and create a health hazard.
Step 2: Seal HVAC equipment and fire alarms.
- Major cross contamination can occur if supply lines or cold air returns are left uncovered during the mold remediation.
- The dust created by demolition can trigger certain styles of fire alarms. Often they can be covered with a plastic bag. However, check with your local fire department before disabling or altering any fire alarm or suppression system.
Step 3: Protect flooring
- Any material besides concrete must be protected prior to remediation. We recommend a combination of poly sheeting and hard board. In many instances, temporarily removing the carpeting is simpler than trying to protect it during the remediation. Hard surface flooring, though easily cleaned, are readily damaged by dropped tools, and therefore must be protected.
Step 4: Construct walls
- Containment walls are typically constructed of 4-6 mil poly sheeting, supported by adjustable tension poles. Clear sheeting is preferable, as it allows ambient light to enter the work space.
- Painters tape (blue or green) is then used to seal the containment walls to the existing structure. If sufficient CFM is acheived by the air scrubber, taping the ceiling junction is often unnecessary.
Step 5: Negative pressure
- Negative pressure is the most important aspect of constructing mold remediation containment. As the name implies, the technique creates a negative pressure differential between the containment zone and the adjacent area. This is achieved by drawing air from the containment zone and dispersing it to the outside. Typically this is performed with a HEPA air scrubber.
- Negative pressure must be sufficient to provent mold spores, fiberglass particles or other debris from leaving the air space. The pressure also must overcome the effects of opening the containment door when entering the work space.
Step 6: Air Scrubbers
- Air scrubbers are used to remove particulates, especially mold spores, from inside the remediation zone. This is achieve by using a fan to force large amounts of air across a HEPA filter media. As the air passes through the filter, the mold spores are trapped, while the clean air continues back into the room. When used in conjunction with ducting, an air scrubber can serve dual purposes as both a negative air machine and a filter.
REMOVE MOLD DAMAGED MATERIALS
Before beginning a mold remediation project, you must decide which materials you will dispose and which can be salvaged. Often the decision must involve both the remediation contractor and the building owner. Some materials are quite obvious; if carpeting contains visible mold growth, it must be discarded. Others, like books, leather goods and family heirlooms often have a value beyond mere dollar figures. Thus, the true value of the object must be weighed against the expense of cleaning.
Examples of materials typically disposed of during mold remediation:
- Damaged carpet and padding
- Sheetrock with significant mold growth
- Mold damaged contents, such as clothing
- Stuffed animals, soft toys
- Base trim
Examples of materials often salvaged during remediation:
- Non-upholstered furniture
- Sheetrock with light mold growth
- Electronic appliances and equipment
- Metal and hard plastic materials
Removing specific materials
- Unless the mold damage is exceedingly severe, the mold growth will only occur on the underside of the wood. Because of this, cleanup is rarely an option. After removing the hardwood floor, the subfloor must be evaluated for damage. In many cases, the sub floor does not require replacement, though dryout is often necessary. The key determinant in whether the subfloor requires replacement is the structural integrity of the material. Even if the mold growth is quite severe, structural damage may not be present. However, if delamination, bubbling or sponginess are present, replace it.
Laminate / Pergo
- Though extremely resistant to impacts and scratching, laminate floors are very sensitive to moisture. This is primarily due to the particle board construction found beneath the top layer of plastic. Like hardwood flooring, laminate flooring will rarely exhibit visible mold growth on the top surface. Even the backside of laminate is fairly resistant to mold growth. The problem occurs when the material swells and delaminates, causing irreparable damage. This can occur with or without mold growth. The pad installed beneath the laminate is most often the source of mold growth and musty odor.
- Removing laminate is straightforward, as nail and glue is rarely used. If installed above a subfloor, investigate for further damage or dryout.
- IICRC guidelines call for carpet removal in two situations: 1.) water saturation time exceeds 72 hours and 2.) Carpeting was exposed to category 2 or 3 water. I would add a third category: when the carpet in question is installed in a room suffering from a severe mold issue. Even if the carpet itself doesn't show signs of mold growth, the material acts like a giant sponge and absorbs any particulates in the air. This renders cleaning ineffective and in most cases, necessitates removal.
- Carpet should be removed by first cutting it into 3' wide rolls. Anything larger and the carpet won't fit into garbage bags. Unfortunately, this advice is often ignored. However, there is nothing more useless than setting up containment and HEPA air scrubbers, only to carry mold contaminated carpeting through the clean portion of a home.
- Removing vinyl flooring can range from quite simple to total nightmare. The difficulty depends upon two variables: 1.) How much glue was used 2.) How friable is the vinyl?
- If you're lucky, the vinyl will pull up in large, even sheets, as seen in the photo to the right. This is more likely to occur if the vinyl is relatively new (installed in the last 10-15 years). Older vinyl can become brittle and friable, requiring the removal of hundreds of fist sized pieces.
- After the vinyl itself is removed, use a floor scraper to remove the glue remnants. If the building owner intends on installing new vinyl in place of the old, the surface must be left very smooth. If carpeting will be installed instead, minor roughness or variations are acceptable.
- Removing sheetrock is a very common component of mold remediation. Thankfully, it is one of the easier materials to remove.
- Double check your carpet protection. Sheetrock dust ground into carpeting is very difficult to remove.
- Minimize the usage of circular saws when removing sheetrock. The aerosolized dust wreaks havoc on HEPA air scrubbers.
- Always use a utility knife to cut a border of the section to be removed. Even if the section slated for removal ends in a corner, always run a knife along the line. This will prevent tear out of the adjacent section. Use a level or chalkline to establish your cutline. It will produce a clean look and make the restoration contractor's life much easier.
- Remove as large of section as possible. This is best achieved by using your hands and a large 3' crowbar. A hammer will only produce small pieces, requiring extensive cleanup.
- Exterior corners must be dealt with carefully to avoid damaging the adjacent wall. A cat's paw is helpful for removing the nails beneath the corner bead.
Lathe & Plaster removal
- Heavy and highly friable, lathe and plaster ranks among the worst materials to remove. The following guidelines won't eliminate the annoyance, but they will certainly reduce it.
- Use a skill saw to cut the perimeter of the damaged section. If the area of removal extends to an interior corner, use a reciprocating saw with a fine tooth blade. A standard demo blade will often vibrate the wall excessively and damage adjacent areas. A multi-master tool can work well for small sections.
- Do not fill garbage bags completely full. The weight of the lathe & plaster will either blow out your back or explode the bag.
- If the building layout allows for it, use a wheelbarrow to transport the heavy garbage bags. Position the wheelbarrow directly outside of the containment area.
- Though mold growth on fiberglass is fairly rare, the material often must be removed as part of the overall remediation project.
- Removal is best done by hand - roll and place in garbage bags.
- If both fiberglass batts and blown-in insulation are encounter an attic space, batts are typically removed first. This is advantageous, even if they're on the bottom. By removing the batts first, this will allow you to make one pass with the insulation removal vacuum.
- Rockwool often comes in batt style pieces, which crumble when you attempt to remove it. These are too clumpy for the vacuum, but not consolidated enough to easily place in a garbage bag. There is simply no good way to remove them other than long hard work. A specially modified plastic rack can work well for dragging the insulation toward the center of the attic.
CLEAN REMAINING CONTENTS & MATERIALS
Nearly every mold remediation project involves a large amount of cleaning. For example, if the sheetrock was removed during Step 3, the underlying framing will likely require cleanup. Many remediation projects don't involve any material removal and are entirely limited to cleaning. The following is a brief outline of how mold remediation is often performed on specific materials.
Sheetrock mold cleanup:
- Lightly spray with water/mildicide mix.
- Wipe surface with disposable paper towels. Minor residual staining is acceptable. This will be dealt with during the encapsulation phase.
- Encapsulate with stain blocking latex primer.
- Notes: As a good rule of thumb, if the removal of mold growth also removes the sheetrock texture, stop cleaning and remove the sheetrock.
Framing mold cleaning:
- Spray entire area with mildicide. Allow surface to dry.
- Remove remaining 3 dimensional mold growth with wire brush or dry ice blasting.
- HEPA vacuum area.
- Apply stain blocking encapsulant. (Never apply encapsulant to wet wood!)
Carpet mold removal:
- Carpet cleaning should only be used in cases of low-level exposure. If direct mold growth on the carpeting has occurred, the carpet must be removed. Examples of low-level exposure include: 1.) Minor mold growth due to a plumbing leak on a nearby wall. 2.) Minor condensation based mold on wall behind bed.
- Carpeting cleaning must not leave behind significant quantities of moisture. Many commercial carpeting cleaning processes leave behind large amounts of residual steam or water. This of course defeats the purpose of mold remediation by creating a damp environment conducive to mold growth.
- Visually assessing the effectiveness of cleaning will not provide accurate results. Cleanliness must be assessed either by a non-viable air or a Carpet-Check style sample.
- Standard HEPA vacuum units, as described in the equipment section, are typically ineffective at carpet cleaning. This is due to their lack of an agitator unit mounted on the head. Without this, the vacuum misses the vast majority of the particulate matter and mold spores found deep within the carpet fiber.
Metal, Plastic or other hard non-porous surfaces:
- Spot test mildicide on an hidden portion of the material.
- Apply mildicide.
- Wipe down surface with disposable paper towels.
- Encapsulation is not necessary, as staining typically will not occur on non-porous materials.
Removing mold from clothing:
- If visible mold growth is occurring on clothing, disposal is recommended. If the item is of unusual value, cleaning can be attempted. The following mold remediation recommendations assume the clothing itself did not suffer from direct mold growth, but rather from settled spores due to nearby growth.
- Clothing that doesn't require dry cleaning can be laundered in a normal washing machine. Borax works well as a mild mildicide safe for most fabrics.
- If odors remain, consider dry cleaning.