WATER and MOLD DAMAGE REMEDIATION OF SHEAR PANELING

by Patrick Moffett 

DISCLAIMER

Building codes and regulations change all the time. This paper is not designed to be current on federal, state and local building codes; shear panel, seismic and fire codes. 

Depending on a professional's license and experience, it is not unusual for professionals to provide differing opinions about how water damaged and mold contaminated shear paneling should be treated.  This paper provides valuable information to abatement, remediation and restoration contractors in respect to water and mold remediation of shear paneling. 

This paper is not to be relied upon as state of the art guidelines for mitigating a particular project where the structural integrity is or will be compromised by removing damaged shear paneling. It is up to every contractor to ensure they appropriately remove, secure and maintain the building's structural integrity at all times. 

This paper is limited in scope and purpose--it does not cover fire codes and fire rated materials, their removal or replacement. 

Due to different building code requirements across the U.S., Canada and UK, this paper may only provide limited advice to contractors. Seek further advice about job-specific problems involving restoration, when needed. 

Buildings already damaged from fire, earthquake, poor maintenance, structural modification and upgrades are outside the scope of this paper. It is up to each contractor to identify conditions that are not outlined in this paper and determine the most appropriate corrective action. 

This paper focuses on addressing water and mold problems in shear paneled walls and wall voids having lightweight building construction. This paper does not focus on construction design problems and challenges dealing with multi-story, commercial and industrial buildings. 

It is expected that all contractors reading this paper are licensed contractors in their respective state and jurisdiction, and they follow regulatory codes affecting building construction, demolition and repair. 

When the contractor is unsure about the mitigation or repair of shear panel sheathing, they must seek professional advice from a licensed structural engineer, building inspector or other qualified professional. 

PART 1

FUNDAMENTAL INFORMATION

INTRODUCTION  

One of the least understood aspects of water damage restoration and mold remediation is how to manage structural paneling when the building envelope becomes wet and moldy. When it comes to structural drying and structural remediation requiring contractors to cut into shear paneling (structural sheathing) to remove water, moisture and mold growth or replace wet or damaged insulation, industry (e.g., IICRC, AIQA, RIA/NIDR, BDMA, APA) provides virtually no assistance to the contractor (restorer). In other words, after evaluating industry standards of care, methods and procedures for drying and remediating shear paneling in situ or replacing damaged sheathing, industry guidelines don't exist.  

This paper is intended to provide the restorer and other parties with recommended guidelines. However, the building inspector and structural engineer are the final authority on what must be done to mitigate and repair shear panel damage or wall cavity damage behind shear.     

WHAT IS SHEAR PANELING USED FOR?  

Uses

• Construction: o Shear panels are designed to counteract lateral stress and load, ensuring the structure remains sound even when the building is subjected to violent movement.

o A rigid vertical construction diaphragm is capable of transferring lateral forces from exterior walls, floors, and roofs to the ground foundation in a direction parallel to their planes.  § Shear panels maintain structural integrity in multi-story buildings. 

§ In some cases, shear paneling is designed to provide additional fire protection.

 

• Earthquake and Wind: o Lateral shear is especially common in earthquake country when structures are designed to move back and forth as the ground vibrates.

o Shear paneling protects buildings from high winds and eddy turbulence during storms.

o While buildings are designed as rigid components they must be flexible at the same time. 

Shear Panels are Called by Different Names: Shear walls, structural sheathing and bracing (or braced) panels. 

• Depending on the type of construction and load characteristics, shear panels are constructed by nailing or bolting a number of lateral supports to the external side and roof framing of a building, along with the internal shear panels on flooring, walls, ceiling and roof. These supports also stabilize the structure from drifting and racking.
• The strength of resistance depends on the size of the structure, the width of the shear panel, load, and types of construction materials.

 Construction Design

• In order to be structurally sound, a shear panel must be both strong and stiff. o Strong means materials are able to resist the tearing forces involved with lateral shear.
• o Stiffness means shear panels are able to hold its position in addition to remaining intact during a disaster. The amount of strength and stiffness required to meet building loads and environmental factors is calculated by the projects engineer or architect.

 

• Shear walls can be load bearing or non-load bearing, but in both cases, they maintain structural integrity throughout the building's life.
• Local building codes now follow national and international uniform building codes that err on the side of caution. What this means: Shear paneling is required in regions of the country where high winds and earthquakes are rare. The building design must consider unknown forces that could affect its construction over the life of the structure.
• Shear calculations must also take into consideration uneven ground and foundation settlement loads.
• Wood framed buildings having lots of openings (windows and doors) experience a shear value reduction. This situation requires the design architect to increase the building's shear strength capacity.  

HISTORY OF SHEAR AND SHEAR PANELING  

History

Before the time of Christ, Romans figured out how to some elements of shear force by using curves of arches. They knew that compression and tension can work to the same end by balancing gravity. Roman engineers knew if you had a stack of three blocks, the block on top has no upward force but it has tremendous downward force. The middle block cancels the upper blocks gravity. The lower block is now responsible for all forces: it has an upward force but it is carrying its weight and the weight of the other two blocks. Transferring weight load depends on the size of the blocks, structural makeup and the foundation they are sitting on. This theory is similar to how shear panels work today.    

Early in the 4th century the Greek mathematician Pepose declared the honeycomb represents the most effective labor of nature.  Even today, the hexagonal shape of a honeycomb is known as one of the strongest shapes. It has natural shear properties called the "honeycomb guess" because it is made with the least amount of beeswax to give it its structural shape and strength. It can support many times its own weight. Today, the honeycomb guess is responsible for making hundreds if not thousands of products including doors and panels. 

Over the centuries there has been a lot of information on the history of different types of shear including wind shear but there doesn't appear to be a long history of technical information dealing with shear in building construction and structural paneling. The first science-based test I'm familiar with is the Five-Point Bending Test for Determination of Edgewise Shear in Structural Panels (ASTM test method).   

In the late 1950's and early 1960's, plywood walls were proposed simply as alternates to diagonally braced wall sections. Their acceptance for this purpose was based on their ability of a wall to meet certain load/deflection criteria as set forth by the Federal Housing Administration (FHA). 

A wealth of data has become available since 2001 about the performance of drywall shear walls under cyclic loading. Drywall and stucco were the only earthquake lateral force-resisting system in residential buildings, especially single-family homes built in the 1970s and earlier. Many of these buildings stand today and their owners may not realize their susceptibility to earthquake damage. (See issues dealing with older building remodeling beginning on the next page.)  

Since the 1980's fastener size for shear walls has become the common 8d and 10d nail. Shear paneling must have a 3 inch nailing pattern at the panel's edge. Shear panel assemblies limit the distortion of building framing by preventing the frame from drifting and racking. Shear assemblies are an engineered design to specifications set forth by the architect in approved plans that are signed off by a building inspector (APA T94-9: Approved Plans and Specifications). 

Today

Over time and experience:

 

• We've learned that vertical joints of structural sheathing must occur over studs while horizontal ends must be nailed into the top plate and sill plate (hold down plate).
• Middle wall horizontal joints must be sealed over blocking having 1½ inch thickness.
• Shear by itself cannot provide the correct forces needed to protect the building.
• Shear elements must include a solid material that is nailed into the edge and middle of the shear.
• Water damaged and wood-rot damaged shear can result in swelling, air gaps, damage to the nailing pattern and loss of structural integrity.
• The edge of each panel must transfer shear forces to an adjoining panel.
• The bottom plate acts as the hold down stud.
• The edge nailing pattern must be to the hold down studs which connects to the hold down.
• Incorrect nailing pattern and spacing at the structural panel reduces design characteristics.

In light, wood framed construction, the typical vertical elements in the seismic load path are shear walls. 

• Shear walls are generally framed with vertical wood studs with horizontal wood top and bottom plates.
• Wood framing is sheathed on one or both sides with one of several materials such as plywood, oriented strand board (OSB), gypsum wallboard and/or Portland cement plaster (stucco).
• Sheathing is nailed, stapled or screwed to the wood framing and provides the structural capacity to transfer the horizontal seismic forces from the top of the wall to its base.
• Sheathing materials are usually considered to be loaded in a state of "pure shear," meaning, the sheathing only resists racking. Other elements in the wall are designed to resist any vertical forces that may occur.

Most structures in the western United States are designed according to provisions in the Uniform Building Code (UBC) published by The International Conference of Building Officials (ICBO). 

• UBC provides the parameters and equations required to calculate a seismic load or demands on the entire building, or portion of a building such as a shear wall.
• UBC also provides allowable strengths or capacities for various structural elements including shear walls.
• The UBC analysis and design methods commonly used are "static" design methods in that they are not time based although they are intended to represent the dynamic effects of an earthquake.
• Basically, a static equivalent lateral force, representing the dynamic load, is applied to the analytical model of the building.
• Linear elastic mechanics is then used to determine the force in individual portions of the building.
• The size and detailing of individual portions is then determined from the output of the analytical model. (McMullin, K and Merrick, D: Seismic Testing of Light Frame Shear Walls. Washington State University).

 

Retrofit Upgrades and Shear

While new construction is subject to updated regulations designed to make the structure better able to withstand shear forces, this does not address the issue of countless older houses,  apartment buildings  and other buildings still in use. 

With many structures, retrofitting to enhance shear resistance can be as complex and expensive as rebuilding. Further, if this expense is undertaken, the reinforcement may add strength to the wall only and not the overall structure, as is necessary to prevent collapse under intense, repeated shearing conditions.

Water damage restoration contractors should be aware of buildings that have undergone remodeling and retrofit upgrades. It is likely they will find flaws in some of the workmanship that may affect the restoration and repair of the building.  

Retrofitting shear in an existing older building requires reinforcement consisting of "diaphragming." 

• This process involves removing both existing interior and exterior surfaces and attaching a solid sheet of material on each side.
• Builders typically use plywood for wood frame construction, to wall studs, nailing the plywood to the wall studs around the plywood sheet's perimeter at spacing's that are dictated by engineering standards.
• This method relies upon the structure's frame alone for support but it provides no means for enhancing shear resistance by attaching the shear panel independently to the structure's foundation.
• Retrofit repair provides limited shear resistance during the repeated exposure to shearing forces such as occurring during aftershocks of a major earthquake.
• Stresses to nails and plywood can shear off nails and splinter the plywood.
• Since retrofit shear panels are not attached to the foundation, there is no resistance to uplift or allow lateral motion of the entire structure.
• Further, the specified shear resistance requires modification of large areas of the wall to attach a sufficient amount of plywood to provide the required reinforcement, which can be expensive and highly disruptive considering the fact that both the exterior and interior surfaces must be removed and replaced.
• Poor construction practices and substandard homeowner remodeling has added to the problems of correcting shear panel damage in water damage remediation.

 PART 2

 WATER DAMAGE REMEDIATION

 WATER DAMAGE REMEDIATION CHALLENGES

 Water Damage Restoration

As a procedural standard of care, professional water damage restoration contractors are expected to follow accepted industry practices such as those outlined in the ANSI/IICRC S500-2006 Standard and Reference Guide for Professional Water Damage Restoration. In water damage restoration, the goal of the restorer is to dry wet building materials as fast as possible. 

Structural Drying

In water damage remediation and restoration, restorers should be able to dry wet shear panels including floor and roof sheathing, building framing and insulation with various types of dehumidification equipment before mold growth occurs. As stated previously, the drying time to dry wet building framing (including drywall) may be only a matter of days before mold growth begins. Therefore, an aggressive response by the water damage restoration contractor is required to force-dry wet building materials. 

In the water damage remediation and restoration industry most water damages affect lower walls and flooring, since water tends to migrate throughout a flat area then it absorbs into walls and framing. In other cases when the flood is on an upper floor, water migrating downwards can damage upper walls and ceilings on lower floors. 

One of the difficult tasks in water damage restoration is to dry a building back to a pre-loss condition before structural damage and mold growth occurs. This means the restorer has a small window of time, generally 1, 3 or 5 days after a water damage event occurs to accomplish the following:

 

• Inspect visible water damage;
• Consult with the building owner and get a contract signed;
• Extract standing water;
• Remove water damaged and non-salvageable materials;
• Relocate contents to a safe place;
• Reassess the extent of water damage using electronic moisture sensors and thermal imaging;
• Moisture map affected areas including wet building framing that are not visually apparent including behind cabinets, vanities, tubs and showers, sound and shear paneling;
• Engineer a building drying system that manages the wet building envelope and compensates for temperature and humidity outdoors, indoors and trapped moisture and humidity inside wet walls, ceilings and flooring;
• Monitor the structural drying process on a daily basis ensuring all wet materials dry evenly and completely.

 

• Open up and expose walls, cabinets and flooring that are not accessible or unable to be dried and returned back to a pre-loss condition within a reasonable period of time before secondary damage including mold growth occurs.
• Remove wet insulation, drywall and other materials and finishes that experience damage.
• Check metal parts, electrical systems, gas and HVAC appliances for corrosion and oxidation that must be corrected;
• Check building framing including shear paneling for signs of physical damage including swelling and deterioration that must be repaired or replaced;
• Ensure restoration is complete so the building can be restored to a structurally sound and healthy condition.

SHEAR PANELING AND WATER DAMAGE REMEDIATION

Building Inspectors' Point of View

In consulting with building inspectors that do not know the water damage restoration industry, most- "do not want any part of the building's structural diaphragm cutout and removed." It appears there is a consensus among them that says: 

 

• If a critical portion of shear paneling is cutout, the entire panel should be removed and replaced.
• Replacing just a cutout section of shear requires new blocking to be installed to transfer energy and the load away from the repaired section of shear.
• An engineer or contractor may need to submit repair plans to the city for approval depending on how much shear was damaged, removed or required replacement.
• At a minimum, a 4' x 4' section of shear paneling will need to be installed.

 

Advise Building Inspectors about the Restoration Industry's Remediation Criteria

The restorer's point of view is: "We must be allowed to go into a building and dry all of its wet parts before additional damage occurs. This includes removing standing water, removing water and moisture from under subfloors, water trapped in ceilings and water and moisture inside wall cavities followed by completing the framing drying process."  Some inspectors and engineers could care less about how a restorer completes their job as long as they do not compromise structural integrity.    

Contractor Remediation, Restoration and Build-back Considerations

 

• What is Best - o When it is necessary to cut into shear paneling for one reason or another, the entire sheet of shear paneling may have to be removed and replaced with a new solid APA-rated sheathing Structural 1 (premium grade of CDX and OSB) panel so the new panel tie: § Back into the upper top plate, the bottom hold down plate, vertical wood stud framing, and the new panel butted up to 1/8 inch of an adjoining panel. An 8 foot tall wall is actually 8' ¾" to allow for the gypsum wallboard installation on the ceiling. o As a result, a common 8-foot sheet of wood structural paneling does not span the full height of the wall. § In this case, the best solution is to install an oversized sheet of 9 or 10 foot paneling and cut it to size.

§ Shear panels are sold in full sheets usually 4' x 8' or 4 x 10'. They are available in 4' x 12' size and can be custom ordered in larger panels. Installing anything less than a full panel requires additional framing (blocking) of cut panel edges. 

• Insulation - o When wet wall insulation cannot be dried to a point there isn't a loss in loft and R-value, wet insulation should be removed as soon as possible and replaced with new dry material once building framing is dry. § This requires removing a section or possibly the full panel of shear paneling.

    

• Who Has Access to Wet Wall Cavities Supported by Shearing Paneling? - o When it is necessary to cut access holes in shear paneling to remove wet insulation, dry interior wall cavities or provide mold remediation services, shear paneling should only be cutout by a licensed framer or general contractor.

o When it is necessary to drill access holes in structural plywood to ventilate out moisture or install structural drying equipment, a licensed framer or general contractor is expected to complete this service.  § Restorers who are non-licensed contractors should hire a licensed framer or general contractor to complete this service, including framing and paneling repair.

 

 

• In-place Drying - o Multiple holes drilled into shear paneling for ventilation and Injectidry-type drying system should: § Remain small (e.g., an inch or less in size)

§ Should space holes no closer than 6 inches apart and no closer than 6 - 8 inches to the top plate, hold down plate or side edges of the panel.  • There is a greater chance a shear panel will fail to perform as designed during wind storms and earth movement when holes and cut-ins are made close to the top, bottom or side panel edges.  o Oakland California earthquake guide suggests paneling may be vented by drilling holes no larger than 3-inches and centered between studs: http://www.ci.oakland.ca.us/documents/GetRetrofitHandbook.pdf  

 

  

• Controlling the Size of Cutouts - o Saw cutouts including holes and notches in the center of paneling should not exceed an accumulation of 20% of the framing panel width. § This percent may vary for some building panels since load and stress concentrations and buckling behaviors may change geographically, including building type, construction, materials and other factors. (Guo, S.J: Stress Concentration and Buckling Behavior of Shear Load Composite Panels with Reinforced Cutouts. 2006; Seismic Retrofit Training for Building Contractors & Inspectors. Assn. of Bay Area Governments)

 

o Lower shear panel cutouts should be a foot above the floor and large enough to remove and replace wet wall insulation and complete the structural drying process.  § Access holes must be large enough to allow new blocking to be framed in, followed by replacement of damaged shear paneling.

§ Access holes should be large enough to frame in new blocking from stud to stud.  • Note: Some building inspectors and engineers will only allow a minimum of a half sheet of new shear paneling to be installed even though a cutout access hole was much smaller in size. 

 

 o Lower wall cutouts along the base plate of a long wall having many damaged panels may require new panels to be replaced; or, installing new panels at different heights in order to offset cuts and transfer lateral forces of new materials with the existing materials.  § Meaning, the building inspector or engineer may allow a new 4' x 2' section of paneling followed by installing a new 4' x 4' section of paneling, and so on. 

 

o The inspector or engineer may require a half to a full sheet of shear panel to be replaced, including additional blocking, for lower wall cutouts of damaged shear paneling that are at or close to the hold down plate (e.g., within one foot from floor height where water usually migrates up into wall cavities). 

 Blocking - o Wood blocking must be made of the same material and size that is present in framing.

• o Adding new blocking to support shear panel cuts may require plans to be approved.
• o A building inspector may need to inspect the installation of blocking before shear paneling is installed.

 

 Nailing - o The new nailing pattern "must not" follow the previous nailing holes.

o Nails are to be of the same size and type of the original construction. Depending on the thickness of plywood and OSB, nailing is installed with common 8d or common 10d nails (not boxed nails, cooler or sinker nails).  § Common nails have less slip than box nails due to their increased shank diameter. 

§ Hot-dip galvanized boxed nails may be used for plywood siding, common nails are recommended to fasten wood structural panel shear walls. 

 

 § Panels with thickness from 3/8 to 15/32-inch can use common 10d 2-3/8-inch length nail. 

§ Panels with thickness from ½-inch or thicker must use the full length common 10d 3-inch nail. 

§ The nailing pattern depends on the type of sheathing and material thickness and load values. Typically common 10d nailing requires nailing every 2 to 3 inches at the top and hold down plate and every 12-inches along interior studs and cross bracing in the field area.  • Additional nails should not be used because of minimum spacing requirements can compromise the nailing field. 

 

§ The 1994 UBC it recommends nailing 3/8-inch from the panel edge, however, the 1997 UBC recommends installing nails ½-inch from the edge.

§ For further nailing instructions refer to UBC Table 23-1-K-1 or local building codes. 

WATER DAMAGE RESTORATION RECOMMENDATIONS

 

• Building Inspection - o When a restorer finds substandard, poor construction, unsafe building conditions or framing that is in the way or that compromises their ability to provide appropriate water damage restoration or mold remediation services (i.e., shear paneling, electrical, gas, plumbing), they are expected to consult with and hire a state licensed contractor or structural engineer; or consult with the local building inspector for further advice and direction, before attempting to cut or drill into or remove any structural, fire rated and seismic component.
• o When a restorer finds potentially hazardous conditions and materials at a jobsite such as asbestos, lead-based paint, chemicals and fumes, they must contact qualified environmental professionals that are licensed or certified by the state or province to oversee this portion of the project.

 

  Water Damage Restoration - o General: § The restorer and field technicians are to be certified by industry to complete water damage restoration and remediation services to a standard of care.

§ The restorer is to determine the best method to remove unbound, trapped and absorbed water followed by drying these materials back to pre-loss condition without coring or cutting into fire-rated, shear panel and seismic-rated materials. 

§ The restorer must be appropriately licensed by the state licensing board in construction before coring, cutting and removing fire-rated, shear panel and seismic-rated materials.

§ When the restorer is an unlicensed contractor, the restorer must hire a state licensed tradesperson that is appropriately licensed by the state licensing board in construction before coring, cutting and removing fire-rated, shear panel and seismic-rated materials.

 o Definitions of Categories of Water Damage and Common Remediation Practices: § Category 1 water originates from a fresh water source such as potable water, or a hot or cold water pipe break.  • Most Category 1 water damages do not require removal of building materials that can be dried before secondary building damage occurs. 

• To assist with the building drying process it is industry practice to remove cove base, trim and toe kicks that have trapped water behind them; create aeration and drying holes in walls to vent out moisture and humidity that is trapped within building voids and dry building framing.

 

§ Category 2 water contains significant contamination from organic and inorganic substances such as a fish tank, waterbed, and contamination from other unsanitary sources.  • Most Category 2 water damage situations require the carpet pad to be disposed. 

• When drywall is saturated it often is a sanitary practice to cut out wet drywall and insulation followed by detergent washing, rinsing and drying building framing.

 

§ Category 3 water is grossly contaminated and can contain pathogenic, toxigenic, chemicals, pesticides and other harmful agents. Common sources of sewage wastewater are from overflowing toilets and soil and water coming from other unsanitary sources. • Most Category 3 water damage situations require the carpet and pad to be cutout and disposed. 

• Industry practice and practices common to health departments and the EPA support cutting out saturated drywall and insulation followed by detergent washing, rinsing, sanitizing and drying building framing.

 

 

o Inspection: § The restorer identifies situations and conditions that cannot be controlled or mitigated without coring or cutting into fire-rated, shear panel and seismic-rated materials.  • Some of these situations and conditions include:  o Category 2 and Category 3 types of contamination;

o Mold and sewage contamination;

o Wood rot, swelling and warping;

o Rust and corrosion; 

o Storms, fires and earthquakes that affect the structure; 

o Pre-existing conditions.

 

 o Structural Drying Goal:  § In Category 1 water damage remediation situations, drying shear paneling, wet wall studs, sill plates and insulation can often be accomplished by creating a drying chamber close to shear paneling, then installing dehumidification equipment. In other cases drilling a series of small holes in shear walls to force in dehumidified air will assist in the wall drying process.  

 

 o Insulation: § When insulation is wet from a Category 1 flood, and the insulation is "not" behind a fire-rated, shear panel or seismic-rated material, the insulation should be dried in place by drilling ventilation holes and appropriately positioning drying equipment up to walls and ceilings.

§ In an attempt to dry Category 1 wet wall cavities and saving fiberglass insulation, it is industry practice to core or cut into the wall to dry the wall cavity and insulation.

§ When the wall is constructed of fire-rated, shear panel and/or seismic-rated materials, only a licensed contractor can core or cut into the wall to either dry in place or remove wet insulation.

§ All types of wet insulation that cannot be dried before it loses its loft and/or R-value, including closed batt, blown-in Rockwool or vermiculite and aluminum foil should be removed from the wall cavity so other components of the wall cavity can be dried before secondary damage occurs.   

 

o Cabinets and Vanities: § Cabinets and vanities are often attached to outside facing walls. In today's construction, many outside facing walls have shear paneling on one or both sides of framing studs. 

§ It is not uncommon to have cabinets and vanities attached to the inside of a house facing garage walls. The garage wall often has shear paneling and fire-rated drywall. 

§ In apartment and condominium complexes walls separating units should be fire-rated and have shear paneling. Walls separating apartments and condos usually have cabinets and vanities attached to them.  • It is common industry practice to drill aeration holes through the toe kick and base of the cabinet and enter the back of the cabinet and wall.  o This process is intended to remove trapped water in walls, dry the base of the cabinet, insulation and wall cavities.

 

• Often restorers do not realize they are drilling into fire-rated drywall, shear paneling and the hold down plate.

 

§ Unless the cabinet or vanity is detached from the wall no one is aware: • If the water damage restoration contractor appropriately dried walls and cabinets or who damaged shear paneling.

• Fire-rated walls may have been compromised.
• Shear paneling may have been drilled into close to the hold down plate.
• The hold down plate may have been cut through.
• Rusty nails no longer support the walls shear-strength and there is a greater possibility of shearing nail heads during movement.
• Insulation may have lost its loft and R-value.
• A damp wall space may support mold growth and wood rot.

  

PART 3

MOLD DAMAGE REMEDIATION 

BUILDING AND SHEAR PANELING MOLD REMEDIATION

 Note: Some companies are promoting that they can adequately spray an encapsulating antimicrobial material on and in wall cavities to stop mold growth and prevent future mold growth from occurring. That application and others like it are outside the scope of this paper.

 Two Basic Types of Mold Remediation

 

1. Type-1 Surface Mold Growth Remediation - Mold growth that usually occurs from a single water damage event. This type of mold growth results in surface mold that has not damaged structural components but over time, mold rooting structures can damage and decay building materials if it is not removed.  a. Type-1 surface mold growth may be capable of causing indoor environmental problems that affect building occupants.  

b. Surface mold growth can be removed through processes of sanding and other means of abrasion, cleaning and disinfection.  i. Standards of care involving mold remediation are covered in the ANSI/IICRC S520 Standard, 2008 second edition.

  

2. Type-2 Water Damage and Wood Rot Remediation - Mold growth resulting from building framing having contact with water for an extended period of time resulting in framing damage and decay. a. Removing surface mold growth is not the issue here - removing damaged building framing until structurally sound wood is found is. i. Standards of care involving building demolition and repair are found in state and local building codes. However: 1. Building codes do not address the need for containment and protection of the building envelope where building occupants and workers can be exposed to potentially harmful mold spores and mycotoxins.   

  

Mold Remediation and Licensed Contractors

Some mold remediation contractors are not state licensed contractors. Therefore, their knowledge and ability to follow and mitigate structural mold damage and structural wood rot framing in accordance to UBC/IBC's codes; state codes such as California Building Standards Code; city codes such as Los Angeles Building Code is limited. 

ü It may be required by state law for non-licensed restorers to become state licensed contractors if they intend to remove and remediate mold damaged structural components including drywall, plaster shear paneling, subflooring, insulation and framing. 

ü It is recommended that state licensed contractors become current on updated codes and regulations including state and city codes involving shear paneling and sheathing, and the removal and replacement of fire, wind and seismic components.

  

S520 Mold Remediation and Structural Building Component Issues

 

Getting inside wall cavities, ceilings and subflooring to remove damaged insulation and mitigate mold growth on building framing requires the removal of cabinets, vanities, tubs, shower enclosures, drywall and plaster materials and insulation. There is no magic wand that can be waved over the surface to make water damage, mold growth and wood rot to go away. 

• The ANSI/IICRC S520 Standard and Reference Guide for Professional Mold Remediation, 2008 second edition provides the most up to date prescriptive advice and direction in for dealing with moldy building framing and components. However: o The S520 Standard is not designed to mitigate building damage resulting in structural framing wood rot.
• o The S520 Standard does not provide direction for removing damaged structural components or the removal of shear paneling of walls and flooring that harbor mold growth and decay.
• o The S520 Standard defers to established building codes when removing structural building components.
• o The S520 Standard defers to established building codes when it's necessary to cut into or remove fire rated wall, ceiling and floor assemblies including shafts that are mold contaminated or damaged.

 Maintaining Structural Integrity through Shoring

 This paper is not intended to address procedures for maintaining structural integrity in order to remove shear paneling, roof sheathing and subfloors including removing rotted framing. The restorer is expected to be licensed in building construction and knowledgeable about these issues.  

Shoring part of the building or temporarily transferring weight loads to other building parts may be required when mold growth and wood rot is present. 

• Anytime building framing is water or mold damaged or when wood rot is identified, a more thorough inspection of building framing is required.
• When removing drywall and plaster walls to get to damaged building framing, the restorer must consider that the drywall or lathe and plaster may add to the shear strength of that wall. o In such cases, it may be necessary to add temporary shear and supports until water damage, mold growth or wood rot is completely removed and the structure is repaired.

 

• Cutting out a subfloor diaphragm can cause drifting and racking. o In such cases, the restorer may need to stage the removal and replacement of damaged sections of subfloor to eliminate drifting and racking from occurring. § Once drifting or racking takes place, emergency action may be required to remove occupants and immediately support the structure.

  

Water, Mold and Wood Rot Damage behind Shear Paneling

A thorough investigation of building framing components is required. (Hopefully a current set of building plans exist that identify the location of shear paneling and load-bearing walls.) 

• Surface core samples from dry and wet drywall and plaster should be able to identify building framing having shear paneling attached to it.
• When shear paneling is present on one wall, consider going to the opposite side and core sample into it. More than likely only one side of a wall cavity has shear paneling. It is that side where the water, mold and wood rot remediation phase should be completed.

Investigating walls having shear paneling on both sides may require a risk management decision to be made. For example:

• Which side requires cutting? o Cutting the outside facing shear for the purpose of removing mold growth on building framing, plates and the backside of interior shear will result in a partial destruction of the outside finish, shear panel and vapor retarder.
• o Cutting into inside shear requires drywall or plaster attached to shear to be removed including cabinets.

 

• In cases where shear paneling is on both the outside and inside wall, cutting into or removing a section of paneling for investigation or drying purposes should be completed by a licensed framer or contractor qualified and competent in shear removal.

 

Mold Damage Investigation

As a procedural standard of care, professional mold remediation investigators and contractors are expected to follow accepted industry practices such as those outlined in the ANSI/IICRC S520 Standard and Reference Guide for Professional Mold Remediation, 2008 second edition. 

Removing building components to identify cause and origin of water damage and wood decay may be required to be completed while building materials are wet:

• It is not unusual for the investigator to discover the source and cause of water damage and building decay. o The cause of damage and the extent of damage should be carefully documented in cases of first-party insurance claims and third-party liability. § When a water pipe is the cause of water damage and framing decay, it is necessary to document the source with pictures. It may be necessary to stop water damage by turning off supply water.
• In some situations plumbing pressure tests and independent plumbing reports may be required before plumbing repairs are completed.
• In an attempt to avoid spoliation of evidence, when possible, the cause and origin must be saved and kept in archive or turned over to a responsible party.
• When soil has contact with the building or a pooling of water from a planter is the most probable cause of mold growth and framing damage, documenting the cause and origin followed by recreating the cause may be required before removing building material damage.

In mold investigation situations, the goal of the restorer is to have physical contact with all moldy surfaces in order to determine the extent of mold growth and wood rot:

 

• Once mold growth occurs and mold damage is significant to warrant remediating building framing, mapping moisture is necessary to track currently wet framing. o However, relying on a moisture map to chart previously wet building faming produces limited results. § In this situation, the standard of care is to look into all materials suspect of having water damage and mold growth, and follow the visible evidence path to wherever it takes the contractor. Situations where using visible evidence is not possible or gaining access to certain areas of building framing is not practical, using scientific means to detect hidden mold growth may be required.
• For example, scientific instruments can extract air from cavities. This process may be capable of identifying fungal anomalies suggesting or confirming the presence of hidden fungal growth.

 

• In order to identify the true extent of mold damage affecting building framing, it may require detaching cabinets, vanities, shelving and other finishing materials, including paneling, carpet and drywall.

 Duty of Care in Protecting the Building Envelope, Occupants and Workers

 

• The mold investigation process can take on a life of its own since building occupants and contents are expected to be removed from water damaged and moldy parts of the building to allow for a complete and thorough investigation.
• As part of the investigator's duty of care responsibilities: o Setting up plastic containment and maintaining negative air pressure is required in occupied buildings to keep dust and mold spores from leaving the investigation area.

o Setting up plastic containment and maintaining negative air pressure may be limited or not required in non-occupied buildings.  § Worker protection is the same no matter if the building is occupied or not.

 

 

• Once the mold investigation process is complete and it identified mold growth on building materials and framing, plastic containment and negative air pressure is expected to remain in place and operating until the mold remediation process is complete, and if necessary, environmental testing provides clearance for all parties.

Mold Growth and Structural Building Drying

When building framing has high moisture content (above 17 to 20%), building framing should be dried before mold remediation begins. 

• It does little good to mold remediate wet wood framing when the condition that allowed mold growth to occur in the first place continues to exist.
• Building framing having a moisture content below 15% is considered acceptable for most wood framed construction. o However, in water damage restoration, the structural drying industry prefers the moisture content to be below 15%; and when possible, they would like to have an equilibrium moisture content close to 12%.

 

• As previously discussed, it may be required to drill ventilation and forced-air drying holes in wet walls, ceilings and flooring to allow structural drying equipment to dehumidify wet building framing, shear, insulation, cabinets and finishing materials within a very short period of time before interior wall cavity mold growth occurs.

 

Background Mold Growth Considerations

In mold remediation of structural framing it is seldom possible to just return building framing back to normal construction grade (background) or pre-loss conditions. 

• Most all lumber comes from the construction site with some element of mold growth on it.
• Lumber yard mold caused by a type of sap staining fungi (Ophiostoma/Ceratocystis group). It produces a type of black staining mold on the sap of non-kiln dried wood.
• Lumber yard mold group is not known to be harmful to wood framing; and at the time of publishing this paper, there are no known environmental studies reporting lumber yard mold that is stable on wood framing is harmful to humans.
• However, when mold remediation is necessary, all visible signs of mold growth, no matter what its fungal taxa is all signs of mold growth should be removed.
• The restorer is not qualified to identify some molds and leave other molds behind. In fact, it is not possible or practical to remove certain toxic and wood damaging molds from building framing while leaving other molds like lumber yard mold in place.
• In other words, there are no accepted practices to separate normal fungal ecology as background flora from harmful flora since all molds that can have contact with humans in significant number of spores and mycotoxins may cause health problems (allergies and asthma) in some sensitized persons.
• When it becomes necessary to remove surface mold growth from building framing, all visible signs of mold growth are expected to be abated. Through proper abatement, it will lessen a future chance building framing will again become moldy.
• Target mold of medical interest include but are not limited to mycotoxin producers that can affect human health such as Stachybotrys, Penicillium and Aspergillus.

Wood Rot Damage

Building construction is destroyed more often each year by decay that by all building fires, floods and termite damage combined!  The term dry rot is often a misnomer since water is required to result in wood rot in most cases. Determining the extent of wood rot damage to building framing is not as easy as one may think. Visible wood rot should be easy to identify; but identifying hyphae (mold rooting structures) that are actively digesting the cells of wood cannot be seen by the naked eye. 

There are three categories of wood rot: brown rot, white rot and soft rot (Fungal Biology, 2005).

• Dry rot refers to brown rot - Brown rot commonly attacks soft wood such as building lumber turning softwood to a brownish color. In advanced stages of decay, brown rot cracks wood against the grain, causing it to split, cube and crumble; it may look like fire damaged lumber or lumber may look like a checkerboard. In advanced stages of brown rot decay, after the rot has removed nutrients out of wood, the remaining wood becomes dry and powdery.
• White rot - White rot attacks the cellulose and lignin in wood, giving wood its off-white or yellowish appearance. White rot typically attacks hardwood and it lacks the cubical checking appearance of brown-rot wood. In advanced stages of decay, white rot makes wood look stringy and it may feel spongy or springy.
• Soft rot - Soft rot decay is rare inside buildings but it does occur in extremely wet framing. Soft rot is mainly a wet climate mold that attacks fencing, wood siding, window frames and roofing shingles. However, soft rot can occur even in dry climates including inside dry buildings. Hardwoods are more susceptible to soft rotting than softwoods (USFS Research Paper FPL 48).

 

A Word about Poria

Certain wood decaying molds are considered a cancer to building framing. They can decay wood framing in a matter of months to a point portions of the structure can no longer support its own weight. Poria incrassata (Meruliporia incrassata) [Poria], is a type of brown rot often responsible for extensive wood framing damage. When Poria is identified or suspected, a trained environmental professional with extensive forensic investigation knowledge and a strong mycology and construction background should be hired to investigate the extent of building damage. In other words, it is critical that the inspection process identify cause and origin and determine extent of damage.

• One unique problem with Poria infestation, this mold may not go away just because damaged wood was cut out. When the rooting ball is not discovered and removed, the new replacement wood becomes additional food source for new Poria growth. It is not unusual to find increasing building damage from a second Poria infestation.
• The rooting structures of Poria often follow damp or colder plumbing lines under a concrete foundation, and they even follow tree roots. Poria has been seen growing up concrete foundation walls and steel framing to get into nutrient rich building framing.

 

About the Author: 

Patrick Moffett is a senior consultant and partner of Environmental Management & Engineering, Inc., located in Huntington Beach California. 

Patrick is a licensed general contractor in several states, a California registered environmental assessor, certified hazardous materials manager, master restorer, senior environmental/industrial hygienist, certified building science thermographer; and he holds other certifications in water, mold and fire damage building remediation and restoration. 

 For over 25 years Patrick lectures and teaches classes across the U.S., Canada and U.K., on remediating chemical and biological contamination in buildings; OSHA safety codes and regulations.  

Patrick has published over 50 articles and 5 books on environmental and building remediation practices. 

Patrick provides mediation, arbitration and expert witness testimony across the U.S. involving causation associated with water, mold, sewage and fire damaged properties; Patrick also provides expert testimony in industry standards of care and OSHA compliance. 

Contact Patrick Moffett through his office phone: 714-379-1096. Cell phone: 714-928-4008. Email PMoffett@emeiaq.com  or PatMoffett@att.net . 

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