INTRODUCTION TO
COMMERCIAL ROOFING
James L. Hoff, DBA
Commercial Roofing
• Historical Perspective
• Modern Roofing Materials
• Membranes
• Insulations
• New Roofing Trends
Introduction to Commercial Roofing
A Brief History of Commercial Roofing
Historical Background
Pre-1900: Before the Modern Age
• Roofing materials selected for durability and
appearance
• Slate
• Tile
• Metal
• Roofing systems designed to shed water
•
•
•
•
•
•
•
Gables
Hips
Valleys
Crowns
Saddles
Gutters
Downspouts
Historical Background
1920s : The Bauhaus
• Lightweight Framing Systems
• Roof weight becomes a consideration
• Rectangular, Low-Rise Profiles
• Roof plane becomes virtually level
• Facades and Parapets
• Roof becomes an isolated sump
As a result, roofing materials
were selected on the basis of
durability and weight, while roof
systems were designed to resist
water.
Historical Background
Today : The “Big Box”
What started as architectural theory is now economic fact
“Steeply sloped roofs on the large, sprawling buildings that dominate today’s
construction would dramatically cut the costs of re-roofing, repair and litigation. but
they would raise construction costs by a far greater amount … the costs of steeply
sloped roofs over the vast acreages covered by modern buildings are simply too high a
price to pay to avoid the problems posed by low-slope roof systems.”
(C. W. Griffith & R. Fricklas, Manual of Low-Slope Roofing Systems, 1996)
Historical Background
1840s – 1970s: Built-Up Roofing
Historical Background
1840s – 1970s: Built-Up Roofing
• Originally employed to waterproof ships
• Redundant layers of bitumen & felts
• Bitumen serves as adhesive and waterproofing
• Felts stabilize and strengthen the bitumen
• Frequently surfaced with aggregate
• Traditional “tar & gravel” roof
Historical Background
1840s – 1970s: Built-Up Roofing
• Dominated commercial roofing for over a century
• Provided a satisfactory barrier to water entry
• Success attributed to redundancy of design and wellunderstood application standards
Historical Background
1970s: The Perfect Storm
• Asbestos health concerns


Traditional roofing “felts” relied on
asbestos fibers for strength
Asbestos fibers replaced by lower strength
organic (paper) fibers
• OPEC oil embargo


Quality of roofing asphalt decreased as
more gasoline was extracted from every
barrel of oil
Roofing asphalt became more brittle, less
plastic
Historical Background
1970s: The Perfect Storm
• The response: Roof insulation
increased to save energy
• “R” value doubled or tripled
• Roof surface isolated from building interior
• Roof surface daily temperature swings up
to 150ºF
The result: Premature roof aging
& failure
• Non-asbestos felts lacked strength and
moisture resistance
• Asphalt became brittle
Historical Background
1970s: New Answers – And Plenty of Them
• Tire manufacturers introduce Rubber Roofing
Neoprene, Butyl, EPDM
• Textile manufacturers introduce Thermoplastic Roofing
PVC, PE, CPE, CSPE, E-P, TPO
• Asphalt manufacturers introduce Polymer Modifiers
APP, SBS, SEBS
“According to industry estimates, over 100 new manufacturers of roofing
products emerged during the ‘70s and early ‘80s, each offering the
‘miracle’ answer for roofing performance.”
(J.L. Hoff, “The Commercial Roofing Industry: New Directions in Construction Quality”, 2003)
Historical Background
1980s: A Steep Learning Curve
• Rubber roofing:
Leaks at adhesive seams
• Thermoplastic roofing:
Membrane cracking
• Modified bitumen roofing:
General workmanship issues
Historical Background
1980s: The Lesson for the Roofing Industry
"As an industry, we have
spent far too much time and
far too many dollars fixing
past problems related to
durability not to become
unflinching advocates for the
utmost importance of
durability…”
James L. Hoff. “Advancing Sustainable Roofing: LEED and the Commercial
Roofing Industry." Proceedings of the 20th International Convention of the
Roof Consultants Institute, Miami Beach, Florida, March, 2004.
Historical Background
1990s: Consolidation / Standardization
• Rubber roofing consolidates around EPDM
• New seaming technologies dramatically reduce leaks
Thermoplastic roofing consolidates around PVC & TPO
• Improved formulations offer long-term stability
Polymer modification (APP & SBS) integrates into
traditional asphalt roofing
• Hybrid asphalt roofs use a combination of traditional BUR
with modified flashings and cap sheets
Introduction to Commercial Roofing
Modern Roofing Materials
U.S. Low-Slope Commercial Roofing Market
Key Membrane Segments
Single-Ply
Rubber Roofing
(EPDM)
(Millions of Square Feet, 2003)
Asphalt
17%
Built-Up Roofing
(BUR)
30%
30%
Thermoplastic
(PVC & TPO)
23%
Modified Asphalt
(APP & SBS)
Source: TEGNOS Research Estimate
Modern Roofing Membranes
Single-Ply
• THERMOSET
• EPDM
• THERMOPLASTIC
• PVC
• TPO
Modern Roofing Membranes
EPDM
+ Large panel sizes for fast coverage
+ Outstanding resistance to weathering
+ High elongation to accommodate
building movement
Modern Roofing Membranes
EPDM: Ballasted System
Stone Ballast or Pavers
Membrane
Insulation
Deck
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Simple, economical design provides proven performance
Stone ballast provides Class A fire rating
Compatible with most insulations
Large panels provide efficient coverage of large roof areas
Modern Roofing Membranes
EPDM: Ballasted System
Modern Roofing Membranes
EPDM: Ballasted System
Modern Roofing Membranes
EPDM: Adhered System
Membrane
Insulation plates &
fasteners
Adhesive
Deck
Insulation
 Design Flexibility - Adapts easily to unusual roof profiles
 Excellent for high wind conditions
 Time-proven application method provides high dependability
Modern Roofing Membranes
EPDM: Adhered System
Modern Roofing Membranes
EPDM: Adhered System
Modern Roofing Membranes
EPDM: Mechanically Attached
Membrane
Metal Or Polymer Batten
Embedded In Field Seam
Deck
Seaming Tape
Insulation
 Light weight - adapts to most roof decks
 Reduced labor input
Modern Roofing Membranes
EPDM: Mechanically Attached
Modern Roofing Membranes
EPDM: Mechanically Attached
Modern Roofing Membranes
Thermoplastic
+ Heat-reflective white surface
+ Fast, simple welded panel
seams
+ Available in variety of colors
Modern Roofing Membranes
Thermoplastic Installation
Modern Roofing Membranes
Thermoplastic Installation
Ice Mountain Bottling
Stanwood, MI
Modern Roofing Membranes
Asphalt
• Built-Up Roofing
• BUR
• Modified Bitumen
• APP
• SBS
Modern Roofing Membranes
Built-Up Roofing (BUR)
Gravel Surfacing
Cover Board
Insulation
Ply Felts Set
In Asphalt
Modern Roofing Membranes
Built-Up Roofing (BUR)
Roofing Felts in Hot Asphalt
Modern Roofing Membranes
Built-Up Roofing (BUR)
Gravel-Surfaced BUR
Modern Roofing Membranes
Modified Bitumen
Modern Roofing Membranes
Modified Bitumen
Cap Sheet
Cover Board
Insulation
Base Sheet
Modern Roofing Membranes
Modified Bitumen
Asphalt Modifiers
APP
SBS
• Atactic Polypropylene
• Styrene-Butadiene-Styrene
• Thermoplastic Polymer
• Thermoset (Rubber) Polymer
• Adds Flexibility
• Adds Flexibility & Memory
• Excellent High Temp. Strength
• Excellent Low Temp. Flexibility
• Excellent uV Resistance
• Requires uV Resistant Surfacing
Modern Roofing Membranes
Modified Bitumen
Hot Mopped
Torch Applied
Cold Applied
Modern Roofing Membranes
Modified Bitumen
Modern Roofing Membranes
Modified Bitumen
Miami Beach Convention Center
Miami Beach, FL
Swenson Skills Center
Philadelphia, PA
Modern Roofing Membranes
How Long Do They Last?
Membrane Type
Single-Ply
Built-Up Roofing
Modified Bitumen
Average Service Life
16.8 – 18.4 Years
13.6 – 18.1 Years
17.6 – 18.2 Years
“A documented historical performance of roofing assemblies in the United States: 1975–1996”. K. G. Schneider & A. S.
Keenan.. Proceedings of the Fourth International Symposium on Roofing Technology (pp. 132-137). Rosemont, IL: National
Roofing Contractors Association, 1997.
“…Life span is defined as the time period from the initial roofing
membrane installation through recover/re-roof. Based on the results of
the statistical model, the current average low slope roofing life span is
estimated to be 17.45 years”
“Comprehensive Nonresidential Building Analysis to Estimate the Current Reality of Roofing Longevity”, Ducker Research, 2003.
Modern Roofing Membranes
Performance Features
BUR
+
+++
++

Ultraviolet Aging
Roof Traffic
Chemical Exposure
Building Movement
+++
Reflectivity
Color Options
High Production
+++
Work Area Limitations ++
PVC/TPO
+
+
+ (PVC)
+
++
++
++
++
+++
+
+++
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Relative Cost
1.1 - 1.3
1.2 - 1.4
1.1 - 1.3
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EPDM
+++
+
1.0 - 1.2
Mod Bit
+
++
+
Modern Roofing Materials
Roof Insulation
One Component
Three Functions
Roof Insulation:
Thermal Barrier
7
Typical “R” Value per Inch Thickness
6
5
4
3
2
1
0
Polyiso
XPS
EPS
Fiber
Glass
Perlite
Fiber
Board
Roof Insulation:
Working Platform
Roof Insulation:
Drainage Structure
Roof Insulation
Slope
Drainage Issues
Typical
2-Way
Structural
Slope
Roof Insulation
Drainage Issues
Interior Drain (Typ.)
Typical
2-Way
Structural
Slope
Roof Insulation
Drainage Solution
4-Way
Slope using
Tapered
Insulation
Detailed Tapered
Roof Insulation
Plan
Introduction to Commercial Roofing
New Roofing Trends
•
•
•
•
Cool Roofs
Vegetated Roofs
Solar Roofs
Green Materials
Cool Roofs:
Saving Energy & Reducing Urban Heat Islands
Cool Membrane Roofs
Ice Mountain
Brea, CA
Cool Metal Roofs
Lindberg Terminal
St. Louis , MO
 Peak Cooling Loads Reduced
 Ambient Air Temperatures Reduced
Cool Roofs:
The Urban Heat Island Effect
Temperature Profile of Atlanta
1972 v. 1993
Source:
CNN.Com
Source:
LBL Heat Island Group
Cool Roofs:
Saving Energy & Reducing Urban Heat Islands
Potential net energy savings from changing roof reflectivity.
Savings are measured in dollars. Note that the net savings are the
savings of cooling energy use less the penalties of heating energy
use. (Source: LBL Heat Island Group)
Cool Roofs:
Current Issues & Concerns
How Do You Maintain Surface Reflectivity?
Minute Maid Stadium
Houston, TX
Cool Roofs:
Current Issues & Concerns
Are Cool Roofs Right For All Climates?
(-$100)
(-$50)
$0
$100
$200
(-$50)
Detroit
$0
$100
$200
$300
Ok. City
$300
$400
Jacksonville
$500
$400
$500
Annual Heating / Cooling Cost Savings:
Reflective Roof versus Non-Reflective Roof
(Dollars per 20,000 Sq. Ft. Roof Area / R-20 Insulation)
New Cool Roof Alternative:
Stone & Paver Ballasted Systems
Envelop Systems Research
Apparatus
Oak Ridge National
Laboratories
New Cool Roof Alternative:
Stone & Paver Ballasted Systems
Black Roof
Standard Ballast
White Roof
Heavy Ballast
Concrete Pavers
Comparative Surface Temperature & Heat Transfer
Ballasted roofs can provide the same peak energy savings
and reduced air temperatures as “cool” roofs …and their
performance doesn’t degrade over time!
Vegetated Roofs:
Saving Energy & Reducing Pollution
Chicago City Hall
Chicago, IL
US Environmental Protection Agency
Denver, CO
Vegetated Roofs:
Reducing Storm Water Runoff
Both Cumulative…
And Hourly…
Source: Penn State University Cool Roofing Program
Vegetated Roofs:
Intensive Green Roofs
Heavy Weight
Plants &
Shrubs
Soil
12” – 36”
Root Barrier / Drainage Mat
Insulation
Roofing / Waterproofing Membrane
Very Heavy Weight
Shrubs &
Trees
Soil
36”+
Vegetated Roofs:
Extensive Green Roofs
Lightweight
Sedum
Media
2” – 4”
Root Barrier / Drainage Mat
Insulation
Roofing / Waterproofing Membrane
Moderate Weight
Flowering
Plants
Soil
4” – 6”
Vegetated Roofs:
Extensive Green Roofs
Tray Systems
Vegetated Roofs:
Extensive Green Roofs
Hybrid Ballasted / Vegetated Roof
Vegetated Roofs:
Benefits & Concerns
Benefits:
 Ambient air temperature
reduced
 Storm water runoff mitigated
 Wide variety of hardy plants
available
 Require as little as 2 or 3 inches
of planting medium
 Can be combined with “cool”
ballasted roofs to minimize
initial costs
 Tray systems available to
minimize maintenance needs
Current Concerns:
 Underlying roof system
must accommodate
increased maintenance
traffic
 Underlying roof system
must be designed to meet
or exceed to expected
garden service life
 Leak detection may be
difficult
 Roof repair and
maintenance may be
difficult when needed
Solar Roofs:
Clean Energy Production
Shiseido
Windsor, NJ
Target Store
Stockton, CA
Solar Roofs:
Benefits & Concerns
Benefits:
Current Concerns:
 Clean energy generated
 Economics not yet at “grid parity”
 Peak energy demands
reduced
 Underlying roof system must
accommodate increased
maintenance traffic
 Underlying roof system must be
designed to meet or exceed to
expected solar system service life
 Leak detection may be difficult
 Roof repair and maintenance may
be difficult when needed
Green Materials:
Reducing Volatile Organic Compounds (VOCs)
VOCs
Standard Roofing
Adhesives
Source: US EPA
Green Materials:
VOCs and Ground Level Ozone
Source: US EPA
Green Materials:
Reducing Volatile Organic Compounds (VOCs)
Low-VOC Alternatives
• Water-based adhesives
• High-solids adhesives
• Urethane adhesives
Green Materials:
Low-VOC Alternatives
Alternative:
Typical Example:
Concerns:
Water-Based
Latex Paint
Freezing, Slow
Flash-Off
High-Solids
Tapes
Primer Frequently
Required
Urethanes
Foam Adhesive
2-Part Adhesive
Complicated &
Expensive
Green Materials:
Construction Waste
Annual U.S. Landfill Waste
• 160 Million Tons Of Construction Waste
• 40 Million Tons of Roofing Waste
•
25%+ of Total Construction Waste
Source: US EPA (1998)
Green Materials:
Roof Membrane Recycling
Cookson
Elementary
School
Troy, Ohio
1
3
2
Windrow & Sweep
4
6
5
Grind
Chop
Cut & Stack
Sieve & Package
Recycle
Roof Membrane Recycling:
Benefits & Concerns
Benefits:
 Landfill waste reduced
 Overall environmental
impact reduced
Current Concerns:
 Economics do not currently
support recycling
 Only available in a regional pilot
program for selected products
 Logistics (removal, storage,
transportation) are difficult
 Recyclers must have an assured
supply before end markets can
be fully developed
Commercial Roofing:
Looking to the Future
 Roofing materials will be thinner and lighter – all
bringing new challenges for durability
 Roofs will be installed with eventual removal in mind
 Maintenance programs will become more
sophisticated in order to extend service life
 The primary concern of the building owner will
continue to be durability