Indoor Environment Quality-Mold In Existing Buildings And During Construction

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Navaid Ur Rehman,PMP,
M.Eng (Construction Management)
University of Alberta

This term paper is prepared as part of the graduate degree requirement. The report consists of two parts:
Part 1: Mold growth in existing buildings
Part 2: Mold during construction

In Part 1 four areas are discussed:
(1) What mold is, how and where it resides and the reason for mold growth (2) Mold health concerns (3) Investigation and evaluation of mold and (4) Mold control if it resides in indoor environments and what should the preventive measures be.

In Part 2 two main areas are discussed: (1) Mold free construction, preventing mold growth before construction and checks during and post construction (2) Toxic Mold Litigation and the number of mold claims have exploded in recent years in the US and Canada.

Mold, Health Concern, Risk Factor, Risk Control, Mold free Construction, Construction Claim, Moisture

Mold is a natural occurring fungi and is a part of the natural environment. It is found in nature, reproduces in the form of tiny spores, is invisible to the eye and floats through air. It grows indoors when mold spores land on surfaces that are wet and they can grow anywhere in the building when moisture is present. There are many types of mold, and they all grow in the presence of water or moisture.


There are over 100,000 mold species, According to The Centers for Disease Control and Prevention (CDC). Every mold could be harmful or dangerous to health or property. Following are the some common types of mold present in a building:

• Stachybotrys chartarum (also known as Stachybotrys atra) or Black mold
• Aspergillus
• Penicillium
• Fusarium
• Trichoderma
• Memnoniella
• Cladosporum
• Alternaria

black mold

Stachybotrys chartarum and Stachybotrys atra which is also called Black Mold is common in indoor environments. It is black in color and can spread by means of spores and the growth of root –like structures.

Mold can be found anywhere in the indoor environment and it can grow in the presence of moisture or dampness; mostly mold can expose on the following:

• Wood
• Drywall (plaster/gypsum/Sheetrock(R)
• Fabric
• Wallpaper
• Drapery
• Ceiling tiles
• Carpeting

Mold can also grow on the surface of materials that provide no nutrients, like steel and plastic. In such cases, mold utilizes deposited organic dusts. These dusts allow mold to grow on fiber glass filters. Mold also grows on metal and plastic furniture that has been subject to human handling (hand oils/skin scales apparently serve as the nutrient source).

Mold growth in buildings is not always visible. The majority of indoor mold growth issues are hidden inside walls, behind wall paper, underneath flooring or behind built-in cabinetry.

molds on walls

Moisture and water is the main culprit for indoor problems including mold growth. Conditions that are favourable in growth of mold spores are temperatures of 5.5°C to 55°C and moisture (Relative Humidity 70% or the presence of water on surfaces for 24 hours or longer periods of time but once infestation has taken place, mold growth can continue at lower relative humidity).

High relative humidity, cold floors, condensations, water intrusion and leakage and flooding are the main reason of mold growth.


4.1 High Relative Humidity
High relative humidity (?70%) is common in building environments, particularly residential buildings and houses. It occurs during wet weather. An inadequate drainage system is another factor and causes humidity. A high water table causes wetness in basements and substructures and water in the form of vapour moves into building interiors and relative humidity increases in the building. High relative humidity is due to the following reasons as follows.

4.1.1 Wet building sites
Wet building sites affect both the absolute and relative humidity in buildings. At a given absolute humidity, relative humidity increases as temperature decreases. Buildings maintained at relatively low temperatures and materials in basements 13°C are potentially subject to mold infestation. Significant mold growth may also occur on soil in crawlspaces because of wet surfaces and/or high relative humidity.

4.1.2 Occupant practices
High relative humidity also depends on behaviour and attitude of building residents. When thermostat reading is change just before sleeping time, relative humidity increases corresponding to the temperature decrease. Decreases in temperature will cause mold and mildew growth on cool surfaces. If Interior temperature drops 3 to 5°C then building or house may experience night time relative humidity around 70%. Consequently, mold infestation of building materials and furnishings such as draperies, mattresses, and carpeting may be common.

4.1.3 Water vapour-generating sources
High relative humidity occurs by using vapour-generating sources such as swimming pools, spas, steam baths, large fish tanks, and decorative recirculating fountains, pools, waterfalls and streams.

4.1.4 Poor air circulation
Air circulation plays a vital role. Poor air circulation is only a problem if combined with nutrient sources and increases of relative humidity. When furniture obstructs walls, it prevents heat transfer to wall surfaces, and wall cooling causes high relative humidity. Poor air circulation in homes that are not heated, have closed-off rooms and where furniture or other large objects are placed too close to walls could cause mold to grow.

4.2 Cold Floors
Mold infestation of carpeting in basements is common because floor surface temperature is approximately 13°C – the same as that of the ground surface temperature. Insulation systems should be adequate to prevent the cold floor surface.

4.3 Condensation
Condensation on interior building surfaces, within wall cavities is relatively common in residential buildings. Condensation problems may occur on or in exterior corners, at exterior wall/roof intersections, on thermal bridges, inside wall cavities, in ceiling areas, and on windows. Condensation commonly occurs on non-insulated plumbing lines and fixtures. These cold water lines in a relatively humid environment can result in considerable “sweating” and subsequent wetting of adjacent materials. Sweating occurs on toilet fixtures as well. Such sweating may cause mold infestation.

4.4 Water Intrusion
Intrusion of water from rain or snow melt is a common problem in both residential and non-residential buildings. Risk factors for the penetration of water through the building envelope include poor construction practices; deterioration and inadequate maintenance of roofing, flashing, and cladding; and storms that may cause minor to severe damage to roofing and cladding materials. Evidence of water intrusion in residential buildings has been shown to be a significant risk factor for elevated total airborne mold levels.

4.5 Plumbing Leaks and Flooding
Plumbing breaks cause major floods in buildings. Small plumbing leakage is common and causes mold infestation if maintenance does not occur in time. The chances that mold infestation will occur also depends on how quickly building facilities dry the wetted materials. If this can be accomplished within 24 to 36 hours, little to no mold infestation should occur. Sewage backups create mold infestation. Overflow of sinks and bathtubs are most common sources of flooding. Shower facilities are another cause.

Mold exposure poses significant health risk to humans. Mold is not usually a direct cause of infectious illness. More often, they trigger symptoms of allergies or sensitivities. They can be from mild, temporary reactions to acute or chronic illness.

One of the molds of greatest concern is black mold. This particular fungus can cause bleeding in the lungs, which can be potentially fatal for infants and pregnant women. When stachybotrys spores are inhaled into the lungs, they can weaken blood vessels and may cause nosebleeds or bleeding elsewhere in the body. This mold is found in wet areas.

The effects of inhaling mold spores includes three basic categories of disease:
• Infections
• Allergenic/Immunological illness, and
• Non allergic illness.

5.1 Medical Tests
Building residents may have mold allergies that cannot be accurately diagnosed using existing allergy tests. When a person is allergic to a mold, the tests cannot determine the exposure to the mold that where or when that person was most recently exposed.

Similarly, there is no specific blood, urine, or other medical test that can determine whether someone has been exposed to a mold toxin. Research work is being continuously conducted to develop such tests, but none have been shown to be accurate.

5.2 Studies Conducted Regarding Mold Health Concerns in US and Canada
Following studies have been taken from Health Canada and these studies were conducted in US and Canada. Studies show the trends of diseases due to mold. Trends show the increased rates of respiratory disease and asthma.

“Since 1982, in North America, approximately 30 studies have been conducted on the association between dampness, mold and respiratory health in residential housing. Studies in the United States and Canada have involved the largest number of people. A study of the respiratory health of 4,600 children from six cities in the northeast United States demonstrated that the presence of mold and dampness in their homes was correlated to several respiratory symptoms as well as a number of non-specific symptoms. The effect on the children was of similar dimension to parental smoking (Brunekreef et al. 1989). Two studies involving 15,000 children and 18,000 adults from 30 communities in Canada came to similar conclusions. The mold contamination was associated with a 50% relative increase in asthma and a 60% increase in upper respiratory disease (Dales et al. 1991a, 1991b). Data from a further 13,000 children from 24 cities across the United States (19 cities) and Canada (5 cities) show the same pattern (Spengler et al. 1994). The upper boundary attributable risk for mold-caused asthma in Canada was estimated at 20% (Dekker et al. 1991). The health effects of fungal contamination in housing remain significant even after adjustment for socio-economic factors, pets, household smokers, endotoxins and dust mites (Dales and Miller 1999; Dales et al. 1999).


A review published in 1995 by Health Canada and the Federal-Provincial Advisory Committee on Environmental and Occupational Health (CEOH) concluded that “. . . epidemiological studies have consistently detected an association with respiratory symptoms and home dampness and mold growth, but causality in these studies has not been established” (CEOH 1995a). The evidence linking exposure to indoor molds with adverse respiratory outcomes has also been reviewed by Verhoeff and Burge (1997). More recently, the US National Academy of Sciences Institute of Medicine released a report on asthma entitled Clearing the Air: Asthma and Indoor Air Exposures. The panel found that there was insufficient evidence on a population health basis for the association between indoor residential molds and the development of asthma, but that indoor mold was associated with exacerbation of asthma in mold-sensitized individuals, and exposure may be associated with respiratory symptoms. The percentage of mold-sensitized asthmatics is not known; estimates range up to 40% (Institute of Medicine 2000).

The purpose of this section is to update the review conducted by the Federal-Provincial Advisory Committee on Environmental and Occupational Health (CEOH) in 1995 by reviewing the research published since then on health effects due to exposure to molds in residences and nonindustrial workplaces (mostly office buildings and schools), and to determine whether the current evidence warrants more definitive conclusions. Health problems, such as hypersensitivity pneumonitis (HP) and organic dust toxic syndrome (ODTS) identified in industrial and agricultural settings due to greater exposure to molds (and, in some instances, other biological contaminants such as thermophilic actinomycetes)”.

5.3 Studies Conducted Mold Health Concern in Other Part of the World
These studies were taken from the Institute of Medicine (U.S.), and studies demonstrate the sufficient evidence of respiratory disease and asthma. There have been more than a thousand studies on the effects of mold in other parts of the world. Two studies of general interest found a correlation between the presence of mold and illness.

“Study, conducted in Finland, involved surveying more than 10,000 university students. The survey inquired about the dampness of their homes, whether they had asthma or other allergies, and how often they developed colds and other respiratory infections. Students who reported visible mold in their homes were more than twice as likely to have asthma.

A study conducted in the Netherlands evaluated 259 children with chronic respiratory symptoms and compared their medical histories with 257 children who had no symptoms. Among the children with respiratory symptoms, testing found that 24 children had elevated antibodies to mold. (Antibodies are an immune defense. This study tested for antibodies specific to mold, which would suggest the presence of a mold allergy.) Among the children with no symptoms, only 2 had elevated mold antibodies.”

Identification of mold shows the need for a solution to fix the mold problems and a detailed plan of how the mold is to be removed should be obtained.

6.1 Triggers for an Investigation for Mold
• Adverse health concerns
• Observations of growing mold
• Musty or Unusual odours
• Water intrusion
• High Relative Humidity

6.2 Evaluation of Mold
Canada Mortgage and Housing Corporation has given the recommendations in Table-1 & 2 on the basis of total affected surface area in sq.metres.

Table 1: Total surface area affected by Mold (Canada Mortgage and Housing Corporation
CMHC booklet Clean-up Procedures for Mold in Houses)

Total Surface Area Affected by Mold
1 or more patches, one of which is greater than 3 sqm 1 or more separated

patches, each smaller than 3 sqm

More than 3 patches, each smaller than 1 sqm 3 or fewer patches,

each smaller than 1


Expert Assessment and Cleanup required Expert assessment recommended, but homeowners may attempt cleanup using proper precaution Homeowner can attempt cleanup using proper precautions

Recommendations CMHC booklet Clean-up Procedures for Mold in Houses

Mold assessment is important to determine whether the building is indeed contaminated. A Proper mold assessment is based on the following:
• Interviewing
• Visual Inspection
• Tests
• Sampling

7.1 Interviewing
Canada Mortgage and Housing Corporation (CMHC) has given the following guideline for self interviewing or an Interview by a Mold Consultant to building occupants:

1. Does anyone in the building have symptoms related to indoor environment.
2. Does the house have a basement or crawl space.
3. Is it damp.
4. Does basement have a soil floor.
5. Are items that are stored in basement or crawl space stained, discoloured or have fuzzy growth or musty smell.
6. Does house have history of any of the following:
• Plumbing leak
• Flooding or water leakage
• Leaking roof, walls or windows
7. Are any areas of the house excessively cold and or drafty during winter.
8. Does condensation form on the walls or windows during winter.
9. Are there any water stains or mold on non-bathroom surfaces.
10. Has occupant or outsider noticed musty or earthy smell upon entering the house, basement or crawl space.

7.2 Visual Inspection
According to Jeffrey C. May, author of Mold Survival Guide, the first part of the investigation is a thorough walk-through, inside and out, including a look at all the mechanical equipment.

The aim of this inspection is:
• To find out the moisture problems
• To locate the amount of surface area that is affected by mold growth.

7.2.1 Conducting the Investigation
According to Canada mortgage and Housing Corporation, start inspection from the outside from top to bottom then the inside from bottom to top. Exterior or Outside Inspection
• Missing or lifting shingles, damaged siding
• Chipped or cracked brickwork or foundation
• Leaky or clogged eavestroughs
• No downspout or extension missing
• Water pooling against the foundation, soggy soil, moss, etc.
• Roof
• Chimney
• Flashing
• Cladding/Siding
• Windows
• Foundation walls (Concrete and masonry and preserved wood foundation)
• Drainage Interior or Inside Inspection
• Basement
• Wood framing
• Floors and flooring
• Ceilings
• Sump
• Living area
• Storage area
• Laundry area Mechanical Systems
• Heating and cooling system
• Humidifier/Dehumidifier
• Plumbing Exhaust ventilation
• Dryer
• Range hood
• Bathroom fans Miscellaneous
• Aquarium tanks
• Houseplants

7.3 Tests
CMHC booklet Clean-up Procedures for Mold in Houses has explained the mold and moisture tests that give the information of mold and moisture presence in the house or building.

7.3.1 Mold Tests Paper Swipe Test

Take a small strip of coarse paper and rub the suspected area of mold; if powdery residue rubs off onto the paper, it may be possible that this is mold. Bleach Test
Mark the stain with undiluted chlorine laundry bleach and check if color changes; after one or two hours if the color is removed, it means stain is organic and it can be mold. Flashlight Test
In dark area, hold your flashlight against the surface of suspected mold, shining the beam of light across or parallel to the surface; any irregularities of the surface like mold growth, appear as a fine fuzz.

7.3.2 Moisture Tests Sticky Tape Test

Check the dampness by using a small strip of tape but making sure failure to stick is not due to something other than dampness. Plastic Patch Test
This method can apply on walls or floors by affixing a piece of clear and medium weight plastic directly against the material. Seal this with tape and leave the plastic on overnight or longer and then remove the plastic and check any condensation on the plastic and that indicates the moisture. A longer time period for observation is needed. Moisture Meter Testing
Moisture meter testingis one of the most common tools or equipment especially in the construction industry to find out the moisture content of building materials such as wood, concrete and drywall.

7.4 Sampling
According to Jeffrey C. May, author of Mold Survival Guide, when doing sampling, make certain that:

• Every window and door in the house is closed
• Mechanical systems are shut off for at least an hour before investigation
• As few people as possible are in the house
• No pets in the house
• Be in the house
• No cleaning or other maintenance work be undertaken

Basically there are three types of sampling:
10 Bulk sampling
10 Air sampling
10 Surface sampling

7.4.1 Bulk Sampling
It involves the removing of part of the contaminated material and placing it in a sterile container and for lab analysis; if sample is dry it should keep in airtight container (plastic).

7.4.2 Air Sampling
There are two types of air sampling; the first type is culturable air sampling and the second type is spore-trap sampling. In the first type, sampling is undertaken to identify if spores are alive and can grow. In this type, spores are sucked by vacuum pump into impactor and trapped in a Petri dish which has a nutrient surface and then the sample is placed in lab incubator and left for 7 to 10 days. In Second type of air sampling, air is drawn through blower and pump, and suspended particles including viable and dead spores are trapped on a sticky surface such as grease or tape. Then the sample can be stained and examined under a microscope. Author suggests that one or two samples should also be taken of outdoor air for comparison.

7.4.3 Surface Sampling
In surface sampling, settled dust or growing mold is removed by vacuum or with sticky tape or wiped with dry swab and observed under the microscope. Another way of surface sampling is to rub a damp cotton swab on surface and place it in a sterile container. The organism on the swab is then transferred to nutrient and incubated.

Author recommends sample the dust because air sampling is expensive and he also suggests the occupants to take carpets, cushions, pillows and then send these samples to lab. Concentration Qualitative Assessment of Contamination
American academy of allergy, asthma and Immunology (AAAAI) presents the total concentration of spores:

Low concentration——- —–fewer than 6,500 spores per cubic meter of outside air.
High concentration———— above 13,000 spores per cubic meter
Moderate concentration—– between 6,500 and 13,000 spores per cubic meter
Very high concentration——above 50,000 spores per cubic meter

All mold contamination can be removed or controlled. There are two approaches to deal with mold problems; one is preventive action and the second is to fix the problem after mold exposure.

8.1 Moisture Control
Excessive moisture in the air is main and complex problem, but it can be resolved. Some of the indications of excessive moisture in the home are:

• Condensation, on the inside surface of windows.
• Damp spots or stains on ceilings or inner surfaces of exterior walls.
• Mold growth on walls and ceilings.
• Peeling or blistering of exterior paint.
• Moisture on basement walls and floors.
• Sweating water pipes.

8.1.1 Controlling Humidity
Relative humidity is maintained within the ranges of 25 to 50 percent. Maintaining a proper humidity level isn’t always easy.

Basic life style such as cooking, cleaning, bathing, washing clothes and dishes, drying clothes, breathing and perspiring can raise the humidity level too high. To avoid humidity it is necessary to deal with the amount of water vapor in the house. We can control humidity by two means; one is by changing living style habits and the second is by using mechanical equipment like exhaust fans in kitchen and bathrooms, dehumidifiers in living and bedrooms, and air-to-air heat exchangers.

8.1.2 Vapor Barriers
Use those construction materials that have highly resistant to vapour movement.

8.1.2 Ventilation
Proper designed ventilated areas to improve air movement. Use fresh air ventilation.

8.1.3 Condensation
Cold areas where condensation occurs, make that surface warm.

8.2 Fixing the Mold
US EPA and CHMC have defined several methods of cleaning and removing the mold contamination permanently. Cleaning of mold with different methods can fix the problem.

8.2.1 Wet Vacuum
Wet vacuums collect water. Vacuum water from the area where water is present such as floors, carpets, and hard surfaces. Avoid using vacuum porous materials, like gypsum board. It can only be used when materials are still wet; if sufficient amount of water is not present this vacuum may spread mold.

8.2.2 Damp Wipe
Mold is allergenic and toxic. Mold generally cleans from hard surfaces by wiping or scrubbing with water, or water and detergent. Dry these surfaces quickly and completely to avoid further mold growth. Since molds infiltrate porous substances and grow on or fill in empty spaces or crevices, the mold can be difficult or impossible to remove completely.

8.2.3 HEPA Vacuum
HEPA (High-Efficiency Particulate Air) vacuums normally are used for final cleanup of remediation areas after removal of contaminated material.

8.2.4 Discard
Building materials and furnishings that are contaminated with mold growth and are not retrieved can usually be discarded as ordinary construction waste. Mold contaminated materials should be placed in sealed bags before removal from the effected area to minimize the spread of mold spores throughout the building.

US EPA has explained mold remediation and cleanup guidelines in Table 3 & 4.

Table 3: Water Damage Cleanup and Mold Prevention (US EPA)

Water Damage


Action needs to be taken
Books and papers •  For non-valuable items, discard books and papers.

•  Photocopy valuable/important items, discard originals.

•  Freeze (in frost-free freezer or meat locker) or freeze-dry.

Carpet and backing – dry within 24-48 hours •  Remove water with water extraction vacuum.

•  Reduce ambient humidity levels with dehumidifier.

•  Accelerate drying process with fans.

Ceiling tiles •  Discard and replace.
Cellulose insulation •  Discard and replace.
Concrete or cinder block surfaces •  Remove water with water extraction vacuum.

•  Accelerate drying process with dehumidifiers, fans, and/or heaters

Fiberglass insulation •  Discard and replace.
Hard surface, porous flooring (Linoleum,ceramic tile, vinyl) •  Vacuum or damp wipe with water and mild detergent and allow drying; scrubbing if necessary.

•  Check to make sure under flooring is dry; dry under flooring if necessary.

Upholstered furniture •  Remove water with water extraction vacuum.

•  Accelerate drying process with dehumidifiers, fans, and/or heaters.

•  May be difficult to completely dry within 48 hours. If the piece is valuable, you may wish to consult a restoration/water damage professional who specializes in furniture.

Wallboard  (Drywall and gypsum board) •  May be dried in place if there is no obvious swelling and the seams are intact. If not, remove, discard, and replace.

•  Ventilate the wall cavity, if possible.

Window drapes •  Follow laundering or cleaning instructions recommended by the manufacturer
Wood surfaces •  Remove moisture immediately and use dehumidifiers, gentle heat, and fans for drying. (Use caution when applying heat to hardwood floors.)

•  Treated or finished wood surfaces may be cleaned with mild detergent and clean water and allowed to dry.

•  Wet paneling should be pried away from wall for drying.

Table 4: Remediation guidelines for building materials (US EPA)

Material Affected Cleanup Method

Small – Total Surface Area Affected Less Than 10 square feet (ft)

Books and papers HEPA Vacuum
Carpet and backing Wet Vacuum, HEPA Vacuum
Concrete or cinder block Wet Vacuum, HEPA Vacuum
Hard surface, porous flooring (linoleum, ceramic tile, vinyl) Wet Vacuum, Damp Wipe, HEPA Vacuum,
Non-porous, hard surfaces (plastics, metals) Wet Vacuum, Damp Wipe, HEPA Vacuum,
Upholstered furniture & drapes Wet Vacuum, HEPA Vacuum
Wallboard (drywall and gypsum board) HEPA Vacuum
Wood surfaces Wet Vacuum, Damp Wipe, HEPA Vacuum,

Medium – Total Surface Area Affected Between 10 and 100 (ft)

Books and papers HEPA Vacuum
Carpet and backing Wet Vacuum, HEPA Vacuum, Discard
Concrete or cinder block Wet Vacuum, HEPA Vacuum
Hard surface, porous flooring (linoleum, ceramic tile, vinyl) Wet Vacuum, Damp Wipe, HEPA Vacuum,
Non-porous, hard surfaces (plastics, metals) Wet Vacuum, Damp Wipe, HEPA Vacuum,
Upholstered furniture & drapes Wet Vacuum, HEPA Vacuum, Discard
Wallboard (drywall and gypsum board) HEPA Vacuum, Discard
Wood surfaces Wet Vacuum, Damp Wipe, HEPA Vacuum

Large- Total Surface Area Affected Greater Than 100 (ft)

Books and papers HEPA Vacuum
Carpet and backing Wet Vacuum, HEPA Vacuum, Discard
Concrete or cinder block Wet Vacuum, HEPA Vacuum
Hard surface, porous flooring (linoleum, ceramic tile, vinyl) Wet Vacuum, Damp Wipe, HEPA Vacuum,Discard
Non-porous, hard surfaces (plastics,


Wet Vacuum, Damp Wipe, HEPA Vacuum,
Upholstered furniture & drapes Wet Vacuum, Damp Wipe , Discard
Wallboard (drywall and gypsum board) HEPA Vacuum, Discard
Wood surfaces Wet Vacuum, Damp Wipe, HEPA Vacuum, Discard

Mold can affect health and damage the home. It can spread everywhere. Inhalation and smell of the mold can cause health problems. Asthma, respiratory, allergies, irritation and headache are the common diseases.

Fix or control the moisture and water to get rid of mold. Try to avoid wetness or dampness in the home that causes mold growth. Reduce high relative humidity and keep it below 70%, reduce condensation. Dry wet building materials if there are any.

It is difficult to eliminate all mold but it can be controlled. Clean and dry the affected area of mold. Provide basic awareness of mold contamination to residents on government levels and encourage them to keep their houses clean and moisture free. Once mold exposes to indoor environment take immediate necessary action according to the severity of the problem and prevent the spread of mold spores to everywhere in the house.


Mold is the main concern now days in construction industry. Growth of mold during construction cause delay and increase cost of construction jobs. Biological contamination like mold can grow during each phase of construction. During execution of the construction project mold can settle on building materials in the form of spores. Mold free construction reduces the chance of future liabilities.

Mold can destroy the property and can expose to million dollar damage lawsuits. Mold claims generally fall into two categories: property damage and personal injury.

10.1 Mold During Construction
Following are some reasons and causes for mold growth during a construction project:
• Uncontrolled moisture
• Condensation
• High relative humidity
• Dampens building materials
• Site Issues
• Poor site drainage
• Inadequate building protection, stored building materials get wet when water stands in basements and crawlspaces
• Design problem

Sometimes contractor does not store building materials like lumber and drywall properly and materials get exposed to rain or snow. Construction labours does not care to cover the structure under construction with proper sheet covers after closing the construction site everyday. This negligence leads to develop moisture in lumber and plywood and causes mold growth.

10.1.1 Preventive Check
St. Paul Fire & Marine Insurance Company has presented the paper at the Construction Safety Councils’ 13th Annual Construction Safety & Health Conference & Exposition, Rosemont, Illinois, February 2003 and they provide methods of preventing mold growth and the mold in construction check list. This checklist explains the pre construction task, during construction checks and post construction action. Table 5 explains the pre construction task, table 6 explain the check list during construction and table 7 presents the post construction checklist.

Table-5: Pre Construction tasks (Electronic library of Construction Occupational and safety)

Pre-Construction Checks
• Building materials should dry before, during and after installation
• Inform project manager any water damage, leaks or intrusion on job site
• Dry out any wet material immediately
• Follow designs and specifications to avoid any misconduct of work that would lead to water and other damage
• If any water intrusion or moisture accumulation occur before construction, let architects know the design flaw
• During the design phase, carefully review the details with specific attention to ensuring an impermeable envelope
• Take third party opinion with envelope engineer on water tightness of the envelope for geometrically complex building
• Survey the existing building or renovation area for pre existing mold exposure in the building or construction site
• Establish a partnering program with the owner and promote a peer review for the mechanical system and the building envelope designs
• Consult manufacturers of moisture critical products to confirm the product’s application and recommend standard details, and provide preferred installers
• Schedule Delivery of interior materials so they will arrive after exterior of building has been sealed
• Provide dry area for materials storage and minimize storage time
• Cover materials with plastic sheeting or tarps to secure
• Pre arrangement for drying equipment (fans, dehumidifier, Vacuums, etc)

Table-6: During Construction Checks (Electronic library of Construction Occupational and safety)

During Construction Checks
• All materials should be inspected when deliver on site for pre existing mold contamination
• Indoor building materials should be installed in dry condition as per manufacturers’ specifications
• All water services and waste lines should be checked for proper installation, Connections and for leakage
• Water lines (hot and cold water) properly insulated
• Inspection should be made for filling or hydro test of sprinklers
• All building penetrations should (doors, windows, balconies and decks, roof, ventilation and exhaust ducts) install properly and checked for leakage
• All tears, openings or punctures in vapor barriers have been repaired
• All roof drains should be drained away from the foundation
• Roof drains properly supported and braced for large volume storms
• All moisture-generating equipment vented outdoors
• Provide proper ventilation to attics, crawl spaces or other enclosed areas
• All duct joints should be sealed
• Perform interim inspections; invite the Architect, Envelop Engineer, Mechanical Engineer, manufacturer’s representatives to inspect for mold related issues

Table-7: Post-Construction Checks (Electronic library of Construction Occupational and safety)
Post-Construction Checks
• Ask manufacturers to inspect installations for warrantee purposes
• Brief the facility owner on their responsibilities to prevent mold growth
• Fix leaky plumbing hot and cold lines and leaks in the building envelope as soon as possible
• Make observation for condensation and wet areas. Fix source of moisture problem as soon as possible
• Prevent moisture due to condensation by increasing surface temperature or reducing the relative humidity. To increase surface temperature, insulate or increase air circulation. To reduce the relative humidity in air, repair leaks, increase ventilation, or dehumidify
• Keep heating, ventilation and air conditioning (HVAC) drip pans clean
• Maintain indoor humidity; keep relative humidity within the range of 30-60 percent, High relative humidity (?70%) leads to mold growth
• Perform regular building/HVAC inspections and maintenance and make corrective actions if necessary
• Install and maintain proper air filters
• Clean and dry wet or damp areas or material within 24 to 48 hours
• Ensure new building penetrations are properly sealed
• Landscape watering system does not spray building foundation
• Conduct final visual inspection of Pipe chases ,Utility tunnels and areas above drop ceilings that are exposed to water or waste lines or that are directly below roof

10.2 Mold Free Construction
Remediation at the beginning of construction is easy and economical than dealing the problem of mold after construction.

Douglas Hoffman, the author of “Mold Free Construction” book has described the construction process that is safe and prevents the mold during execution. He discussed the following:
• Foundation
• Plumbing
• Dry-In
• Roofing
• Finishes

10.2.1 Foundation
Location of the land is important as environment (weather) affect the construction process. Drainage is one of the important factors that affect foundation. Foundation is dried if drains away from the construction land. Water should carry using underground piping from front yard to the back yard of the lot. Second important factor is elevation; finished floor elevation should be above the elevation of the road as per city standards and specifications. Monolithic slab construction should be used where elevation difference is very small almost flat surface. Stem wall and piling construction should be used for slope.

City of Edmonton provides the specifications for slope and drainage:
Minimum Grade from Foundation Walls and Concrete Slab-on-Grade
A sloped surface is required to effectively drain water away from all foundation walls and concrete slab-on grade buildings.

Minimum grade requirements:
• 10% for the first 2.0 m – Minimum 20 cm drop for final landscaping.
• 0.75% for concrete, asphalt or other impervious surface treatment

Minimum swale slope requirements:
• 1.5% for a grass drainage swale
• 0.75% for a concrete drainage swale

Depth of Foundation Drain Service and Sewer
Provide a minimum depth of 2.4 m from the finished grade to the obvert of the service at the property line

My recommendations for foundation design and selection include soil type, load of the structure that comes directly on footings and bearing capacity of soil.

10.2.2 Plumbing
Mainly there are two major sewer systems install in the house, one is sanitary sewer and other is water supply system. Sanitary system carries the used water from home to any treatment plant or disposal area. Water supply system brings water to home from supply source. Leakage is main issue in plumbing. Sanitary system, water supply system should install accurate and as per specifications to avoid leakage.

City of Edmonton provides the design specifications for sanitary sewer design:
Minimum Slopes: minimum slope of >0.4% with 200mm minimum dia pipes.
Velocity: between 0.6 metres/second and 3.0 metres/second
Depth: minimum of 2.74 metres deep from the ground surface
Pipe Materials: non-reinforced concrete pipe, reinforced concrete pipe, and PVC
(polyvinyl chloride) pipe.

Epcor provides the following specification and information regarding water supply.
The water pressure for residential supply is dependent on the ground elevation and the design of the plumbing within a house. The higher the ground elevation, the lower the water pressure. The operating pressure in Edmonton is 240 kPa to 700 kPa. 140 kPa is the minimum pressure allowed by the Canadian Plumbing Code.

City of Edmonton recommends the bend types for joints (450, 600, and 900). Use of proper bend type prevents the leakage problem.

10.2.3 Dry-In Process
Dry-In process is the period of time between the completion of the exterior framing and the point where doors and windows are installed. When dry-in process starts, seal the cracks appear on the concrete floor if any. Seal the cracks between wood-framing and floor. Once dry-in process complete, allow some time to dry the wood-framing members. Windows and doors should be installed as per manufacturer’s recommendations.

10.2.4 Roofing
Roof is the common area for water intrusion and it is most significant because rain and snow fall directly on roofing system. Manufacturer’s specifications should be followed during installation of the roofing system.
There are several types of roofing system use in North America, based on shape and materials. Shape can be flat or gable and material can be timber or metal. Therefore design consideration is important decision.
Flat roof acts as a pool when rain falls and water stands for long time if proper drainage is not available. Slope roof can be designed according to the standards and specifications.

City of Edmonton provides the specifications for slope of the roof. Maximum height should be 3.7m for slope less than 200and 5.2m for slope greater than 200.

National Research Council Canada has explained the rain or water management on roofs.
They advise following three basic approaches for rain or water management.
• Flashing
• Insulated membrane
• Drainage system Flashing
Flashing prevent water from penetrating and it intercepts water flowing down parapets, down walls of higher adjacent construction and down roof penetration. Flashing diverts the water towards membrane and then carries it to the roof drains. There are four locations where a flashing is needed (Terminations, Junctions, Projections, and Joints) Drainage
Design properly for good drainage and make sure that sufficient slope and number of drains, properly located. Deign an interior drainage system that carries the rainwater through the building interior. Interior drainage can be design along building columns. In a peripheral drainage system, rainwater flows from elevated surface to the building outside and drains through scuppers. Insulation
Use different type of insulation to protect membrane from environmental elements such as wind, rain and snow. Waterproof and porous tiles can be used for insulation purpose.

10.2.5 Finishes
Finishes including floor covering and wall covering are the final stage of construction process. Normally concrete floor is poured on vapour barrier that install between floor and foundation ,if the cracks are more than ¼ inch than they should be sealed properly because these cracks allow the moisture to creep up and great chances for mold growth under the floor covering. When painting and wallpapering the wall, use proper additive to avoid mold growth.

10.3 Role of Construction Manager On-Site
Mold prevention management plan should be prepared and implemented on-site. Construction manager should do the following: (C. Bradley Cronk, RA, and David J. Pfeffer, Esq, Spring 2008)

• Control, sequence, and coordinate phased work where interior finishes are installed.
• Moisture intrusion protection should be provided for site areas and materials susceptible to water damage.
• Maintain a clean site, free of uncontrolled water.
• Identify any other contractor responsible for care, and control of specific site areas.
• Prequalify mold abatement contractors with proven experience and mold-inclusive insurance policies.
• Strictly stick on to the contract documents, with respect to value-engineering and material substitutions that could alter the design.
• Provide for and immediately respond within 24 to 48 hours to any exposure of water intrusion or mold.
• Coordinate any measurement, remediation, and reconstruction should water infiltration or mold growth occur during construction.

Mold can damage the property and effect on human health or bodily injury and cause lawsuits. There are many lawsuits and claims in US and number of claims in Canada is also grown up.

In the United States Construction defect during execution is the major reason for mold claims. This is either due to labor or materials. (Simonet Duplessis, 19 August 2005)

11.1 Mold Claim Criteria
There are many reasons that could lead to lawsuits. It could be because of faulty design, construction, products and their installation, faulty maintenance, bad faith in first party claim, improper cleanup, failure to warn and disclose. (Glenn Gibson & David Pym Sr, 2001)

11.2 Defendants in Mold Related Litigation
Following can likely to be sued

• Buildings sellers
• Real Estate Agents
• Contractors
• Sub-contractors
• Architects
• Engineers
• HVAC designers
• Building owners
• Developers
• Property owners or managers
• Insurers
• Insurance adjusters
• Schools
• Product manufacturers
• Government building inspectors
• Renovation specialists
• Restoration companies
• Remedial companies
• Public Entities
• Health Care facilities

11.3 Claims in Figure
2000 and earlier, there were less awareness and few mold claims were filed. Claims could be up to $5,000 or less during that period of time.

Today, mold claims by homeowners or landlord is more than $100,000. Mold claims in the commercial market often exceed $1 million. From 2001 to 2003, the claims of mold have more than doubled.

Mold claims are expensive to defend and also for plaintiff due to high cost of inspection and documenting. Sometimes one or more physical examination is required. The complex job need various expert witnesses for example industrial hygienists, engineers, architects, allergists, neurologists, toxicologists, epidemiologists and contractors to address who caused the mold.(Richard Morgan and Charles Schoenwetter Jun2005, Vol. 99 Issue 6, p48-51, 4p,)

11.4 Mold Claim Statistics
According to Albert Warson of REC (Restoration Environmental Contractor), statistics shown in United States are:
• 1999 – 12 claims
• 2000 – 499 claims
• 2001 – 10,000 claims
• 2002 -39,000 claims

Statistics show an increase in mold claims every year and it gives the warning alarm to defendants. Results also show that how rapidly mold growth problems occur. Canada has identical trend of mold growth.

11.5 Mold Claims in US
In 1997, Centex-Rooney Construction Co. v. Martin County became the first major mold case heard by a U.S. appellate court

A Texas jury awarded $32 million US to Melinda Ballard, age 48, a marketing representative, in 2001 after her insurance company failed to identify promptly and remediate mold in her house. This claim is the biggest individual claim against mold in the world. This claim was wake up call for Canada.

11.6 Mold Claims in Canada
The first Canadian attempt at mold related class litigation was Taub v. Manufacturers Life Insurance. Taub was brought on behalf of the tenants of an apartment building following the discovery of mold.

In 2000, the Courthouse in Newmarket Ontario was closed while they removed almost all of the walls and ceilings in this 165,000 square foot facility in order to remove “mold”

More recently, the Alberta ‘Court of Appeal’ building in Calgary was forced to temporarily relocate their premises to Edmonton as a result of “Toxic mold infestation.” Early reports suggested that two thirds of the staff were experiencing “mold-related” health problems

In Year 2000, the Province of Ontario paid out $40 million in grants to school boards to correct “mould contamination problems” in schools

Since 1995, the Ontario, Saskatchewan, Manitoba and British Columbia governments have developed guidelines for the detection and elimination of potentially hazardous mold. (Albert Warson, 1999-2007)


Mold growth is one of the major concerns in private, commercial, industrial, and institutional sectors and especially for construction industry and it directly effects on construction schedule and total cost of the project.

Mold Prevention and Response Plan should be prepared and Construction manager can play vital role to implement the Mold Prevention and Response Plan during construction process and should take preventive action before construction to avoid moisture or wetness at construction site that leads to mold growth.

Mold claims could be against property damage and bodily injury. Mold claims and litigation in Canada is relatively low in numbers as compare to US but this is warning alarm for Canada.

1. Bock, Kenneth. Germ Survival Guide Blacklick, OH, USA: McGraw-Hill Companies, the, 2003. p 66
2. Canadian Centre for Occupational Health and Safety
3. Contributor: Institute of Medicine (U.S.), Committee on Damp Indoor Spaces and Health Staff(CB)- University of Alberta library resource
4. Library of Congress Cataloging-in-Publication Data Indoor environmental quality Thad Godish -2000. University of Alberta library resource
5. Fungal Contamination in Public Buildings: Health Effects and Investigation Methods -2004 (Health Canada)
6. A brief guide to mold, moisture and your home by US EPA (United States Environmental protection Agency)
7. Jeffrey C.May and Conniel L.May ,Mold Survival Guide,2004
8. James Scott, PhD, Clean-up procedures for mold in houses,2005 (This book is prepared for Canada Mortgage and Housing Corporation, CHMC)
9. Institute of Medicine (U.S.), Committee on Damp Indoor Spaces and Health Staff (CB) Damp Indoor Spaces and Health. Washington, DC, USA: National Academies Press, 2004. p 194
10. D. Douglas Hoffman, Mold Free Construction,2005
11. Joel Herz and Kimberly Taylor, Toxic Mold Litigation,2005
12. Albert Warson, Restoration Environmental Contractors,2007
13. C. Bradley Cronk, RA, and David J. Pfeffer, Esq., Practice Management Digest, spring 2008
14. William S. Dick Guild, Yule and Company LLP, Toxic Mold Litigation Issues
15. Manitoba Intergovernmental affairs and trade, Controlling Mould and Moisture
16. NEW – CCA 82 – Mould Guidelines for the Canadian Construction Industry CAA
17. Electronic Library of Construction Occupational Safety and Health, Mold in Construction Checklist
18. Nasrin Dhanani, Mold, Office of Environmental Health & Safety University of Alberta

We at are thankful to Er. Navaid Ur Rehman for submitting this very useful research to us. We hope this will of immense use to all those looking for research in this field.

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