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Retrofit roof systems edc1
1. Retrofit Roof Systems
AIA Course: EDC0714D
GBCI Course: AIA/GBCI Logos
1 AIA HSW/LU and 1 GBCI CE Hour
2. 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.
3. Learning Objectives
3
+ Explain the benefits of retrofitting a roof, including
energy efficiency, energy savings and building
performance.
+ Discuss the various applications for retrofit roof
systems.
+ Analyze the framing fundamentals required to ensure
the integrity of the retrofit.
+ Be able to properly assess the existing roof and offer
appropriate design considerations for a project.
4. 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
4
Source: 2010 Freedonia Roofing Report
NOTE: All data is in squares.
5. 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
5
Source: 2010 Freedonia Roofing Report
NOTE: All data is in squares.
6. 6
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
8. 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
8
9. v Durable
v Sustainable
v Aesthetics
Metal Roofing Benefits
Attributes Benefits
Reduces maintenance; longer life
Contributes to LEED points
Increases property value
9
10. 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
10
11. 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
11
*Source: Corps of Engineers 2007
12. 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
12
13. 13
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
14. 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
14
16. 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
16
17. 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
17
18. 18
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
SawtoothStepped Increase Slope
Reverse Slope
Remove Barrel
Curved over Flat
19. 19
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
23. 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
23
24. Bracing
Common members include:
v Struts
Transverse and Horizontal
v Vertical Bracing
Diagonal Transverse and
Longitudinal
Transverse
Bracing
Longitudinal Bracing
24
25. 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
25
29. 29
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
31. 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.
31
32. Point Load
New Column
New Zee
Purlin
Intermittent
Base
New Valley
New Ridges
Parallel Framing Example
32
33. 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.
33
34. New Pitch break
New High Eave
Continuous
Base
Point Load
New Column
New Zee Purlin
Perpendicular Framing Example
34
35. 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
35
36. 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
36
37. 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
37
38. Remember
The existing roof’s physical footprint and other rooftop conditions
will more than likely control the new roof’s geometry.
38
40. 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
40
41. 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.
41
43. 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
43
45. 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.
45
46. Inspect the Existing Roof System
Locate Rooftop Equipment
v Electrical
v HVAC locations
v Plumbing
?
12
?
HVAC
A
B
C
Document
46
47. Inspect the Existing Roof System
Evaluate existing
substrate for:
v Trapped moisture
v Deterioration
v Presence of harmful
material (i.e. asbestos)
47
48. Inspect the Existing Roof System
Conduct pull-out
testing so anchorage
requirements can be
determined.
48
50. 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.
50
52. Insulation/Deck Deterioration
v Remove membrane and insulation
v Inspect decking for possible damage
(rust, rot, etc.)
Insufficient Compressive Resistance
52
53. 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
53
55. 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
55
58. 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.
58
59. 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
59
61. Framing System Anchorage
Make sure you enlist experienced
registered professional engineers,
manufacturers and installers to ensure
the best results.
61
62. 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
62
64. Qualifying a Manufacturer
v Retrofit Design Manual in
Place
v Certify Contractors
v Reliable Weathertightness
Warranties
64
65. 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
66. Qualifying a Contractor
v History of retrofit projects
v Certified by a manufacturer
v Insured and bondable
66
67. Performance with a Payback
v Retrofit metal roofing is the only roof replacement
system that provides long-term reliable
performance with a “payback”
67
68. THANK YOU FOR YOUR ATTENDANCE
QUESTIONS?
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This concludes the American Institute of Architects
Continuing Education Systems Program
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