Retrofit Roof Systems NURF-1 (1 credit hour)

AIA PRESENTATION

Best Practice Slide

v MBCI is a Registered Provider with the American Institute of Architects Continuing Education Systems. Credit earned on completion of this program will be reported to CES Records for AIA members. Certificates of Completion for non-AIA members are available on request.

v This program is registered with the AIA/CES for continuing

professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.

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Learning Objectives

Define and better understand v Market Demands

v Benefits

v Various Applications for Retrofit Roof Systems

v Framing Fundamentals

v Project Considerations

v Assessing the Existing Roof

v Design Considerations

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Overall Roofing Market – New Construction

v Market size 2009-2014: 102 Million • New Roofing 21.5 Million

• Metal 6.5 Million • Modified 4.9 Million • Shingle 2.6 Million • EPDM 3.6 Million • Plastic 2.5 Million • Other 1.4 Million

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Source: 2010 Freedonia Roofing Report

NOTE: All data is in squares.

Overall Roofing Market – Reroofing

v Market size 2009-2014: 102 Million • Reroofing 80.5 Million

• Modified 27.1 Million • Shingle 16.4 Million • EPDM 13.5 Million • Metal 12.8 Million • Plastic 8.5 Million • Other 2.2 Million

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Source: 2010 Freedonia Roofing Report

NOTE: All data is in squares.

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v For the purpose of this presentation retrofit is defined as: • Relative to the metal construction industry, the term

means complete fully-engineered structural roof systems used

• for adding slope to existing buildings with flat or nearly flat roofs

• for correcting problematic roof geometry • for reroofing over existing sloped roofs • for extending the life expectancy of a roofing system

• The systems include light-gauge support framing with metal roof/wall cladding

Retrofit Defined

WHY RETROFIT WITH METAL? Benefits of Retrofitting

When to Retrofit Framing Systems

v Replace leaking roof v Structural changes v Correcting roof geometry v Provide thermal upgrades

v Regulation/code requirements v Aesthetics v Improve ventilation v New building construction

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v Durable v Sustainable v Aesthetics

Metal Roofing Benefits

Attributes Benefits Reduces maintenance; longer life

Contributes to LEED points Increases property value

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v Available in Cool Colors v Virtually 100% Recyclable v Long Service Life

Reduces heat-island effect Reduces land fill waste Life cycle performance

Metal Roofing Benefits

Attributes Benefits

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Metal Roofing Benefits

v Each year, an estimated 9 to 10 million tons of asphalt roofing waste goes to U.S. landfills, costing more than $400 million on disposal fees*

v A metal roofing retrofit eliminates the need to tear off the existing roof in most cases

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*Source: Corps of Engineers 2007

v Life Expectancy v Maintenance

41.6 vs. 20.5 years $0.10 vs. $0.26/ft2/yr

Metal Roofing Benefits Over Single Ply

Features Benefits

Source: Metal vs. Single-Ply - 2007 Ducker Worldwide Report

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Improving Our Energy Efficiency

vTax incentives now extended through 2013 on commercial buildings

vFor up-to-date listing of adopted areas, go to www.energycodes.gov or www.bcap-energy.org

Retrofit Benefits Cost vs. Savings

BUR (asphalt) Tear Off & Replace Retrofit Roof Replacement

$1.5M $1.6M

<$100K>

Estimated Energy Savings ($0.10 / sq ft x 108,000 sq ft)*

$10,800

Estimated Reduction of Maintenance Cost ($0.10 / sq ft vs. $0.17 x 108,000 sq ft)*

$7,560

Estimated Savings based on not having to Reroof BUR (Asphalt) (Avg. BUR Reroof cost of $3.75 / sq ft* annualized based on 23 yr service life* and 3.12% inflation rate)

$35,695

Estimated Annual Savings $54,055

Estimated Maintenance & Energy Payback of $100K Initial Retrofit Cost Difference 5 ½ Years

Estimated Maintenance, Energy and Future Replacement Cost Payback of $100K Initial Retrofit Cost Difference

2 Years

Initial Cost vs. Energy & Maintenance Savings

v High School v Winchester, Ind. v 108,000 Square Feet v 6” Insulated Attic v Ventilated v Existing Roof = BUR

(asphalt)

*Source: 2007 Ducker Worldwide Report

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RETROFIT APPLICATIONS Low-Slope, High-Slope, Geometry Issues and Metal Roofovers

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Low-Slope

v Typically driven by economy, these utilitarian applications are designed to simply discharge rainwater from the roof without improving the “curb appeal” of the existing building

v Roof slopes from ¼ to 2:12 v Common metal roof systems

are: • Trapezoidal Standing

Seam • Exposed Fastened Rib

Panel

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High-Slope

v These architectural applications are employed when the roof will be a design element in the beautification of an existing school or during additions where the existing buildings are upgraded to match new construction

v Roof slopes typically above 2:12

v Embraced by Schools and Federal, State and

Municipal Government for over two decades

v Ideal for Cool Roof rated metal roof

v Recommended metal roof system is: • Vertical Rib Standing Seam

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Problematic Roof Conditions

v Retrofit systems can be employed on building facilities that have undesirable issues with discharging rainwater

v Correcting Roof Geometry Issues • Fill-ins and Crickets • Multi-Gable or Stepped • Increase Slope • Reverse Slope • Remove Barrel

Sawtooth Stepped Increase Slope

Reverse Slope

Remove Barrel

Curved over Flat

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Reroofing Over Sloped Roofs

v When the existing roof is being replaced with a new long-term performance (typically lasting 40 years or more) standing seam metal roof system • Metal over metal • Metal over composition

and other conventional membranes

• Corrective alternative to failed roof systems

• Wind Load and FM upgrades

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FRAMING FUNDAMENTALS Components, Design and Layout

Base Members

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Continuous Base

Base Shoe

Angle Clip

Columns

Column

v Typically cee-shaped v Sizes vary from 4” to 8” v Usually field cut from standard

lengths v Also referred to as post

or stanchion

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Purlins

v Spaced to support roof membrane

v Typically zee-shaped v Sizes vary from 3½” to 10” v Field cut or detailed to

required lengths

Purlin

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Bracing

Common members include: v Struts Transverse and Horizontal

v Vertical Bracing Diagonal Transverse and

Longitudinal Transverse

Bracing

Longitudinal Bracing

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Common Existing Roof Assemblies

v Wood framed • Dimensional lumber • Glue-laminated • Heavy timber

v Structural concrete • Steel Beam and Deck • Concrete Beam supported • Concrete tee

v Steel framed • Beam and metal deck

• Open-web joist and metal deck

• Bulb tee over joist with Tectum

• Metal building systems

• Purlin

• Open-web joist

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Framing System Adaptability

v Systems can be designed to adapt to various existing roof assemblies and support systems

Steel

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Framing System Adaptability

v Systems can be designed to adapt to various existing roof assemblies and support systems

Concrete

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Framing System Adaptability

v Systems can be designed to adapt to various existing roof assemblies and support systems

Wood

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Understanding Roof Grids

v Nearly all existing building roofs are constructed using a primary and secondary structural grid layout regardless of the support method or type of system employed

v Retrofit framing systems employ a structural grid that imposes a series of concentrated point loads into the existing roof system

v These two grid systems must be compatible to ensure the existing roof’s structural integrity is maintained

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Existing Joists

Framing Design

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Parallel Framing

Parallel Framing v Base shoe or channel v Usually field drilled for anchor

installation v Width varies based on column width

The type of base member is dictated by the existing roof’s secondary structural

span and orientation.

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Point Load

New Column

New Zee Purlin

Intermittent Base

New Valley

New Ridges

Parallel Framing Example

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Perpendicular Framing

Perpendicular Framing v Continuous Zee v Usually field drilled for anchor

installation v Continuous base member spacing

dictated by purlin spacing of new roof

The type of base member is dictated by the existing roof’s secondary structural

span and orientation.

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New Pitch break New High Eave

Continuous Base

Point Load

New Column

New Zee Purlin

Perpendicular Framing Example

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Load Distribution: Base Members

Continuous Zee

Base Shoe Spacing is per design

Retrofit Purlin Spacing on flat

Continuous Zee Base Shoe

Example shows both continuous zee and base shoe framing systems

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Load Distribution: Vertical Framing

Retrofit Purlin Spacing on flat

New Retrofit Columns

Continuous Zee Base Shoe

Spacing is dictated by the existing roofs secondary spacing and span orientation

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Load Distribution: Bracing and Purlins

Retrofit Purlins

Valley Support Framing

Continuous Zee Base Shoe

Bracing resists lateral forces Purlins withstand live and dead loads

Bracing

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Remember

The existing roof’s physical footprint and other rooftop conditions will more than likely control the new roof’s geometry.

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ASSESSING THE EXISTING ROOF

Project Scope Considerations

v Define and Provide Existing Roof Plan • Perimeter Conditions • Rooftop Obstructions • Roof Support System • Substrate Assembly

v Define and Provide New Roof Plan

• Ventilation System • Insulation • New Roof System

v Perform pre-bid design analysis and testing v Partner with a Manufacturer for expertise

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Testing and Inspection Responsibility

The Owner or Design Professional is accountable for the inspection and testing of the existing structure and for providing this information to the manufacturer.

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Existing Roof Information

Detail v Existing roof footprint v Expansion

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Existing Roof Information

Detail v Existing roof footprint v Expansion joints v Roof perimeter

construction such as gravel stops and parapets

v Interior firewalls v Existing drainage systems

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www.steeljoist.org

Inspect the Existing Roof System

For existing joists and their support identify: v Type v Size v Spacing v Span orientation

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Inspect the Existing Roof System

Determine all collateral loads on the exterior and interior of the existing building: v HVAC v Electrical v Plumbing v Ceilings v Sprinkler, etc.

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Inspect the Existing Roof System

Locate Rooftop Equipment v Electrical v HVAC locations v Plumbing

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HVAC

A

B

C

Document

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Inspect the Existing Roof System

Evaluate existing substrate for: v Trapped moisture v Deterioration v Presence of harmful material (i.e. asbestos)

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Inspect the Existing Roof System

Conduct pull-out testing so anchorage requirements can be determined.

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Compressive Resistance Test

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Compressive Strength

When retrofitting a roof, compression strength is defined as the ability of the

existing roof substrate to resist the forces created by the attachment of the

retrofit roof framing so that the underlying material is not crushed and excess deflection is not introduced in

the new roof.

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Existing Substrate

Compressive Resistance Imposed Load

Determine if the base member’s bearing surface area is adequate (min. 25 psi).

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Insulation/Deck Deterioration v Remove membrane and insulation v Inspect decking for possible damage (rust, rot, etc.)

Insufficient Compressive Resistance

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Bid Document Summary

Provide:

v Comprehensive roof plan

v Information on joists and their support

v Internal and external collateral loads

v Existing substrate assessment

v Pull-out test

v Compression resistance evaluation

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DESIGN CONSIDERATIONS

Adding Insulation

Include the insulating values of the existing material in any R-Value requirement

* Typically, older roof assemblies and materials do not offer adequate thermal protection

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Ventilation

A properly designed ventilation system is crucial

Consult a Mechanical Engineer to ensure proper ventilation

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External Loads

Assess external loads including: v Live Loads v Wind Uplift v Snow Loads v Dead Loads v Seismic Loads

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Additional Weight

Beware of unplanned snow drift loads on: v Ridges (unbalanced) v Valleys v Adjoining roof and wall v Penetrations caused by existing roof conditions v Adjacent buildings

Wind

The design professional should evaluate these added loads for required

remediation of the existing structural system.

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Anchorage Requirements

v Wood or steel frame v Structural concrete v Anchor Length

Joist type Strength and deck thickness Thickness of existing roof assembly

Characteristic Determined by:

Anchor installation into steel and wood joists should be closely monitored

Due to probable moisture content in the existing substrate, anchors should have a corrosion resistant coating

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Framing System Anchorage

Most retrofit failures are caused by improper anchorage

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Framing System Anchorage

Make sure you enlist experienced registered professional engineers,

manufacturers and installers to ensure the best results.

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To reduce moisture penetration caused by anchors: v Specify shims to elevate continuous base members so not to obstruct the existing drainage system v Require all anchorage penetrations to be sealed with compatible sealant

Anchorage Installation Tip

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SELECTING THE RIGHT PARTNERS

Qualifying a Manufacturer

v Retrofit Design Manual in Place

v Certify Contractors v Reliable Weathertightness

Warranties

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Retrofit Manufacturer

What should the retrofit system manufacturer provide you? v Framing layout drawings v Sealed design calculations

including: • Positive (gravity) and

negative (wind uplift) imposed loads at each framing attachment location

• Lateral wind forces at gable ends and other vertical surfaces

• Shear requirements from bracing

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Qualifying a Contractor

v History of retrofit projects v Certified by a manufacturer v Insured and bondable

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Performance with a Payback

v Retrofit metal roofing is the only roof replacement system that provides long-term reliable performance with a “payback”

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Please Note Contents on your CD:

• Performance Specifications

• CSI Format and MasterFormat 2004

• Frequently Asked Questions

• Roofing Components Reference Information

• Required information needed for a contractor to obtain an Estimate

• RFI Form

• Standard Details

• ACAD

• PDF

MBCI’s other CES Program Opportunities: * Retrofit Roof System Design and Application (3-hour) * Insulated Metal Panels (1-hour) * Standing Seam Roof Systems (1 and 3-hour) * The Devil is in the Details (1-hour) * Weathertightness Warranties (1-hour)

Retrofit Roof Systems NURF-1 (1 credit hour)

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