COMMERCIAL ROOFING

1
COMMERCIAL ROOFING

• Tapered Insulation Systems

2
Learning ObjectivesTapered 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

3
Tapered Insulation Systems

• What, Why, and How?

4
Tapered Insulation

• Rigid roof insulation
• Made from various materials
• Polyiso
• Extruded Expanded Polystyrene
• Perlite
• Typically 2x4 or 4x4 panels
• Provides r-value and slope
• Typical slopes available
• 1/8/ft., ¼/ft., ½/ft.
• Arranged by a designer into a tapered system to
  promote positive drainage

5
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

6
Why is it Important?

• Ponding may void the roofing warranty

7
Why is it Important?

• Prevents the potential for roof collapse from
  excess weight

8
Why is it Important?

• Prevents growth of vegetation, fungi, and
  bacteria.

9
Why is it Important?

• Extends the overall life of a roofing system.

10
Why is it Important?

• National Agencies Code Groups require a minimum
  slope
• 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

11
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
12
One Way Slope to Gutter

• Most basic design
• Simple installation

13
Two Way Slope to Gutter

• Second most basic design
• Roof is cut in half which reduces the maximum
  thickness
• Simple installation

14
Valley and Cricket to Drain

• Commonly used design with drains
• Cheapest material cost in most cases (versus
  4-way slope design)
• Potential small ponding along cricket edges
  (typical)
• Not the most effective drainage design

Potential ponding area
15
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

16
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

17
Common Attempt to Show a 4-Way Slope Design
Randomly drawn valley lines at no specific angles
18
Correct Way to Show a 4-Way Slope Design
19
4-Way Slope Design
Valley Lines should be drawn at a 45 degree angle
out of each drain
20
45 Degree Valley Miter
45 degree angle
21
4-Way Slope Design
WHAT ARE VALID REASONS TO NOT USE A 4-WAY SLOPE
DESIGN?
22
Reasons to Alter 4-Way Design
Complex existing drain locations
23
Reasons to Alter 4-Way Design
Constant perimeter height is required
24
Reasons to Alter 4-Way Design
Multiple drains at low point with no overflow
drains
Overflow drains added
25
Reasons to Alter 4-Way Design
When cost is a bigger issue than performance
4-Way Design -Most effective drainage -Higher
material cost
Valley Cricket Design -Least effective
drainage -Lower material cost
26
Reasons to Alter 4-Way Design
Multiple roof top units prevent layout from
draining
27
Tapered Crickets

• Used on both
• Full tapered systems
• Structurally sloped decks

Tapered Cricket
28
Tapered Crickets

• Also called
• Saddles
• Hog Backs

29
Tapered Crickets

• Secondary application of insulation used to
  divert water from roof top curbs, valleys, and
  low points to drains or scuppers

Tapered Crickets
30
Tapered Crickets
Secondary application of insulation used to
divert water from roof top curbs, valleys, and
low points to drains or scuppers
31
Tapered Crickets
32
Types of Crickets
33
Types of Crickets
34
Types of Crickets
½ - Diamond Cricket
35
Types of Crickets
36
Types of Crickets
37
Tapered Crickets
Incorrectly drawn crickets
Correctly drawn crickets
38
Tapered Crickets
39
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
40
Tapered Crickets
41
Tapered Crickets
42
Tapered Crickets
RTU
43
Tapered Crickets
44
Parts of a Tapered Cricket
Cricket Width (Points 4 to 5)
45
Parts of a Tapered Cricket
Cricket Length (Points 1 to 2)
46
Parts of a Tapered Cricket
The slope that is created by the structural deck,
tapered insulation or a combination of the two.
47
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.
48
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.
49
Tapered Crickets

• Caution!
• If not designed properly crickets can pond

Tapered Cricket
50
Three Main Contributors to the Working
Effectiveness of a Cricket
1. Roof Surface Slope
Crickets divert water, so the greater the Roof
Surface Slope the better they will perform!
51
Three Main Contributors to the Working
Effectiveness of a Cricket
2. Cricket Surface Slope
The Cricket Surface Slope pushes the water into
the Cricket Valley. Therefore it should be at
least twice the Roof Surface Slope!
52
Three Main Contributors to the Working
Effectiveness of a Cricket
3. Cricket Width!!
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!
53
Calculating Cricket Valley Slope
Step 5
Step 1
Step 3
Step 4
Step 2
54
Getting an Accurate and Functional Tapered Design

• Be clear and concise so that guessing by the
  tapered designer and contractor is eliminated!

55
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

• Expansion and control joint locations
• Existing height restrictions
• Existing unique field conditions

56
What Else Can You Do?
Add charts to the roof plan page to clearly
designate what insulation should be provided for
each roof area.
57
What Else Can You Do?
Use a Roof Legend to clearly label existing
conditions and to call out what is needed and
where.
58
What Else Can You Do?
Note desired minimum and maximum thickness.
59
What Else Can You Do?
60
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

61
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

62
Locating Roof Drains

• Provide overflow drain no more than 2 above
  primary
• Avoid having roof top units or penetrations near
  drains

63
Summary

• 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

64
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

65
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

66
QUESTIONS?

• This concludes the American Institute of
  Architects Continuing Education Systems Program
• Firestone Building Products

67
Thank you!