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Concrete the mold solution: outlines the cause for mold and the solution with concrete
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Continuing
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Concrete Masonry and Mold
Program #: 000515 NCMA
Continuing
Education
Services This program is registered with the AIA/CES for
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.
AIA Disclaimer Notice
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Is Concrete Masonry the Solution to Mold?
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Benefits of Concrete Masonry
•Form and function
•Versatile designs
•Long-term durability
•Fire-resistant
•Energy efficient
•Sound insulation
•Strength
And - does not provide a
source of food for mold
growth.
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Overview
•What is mold?
•Why the fuss?
•How should concrete masonry be
designed and constructed to limit mold
growth potential?
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What is Mold?
• Members of the Fungi Kingdom –
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.
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Types of Mold
• More than 100,000 known species
worldwide.
• Most types found in homes and buildings
are not harmful to people.
• Harmful types include:
– Stachybotrys Chartarum
– Aspergillius versicular
– Various species of penicillium
• Most harmful when they become airborne
(such as in air handling systems).
Black mold - requires high
levels of moisture, and
cellulose containing materials.
Greenish-black. Slimy and wet
to the touch.
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Requirements for Mold Growth
• Food Source – Any 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.
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Health Effects
• 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.
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Litigation Issues
• 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
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Insurance Response
“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.
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Learning Curve
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?
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Mold in Schools
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
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Building Code Requirements
For controlling mold, esoteric at best…
Keep in mind building codes address
minimum life safety requirements.
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Building Code Requirements
• 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.
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Options for Limiting Mold Growth
• Limit Food Source – Nearly impossible. 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.
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Options for Limiting Mold Growth
• Air conditioner operation
• A/C selection
• A/C sizing
• Thermostat set point/ceiling fans
• Interior doors
• Space pressurization
• Measure RH in home
• No vinyl wallpapers
• Return air pathways
• Bathrooms
• No open windows or whole
house fans during humid
weather (esp at night)
• A/C maintenance
• Exterior water management
• Repair small leaks
• Water damage
• Moisture condensation
• Exhaust fans
• Closets
• House plants
• Construction moisture
• Unvented attics
• Central dehumidification
• Consider a/c with variable
speed air handlers and with
enhanced dehumidification
mode
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Mold
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Is Mold Present?
• Musty smell
• Pink or yellow splotches on vinyl wall
cover
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Eliminate the Moisture
Exterior
• Rain
• Vapor
Interior
• Vapor
• Air
Keeping indoor
relative humidity low
will decrease dew-
point temperatures,
reducing chance of
condensation.
Also - ensure
continuation of
insulation and air and
vapor retarders.
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Moisture in Building Materials
Be careful of
sealing in moisture
that is present
within building
materials.
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Associated Effects of Moisture
• Efflorescence
• Corrosion of Metals & Reinforcing
• Staining/Mold/Mildew
• Leaks
• Rotting & Disintegration of
Insulation/Wood/etc.
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Keys to Providing
Moisture Penetration Resistance
• Quality Materials
• Good Design and
Detailing
• Good Construction
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Construction Materials: Concrete Masonry Units
ASTM C 90 Properties
• Compressive
Strength
• Absorption
• Dimensional
Tolerances
• Density
Definitions
• Linear Drying
Shrinkage
Properties Not in C 90
– Color
– Texture
– Density
– Water Repellency
– Fire Ratings
– Thermal Properties
– Sound Properties
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Which Mortar is the Best?
Cement/Sand
Mortar
Sand/Lime
Mortar Optimum
Range
•Workability
•Water Retentivity
•Late Strength
•Autogenous Healing
•Strength
•Early Setting
•Bond
•Durability
O N S M
ASTM C 270 Mortar Selection Guide:
• Exterior walls – Type N (alternatively S or M)
• Below grade – Type S (alternatively M or N)
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Barrier Single-Wythe Cavity
Design Considerations:
Basic Concrete Masonry Wall Types
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Barrier Wall
• 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
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Cavity Wall
Air Space: Clear and free and 2 in. minimum
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Rain Screen Wall
• Equalizes pressure within cavity
• Vents at top and bottom of wall or panel
• Flashing and weep holes
• Compartmentalized
• Allows for ventilation and evaporation
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Components for Moisture Mitigation
• Flashing
• Weeps
• Vents
• Water Repellent Admixtures
• Sealants & Coatings
• Vapor Retarders
Successful
Mitigation
Requires
Consideration
of ALL
Components
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Services Level of
Defense
1
2
3
Surface Protection
• Mortar Joints
• Sealants /Coatings
Internal Protection
• Integral Water Repellents
Drainage
• Flashing, weeps and vents
Defense Mechanism
Best Performance Is Achieved
By Redundancy
Vapor
Barriers
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Surface Protection:
Clear Surface Treatments
• Acrylics - form elastic film over surface.
Quick drying. $
• Silicone Resins - good penetration.
Drying time 4-5 hours. $
• Silanes - good penetration. More volatile.
Can be applied to damp surfaces. $$
• Siloxanes - similar benefits of silanes.
Effective on wider variety of surfaces. $$
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Surface Protection:
Opaque Surface Treatments
• 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. $
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Internal Protection:
Integral Water Repellents
If the surface barrier compromised, moisture
can move through the wall by:
• gravity
• pressure
• capillary action
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Integral Water Repellents
• 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.
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Drainage:
Flashing Material Options
• Sheet Metals
• Composite Materials
• Plastic and Rubber Compounds
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Durable,
non staining
Flexible, durable,
easy to work with
Easy to paint and
durable
Hard to form
Damaged by
excessive flexing
and can stain
Corrodes early in
acidic and salty air
Advantages Disadvantages
Flashing Materials Metals
Stainless
Steel
Cold-Rolled
Copper
Galvanized
Steel
Durable,
non staining
Flexible, durable,
easy to work with
Easy to paint and
durable
Hard to form
Damaged by
excessive flexing
and can stain
Corrodes early in
acidic and salty air
Material Advantages Disadvantages
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EPDM
Rubberized
asphalt
Flexible, easy to
form, non-staining
Fully adhered, self
healing, flexible,
easy to form and
join
Aesthetics, full
support
recommended
Full support required, degrades in UV light, metal drip edge required
Material Advantages Disadvantages
Flashing Materials Plastic and Rubber Compounds
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PVC Easy to form and
join, non-
staining, low cost
Easily damaged,
full support
required, metal
drip edge
required,
questionable
durability
Material Advantages Disadvantages
Flashing Materials Plastic and Rubber Compounds
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Flashing Locations
Needed anywhere the downward vertical
path of water to the weeps is interrupted:
• Base and foundation
• Lintels
• Bond beams
• Parapets
• Intermediate roofs
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Flashing Detail at
Reinforced Cell
Typical detail at inside of faceshell
b) Unreinforced cell
of washed pea stone. Alt. — leave out every other reduced size facing unit on top of flahing to serve as cleanouts unitl the wall is completed.* Cavity filter is any material used in conjunction with mortar nets to prevent mortar droppings from cloggin the weeps, i.e. filter paper or 2 in. (51 mm)
a) Reinforced cell
off to fit (typ. a & c)and part of webs cut
Cavity filter*
o.c. partially open2 ft. 8 in. (813 mm)Weep holes @
(typ. b & c)
1 in. (25 mm)
joints"L-shaped" head
Architectural unitwith inside faceshell
Edge of flashing
Solid unit or
Cavity filter*
from joint
to support flashingfilled hollow unit
sealed by mortar
1 in.
e) One-piece flashing
d) Two-piece flashing
Bond beam, lintel orfoundation (typ.)
c) Optional unreinforced masonry
4 in. (102 mm) unit
Drip edge (typ.)
48 in. (1219 mm) o.c.#5 (#16) min. @
Mortar net*
(25 mm)
Flashing
inside of faceshellStop flashing at
> 8 in. (203 mm) wall4 in. (102 mm) unit for8 in. (203 mm) wall,3 in. (76 mm) unit for
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Flashing Detail at
Unreinforced Cell
Typical detail at inside of faceshell
b) Unreinforced cell
of washed pea stone. Alt. — leave out every other reduced size facing unit on top of flahing to serve as cleanouts unitl the wall is completed.* Cavity filter is any material used in conjunction with mortar nets to prevent mortar droppings from cloggin the weeps, i.e. filter paper or 2 in. (51 mm)
a) Reinforced cell
off to fit (typ. a & c)and part of webs cut
Cavity filter*
o.c. partially open2 ft. 8 in. (813 mm)Weep holes @
(typ. b & c)
1 in. (25 mm)
joints"L-shaped" head
Architectural unitwith inside faceshell
Edge of flashing
Solid unit or
Cavity filter*
from joint
to support flashingfilled hollow unit
sealed by mortar
1 in.
e) One-piece flashing
d) Two-piece flashing
Bond beam, lintel orfoundation (typ.)
c) Optional unreinforced masonry
4 in. (102 mm) unit
Drip edge (typ.)
48 in. (1219 mm) o.c.#5 (#16) min. @
Mortar net*
(25 mm)
Flashing
inside of faceshellStop flashing at
> 8 in. (203 mm) wall4 in. (102 mm) unit for8 in. (203 mm) wall,3 in. (76 mm) unit for
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Detail at Inside Face Shell
Typical detail at inside of faceshell
b) Unreinforced cell
of washed pea stone. Alt. — leave out every other reduced size facing unit on top of flahing to serve as cleanouts unitl the wall is completed.* Cavity filter is any material used in conjunction with mortar nets to prevent mortar droppings from cloggin the weeps, i.e. filter paper or 2 in. (51 mm)
a) Reinforced cell
off to fit (typ. a & c)and part of webs cut
Cavity filter*
o.c. partially open2 ft. 8 in. (813 mm)Weep holes @
(typ. b & c)
1 in. (25 mm)
joints"L-shaped" head
Architectural unitwith inside faceshell
Edge of flashing
Solid unit or
Cavity filter*
from joint
to support flashingfilled hollow unit
sealed by mortar
1 in.
e) One-piece flashing
d) Two-piece flashing
Bond beam, lintel orfoundation (typ.)
c) Optional unreinforced masonry
4 in. (102 mm) unit
Drip edge (typ.)
48 in. (1219 mm) o.c.#5 (#16) min. @
Mortar net*
(25 mm)
Flashing
inside of faceshellStop flashing at
> 8 in. (203 mm) wall4 in. (102 mm) unit for8 in. (203 mm) wall,3 in. (76 mm) unit for
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Optional Flashing Detail at
Unreinforced Cell
Typical detail at inside of faceshell
b) Unreinforced cell
of washed pea stone. Alt. — leave out every other reduced size facing unit on top of flahing to serve as cleanouts unitl the wall is completed.* Cavity filter is any material used in conjunction with mortar nets to prevent mortar droppings from cloggin the weeps, i.e. filter paper or 2 in. (51 mm)
a) Reinforced cell
off to fit (typ. a & c)and part of webs cut
Cavity filter*
o.c. partially open2 ft. 8 in. (813 mm)Weep holes @
(typ. b & c)
1 in. (25 mm)
joints"L-shaped" head
Architectural unitwith inside faceshell
Edge of flashing
Solid unit or
Cavity filter*
from joint
to support flashingfilled hollow unit
sealed by mortar
1 in.
e) One-piece flashing
d) Two-piece flashing
Bond beam, lintel orfoundation (typ.)
c) Optional unreinforced masonry
4 in. (102 mm) unit
Drip edge (typ.)
48 in. (1219 mm) o.c.#5 (#16) min. @
Mortar net*
(25 mm)
Flashing
inside of faceshellStop flashing at
> 8 in. (203 mm) wall4 in. (102 mm) unit for8 in. (203 mm) wall,3 in. (76 mm) unit for
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Good Flashing Detail
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Poor Detail
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Drip Edge
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End Dams
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Weep Holes
At 32 inches max.
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Weep Holes
• Cotton sash cord
for drainage path
(remove after wall
is laid up)
• Partially open
head joints
(preferred)
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Products & Workmanship Tying it all Together
• 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
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Mold Susceptibility
Building
Material
Susceptible to
mold growth?
Provides food
source for mold?
Deterioration
from mold?
Concrete Masonry Yes No No
Gypsum Wallboard Yes Yes Yes
Wood surfaces Yes Yes Yes
Vinyl, linoleum Yes No (except for
adhesisves)
Yes
Plastics, metals Yes No No
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Mold Remediation
Building
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
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Summary
Masonry is a good
choice!
Simply choosing
masonry is not
enough - attention
needed for design,
construction and
maintenance.
NCMA