final aia roofs 2011 version 20

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Roofing Durability: How Cover Boards Contribute

Reinhard Schneider DensDeck Technical

Manager

Archivewww.roofingcontractor.com

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Durability: How Cover Boards Contribute

Version 2.0

Georgia-Pacific Gypsum LLC is a Registered Provider with the Construction Specifications Institute Construction Education Network (CEN). Credit earned for completing this program will automatically be submitted to the CSI CEN. Completion certificates can be obtained by contacting the Provider directly.

This program is a registered educational program with the Construction Specifications Institute of Alexandria, VA. The content within the program is not created or endorsed by CSI nor should the content be construed as an approval of any product, building method, or service. Information on the specific content can be addressed at the conclusion on the program, by the Registered Provider.

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© 2011 Georgia-Pacific Gypsum LLC

Durability:

How Cover Boards Contribute

• Structural Deck (Steel, Wood, Concrete)

4 Main Elements of Low Slope Commercial Roofing

Structural Deck


• Insulation (ISO, EPS, Fiberglass)


Structural Deck

Insulation



• Membrane (BUR, Mod Bit, Single Ply, Self-Adhesive)


Structural Deck

Insulation

Membrane



• Membrane (BUR, Mod Bit, Single Ply, Self-Adhesive)

• Cover Board (Perlite, Wood Fiber, Gypsum)


Structural Deck

Insulation

Cover Board

Membrane

We’re going to answer these questions:

1. What are the forces that affect roof systems?

2. What is a cover board?

3. Why do you need a cover board?

4. How can cover boards overcome these forces?

5. Which cover board is my best choice?

What are the forces?

Fire

Wind Uplift

Hail Impact

Foot Traffic

Water Intrusion

Sound

Fire

Issues associated with fire:

• External Exposure

• Internal Exposure

• Code Compliance

• Life Safety Issues

• Insurance Premiums

• Entire roof assembly must provide fire resistance, not just individual products within system.

• Cover board can enhance or detract from fire resistance.

• Two predominant testing bodies:

• Underwriters Laboratories (UL)

• Factory Mutual Research Corp. (FM)

Fire

Underwriters Laboratories, Inc.

• Mainly concerned with life – safety issues

• Exterior Classifications• UL A

• UL B

• UL C

• Hourly Fire Resistance Ratings• “P” Numbers

Fire

UL Class A, B, & C

Intermittent Flame Test

Fire

FM Global

Mainly concerned with loss prevention

• Exterior Fire

• Calorimeter

• Wind Uplift

• Hail Resistance

• Corrosion Resistance

• Foot Traffic Resistance

• Water Leakage

Fire

Wind Uplift

• Blow-Off Resistance

• Minimizing Property Damage

• FM Guidelines

• Insurance Premiums

Hurricane Charlie

Source: Tecta America

Wind Uplift

Hurricane Katrina

Source: www.globalsecurity.org

Wind Uplift

Fully Adhered Membrane

•Performance relies on the strength of the substrate.

•Cover board transfers forces through adhesive or fasteners to deck.

WIND

UPLIFT

Wind Uplift

Mechanically Attached System with No Cover Board

WIND

UPLIFT

Wind Uplift

Wind Uplift

WIND

UPLIFT

Mechanically Attached System with Cover Board

• Property Damage

• Roof Repair

• Insulation

• Contents

• Loss of Use

• Maintaining R-Values

Hail

Impact Force

• Damage during installation

• Construction damage by other trades

• Maintenance of roof equipment

Foot Traffic

Resist damage caused by construction traffic

Resist damage caused by maintenance traffic

ISO without Cover Board

ISO with Glass-Mat Gypsum Cover Board

• Roof Leaks

• Introduced During Construction

• Condensation

Sources of Water Intrusion:

Water Intrusion

Minimize Moisture in AssemblyWater Intrusion

WATER SATURATES OVERLAYMENT

Northern climate example

Exterior (Cold)

Interior (Warm)

When a roof assembly gets wet, it can deteriorate and collapse if the cover board doesn’t offer wet strength.

Mold and mildew can grow in a wet environment.

Water Intrusion

Source: University of Florida, Doctors Peart and Kimbrough

Water IntrusionMold requires these conditions to grow:

Water Intrusion

Steps to Avoid Mold Growth

• Design assemblies with ventilation and vapor retarders to eliminate condensation buildup.

• Keep moisture out in first place.

• Repair leaks promptly.

• Use components that will retain as little moisture as possible and not support the growth of mold.

• Airports

• Traffic

• Equipment Noise

Sound

Noise Source Decibels

Jet take-off, artillery fire 120

Loud street noise, loud band 100-120

Overhead airplane, unmuffled truck 80-100

Average radio or TV 70-90

Human voice at 1 meter 55-60

Background noise in office 35-40

Quiet home 24-30

Threshold of hearing 20

Sound

Sound Transmission Class (STC) Ratings of Steel-deck Roof Assemblies Using Glass-Mat Gypsum Roof Boards

Sound

STC* Underlayment Insulation Cover Board Membrane System Attachment

28 None 6” ISO None None Mechanical **

29 None 6” ISO None None Mechanical

36 5/8” Glass-Mat Gypsum Roof Board

3” ISO 1/2” Glass-Mat Gypsum Roof Board

EPDM Mechanical/EPDM-Adhered



EPDM All components adhered ***



SBS Mod Bit Mechanical SBS/Mod Bit-Torched


6” EPS (Extruded)

Two layers

5/8” Glass-Mat

Gypsum Roof Board

None Mechanical

* STC rating is calculated in accordance with ASTM E 413

** Typically 9 fasteners: 3” round steel plates with screw penetrating deck

*** Olybond 500 adhesive; 1/8” Glass-Mat Gypsum Roof Board down/EPDM adhesive for membrane penetration

65 dB (sound source)

Sound Isolation

38 dB STC

27 dB

What is a cover board?

• A semi-rigid, relatively thin board installed over the insulation and under the roofing membrane.

• It provides protection, separation and support for the membrane.

Cover Board Types

• Asphaltic Board

• Plywood / OSB

• Wood Fiber Board

• Perlite

• Cellulose Fiber Reinforced Gypsum

• Paperfaced Gypsum

• Glass-Mat Gypsum

Asphaltic Boards

Description:• Asphalt core with fiberglass faces on both sides

Types of systems:• Typically used as substrate for BUR, torch-down

and cold mastic systems

Plywood/OSB

• PlywoodProduced from thin sheets of wood veneer arranged in layers.

• OSBNon-veneer panel composed of three cross-laminated, compressed layers of mechanically oriented, resin-bonded wood strands.

Description:

Plywood/OSB

• Organic• Hard Surface• Structural

Description:

• Single-ply

Types of Systems:

Wood Fiberboard

• Various wood fibers bonded with resins• Non-structural• Offers minimal “R” value

Description:

• All non-torch applications

Types of Systems:

Perlite

• Mineral aggregate board with particles of expanded perlite or vermiculite, selected cellulose binders and sizing agents

• Used for fire performance• Limited insulation properties

Description:

• Hot asphalt and Mod-bit

Types of Systems:

Cellulose Fiber Reinforced Gypsum

• High density gypsum blended with cellulose fibers

• New product with limited approvals• Heavy

Description:

• Most roofing assemblies

Types of Systems:

Paperfaced Gypsum

• Gypsum core with paper facers on front and back

• Easy to cut and install

Description:

• Predominantly single-ply• Can be used in most systems as a fire

barrier

Types of Systems:

Glass-Mat Gypsum

• Treated gypsum core with embedded fiberglass mat facings

• Available in 1/4”, 1/2” and 5/8” thicknesses• Easy to install

Description:

• All commercial roofing systems

Types of Systems:

Why do you need a cover board?

Because …

NRCA Guidelines

NRCA Bulletin 2000-3, March 2000

“Use of cover boards over polyisocyanurate insulation is recommended for all roofing membranes.”

• Facer sheet delamination

• Edge cavitation

• Cupping or bowing

• Shrinkage

• Crushing or powdering

Because …

Protect insulation/membrane from impact damage

Damage

Shrinkage/Warping

Crushing

Water Intrusion

Sound

Foot Traffic

How do cover boards overcome these forces?

Fire

Wind Uplift

Hail Impact

Evaluate Cover Board Characteristics

•Asphaltic Boards

•Plywood/OSB

•Wood Fiberboard

•Perlite

•Paperfaced Gypsum

•Glass-Mat Gypsum

0

1

2

3

4

5

Asphaltic Board

s

Plywood / OSB

Wood Fiber BoardPerlit

e

Cellulose Fiber Reinforce

d Gypsum

Paperfaced Gypsum

Glass-Mat Gypsum

Fire Resistance (On a Scale of 1-5)

0

1

2

3

4

5

Asphaltic Board

s

Plywood / OSB


e


d Gypsum

Paperfaced Gypsum

Glass-Mat Gypsum

Wind Uplift (On a Scale of 1-5)

Hail Impact (On a Scale of 1-5)

0

1

2

3

4

5

Asphaltic Board

s

Plywood / OSB

Wood Fiber Board

Perlite

Cellulose Fiber R

einforced Gypsum

Paperfaced Gypsum

Glass-Mat Gypsum

Foot Traffic (On a Scale of 1-5)

0

1

2

3

4

5

Asphaltic Board

s

Plywood / OSB

Wood Fiber Board

Perlite

Cellulose Fiber R

einforced Gypsum

Paperfaced Gypsum

Glass-Mat Gypsum

0

1

2

3

4

5

Asphaltic Board

s

Plywood / OSB


e


d Gypsum

Paperfaced Gypsum

Glass-Mat Gypsum

Water Intrusion (On a Scale of 1-5)

0

1

2

3

4

5

Asphaltic Board

s

Plywood / OSB


e


d Gypsum

Paperfaced Gypsum

Glass-Mat Gypsum

Sound (On a Scale of 1-5)

Which cover board is your best choice?

One comes out on top and outperforms the rest

Glass-Mat Faced Gypsum Roof Board

final aia roofs 2011 version 20

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cover boards

cover board perlite

cover boardiso

cover board transfers

water intrusionwhen

water intrusionmold

glassmatgypsum cover

concretestructural deck