Water Intrusion Into Buildings
Forensic Investigations
At the same time, the forces of cohesion and surface tension make water molecules stick together
and draw more water molecules up the capillary. The
smaller the tube, the higher the climb. Ultimately,
gravity limits the height of the climb. [M025]
How does water flow? Let me count
the ways.
Major building structural and operational failures are
caused by three problems: water, water, and water.
Water damages surfaces; it can create an unhealthy
environment; and it can result in rot, mold and significant structural damage. Throughout history we have
tried to control water and keep it out of our structures.
While most of us understand that gravity always pulls
water down, we may not consider that water also
moves sideways and even climbs up into cracks
through capillary action. It clings to surfaces and runs
horizontally. It freezes into a solid that can lift buildings
and push in walls. It causes soil to expand and contract.
6. Capillary action also allows water to climb or wick
through cracks and porous materials. It helps water
climb up paper toweling or drywall. It allows water
to move sideways through small openings.
7. Wind or negative pressure (suction) can force
water up and sideways through any opening.
Overhangs are Important
Drip Edge
Flashing
When investigating a water problem, specialists consider the physics behind water movement and may
use sophisticated tools to determine its route. Most
of the work involves understanding how water moves
and how certain building materials and construction
techniques can create problems.
Adhesion
allows water
to cling to
surfaces
Without Overhangs:
Water will run down
siding and windows
causing damage and rot
and enter basement.
Let’s talk about the physics of
water movement and a building:
1. Gravity always makes water flow toward the
ground. (Or so we think!)
2. Cohesion attracts water molecules to other water molecules. This force helps form water droplets and
allows water to peak over the top of a container.
X003
5. Capillary action, which is related to adhesion, allows
water to climb the sides of a capillary (a small tube).
Water Intrusion Into Buildings
Capillary Action
© Tom Feiza Mr. Fix-It Inc.
Water climbs up tubes (or gaps in building materials).
3. Adhesion causes water to be attracted to other
materials. Its “sticky” nature makes water stick to
paper or cloth, climb surfaces, and flow along
horizontal surfaces like wood trim. [X003]
4. Surface tension describes the cohesion of water
molecules that makes the surface act like a film.
Surface tension of water can be strong enough to
support a needle or a small bug.
With Overhangs and
Drip Edge:
Water drips away from
framing and basement.
Water climbs
up tube
Water
Capillary Action - Adhesion of water to the
walls draws water up the tube. The thinner
the tube, the higher the water.
© Tom Feiza Mr. Fix-It Inc.
M025
Page 1 of 14
© Tom Feiza, Mr. Fix-It Inc.
8. Air contains invisible water vapor which flows in
great quantity—up a chimney, through a vent fan,
into an attic, or into a wall.
9. Dew point is the temperature at which air
becomes saturated; at the dew point, water condenses or drops out of air as visible moisture.
When the weather forecaster says current conditions are near 100% relative humidity, the air temperature and the dew point are almost the same.
10. Condensation occurs when the temperature of
air drops below the dew point. Air holds less
water when it is cold. As air cools to a temperature below the dew point, moisture may condense
on a window, on attic sheathing, or inside a wall.
and there is little air make-up. So the homes operate under a negative pressure to the exterior, which
can draw moisture into the structure. [V032]
8. Newer buildings are often placed on the only
available land; some are in low or wet locations
prone to moisture problems.
9. We don’t build them like we used to! We
build them tighter and make them more
comfortable but also susceptible to water
damage, rot, and mold.
11. When air is saturated with water vapor, it is at
100% relative humidity. If you cool that air, it will
rain. Allow the air to touch any cooler surface
and condensation will form.
12. Burning natural gas or any fossil fuel creates a
significant amount of water vapor. We see this as
smoke up the chimney.
Let’s talk about old and newer
construction techniques:
1. Old, drafty buildings leaked lots of air and energy, but we did not care because energy was
cheap. [M008]
2. Old, drafty buildings had significant drying capacity because of air and heat leaks. Want to dry
your hair? Blow it with hot air.
3. Old buildings often had wide overhangs and flashing details that kept water away from the structure.
4. Old buildings were placed on the best locations: high
on the hills and away from surface and ground water.
5. New, tight buildings are energy efficient and comfortable, but they don’t leak air and they don’t dry
like drafty old buildings. We prevent air movement
and drying with vapor retarders (barriers), wind
barriers, efficient (direct venting) heating systems,
better windows, and tight construction techniques.
6. Vapor barriers, synthetic stucco, and similar materials can trap water and water vapor.
7. Newer building can suck. That is, they often have
mechanical fans and appliances that exhaust air,
Water Intrusion Into Buildings
Page 2 of 14
© Tom Feiza, Mr. Fix-It Inc.
Let’s talk about old and newer
construction materials:
1. Old building materials can tolerate wetting without major damage because the materials and construction were different—plaster, solid wood, no
vapor barriers, limited insulation, and so on.
2. Many newer building materials can’t tolerate wetting without damage. This includes drywall, oriented strand board (OSB), and manufactured joists
and beams. They depend on cellulose (processed
wood), paper, and adhesives for strength.
3. Cellulose and paper provide great food for mold
and fungus. Wood contains cellulose and is converted into paper on drywall or OSB, as well as to
wood/glue products, and then installed in our
homes, ready for moisture, mold, and rot.
4. Vapor barriers, OSB, synthetic stucco, and similar
materials can trap water and water vapor. They stop
air and heat movement. They limit drying. [S011]
5. We don’t build them like we used to! We
build them tighter and make them more
comfortable but also susceptible to water
damage, rot, and mold.
Where to look for water problems:
Start at the top—the roof.
Roof materials and flashing products have improved
dramatically over the years. Unfortunately, some of
today’s roof designs are complicated and difficult to
drain. Modern sealants have allowed us to think we
can skip proper flashing techniques.
Contractors also have problems finding quality
employees, and a roofing job may be given to the
lowest bidder. If we are willing to accept low price,
we will have lower quality installations, quicker and
less expensive details, and less experienced installers.
Flashings are often omitted for sealants, and no one
remembers how to make a kick-out flashing.
The chimney can also be the source of significant
water entry into the home or attic. Chimneys need
proper caps and drip edges. Wide chimneys need saddle flashings. Lack of liners for venting energy-efficient heating equipment is a common problem.
Proper design and common problems
include: (Numbers refer to illustrations)
•
Lack of drip edge flashings allow water entry.
[X004, X005]
Roof Edge Flashing - Eave
Shingles (2 layers)
Felt Paper (over flashing)
Sheathing
Rafter
Fascia
(Trim)
Metal Flashing
(Drip Edge)
Water drips
away from trim
Without drip edge,
water enters framing
and wets fascia.
Water
(Rot)
Rafter
© Tom Feiza Mr. Fix-It Inc.
X004
Water Intrusion Into Buildings
Page 3 of 14
© Tom Feiza, Mr. Fix-It Inc.
•
•
Chimneys must have caps with drip edges and
proper liners [F008, F012]
Flashings at sidewalls and chimneys are often
missing, improperly installed, or damaged.
[R015, R009]
Roof Edge Flashing - Rake Edge
Shingles
(2 layers)
Felt Paper (under flashing)
Water
Shingles
(2 layers)
Water
Metal
Rake
Flashing
Roof Deck
Roof Deck
Trim
Drips away
from wood
With Flashing
© Tom Feiza Mr. Fix-It Inc.
X005
Without Flashing
Water wets wood and
enters framing.
(Rot / Mold Potential)
Step Flashing - Sidewall / Building Paper
Building Paper / House Wrap
Step flashing (tins)
woven into shingles
Paper and siding
over step flashing
Building paper or house wrap
should be OVER the step
flashing.
R015
Water Intrusion Into Buildings
Page 4 of 14
© Tom Feiza, Mr. Fix-It Inc.
•
•
The pitch of the roof determines the proper type
of roofing material. [R013]
Ice dams can cause significant leaks. [R002]
Attic moisture problems
Moisture problems in attics may include condensation, mold, mildew, and deterioration of structural
components. Attics need to be separated from the
heat and moisture of the living space by air barriers
and tight construction. We must also ventilate the attic
to remove the moisture that penetrates these barriers.
Excessive moisture can also enter an attic through
leaks at roof penetrations and improper flashings. In
older homes, exhaust fans might channel moisture
into an attic.
Water Intrusion Into Buildings
Page 5 of 14
© Tom Feiza, Mr. Fix-It Inc.
Proper design and common problems
include: (Numbers refer to illustrations)
•
•
Attic ventilation must remove moisture.
[V030, V002]
Exhaust fans must direct moisture through the
attic. [V008, V009]
Water Intrusion Into Buildings
Page 6 of 14
© Tom Feiza, Mr. Fix-It Inc.
•
Air leaking from the heated space puts excessive
moisture into attics. [I005]
Exterior cladding (siding) and
window problems
All siding materials leak. Well, OK, almost all siding materials leak, with the possible exception of properly
installed synthetic stucco. Even brick and cement stucco
allow water to enter the wall cavity. To protect structures
from damage, we must provide a drainage surface behind
the siding and flashings through the siding to direct water
to the outside of the structure. [X002]
Brick Veneer - Flashings
Housewrap or
Building Paper
Wallboard
Paper laps
over flashing
Flashing
Joist
Weep Hole
Water
drains
Concrete
Block
Brick is porous and water enters the wall
cavity and must be drained to the exterior.
X002
Overhangs are Important
Drip Edge
Flashing
Attic - Air Bypass
Adhesion
allows water
to cling to
surfaces
COMMON AIR LEAKS INTO
AN ATTIC
Warm and moist interior air
pushes into the attic
through any opening.
Load-Bearing
Studs
Brick
attached to
frame with
metal ties
All windows and doors leak. Well, OK, almost all leak,
and if they don’t when installed, they often leak with
age. Windows and doors are holes in the siding of the
structure; they should be protected with flashings
over the opening and a pan-type gutter flashing below.
We should use wide overhangs, flashings, and gutters to
protect siding and windows from water. Shallow overhangs always cause problems with moisture intrusion
and surface damage. Shallow overhangs on two-story
walls compound the problem with water intrusion.
Keep the gutter ends out of the siding. Use a kick-out
flashing to direct water from the siding. Step flashings
away from the siding and into the gutter. [ X003]
Sheathing
Without Overhangs:
Water will run down
siding and windows
causing damage and rot
and enter basement.
Around
Chimney
With Overhangs and
Drip Edge:
Water drips away from
framing and basement.
© Tom Feiza Mr. Fix-It Inc.
Wiring
X003
Trap Door
Plumbing
Vents
Electrical
Boxes,
Lights, Fans
Gaps in Drywall
© Tom Feiza Mr. Fix-It Inc.
I005
Water Intrusion Into Buildings
Page 7 of 14
© Tom Feiza, Mr. Fix-It Inc.
All penetrations through the siding and drainage plane
must be protected from water with proper flashings.
Deck attachments to framing are a major problem. All
horizontal surfaces must be flashed and pitched to
direct water away from the wall. [X009, X011]
Exterior insulation finish systems (EIFS) or synthetic
stucco systems are great at stopping water and vapor
movement. When properly installed, they perform
well. When they are not properly installed, they can
create a major problem as they trap water behind the
wall in the wood framing. The same is true for synthetic stone veneers.
Wood surfaces and structures should never be
buried below grade. Wood siding materials should
be set above roofing materials. Exterior wood and
cement board must be painted or sealed to protect
from moisture.
Cantilevered Deck Flashing
Interior floor joists extend to support deck
Housewrap over flashings
Siding
Gap for drainage
Deck Ledger Flashing
Sheathing
Two Part Flashing
Laps over
housewrap
Housewrap or
Felt Paper (over flashing)
Siding
Drywall
Fits and
laps
around
joists and
sealed to
joist
Metal Cap Flashing
Gap for Drainage
Deckboard
Floor
Joist
© Tom Feiza Mr. Fix-It Inc.
X011
Water drains
Deck Joist
Metal or Bituminous
Flashing
Housewrap or
Felt Paper
© Tom Feiza Mr. Fix-It Inc.
X009
Water Intrusion Into Buildings
Page 8 of 14
© Tom Feiza, Mr. Fix-It Inc.
Horizontal Panel Flashing and Problems
Proper design and common problems
include: (Numbers refer to illustrations)
•
Siding and trim need “Z” or cap flashings at horizontal joints. [X006, X007, X008, X013]
“Z” Flashing - Panel Siding
Housewrap
(over
flashing)
Flashing
Here
Vapor
Barrier
Gap open
to drain
Plywood or
Hardboard
Panel Siding
© Tom Feiza Mr. Fix-It Inc.
Building Paper
or Housewrap
Flashing
Drywall
Sheathing
Siding
Rigid Insulation
Gap and NO caulk
here to drain water
Wall
Framing
© Tom Feiza Mr. Fix-It Inc.
X008
Metal “Z” Flashing
or Cap Flashing
Housewrap
over
“Z” Flashing
Horizontal Panel Flashing, Problems
Water drips away
Rot
Rot
Building Paper
or Housewrap
X006
Rot
Horizontal Trim Flashing and Problems
Horizontal Flashing
Siding
Building Paper
or Housewrap
Water
trapped
Caulk
Rot
No Flashing
No flashing. Water
enters through
capillary action
and pressure.
Siding
Caulk
Paper over
Flashing
Rot
Tight joint and
caulk. No slope
traps water.
Water enters and
causes rot.
Flashing tips into
wall and traps
water resulting in
leaks and rot.
© Tom Feiza Mr. Fix-It Inc.
X013
Flashing
Trim
Water
enters
Drip
Trim
© Tom Feiza Mr. Fix-It Inc.
PROBLEM: Caulk always fails.
Water enters wall; causes rot.
X007
Water Intrusion Into Buildings
Page 9 of 14
© Tom Feiza, Mr. Fix-It Inc.
•
Window and door penetrations must have flashings to stop water penetration above and below
the opening. The house wrap or building paper
must be installed shingle fashion to keep water
out of the structure. [X010, X012]
Windows with Nailing Flange - Flashing
Rigid Insulation
Housewrap
or Felt
Basement and foundation problems
A basement is a hole in the ground that supports the
structure and wants to fill with water. A crawl space
is a shallow hole in the ground that wants to fill with
water. Slab on grade construction is a platform just
waiting to be dropped or lifted by changes in moisture content in the supporting soil or by frost.
Siding
Continuous
Caulk under
Nailing Flange
Wrap over
Flange
Flashing Tape
Seals Wrap
We must always protect foundations with proper
grading, gutters, and downspouts. Surface grading
keeps water away from the foundation; gutters collect
rainwater; and downspouts direct rainwater away from
the foundation. We also protect basements with freedraining backfill, drain tiles, and sump pump systems.
Head
No Caulk
Here
Integral Nailing Flange
Caulked to Opening
Lower Flange
over Housewrap
Sill
Proper design and common problems
include: (Numbers refer to illustrations)
•
Basement concrete block – newer construction
[B005]
Flashing Over Window
© Tom Feiza Mr. Fix-It Inc.
X012
Siding
Rigid Insulation
Housewrap or
Building Paper
(over flashing)
Cap Flashing
Drip
(Drainage)
© Tom Feiza Mr. Fix-It Inc.
X010
Water Intrusion Into Buildings
Page 10 of 14
© Tom Feiza, Mr. Fix-It Inc.
•
Measure for proper grading [B011]
•
Basement leaks – top of wall [B013]
•
Grading – incorrect, correct [B003]
Water Intrusion Into Buildings
Page 11 of 14
© Tom Feiza, Mr. Fix-It Inc.
•
Basement leaks at lower block [B012]
•
Efflorescence (salt) stains [B033]
•
•
cause major moisture problems inside homes. All
gas-fired appliances must be vented to the outside
to remove products of combustion and related
moisture. All humidification equipment must be
Sump pump – roots in crock [B052]
Downspout lateral broken [B061]
Mechanical system problems
Improperly installed or improperly operated heating, ventilation and air conditioning systems can
Water Intrusion Into Buildings
Page 12 of 14
© Tom Feiza, Mr. Fix-It Inc.
carefully operated. Air conditioning systems must
drain condensate properly.
Fan systems that move air must be balanced to avoid
a negative pressure. Negative pressure can be created
by a forced-air system without proper returns, largecapacity exhaust fans, or a roaring fire in the fireplace. Negative pressure can make combustion appliances backdraft. Negative pressure can draw water
into cracks and crevices from the outside.
Proper design and common problems
include: (Numbers refer to illustrations)
•
•
Gas water heater with signs of backdrafting [V033]
Backdrafting fireplace, kitchen fan = smell [V031]
Moisture investigation techniques
Moisture investigations start with an interview of the
building occupants and a discussion of the problem
and its history. A visual inspection will reveal symptoms
of a moisture problem: stains, active leaks, condensation, efflorescence, rot, mold, and damaged surfaces.
Water Intrusion Into Buildings
Tracking down the moisture entry or condensation
and the reason for the problem is a little tricky. Often
moisture entry points are hidden and require an understanding of water flow and building construction. If
we are lucky, a simple solution can be identified.
Investigation may also involve the use of meters
that measure moisture content inside a material.
These meters sense the density or electrical resistance to reveal the moisture content. Experience is
necessary for accurately interpreting the reading
from a moisture meter.
Condensation and negative pressure problems may
require a scientific review of the relationship between
mechanical and building systems with sophisticated
pressure and flow testing.
Page 13 of 14
© Tom Feiza, Mr. Fix-It Inc.
Props for a presentation / demonstration:
•
Demo capillary action
•
Trimex meter for EIFS
•
•
Moisture meters and damp materials
EIFS material
Written by Tom Feiza, PE, BSME
Construction Consultant
Tom Feiza - Mr. Fix-It, Inc.
4620 South Raven Lane, New Berlin WI 53151
262-786-7878 e-mail [email protected]
Technical assistance:
Don Cohen, PE, Building Consultant 262-242-9791
Brian McDonald, Ph.D, S.E., 650-688-6946
Water Intrusion Into Buildings
Page 14 of 14
© Tom Feiza, Mr. Fix-It Inc.