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