Concrete Masonry and MoldNCMA Program #: 000515ContinuingEducation Services
AIA Disclaimer NoticeContinuingEducation This program is registered with the AIA/CES for Services continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.
Is Concrete Masonry the Solution to Mold?ContinuingEducation Services
Benefits of Concrete Masonry •Form and functionContinuingEducation Services •Versatile designs •Long-term durability •Fire-resistant •Energy efficient •Sound insulation •Strength And - does not provide a source of food for mold growth.
OverviewContinuingEducation Services •What is mold? •Why the fuss? •How should concrete masonry be designed and constructed to limit mold growth potential?
What is Mold?Continuing • Members of the Fungi Kingdom –Education Services Neither plant nor animal. • Mold Spores – They are everywhere! Sizes from 3 to 40 Microns (human hair is 100- 150 microns). 250,000 can fit on head of a pin.
Types of MoldContinuingEducation Services • More than 100,000 known species worldwide. • Most types found in homes and buildings are not harmful to people. Black mold - requires high levels of moisture, and • Harmful types include: cellulose containing materials. – Stachybotrys Chartarum Greenish-black. Slimy and wet to the touch. – Aspergillius versicular – Various species of penicillium • Most harmful when they become airborne (such as in air handling systems).
Requirements for Mold GrowthContinuingEducation • Food Source – Any Services organic substance. • Moisture – Free water or high relative humidity (greater than 70%). • Hospitable Growing Conditions – Temperature between 40 and 100F, oxygen, darkness, etc. • Mold Spores – Located everywhere.
Health EffectsContinuingEducation Services • Possible reactions: – Runny nose, headaches, sinus infections, coughs, watery eyes, breathing difficulties, and general discomfort. – Asthmatic symptoms: labored breathing, chest constriction and coughing. – Rash • Prolonged exposure reactions – Chronic fatigue, dizziness, shortness of breath, headaches, and nosebleeds. Also muscle cramps, inability to concentrate, and edema.
Litigation IssuesContinuingEducation Services • As many as 60,000 outstanding cases. • About $780 million in claims paid in 2001 (75% in Texas). • Basis for lawsuits: – professional malpractice and negligence for construction defects and defective designs – fraud and failure to disclose problems at time of sale of the property
Insurance ResponseContinuingEducation Services “The costs of cleaning up mold caused by water from a burst pipe are covered under the policy because water damage from a burst pipe is a covered peril. But mold caused by water from excessive humidity, leaks, condensation or flooding is a maintenance issue for the property owner, like termite or mildew prevention, and is not covered by the policy.” - Dr. Robert Hartwig Insurance Information Institute Also, insurance companies in many states are not writing new policies.
Learning CurveContinuingEducation Services Why the recent increase in observed mold infestation… • Media/public awareness? • Tighter construction? • Use of more moisture-sensitive materials? • Non-uniform pressurization of buildings? • Increased construction pace?
Mold in SchoolsContinuingEducation Services Chavez Elementary School - Madison, Wisconsin • First new public elementary school in Madison in 30 years. • Air quality complaints led to finding sizeable mold blooms in 1/3 of the school’s rooms. •$1.5 million mold and remediation program
Building Code Requirements For controlling mold, esoteric at best…ContinuingEducation Services Keep in mind building codes address minimum life safety requirements.
Building Code RequirementsContinuingEducation Services • Model codes do not contain words “mold resistant” • Codes do address minimum conditions which could produce mold and associated effects. – Proper ventilation required. – Exterior envelopes must have vapor retarders, water- resistive barriers, and flashings. • International Property Maintenance Code includes requirements for maintaining viability and safety.
Options for Limiting Mold GrowthContinuingEducation • Limit Food Source – Nearly impossible. Services Reduce use of paper and wood - but still can grow on oil and dust on non-food surfaces. • Limit Moisture – A logical strategy. Good construction details to reduce free water. Reduce humidity since people prefer 40-50% anyway. • Provide Inhospitable Conditions – Tough. Hospitable environments provide the temperatures and oxygen. Darkness enables growth in areas that can no be seen. • Eliminate Mold Spores – Impossible.
Options for Limiting Mold GrowthContinuingEducation • Air conditioner operation • Exterior water management Services • A/C selection • Repair small leaks • A/C sizing • Water damage • Thermostat set point/ceiling fans • Moisture condensation • Interior doors • Exhaust fans • Space pressurization • Closets • Measure RH in home • House plants • No vinyl wallpapers • Construction moisture • Return air pathways • Unvented attics • Bathrooms • Central dehumidification • No open windows or whole • Consider a/c with variable house fans during humid speed air handlers and with weather (esp at night) enhanced dehumidification • A/C maintenance mode
Is Mold Present?ContinuingEducation Services • Musty smell • Pink or yellow splotches on vinyl wall cover
Eliminate the MoistureContinuingEducation Services Keeping indoor relative humidity lowExterior Interior will decrease dew-• Rain • Vapor point temperatures,• Vapor • Air reducing chance of condensation. Also - ensure continuation of insulation and air and vapor retarders.
Moisture in Building MaterialsContinuingEducation Services Be careful of sealing in moisture that is present within building materials.
Associated Effects of MoistureContinuingEducation Services • Efflorescence • Corrosion of Metals & Reinforcing • Staining/Mold/Mildew • Leaks • Rotting & Disintegration of Insulation/Wood/etc.
Keys to Providing Moisture Penetration ResistanceContinuing • Quality MaterialsEducation Services • Good Design and Detailing • Good Construction
Construction Materials: Concrete Masonry UnitsContinuingEducation Services ASTM C 90 Properties Properties Not in C 90 • Compressive – Color Strength – Texture • Absorption – Density • Dimensional – Water Repellency Tolerances – Fire Ratings • Density – Thermal Properties Definitions – Sound Properties • Linear Drying Shrinkage
Which Mortar is the Best?ContinuingEducation Services Sand/Lime Optimum Cement/Sand Mortar Range Mortar O N S M •Workability •Strength •Water Retentivity •Early Setting •Late Strength •Bond •Autogenous Healing •Durability ASTM C 270 Mortar Selection Guide: • Exterior walls – Type N (alternatively S or M) • Below grade – Type S (alternatively M or N)
Barrier WallContinuingEducation Services • Collar joint between wythes acts a barrier to moisture along with the thickness of the wall • Examples – Brick and Block Composite Wall – Solid Grouted CMU Wall
Cavity WallContinuingEducation Services Air Space: Clear and free and 2 in. minimum
Rain Screen WallContinuingEducation Services • Equalizes pressure within cavity • Vents at top and bottom of wall or panel • Flashing and weep holes • Compartmentalized • Allows for ventilation and evaporation
Components for Moisture MitigationContinuingEducation Services • Flashing Successful • Weeps Mitigation • Vents Requires • Water Repellent Admixtures Consideration • Sealants & Coatings of ALL • Vapor Retarders Components
Best Performance Is Achieved By RedundancyContinuingEducation Services Level of Defense Defense Mechanism 1 Surface Protection • Mortar Joints • Sealants /Coatings Vapor 2 Internal Protection Barriers • Integral Water Repellents 3 Drainage • Flashing, weeps and vents
Surface Protection: Clear Surface TreatmentsContinuing • Acrylics - form elastic film over surface.Education Services Quick drying. $ • Silicone Resins - good penetration. Drying time 4-5 hours. $ • Silanes - good penetration. More volatile. Can be applied to damp surfaces. $$ • Siloxanes - similar benefits of silanes. Effective on wider variety of surfaces. $$
Surface Protection: Opaque Surface TreatmentsContinuingEducation Services • Portland Cement Plaster (Stucco) - Cementitious coating. $$ • Cement-Based Paint - good durability (including alkalis). Fills small voids. $ • Latex Paint - water based. Good durability (including alkalis). Breathable. Applied to damp or dry surfaces and cure quickly. Good hiding characteristics. $ • Alkyd Paints - Durable, flexible, quick dry. Low alkali resistance. $
Internal Protection: Integral Water RepellentsContinuingEducation Services If the surface barrier compromised, moisture can move through the wall by: • gravity • pressure • capillary action
Integral Water RepellentsContinuingEducation Services • Polymeric material which does not alter the finished appearance of the block. • Lasts the lifetime of the unit. • Cuts down on possibility of efflorescence. • Incorporate a compatible integral water repellent admixture into the mortar.
Drainage: Flashing Material OptionsContinuingEducation Services • Sheet Metals • Composite Materials • Plastic and Rubber Compounds
Flashing Materials MetalsContinuingEducation Material Advantages Disadvantages Services Stainless Durable, Hard to form Steel non staining Cold-Rolled Flexible, durable, Damaged by Copper easy to work with excessive flexing and can stain Easy to paint and Galvanized durable Corrodes early in Steel acidic and salty air
Flashing Materials Plastic and Rubber CompoundsContinuingEducation Material Advantages Disadvantages Services EPDM Flexible, easy to Aesthetics, full form, non-staining support recommended Rubberized Fully adhered, self Full support asphalt healing, flexible, required, degrades in UV light, metal easy to form and drip edge required join
Flashing Materials Plastic and Rubber CompoundsContinuingEducation Services Material Advantages Disadvantages PVC Easy to form and Easily damaged, join, non- full support staining, low cost required, metal drip edge required, questionable durability
Flashing LocationsContinuingEducation Services Needed anywhere the downward vertical path of water to the weeps is interrupted: • Base and foundation • Lintels • Bond beams • Parapets • Intermediate roofs
Flashing Detail at Reinforced CellContinuingEducation Services Architectural unit with inside faceshell and part of webs cut off to fit (typ. a & c) 3 in. (76 mm) unit for 8 in. (203 mm) wall, 4 in. (102 mm) unit for > 8 in. (203 mm) wall
Flashing Detail at Unreinforced Cell Continuing Education Cavity filter* Serviceshell (typ. b & c) cut& c) Weep holes @ 2 ft. 8 in. (813 mm) t for o.c. partially openall, "L-shaped" headnit for joints wall 1 in. (25 mm)
Detail at Inside Face ShellContinuingEducation Services Edge of flashing Stop flashing at sealed by mortar inside of faceshell from joint Cavity filter* Solid unit or filled hollow unit to support flashing Flashing Typical detail at inside of faceshell
Optional Flashing Detail at Unreinforced Cell Mortar net*ContinuingEducation Services #5 (#16) min. @ 48 in. (1219 mm) o.c. 4 in. (102 mm) unit Drip edge (typ.)
Good Flashing DetailContinuingEducation Services
Weep Holes At 32 inches max.ContinuingEducation Services
Weep HolesContinuingEducation Services • Cotton sash cord for drainage path (remove after wall is laid up) • Partially open head joints (preferred)
Products & Workmanship Tying it all TogetherContinuingEducation Services • The quality and compatibility of material components and care in installation are key to wall performance. • The recommended specification for products and workmanship for masonry construction are covered in the latest edition of Masonry Standards Joint Committee ACI 530.1/ASCE 6/TMS 602
Mold SusceptibilityContinuingEducation Services Building Susceptible to Provides food Deterioration Material mold growth? source for mold? from mold? Concrete Masonry Yes No No Gypsum Wallboard Yes Yes Yes Wood surfaces Yes Yes Yes Vinyl, linoleum Yes No (except for Yes adhesisves) Plastics, metals Yes No No
Mold RemediationContinuing BuildingEducation Services Material Remediation Methods Concrete Masonry Wet vacuum or HEPA vacuum Gypsum Wallboard Remove and discard if possible, or HEPA vacuum Wood surfaces Wet vacuum, damp-wipe or scrub surfaces, HEPA vacuum, or remove and discard if a large area is affected or if there is significant occupant exposure during remediation. Vinyl, linoleum Same as for wood surfaces Plastics, metals Wet vacuum, damp-wipe or scrub surfaces, or HEPA vacuum HEPA = high-efficiency particulate air vacuum
SummaryNCMAContinuingEducation Services Masonry is a good choice! Simply choosing masonry is not enough - attention needed for design, construction and maintenance.