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Credit earned on completion of this course will be reported to AIA CES for AIA members. To receive a Certificate of Completion you must complete and pass the 10 question quiz following this presentation with an 80% or higher, then a certificate of completion will be available for immediate download.
This course is registered with 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.
Learning Objectives
3
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
46
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
65
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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THANK YOU FOR YOUR ATTENDANCE
QUESTIONS?
www.mbci.com
This concludes the American Institute of Architects Continuing Education Systems Program
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