Specifying Metal Roofing Brian Selig, Product Representati ve
Jan 20, 2015
Specifying Metal Roofing
Brian Selig, Product Representative
Focus On Roofing
“According to the National Roofing Contractors Association (NRCA), over 50 percent of all construction litigation in the United States involves roofing . . .”
D’Annunzio, John D. “Proper Roof System Design Standards.” The Construction Specifier January 2004: 34-40.
Objectives
Understand the difference in wind uplift test methods
Learn about the types of metal roofing available
Discuss the capabilities of metal roof panels
Discuss warranties and common exclusions
Metal Roof Panel Testing
Wind Uplift Impact Air and
Water infiltration
Fire
Wind Uplift Testing
Underwriters Laboratories 580 Class 30, 60, 90
American Society For Testing and Materials E-1592
Factory Mutual Research Corporation Standard 4470 1-30, 1-60, 1-90
UL 580: Class 90
Industry Standard Test 10 x 10 chamber
Tests complete assembly
Oscillating pressure 4 hr cycle testing
105 lbs/sq ft negative air pressure
Three stage, pass or fail test
Clip spacing does not vary
ASTM 1592Corps of Engineers
Test 12 x 24 chamber
uses pleated air bag Test Panels
and Clips only One end fixed
1 min. cycle testing increasing in 5 lb increments
System is taken to failure
Clip spacing varies in edges and corners
FM 4470
Test for Factory Mutual Insured Buildings
Similar wind uplift test as ASTM 1592
I-30, I-60, I-90
Types of Metal Roofing
Through fastened
Tile/shingles
Standing Seam
What is a standing seam roof?
Flat metal panels with raised seams that interlock with adjoining panels using concealed fasteners. The interlocking mechanism can be: Mechanically seamed Snapped together
Features of Standing Seam
Suitable for any slope greater than 1/8:12
Can be curved or tapered
Capable of being produced from any metal type
Metals used to form standing seam today
Coated Steel
Aluminum Copper Zinc Stainless
Why Coated Steel?
Advantages Low cost High strength
Disadvantages Susceptible to
corrosion
Galvanized Coated Steel
G-90 is the standard: 0.90 ounces of sacrificial zinc per square foot on both sides
Advantage Can be soldered Less expensive
Disadvantage Corrosion rate is more than Galvalume No warranty
Galvalume Coated Steel
Zinc and aluminum coating Aluminum is
the barrier coating
Zinc is the sacrificial coating
AZ55 is the standard: 0.55 ounces Al/Zn coating per square foot
Advantage• Nine times the
life of galvanized• Normally stiffer
than galvanized• 20 year warranty
Disadvantage• Difficult to weld
Metal Roofing Paint
Types: Kynar (fluorocarbon)
Thermo set coating Best color retention Best chalk fade
resistance Most expensive
Siliconized Polyester Thermo cure
coating Metal building paint
Cool Coatings and EnergyStar High Reflectivity
Coatings Example:
Evergreen % Solar Reflectivity increases from 12.5 to 29.4
Only a select group of colors qualify on slopes less than 2:12
On slopes greater than 2:12, the color selection grows significantly
Categories of Standing Seam Roofing
Structural Installed over
open framing Normally lower
slope (< than 3:12)
Impermeable
Architectural Installed over solid
deck Normally higher
slope (> than 3:12) Water shedding
panel
Two Basic Standing Seam Styles
Snap together (Architectural) Mechanically seamed (Architectural
and Structural)
Selection should depend on: Roof slope Length of panel run Solid or open framing
Mechanically seamed panel Field locked seam Single lock seam
90 degree fold Difficult panel
replacement Double lock seam
180 degree fold Impossible panel
replacement Seam height
1” to 1½” solid deck recommended
2” to 3” structural panel for open frame
Snap Together Panels
Solid deck
Slope greater than 2 to 3 on 12
Easy panel replacement
One piece system Panel and clip
Two piece system Panel, cap,
and clip
What About Curved Roofs? Radius capabilities
based on height and complexity of panel
Simple: 1” tall, 2 piece snap system. Radius can be 2’ 6” or greater (24 GA)
Complex: 3” Tall, Mechanically-seamed. Radius can be 30’ 0” or greater (24 GA)
Managing Expansion
Clips Fixed Sliding - Flexible
Base Floating - Offsets
Retrofit Roofing
Two types: Slope change
Frame system Staggered
height zee purlins
New metal over sloped roof Use hat
channels or zee purlins
Retrofit Roofing
Consistent Slope Curb Technique Ridge and Wall
Application
Metal Building Retrofit Use notched 16 gauge zee and structural standing seam panel
New roof is stronger than original
No disruption of interior work
Added insulation
Warranties
Installer weathertight Normally 2
years
Manufacturer’s weathertight Up to 20 years
Metal coating Up to 20 years
Paint finish Up to 20 years
How do you get a properlyinstalled roof?
Specify a suitable product from reputable manufacturers
Establish quality standards for the installer
QUESTIONS ?
Brian Selig Architectural Building Components www.archmetalroof.com 800-423-1105