Transcript Tapered Crickets

COMMERCIAL ROOFING
Tapered Insulation Systems
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Learning Objectives
Tapered Insulation Presentation
 Tapered insulation – what is it?
 Why do we use it?
 Various designs from good to best
 Crickets function and design
 Specifying a good design
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Tapered Insulation Systems
What, Why, and How?
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Tapered Insulation
 Rigid roof insulation
 Made from various materials
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Polyiso
Extruded & Expanded Polystyrene
Perlite
 Typically 2x4 or 4x4 panels
 Provides r-value and slope
 Typical slopes available
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1/8”/ft., ¼”/ft., ½”/ft.
 Arranged by a designer into a tapered system
to promote positive drainage
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Why use a tapered
insulation system?
 Main Goal
 Eliminate the
amount of
ponding/standing
water on the
membrane when
the roof deck does
not provide
adequate slope
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Why is it Important?
Ponding may void the roofing warranty
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Why is it Important?
Prevents the potential for roof collapse
from excess weight
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Why is it Important?
Prevents growth of vegetation, fungi, and bacteria.
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Why is it Important?
Extends the overall life of a roofing system.
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Why is it Important?
 National Agencies & Code Groups require a
minimum slope
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¼”/ft. minimum in most cases
Provided by structure or a tapered insulation
system
Ponds existing after 48 hours not acceptable to any
of the major code bodies
Tapered Insulation Designs
 Numerous possible
designs even for the
simplest roof
 Individual job
parameters
determine which
design is the best
option
4-way slope
Modified 4-way slope with cricket
Valley & Cricket
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One Way Slope to Gutter
 Most basic design
 Simple installation
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Two Way Slope to Gutter
 Second most basic
design
 Roof is cut in half
which reduces the
maximum thickness
 Simple installation
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Ridge
Valley and Cricket to Drain
 Commonly used design
with drains
 Cheapest material cost
in most cases (versus 4way slope design)
 Potential small ponding
along cricket edges
(typical)
 Not the most effective
drainage design
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Potential
ponding area
Modified 4-Way Slope to
Drains
 Second most
effective drainage
 Used when no
overflow drains
exists
 If one drain is
clogged the water
can flow over to
other drain
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4-Way Slope Design
 Most effective drainage
design (any
compromise will effect
performance)
 Every tapered system
should start with this
design
 Next step is to identify
justifiable reasons to
alter this layout
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Common Attempt to Show a
4-Way Slope Design
Randomly drawn valley lines
at no specific angles
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Correct Way to Show a
4-Way Slope Design
Zoom Window
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4-Way Slope Design
Zoom Window
Valley Lines should be
drawn at a 45 degree angle
out of each drain
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45 Degree Valley Miter
45 degree angle
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4-Way Slope Design
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Reasons to Alter
4-Way Design
Complex existing drain locations
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Reasons to Alter
4-Way Design
Constant perimeter height is required
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Reasons to Alter
4-Way Design
Multiple drains at low point with no overflow drains
Overflow drains added
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Reasons to Alter
4-Way Design
When cost is a bigger issue than performance
4-Way Design
Valley & Cricket Design
-Most effective drainage
-Least effective drainage
-Higher material cost
-Lower material cost
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Reasons to Alter
4-Way Design
Multiple roof top units prevent layout from draining
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Tapered Crickets
 Used on both:
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Full tapered systems
Structurally sloped decks
Tapered Cricket
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Tapered Crickets
 Also called:
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Saddles
Hog Backs
Tapered Cricket
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Tapered Crickets
 Secondary application of insulation used
to divert water from roof top curbs,
valleys, and low points to drains or
scuppers
Tapered Crickets
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Tapered Crickets
Secondary application of
insulation used to divert
water from roof top curbs,
valleys, and low points to
drains or scuppers
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Tapered Crickets
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Types of Crickets
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Types of Crickets
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Types of Crickets
½ - Diamond Cricket
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Types of Crickets
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Types of Crickets
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Tapered Crickets
Incorrectly drawn crickets
Correctly drawn crickets
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Tapered Crickets
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Tapered Crickets
Portion of tapered
panel that is field
trimmed as waste
4x4 Tapered panel
Crickets are created in the field by field trimming tapered panels as shown
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Tapered Crickets
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Tapered Crickets
Full Diamond Cricket
Installed 4x4 Tapered Panels
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Uninstalled Portion
Tapered Crickets
RTU
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Tapered Crickets
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Parts of a Tapered Cricket
Cricket Width (Points 4 to 5)
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Parts of a Tapered Cricket
Cricket Length (Points 1 to 2)
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Parts of a Tapered Cricket
The slope that is created by the structural deck, tapered
insulation or a combination of the two.
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Parts of a Tapered Cricket
The slope of the cricket panels. Recommended to be at least
twice the net Roof Surface Slope that exists. This ensures that
the water is directed into the cricket valley.
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Parts of a Tapered Cricket
The net slope created along the edges of the cricket. (Points 4 to
1, 4 to 2, 5 to 2, & 5 to 1) This directs the water to the drains.
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Tapered Crickets
 Caution!
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If not designed properly crickets can pond
Tapered Cricket
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Three Main Contributors to the
Working Effectiveness of a Cricket
1. Roof Surface Slope
Cricket Valley Slope
Cricket Valley Slope
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Crickets divert water, so the
greater the Roof Surface Slope
the better they will perform!
Three Main Contributors to the
Working Effectiveness of a Cricket
2. Cricket Surface Slope
Cricket Valley Slope
Cricket Valley Slope
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The Cricket Surface Slope
pushes the water into the
Cricket Valley. Therefore it
should be at least twice the
Roof Surface Slope!
Three Main Contributors to the
Working Effectiveness of a Cricket
3. Cricket Width!!
Cricket Valley Slope
Cricket Valley Slope
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The most important factor in
cricket performance! The
wider the cricket is made the
better the resulting Cricket
Valley Slope.
A WIDER
CRICKET IS
BETTER!
Calculating Cricket Valley Slope
Step #5
Step #3
Step #4
Step #2
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Step #1
Getting an Accurate and
Functional Tapered Design
 Be clear and concise so that “guessing”
by the tapered designer and contractor
is eliminated!
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General Required
Information to Insure
Accurate Designs
Provide accurate information about:
 Dimensions of
building perimeter
 Number and location
of drains
 Mechanical unit,
skylight and roof
penetration locations
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 Expansion and
control joint locations
 Existing height
restrictions
 Existing unique field
conditions
What Else Can You Do?
Add charts to the roof plan page to clearly designate what
insulation should be provided for each roof area.
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What Else Can You Do?
Use a Roof Legend to
clearly label existing
conditions and to call
out what is needed
and where.
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What Else Can You Do?
Specify whether slope
arrow is designating a
required tapered slope
or an existing structural
slope.
Note desired minimum
and maximum thickness.
Note all components that are
included in thickness shown.
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What Else Can You Do?
Note desired
cricket widths
on roof plan.
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Locating Roof Drains
 Locate as close to
the low point as
possible
 Locate them
symmetrically and in
line with each other
 Space drains using
2’ or 4’ increments
due to modular sizes
of tapered panels
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Locating Roof Drains
 One drain for every
5000 square feet of
roof area
 75 feet maximum
distance between
drains
 Sizes are determined
by roof area and
average rainfall data
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Locating Roof Drains
 Provide overflow
drain no more than
2” above primary
 Avoid having roof top
units or penetrations
near drains
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Summary
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The goal is to drain water from the roof!
Several tapered designs possible
Use 4-way slope design as often as possible
Draw lines at 45 degree angles from drains
Crickets divert water
3 main factors to cricket performance: roof
surface slope, cricket valley slope, and cricket
width
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Summary
 Be clear and concise on drawings and
specifications
 Provide as much information as possible
 Locate drains symmetrically and in line
as often as possible
 Never space drains more than 75 feet
apart
 Always have a backup drain
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Summary
 You are in control of the project
 Make sure submitted shop drawings reflect the
tapered design that you want
 Reject Non 4-way layouts if that is what you
showed in your bid documents
 Reject layouts that shrink the cricket widths
shown in your bid documents
 You have the power to make sure the most
EFFECTIVE tapered design is submitted and
installed
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QUESTIONS?
This concludes the American Institute of
Architects Continuing Education Systems
Program
Firestone Building Products
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