commercial roofing

Module INS-01Module TAP01

COMMERCIAL ROOFINGCOMMERCIAL ROOFING

Tapered Insulation Systems


Learning ObjectivesLearning ObjectivesTapered Insulation PresentationTapered 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


What, Why, and How?

Tapered Insulation Systems


Tapered InsulationTapered 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


Why use a tapered Why use a tapered insulation system?insulation system?

Main Goal Eliminate the

amount of ponding/standing water on the membrane when the roof deck does not provide adequate slope


Ponding may void the roofing warranty

Why is it Important?Why is it Important?


Prevents the potential for roof collapse from excess weight



Prevents growth of vegetation, fungi, and bacteria.




Extends the overall life of a roofing system.



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


Tapered Insulation DesignsTapered 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


One Way Slope to GutterOne Way Slope to Gutter

Most basic design Simple installation


Two Way Slope to GutterTwo Way Slope to Gutter

Second most basic design

Roof is cut in half which reduces the maximum thickness

Simple installation

Ridge


Valley and Cricket to DrainValley 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


Modified 4-Way Slope to Modified 4-Way Slope to DrainsDrains

Second most effective drainage

Used when no overflow drains exists

If one drain is clogged the water can flow over to other drain


4-Way Slope Design4-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


Common Attempt to Show a Common Attempt to Show a 4-Way Slope Design4-Way Slope Design

Randomly drawn valley lines at no specific angles


Correct Way to Show a Correct Way to Show a 4-Way Slope Design4-Way Slope Design

Zoom Window



Zoom Window

Valley Lines should be drawn at a 45 degree angle

out of each drain


45 Degree Valley Miter45 Degree Valley Miter

45 degree angle


Reasons to Alter Reasons to Alter 4-Way Design4-Way Design

Complex existing drain locations



Constant perimeter height is required



Multiple drains at low point with no overflow drains

Overflow drains added



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



Multiple roof top units prevent layout from draining


Tapered Cricket

Tapered CricketsTapered Crickets

Used on both: Full tapered systems Structurally sloped decks


Tapered Cricket


Also called: Saddles Hog Backs



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

Tapered Crickets


SLOPE OF TAPER

SLOPE OF TAPER

SL

OP

E O

F C

RIC

KE

T

SLOPE OF CRICKET

Secondary application of insulation used to divert

water from roof top curbs, valleys, and low points to

drains or scuppers

RA

IN



Types of CricketsTypes of Crickets


½ - Diamond Cricket



Incorrectly drawn crickets

Correctly drawn crickets



4x4 Tapered panel

Portion of tapered panel that is field trimmed as waste

Crickets are created in the field by field trimming tapered panels as shown




Full Diamond Cricket

Installed 4x4 Tapered Panels

Full Diamond Cricket Uninstalled Portion



RTU


Parts of a Tapered CricketParts of a Tapered Cricket

Cricket Width (Points 4 to 5)



Cricket Length (Points 1 to 2)



The slope that is created by the structural deck, tapered insulation or a combination of the two.



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.



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.


Tapered Cricket


Caution! If not designed properly crickets can pond


Three Main Contributors to the Three Main Contributors to the Working Effectiveness of a CricketWorking Effectiveness of a Cricket

Cricket Valley Slope

Cricket Surface Slope

Cricket Width


Roof Surface Slope

1. Roof Surface Slope

Crickets divert water, so the greater the Roof Surface Slope

the better they will perform!





Cricket Width


Roof Surface Slope

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!





Cricket Width


Roof Surface Slope

3. Cricket Width!!

A WIDER CRICKET IS

BETTER!

The most important factor in cricket performance! The

wider the cricket is made the better the resulting Cricket

Valley Slope.


Calculating Cricket Valley SlopeCalculating Cricket Valley Slope

Step #1

Step #2

Step #3Step #4

Step #5


Getting an Accurate and Getting an Accurate and Functional Tapered DesignFunctional Tapered Design

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


General Required General Required Information to Insure Information to Insure

Accurate DesignsAccurate Designs

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

Provide accurate information about:


What Else Can You Do?What Else Can You Do?

Add charts to the roof plan page to clearly designate what insulation should be provided for each roof area.



Use a Roof Legend to clearly label existing conditions and to call out what is needed and where.



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.



Note desired cricket widths on roof plan.


Locating Roof DrainsLocating 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



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



Provide overflow drain no more than 2” above primary

Avoid having roof top units or penetrations near drains


SummarySummary

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


SummarySummary

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


SummarySummary

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


QUESTIONS?QUESTIONS?

This concludes the American Institute of Architects Continuing Education Systems Program

Firestone Building Products

commercial roofing

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