Damage From Construction Defects and Water Intrusion in

Damage From Construction Defects and
Water Intrusion in Residential Walls :
Understanding What Really Goes On
So You Can Limit Your Liability
George Tsongas, Ph.D., P.E.
Consulting Engineer
Professor Emeritus of Mechanical Engineering
Portland State University
ONE OF THE MAJOR PROBLEMS
WITH CONSTRUCTION DEFECTS:
WATER INTRUSION
! Defects can allow excessive water entry into building
envelope components
! Many construction defects cause wall component
moisture-related damage
! Siding buckling and swelling, mold and decay
“CONSTRUCTION DEFECT” CAUSES
! Improper or poor design
! Lack of sufficient details
! Improper installation of components
! Not following installation instructions
! Sloppy construction
! Lack of attention to detail
! The devil is in the details!!
! Poorly designed or manufactured components
! L-P siding, EIFS, fire retardant treated plywood
! Lack of - or insufficient - maintenance
PROBLEM #1: SIDING WAVINESS
AND BUCKLING
! Deformation of siding out of the plane of the wall
! Cause #1: by elongation of siding in length direction
! Elongation caused by moisture content increase
! From dry summer to wet winter condition
! Common in all wood products, natural or composite
! Cause #2: siding following waviness of sheathing or studs
! Usually occurs during first year after construction
PHOTO: WARPED PLYWOOD WETTED
BY WINDOW LEAK THAT CAUSED
“BUCKLED” SIDING
PHOTO: WAVY SIDING
FOLLOWING WETTED
& WARPED PLYWOOD
Wavy siding
PHOTO: CROOKED STUDS
CAUSING “BUCKLED” SIDING
SIDING BUCKLING CRITERIA
Stud 5/8” out of
plane of wall
! Out of wall plane deformation of greater than ¼
inch is buckling; waviness is less deformation
! Clearly visually unacceptable to
homeowners
! Buckled siding still functions well as a
cladding (keeps rain out)
WHEN DOES BUCKLING OCCUR?
WHEN DOES BUCKLING NOT OCCUR?
! Does not occur when siding nailed to studs spaced at 16”
! Siding sufficiently restrained by such proper nailing
! Studs spaced 16” o.c. is standard construction
PHOTO: BUCKLING WITH NAILING AT
16” O.C. WITH BACKSIDE WETTING
! Siding nailed at 16” o.c., but siding gets excessively wet
on its backside due to water leaks (construction defects)
! Siding nailed at greater than 16” on center
! Larger stud spacings do not provide enough restraint
! Sometimes caused by nails missing studs (“shiners”)
! Sometimes caused by missing nails
! Exacerbated by siding wetted on backside due to leaks
! Exacerbated by lack of required vapor barrier
! Siding follows wavy sheathing or studs
! Siding relative thin (e.g., fiber-cement lap)
PHOTO: BUCKLING WITH NAILING
AT GREATER THAN 16” O.C.
Can occur without backside wetting
24”
Water leak site
Hardboard siding
PHOTO: STUD SPACING UNEVEN AND
OFTEN GREATER THAN 16” O.C.
PHOTO: BUCKLING WITH TRUE NAILING AT
GREATER THAN 16” DUE TO MISSING NAILS
Numerous “shiners”
(missing nails)
PHOTO: BUCKLED T1-11 PLYWOOD PANEL
SIDING DUE TO IMPROPER NAILING
PHOTO: BUCKLED FIBER-CEMENT SIDING
PHOTO: WAVY FIBER-CEMENT SIDING
PHOTO: WAVY
CEDAR SIDING
PHOTO: BUCKLED CEDAR SHINGLE SIDING
PHOTO: PSU LAB BUCKLING TEST SETUP
Buckles
Cedar shingle panel siding
PROBLEM #2: SIDING SWELLING
PORTLAND STATE UNIVERSITY (PSU)
TESTS OF HARDBOARD SIDING BUCKLING
! Sprayed water on shiplap siding of test walls for 8 weeks
to simulate 95-100% outdoor relative humidity condition
! Siding nailed to studs spaced at 16”, 24”, and 32”
! Siding nailed at 16” did not buckle or deform at all
! Siding nailed at 24” & 32” did deform out of plane
SIDING DRIP EDGE SWELLING
! Edge swelling occurs near bottom edges of siding
! Sometimes occurs; typically due to thin or no paint on
siding drip edge of composite wood siding products
! Water drops hang on drip edge with thin or no paint
! Then liquid water absorbed by capillary action up
into the fiber of the siding drip edge
! Water absorption causes the siding to swell
locally at drip edge
! Two types:
! Drip edge swelling
! Face swelling
(sometimes observed as
swelling or “dimpling”
around nail heads)
SIDING DRIP EDGE SWELLING –
ALMOST ALWAYS CAUSED BY THIN
OR NONEXISTENT DRIP EDGE PAINT
! Very slow process---typically takes years for
swelling to become noticeable
! Typically occurs due to poor spray painting of
the siding drip edges
! Violation of siding application instructions
! Typically does not result in siding decay, except:
! Lowest siding course near grade or concrete
! Any course of older OSB siding
PHOTO: LACK OF DRIP EDGE PAINT
PHOTO: DRIP EDGE SWELLING & DECAY
Swollen drip edge
(poorly painted)
Decayed unpainted
bottom drip edge—
too close to grade
PHOTO: NATURAL WOOD TRIM
UNPAINTED CUT END DECAY/SPLITTING
PHOTO: VERTICAL CORNER TRIM WITH AND
WITHOUT CUT EDGE SWELLING/DECAY
Hardboard trim
with unpainted
cut ends
Swollen cut ends
Contact with
flashing
SIDING FACE SWELLING – ALMOST ALWAYS
CAUSED BY WETTING OF SIDING BACKSIDE
! Most typically occurs due to absorption of large amounts of
liquid water on the backside of siding
! Water gets there from leaks caused by construction errors
! Typically much more water gets into the siding than with
poor drip edge paint
! Much more common cause of siding swelling, bowing & decay
! Swelling leads to micro-cracking of drip edge paint
! Note: liquid water does not migrate through proper face paint
No cut end
swelling
No contact
with flashing
PHOTO: FACE SWELLING
(“DIMPLING” AROUND NAIL HEADS)
Leaking behind siding
at siding-trim joint
“Dimpling” or “puckering”
(swelling) around nail heads
PHOTO: MICRO-CRACKING
OF THE SIDING DRIP EDGE
PHOTO: PSU FACE SWELLING LEAK TEST
Drip water inlet
(once each day)
Leak test wall
(new hardboard
siding)
Simulated leak between back of siding and building paper
PSU WALL LEAK TEST
RESULTS
! After only two weeks of daily intermittent
dripping the following was observed:
! Definite bowing of siding at the drip edge
between nails
! Siding swelling
! Micro-cracking of the drip edge paint
PSU WALL LEAK TEST
CONCLUSIONS
! Lab test results duplicated siding deterioration
observed in the field
! Verified cause of siding swelling, bowing between
nail heads, and micro-cracking of drip edge paint
observed in the field
! Due to water being absorbed on siding backside
PHOTO: PSU LEAK TEST SIDING BOWING
Unsealed
joints
PHOTO: SIDING
BOWING
BETWEEN NAIL
HEADS
PROBLEM #3: WOOD DECAY (ROT)
WHEN DOES WOOD DECAY?
! Caused by growth of decay fungi
! Requirements for growth of wood decay fungi:
! Abnormally wet wood (i.e., soaking wet)
! Moisture content greater than 25-30%
! Wood normally wettest in late-winter
! Warm wood temperature
! Optimally 75-90°F
! Little or no growth below 50°F
! Wood typically not so wet during warm weather
! Typically occurs only when siding is excessively wet
during warm weather on unpainted or poorly painted
drip edges
! Occurs often on lowest siding courses due to
repeated, long term wet contact (such as with
concrete or soil), splash back, or sprinkler wetting
! Also occurs commonly when siding or other wall
components get excessively wet due to leakage of
liquid water behind siding due to construction errors
HOW LONG DOES IT TAKE FOR
DECAY TO BECOME VISIBLE?
COMMON DECAY LOCATIONS
! Under the right conditions, decay can start
microscopically in a matter of hours or days
! Under optimum conditions, decay fungal growth
can become visible in a month or so
! More often, decay takes years to progress to the
point where it is clearly visible
! Note: decay can produce significant strength loss
much more rapidly than weight loss (clearly visible)
! Window openings, particularly at corners
! Typically most frequent problems
! Intersection of walls with floors or slab-on-grade
! Intersection of walls with exterior balconies/walkways
! Siding lowest course too close to soil or concrete
! Siding lowest courses wetted by sprinkler spray
! Handrail connections; rail caps (especially fences)
! Belly bands and other plant-on trim
! Confined rakes (gutter ends)
PHOTO: SIDING DECAY BELOW
LEAKING WINDOW TRIM
PHOTO: OSB SHEATHING DECAY
BELOW LEAKING WINDOWS
Unsealed trim joint
PHOTO: SIDING DECAY CAUSED BY
CONTACT WITH WET CONCRETE
PHOTO: DECAYED SILL TRIM
(SIMILAR TO BELLY BAND)
No sealant or
Z-flashing
PHOTO: SIDING DECAY BELOW
IMPROPERLY INSTALLED DECK
Deck ledger directly
up against siding
without flashing
(trapping rain water)
PHOTO: STAIRWAY LANDING LEAKING
INTO WALL & OUT BETWEEN SIDING LAPS
Concrete landing defect:
leaky metal flashing--joints not soldered
Water leak out from
between siding laps
PHOTO: DECAY BELOW
STAIRWAY LANDING LEAK
Gypsum
sheathing
OSB
sheathing
decay
PHOTO: SIDING DECAY
CAUSED BY WATER
LEAK BEHIND THE
SIDING ON EXTERIOR
BALCONY
Decay
Leak
site
Leak site
PHOTO: FENCE
SIDING DECAY
CAUSED BY
WATER LEAK
Decay
PHOTO: RAILING DECAY CAUSED
BY MITER JOINT WATER LEAK
PHOTO: FENCE
POST DECAY
CAUSED BY
WATER LEAK
Decayed
4x4 post
PHOTO: DECAY AT HANDRAIL
CONNECTION TO WALL
PHOTO: DECAY BELOW BALCONY LATTICE
PHOTO: CEDAR
SIDING DECAY
CAUSED BY
EXCESSIVE
WETTING AT
PRIVACY FENCE
RAIL CAP
CONNECTION
Even cedar
can decay
Decay fungi
PHOTO: DAMAGE FROM GUTTER END LEAK
PHOTO: TRIM DECAY
CAUSED BY POOR DESIGN
No kick-out flashing
PHOTO: MAINTENANCE ISSUE---SIDING
WETTED BY ERRANT SPRINKLER SPRAY
PROBLEM #4: MOLD GROWTH
Very common in just about
all multifamily housing
Decayed siding
drip edge (mold
inside wall cavity)
! Mold grows on a surface when the relative humidity
of the air next to it is excessively high (> 80%)
! Due to indoor cold surface temperatures
! Due to excessive indoor air moisture generation
! Due to wet surfaces
! Typically caused by leaks from outside or
contact with or proximity to wet concrete
Sprinkler
wetting
PHOTO: MOLD ON COMMERCIAL BUILDING
CEILING TILE DUE TO LEAK ABOVE
Mold
PHOTO: CEILING &
WALL MOLD FROM
CONSTRUCTION
ERROR (SCUPPER
LEAK INTO WALL)
Mold on top side of
ceiling tile (turned over)
Water stain
POSSIBLE WAYS WATER COULD
ENTER WALL CAVITIES WITH
MINIMAL, IF ANY, ADVERSE EFFECT
TYPES OF WATER ENTRY AND
MOVEMENT MECHANISMS IN WALLS
! Those that do not cause decay or other damage
! Water entry amounts are not excessive
! Those that cause damage to wall components
! Water entry amounts are excessive
SCHEMATIC: WATER ENTRY BY WICKING
LIQUID UP INTO SIDING BOTTOM DRIP EDGE
!
!
!
!
Liquid water through siding nail holes
Liquid or vapor water through siding exterior paint
Rain wind-blown up in between siding laps
Wicking liquid up into bottom drip edge of siding
! Typically not a problem with well-painted drip edges
! Wicking liquid water up between siding laps
! Not a problem for some types of siding
SCHEMATIC: WATER ENTRY BY CAPILLARY
WICKING UP BETWEEN SIDING LAPS
Not a problem
when drip edges
well painted
PHOTO: PSU LABORATORY
WICKING SPRAY TEST SETUP
CAPILLARY WICKING
BETWEEN SIDING LAPS
! Often proposed without basis
! Never confirmed by any scientific tests anywhere in the
world
! Except for PSU laboratory cedar siding spray tests
Spray test wall
PHOTO: DETERIORATED, WATER-LOGGED
PAINT ON CEDAR SIDING
PORTLAND STATE UNIVERSITY
LABORATORY SPRAY WICKING
AND OTHER TEST CONCLUSIONS
! Capillary wicking up between siding laps:
! Does not occur for hardboard and fiber-cement siding
! Proven in numerous laboratory tests
! Does occur with cedar siding in spray wicking tests
! Likely causes staining and paint adhesion problems
WATER STAINING OF BACKSIDE OF
SIDING OFTEN GIVEN AS PROOF OF
WICKING UP BETWEEN SIDING LAPS
Water enters into
siding by wicking
between siding laps
PHOTO: SIDING WHERE BACKSIDE
DRIP EDGE WATER STAINED
No trim-to-siding caulk
Trim-to-siding caulk
! But, staining of backside caused by water leaking
into the backside of the siding due to construction
errors and migrating along drip edge
! Numerous examples of such leaks and
subsequent staining
! Not due to wicking up between siding laps
PHOTO: SIDING BACKSIDE WATER
STAINING FROM DEFECT LEAK
No caulk
leak joint
Water stain
Water leaks in at edge and moves laterally along drip edges
WAYS WATER DOES ENTER WALL
CAVITIES AND CAUSES DAMAGE
! Liquid water leaking behind siding (e.g., around windows)
! Includes moving through weather-resistant barriers
! Liquid water wicking into gypsum sheathing behind siding
! Liquid water wicking up into bottom drip edges of siding
! With poorly-painted or unpainted drip edges
! Siding contact with concrete, or siding too close to soil
and drip edges with little or no paint
! Rain splash back; sprinkler wetting
! Water vapor migrating into walls from inside the house
! Solar-driven moisture transfer from siding into sheathing
! Indoor moisture entry from or through wet concrete floors
! Moisture entry into walls from wet lumber
LIQUID WATER LEAKING BEHIND SIDING
USUALLY DUE TO CONSTRUCTION ERRORS
! Leaks into walls can be a huge source of liquid
water behind the siding
! Liquid water that gets to the siding’s backside
is more readily trapped and absorbed
! Windows commonly leak and flashing and sealant
errors often occur that allow water entry into walls
COMMON LEAK LOCATIONS
! Window openings, particularly at corners
! Typically most frequent problems
! Intersection of walls with floors or slab-on-grade
! Intersection of walls with exterior balconies/walkways
! Siding lowest course too close to soil or concrete
! Siding lowest courses wetted by sprinkler spray
! Handrail connections; rail caps (especially fences)
! Belly bands and other plant-on trim
! Confined rakes (gutter ends)
PHOTO: WATER LEAK HOLE AT
UNSEALED WINDOW HEAD TRIM
SURPRISINGLY LARGE WATER
LEAK FLOW RATES DUE TO
CONSTRUCTION ERRORS
! Small openings are not uncommon in building
construction
! Calculated and lab test proven water flow rates
through small horizontal leak openings:
! 1/8 inch diameter hole: 2 gallons per hour
PHOTO: MORE WINDOW LEAK SITES
No sealant or metal flashing
Decay
Siding
Window head trim
PHOTO: OTHER WINDOW LEAK SITES
No window frame-to-trim
sealant
Unsealed joint in trim
Short L-metal
flashing under
head trim
Z-metal flashing (often missing)
Open kerf (saw) cut in siding
PHOTO: DAMAGE DUE TO SEEPAGE AT
UNSEALED WINDOW TRIM MITER JOINTS
Roof
flashing
leak
PHOTO: SEVERE
STRUCTURAL
DECAY FROM
SMALL ROOF
FLASHING LEAK
No caulk at miter joint
Leak site
PHOTO: SIDING
DECAY DUE TO
STAIRCASE--SIDING
JOINT LEAK
PHOTO: WATER
LEAK HOLE AT STAIR
LANDING BEAM
PENETRATION
Hole into wall
Buckled
siding
Swollen (dimpling
around nail head)
PHOTO: WALL
SIDING WITH LEAK
SITE AT 3RD STORY
WALKWAY
Leak site
PHOTO: THIRD
STORY LEAK SITE
Finger size hole
Leak site
Leak site
PHOTO:
CONSEQUENT MOLD
& DETERIORATION
ON GYPSUM
SHEATHING
PHOTO:
CONSEQUENT MOLD
& DECAY ON BACK
OF REMOVED SIDING
PHOTO: WATER LEAK HOLE
(BALCONY TO SUPPORT COLUMN)
PHOTO: DECAY DUE
TO BALCONY-TOCOLUMN LEAK
Hole
AMOUNT OF LIQUID WATER
REQUIRED TO CAUSE DECAY
! Assume a roughly 16 square foot area of ½ inch
thick wood siding or sheathing
! Assume a moisture content change from normal
(dry) 10% to 30% required to grow decay fungi
! Amount of water required that must be absorbed
into the wood siding or sheathing just to raise its
moisture content that amount is about 1 gallon!
! Laboratory wall leak drainage test results suggest
that at least 10 times as much water drains out of
a wall as is absorbed by the wall components
! Thus, water leaks into walls must be relatively
large (many gallons) when decay occurs
PHOTO: SIDING
DECAY DUE TO
BALCONY-TOCOLUMN LEAK
Approximately 16 sq. ft.
PHOTO: SIDING & TRIM DECAY
CAUSED BY WINDOW TRIM LEAKS
LAB WALL FLASHING LEAKAGE TESTS
! Walls tested with windows properly and
improperly flashed and caulked
! To determine if construction errors allowed
water intrusion that caused resultant damage
! Followed ASTM E 331 standard test protocol
! Full scale walls sprayed in a laboratory for 3
hours to simulate severe wind-driven rain
Windows poorly flashed and sealed
PHOTO: LABORATORY WINDOW
FLASHING LEAKAGE TEST SETUP
PHOTO: WINDOW FLASHING LEAKAGE
TEST RESULT
Surprisingly large amounts of liquid water can
enter wall cavities from small but typical flashing
and sealant errors, especially around windows
Spray rack (9 nozzles)
29 gallons
WINDOW FLASHING LEAKAGE
TEST CONCLUSIONS
PHOTO: SIDING & TRIM DECAY
CAUSED BY A WINDOW TRIM LEAK
No sealant or Z-metal flashing
! Surprisingly large amounts of liquid
water can enter wall cavities from small
flashing and sealant errors
! Especially around windows
! Note: recent Canadian studies show that
all windows eventually leak to some
degree (sometimes significantly)
Decayed trim
PHOTO: WALL CAVITY DAMAGE CAUSED BY
WINDOW LEAK (NO SILL TRIM SEALANT)
No window
frame-to-sill trim
sealant
PHOTO: SIDING AND TRIM DECAY
DUE TO LACK OF SEALANT
No window frame to
siding sealant
Unsealed miter
joint
PHOTO: WINDOW LEAK DETERIORATION
PHOTO: WINDOW LEAK
DRYWALL DAMAGE
Siding backside
Trim backside
RESOLVING LIQUID WATER LEAKAGE
AROUND AND THROUGH WINDOWS
! Water leakage obviously occurs around window trim
! Siding and trim damage common around windows
! Designers and builders should take the approach that
any window may allow water through at some time and
design to handle that water
! Proper window sill sloping and sealing is crucial
! Proper window flashing is crucial
! Improved wall water drainage is crucial
! Building paper or housewrap alone is not enough
LATERAL WATER MIGRATION:
DOES IT OCCUR AND MAKE
MATTERS WORSE?
! Siding and trim deterioration is often obvious near
or below a known water leak entry point
! What about siding deterioration well away from
the point source?
! Often observed
! Is it related to the known leak source?
PHOTO: PSU LATERAL WATER MIGRATION
LAB TEST SETUP
PHOTO: LATERAL WATER MIGRATION
STAINING BEHIND HARDBOARD SIDING
Drip water inlet--leak behind siding
Water entry site
Lateral migration
Lateral migration
test wall--no water
on outside of siding
Water migrated at 16°
angle from horizontal
PHOTO: LATERAL WATER MIGRATION
TESTS WITH REDWOOD SIDING
LATERAL WATER MIGRATION
TEST CONCLUSIONS
Point source water input
Leak
out of
wall
PHOTO: LATERAL WATER MIGRATION
! Once water leaks behind siding it can readily move
laterally to locations well away from the leak source
point
! Such migration not limited to one type of siding
! If sufficient water leaks into a wall, siding,
sheathing, and trim deterioration can be expected
just about anywhere in the wall---even well away
from the leak source point
PHOTO: LATERAL WATER MIGRATION
Unsealed corner trim
(water entry location)
Leak between Unsealed
shutter corner trim
and window to right
Shutter
Siding backside
Decay fungi
Drip edge water staining might suggest wicking between the laps
Decay fungi
Decayed trim
PHOTO: LATERAL WATER MIGRATION
PHOTO: LATERAL WATER MIGRATION
Leak site
Buckling &
swelling due
to backside
wetting
COMPUTER MODELING DRYING RESULTS
RAIN WATER LEAKS ARE A MAJOR
CAUSE OF HIDDEN MOLD AND DECAY
! Leaks are not uncommon in new construction
! Caused by numerous types of construction errors
! Leaks can result in considerable wetting of materials
! Wet building materials do not always dry out quickly
! Wall components can take many months to dry
! Based on computer simulation
! There is ample time for fungal growth
LIQUID WATER GETTING INTO OR BEHIND
SIDING DUE TO CONSTRUCTION ERRORS
! CONCLUSION:
! This is a major cause of the wall
component swelling, mold growth
and decay that exists in buildings
Fiber saturation
WATER ENTRY BY WICKING LIQUID
UP INTO GYPSUM SHEATHING
! In multifamily housing gypsum sheathing often
exists behind siding for fire protection reasons
! Gypsum sheathing behind siding readily wicks water
up from its base that is wetted by:
! Ponding water from rain or spray washing
! Rain or spray washing splash back
! Misdirected sprinklers
! Wet concrete base that gypsum sheathing sits on
PHOTO: MOLD & DETERIORATION OF
BUILDING PAPER ON WETTED WALL
WET GYPSUM SHEATHING
WICKS WATER INTO SIDING
OR STRUCTURAL SHEATHING
SURROUNDING IT
! Leads to moisture damage to those wall
components, including mold and decay
Gypsum sheathing
wetted at its lower
edge
Gypsum
Sheathing
PHOTO: MOLD ON
GYPSUM SHEATHING
& MOLDY, DECAYED
OSB SHEATHING
SCHEMATIC: PSU LABORATORY
VERTICAL WICKING TEST SETUP
OSB
Sheathing
Mold & decay
PHOTO: PSU LAB VERTICAL WICKING
TEST SETUP
PSU LABORATORY VERTICAL
WICKING TEST RESULTS
! In 20 days water wicked up gypsum sheathing
about 4 feet
! Wicked up 10 inches in first day
! In 20 days water wicked up hardboard siding ¼ 2¼ inches
! Wetted gypsum sheathing caused deterioration of
plywood & OSB sheathing
PHOTO: PSU TEST DAMAGE TO PLYWOOD
SHEATHING FROM WETTED GYPSUM
WATER ENTRY BY WICKING UP INTO
POORLY PAINTED BOTTOM DRIP EDGE
Mold
PHOTO: DRIP EDGE SWELLING
CAUSED BY WICKING INTO EDGE
Caused by thin drip edge paint
PHOTO: OLD OSB LAP SIDING WITH DECAY
FUNGI GROWING FROM DRIP EDGES
PAST PROBLEMS WITH OSB SIDING
! OSB siding had design and manufacturing problems
! Drip edge was hard to seal and prone to swelling—
allowed water entry by capillary wicking into siding
! Exterior face surface was a vapor retarder
! Created by resin-coated kraft paper face
! Trapped liquid water wicking into drip edge
! Kept wetted OSB from drying out
! Combination led to swelling, cracking, & decay
! Old OSB siding was inherently defective in my opinion
PHOTO: OLD OSB PANEL SIDING WITH
DECAY FUNGI GROWING FROM GROOVES
Decay fungi
Water wicked into drip edges
that were poorly sealed
Ketchikan, Alaska housing
POSSIBLE FUTURE PROBLEM
WITH FIBER-CEMENT SIDING
! Lack of paint or thin paint on drip edges could allow
significant water to wick into the siding
! Fiber-cement siding is highly absorbent
! Job site wetting prior to painting could do the same
! Solar heating could drive water vapor from the siding
into the sheathing & framing
! Thus increasing its moisture and causing mold or
decay of moisture barriers, sheathing, & framing
! Not readily observed from the outside
WATER ENTRY BY SIDING
CONTACT WITH WET CONCRETE
OR SIDING TOO CLOSE TO SOIL
PHOTO: ANOTHER PROBLEM--CRACKED
FIBER CEMENT LAP AT BUTT END
Longitudinal expansion & contraction
PHOTO: SIDING DECAYED DUE TO
CONTACT WITH CONCRETE
Face swelling (“puckering” around nail heads)
! Contact with concrete readily wicks liquid water into siding
! Poor construction practice
! Violation of some siding application instructions
! Leads to siding decay
! Building codes and manufacturer’s installation instructions
require 6” separation of bottom course of siding from soil
! Splash back in cases with less than 6” separation has led
to siding swelling, mold and decay
PHOTO: T1-11 PLYWOOD SIDING DECAYED
DUE TO CONTACT WITH WET CONCRETE
Decayed siding
PHOTO: SIDING DECAY FROM
CONTACT WITH WET CONCRETE WALL
Decayed panel siding edge
Concrete foundation wall
8’ high concrete wall
PHOTO: SIDING TOO CLOSE TO
GRADE CAUSING DECAY
WATER VAPOR MIGRATING INTO
WALL CAVITY FROM INDOORS
DURING HEATING SEASON
! When indoor temperatures are warmer than
outdoor conditions, vapor drive is from
indoors (warmer) to outdoors (colder)
WINTERTIME VAPOR MOVEMENT IN WALLS
SOME CLADDINGS ARE VAPOR
IMPERMEABLE
! Thus they trap water vapor that is normally
migrating in winter from the warm indoors to the
colder outdoors
! Leading to condensation, moisture buildup in
the materials behind the siding, and decay
! Vapor permeable claddings allow the water
vapor to pass through them to the outdoors
PHOTO: METAL STUD EIFS WALL MOLD
Window leaks
PAST MOLD & DECAY PROBLEMS
WITH OLDER FACE-SEALED EIFS
! External Insulated Finish Systems (EIFS) cladding
! Also known as “synthetic stucco”
! Lack of drainage capability and inability to dry to the
outside with older face-sealed EIFS allowed significant
wetting of wall components that led to mold and decay
! Jury still out on whether new EIFS drainage systems work
! They are designed to help keep walls drier & decay free
Rusted
metal
studs
Mold
Gypsum
sheathing
PHOTO: PLYWOOD SHEATHING DECAY IN
EIFS FACE-SEALED WALL
MOISTURE PROBLEM WITH
SOME VINYL SIDING
! Some vinyl siding acts as an excellent vapor retarder on
the outside (wrong side) of the wall in cold climates
! Traps water behind it and wets moisture barriers,
sheathing, and framing
! Can cause long term mold & decay problems
! Not widely known, since not much vinyl siding
gets removed and wall cavities behind it inspected
4’ overhang
PHOTO: WATER
STAINING DAMAGE
ON GYPSUM
SHEATHING BEHIND
VINYL SIDING &
HOUSEWRAP
PHOTO: DECAY &
MOLD DAMAGE ON
OSB SHEATHING
BEHIND GYPSUM
SHEATHING &
VINYL SIDING
Portland, Oregon
PHOTO: LIQUID WATER DRAINING
OUT OF VINYL-SIDED WALL CAVITY
PHOTO: DAMAGE TO GYPSUM SHEATHING
& TJI BEHIND VINYL SIDING
Between 2nd & 3rd stories of 3-story apartment
TJI
Gypsum
sheathing
(Water stained
& moldy)
Decay
PHOTO: WATER DRIPPING OUT FROM
BEHIND VINYL SIDING
PHOTO: BACK OF SIDING DRIPPING WET
Seattle multifamily housing
Seattle multifamily housing
PHOTO: DRIPPING WET BUILDING PAPER
PHOTO: DRIPPING WET BUILDING PAPER
Wall adjacent covered walkway
Seattle multifamily housing
Seattle multifamily housing
PHOTO: DAMAGED OSB SHEATHING
BEHIND VINYL SIDING
PHOTO: DAMAGE TO GYPSUM
SHEATHING
PHOTO: GYPSUM SHEATHING
WETTING & STAINING AT CORNER
PHOTO: WATER STAINS ON GYPSUM
SHEATHING FROM SIDING CONDENSATION
Portland multifamily housing
PHOTO: DAMAGE AT RIM JOIST
WHERE NO VAPOR BARRIER EXISTS
PHOTO: SIDING CROSS-SECTION
SHOWING BLOCKED WEEP HOLE
Weep holes don’t drain well
Toothpick in weep hole
INDOOR MOISTURE ENTRY FROM WET
CONCRETE SLAB-ON-GRADE FLOORS
CAUSE OF MOLD & DECAY IN DWELLINGS
! Concrete slab floors in apartments & single family homes
! A huge indoor moisture source as the concrete dries
! Most severe during first one-two years
! Often exacerbated by lack of slab edge sealing
! Sand layer below slab can fill with water
! Vinyl floors bubble or discolor (turn moldy)
! Mold and decay fungi grow on 1st story lower wall
sections and under carpets (stained tack strips)
! Mold not found in 2nd story apartments & rooms
PHOTO: MOLD
UNDER VINYL
FLOOR OVER WET
SLAB-ON-GRADE
PHOTO: MOLD ON CARPET TACK STRIP AND
WALL DUE TO WET CONCRETE FLOOR
PHOTO: MOLD ON FLOOR MOLDING
IN POORLY HEATED CLOSET WITH
NEW WET CONCRETE
Moldy carpet tack strip
Mold on
drywall
Mold
New wet concrete floor slab
(carpet pulled back)
PHOTO: LANDSCAPING PROBLEM--IMPROPER GRADING/BERMING
RH/T datalogger
PHOTO: EFFECT OF LANDSCAPING
ERRORS---WET, MOLDY CARPETS
Ground is supposed to
slope away from building-not towards it
Earth
berm
Note carpet stains
Soaking wet soil from
rain & sprinklers
PHOTO: CRAWL SPACE CONCRETE
FOUNDATION WITH WATER STAINING
PHOTO: WHITE MYCELIUM ON COMMERCIAL
BUILDING OSB ROOF SHEATHING
This is decay fungi,
not mold fungi
MOISTURE ENTRY INTO WALLS FROM
WET CONSTRUCTION MATERIALS
PHOTO: BLACK MOLD ON A VERTICAL
STUD IN AN OPENED WALL CAVITY
! Wet green lumber (often stored outside in lumber yard)
! Sometimes with black mold on it
! “Pond-dried” lumber (left stored on site out in the rain)
! Lumber in place in home wetted before roof cover-in
! Often results in serious mold growth
! Even on kiln-dried lumber
Mold
2 x 6 Stud
! Mold from such wet materials becoming a serious issue
to prospective homeowners in new construction
OSB sheathing
PHOTO: MOLD ON WALL FRAMING
EXPOSED TO THE WEATHER
INFLUENCE OF TYPE OF MOISTURE
BARRIER ON DRAINAGE AND DAMAGE
! PSU lab tests for DuPont to compare drainage of different
housewraps and building papers under simulated wall
leak conditions (between siding & paper/wrap)
! Best drainage & least damage with furring strips
! Next best with groove-textured housewrap
! Next best with conventional housewrap
! Worst by far with Grade D building paper & No. 15 felt
! OSB sheathing moldy & decayed at end of 4 month test
in No. 15 felt case (no decay in other cases)
Long term wetting can lead to mold & decay
PHOTO: PSU LEAK DRAINAGE TEST SETUP
PHOTO: WATER
STAINING & MOLD
ON OUTSIDE OF
OSB SHEATHING
COMMON MYTH: BUILDING PAPERS AND
HOUSEWRAPS WORK WELL AT DRAINING
WATER THAT LEAKS INTO WALLS
! While most of the water that might leak into a wall
does, in fact, drain out, a small fraction is
absorbed by the back of the siding and the other
wall components
! Not all the water leaking into a wall drains out at
the bottom of the building paper or housewrap
! That small fraction that is retained in the wall
can result in elevated moisture contents that
lead to deterioration such as mold and decay
CONCLUSIONS FROM MY 30+ YEARS
OF SITE OBSERVATIONS
! The vast majority of walls are usually performing just fine
! Wall components are sometimes deteriorated in a few
locations throughout a project
! Problems occur repetitively at several typical locations
! Problems stem from certain design, construction,
material & maintenance practices
! Not following siding installation instructions
! Poor design and construction practices
! Poor maintenance
! Sometimes due to use of defective products
BE PROACTIVE ABOUT WINDOWS
! Properly install windows and doors and their trim
! Follow ASTM E 2112 (Standard Practice for Installation
of Exterior Windows, Doors and Skylights), published in
September 2002. The largest ASTM standard ever
published, E 2112 provides detailed and comprehensive
step-by-step protocols for installing and flashing
residential and light commercial windows and doors
! Use 9” peel and stick window flashing
! ASTM E 2112 has been largely ignored, but shouldn’t be
PHOTO: IMPROPER HOUSEWRAP
LAPPING/SEQUENCING
A building envelope code inspection
would prevent such occurrences
Housewrap behind
window flange
WAYS TO KEEP WALLS DRIER
AND LIMIT YOUR LIABILITY
! Work hard at avoiding construction errors
! Better training is essential
! The devil is in the details!
! Proper flashing and sealing of all kinds is
critical
WAYS TO LIMIT YOUR LIABILITY:
THE SINGLE MOST IMPORTANT
WALL CONSTRUCTION ITEM
! Build walls using a rain screen approach:
! Provide an air space behind the siding so there is
true drainage for unanticipated water leaks
! Helps avoid mold and decay problems
! Numerous workable, cost effective approaches
! Avoid the use of building papers or regular housewraps
alone without a drainage space or drainage design
WAYS TO PROVIDE A RAIN SCREEN
(WALL DRAINAGE)
! Install furring strips over housewrap or building
paper
! Provides best combination of drainage & drying
! Widely used in new Canadian construction
! Required in Vancouver, BC
! Install drainage type housewrap
! Install drainage mat over conventional housewrap
! Install any other rain screen/drainage type system
PHOTO: RAIN SCREEN APPROACH TO
WALL CLADDING CONSTRUCTION
Furring strips
SCHEMATIC:
RAINSCREEN
APPROACH
USING
FURRING
STRIPS
(STRAPPING)
PHOTO: PLASTIC HONEYCOMB BATTENS
½ OR 3/8 INCH THICKNESS
1-5/8 INCH WIDE
PT furring strips
over housewrap
Siding installed directly
over furring strips
Order from Roland Carlson
@ OrePac: 503 519 9464
PHOTO:PLASTIC BATTEN OVER HOUSEWRAP
PHOTO: SIDING OVER PLASTIC
BATTENS WITH SCREENING
PHOTO: SCREENING WRAPPED AROUND
PLASTIC BATTENS AT BOTTOM OF WALL
RAIN SCREEN WALLS MINIMIZE MOISTURE
DAMAGE WITH ALL CLADDING TYPES
! Best example: brick cladding with air space behind
! Greatly reduces moisture problems with vinyl, fiber cement,
metal, and OSB siding as well as stucco cladding
! Allows leaks due to construction errors to drain
! Siding acting as an exterior vapor retarder no longer a
problem
! Allows water vapor migrating from indoors to vent out
! Improves paint service life
Best drying with open vents top and bottom
THE END