Skip to content

OneClick Ice and Water Shield Calculator

Built for Contractors to get 'the right' IWS value

Unlike basic "rule-of-thumb" calculators that use simple formulas, OneClick Code uses jurisdictional data and IRC references to determine exactly how much Ice & Water Shield you need and whether it’s required by code.

  • Faster (and more accurate) estimates
  • Fewer calls to municipalities or adjusters
  • Documentation you can defend with confidence
Try IWS Calculator for Free
Hero

Calculate precisely how much IWS membrane you need on your roof.

Ice and Water Shield is an expensive line item on Roof Replacement, and is often the most supplemented item. Miscalculating or omitting Ice & Water Shield coverage can eat into margins, complicate claims and be a consumer protection issue.

OneClick Code Ice & Water Shield Calculator is the only solution that combines local jurisdiction building codes with property-specific data. You can trust that every bid you submit is accurate, code-compliant and backed by local data. You need more than just the dimensions of the roof, valleys, and eaves to get the right amount — we have that. 

windows-surface-side-view

We make it easy for you to calculate the exact amount of material needed and provide all the necessary documentation to support your claims.

Garrett Kurtt, CEO of OneClick Code

What Is Ice & Water Shield? Why Is It Important?

An Ice & Water Shield (also called an ice barrier) is a self-adhering underlayment installed beneath roofing materials at eaves, valleys, and penetrations. It's designed as a protective layer to prevent leaks from ice dams, snow and wind-driven rain.

Flexible to climate

It's often mandated by local building codes, especially in northern and high-altitude regions.

cost-savings (2)-1

Compliance

Requirements vary by climate zone, roof slope and municipal amendments.

Efficiency

Avoid violations

Missing or misapplying Ice & Water Shield can lead to expensive water intrusion, insurance claims, and code violations.
Minimize the risk of costly code violations and penalties.

By using our calculator, roofers ensure every estimate includes the correct coverage and meets IRC R905.1.2 / R905.2.7 standards.

Key Features and Benefits

Feature

Code-Backed Accuracy

Built with verified IRC and local jurisdiction data.

Feature

Property-Specific Inputs

Calculates coverage based on the home’s dimensions, not assumptions.

Feature

Evidence-Based Reports

Every result includes code citations and AHJ confirmation.

Benefit

Time Savings

Generate results in seconds instead of hours of manual lookup.

Benefit

Professional Documentation

Simple ‘copy’ and ‘paste’, use reports to validate insurance estimates and supplement claims.

How to Use Our IWS Calculator

Step 01
Step 2 (1)
Step 3-2
Step 4 v2
  • 1

    Input Dimensions

  • 2

    Click Calculate

  • 3

    Select Desired Output

  • 4

    Download Report!

How Our Calculator Works

Each field in the calculator is property-specific. These variables combine with local code data to calculate the correct coverage and provide code citations for complete defensibility.

IWS-3

Roof Size (SQ)

Total area of the roof in squares; defines material coverage.

Predominant Pitch (/12)

Steeper roofs can alter code requirements for underlayment overlap.

Valley Length (LF)

Total linear footage of valleys—critical leak zones that always need protection.

Eave Length (LF)

Linear feet along roof edges where Ice & Water Shield is commonly mandated.

Soffit Depth (IN)

Determines how far the membrane must extend past the exterior wall.

Determines how far the membrane must extend past the exterior wall.

Default 24 inches, referencing IRC R905.1.2 for required extension.

Stud Size (2×4 or 2×6)

Impacts the thermal boundary and, therefore, potential ice-dam formation.

Exterior Type (Brick, Vinyl, etc.)

Exterior materials influence moisture and fastening considerations.

Why Accurate Ice & Water Shield Calculations Matter

Incorrectly estimating Ice & Water Shield doesn’t just risk the level of protection on the roof; it opens you up to code compliance issues and less profit.

  • Underestimating coverage leads to leaks, failed inspections, and warranty claims.
  • Overestimating inflates bids and costs you contracts.
  • Ignoring jurisdictional requirements invites fines or rejected permits.
oklahoma-roofers

Why Accurate Ice & Water Shield Calculations Matter

Incorrectly estimating Ice & Water Shield doesn’t just risk the level of protection on the roof; it opens you up to code compliance issues and less profit.

  • Underestimating coverage leads to leaks, failed inspections, and warranty claims.
  • Overestimating inflates bids and costs you contracts.
  • Ignoring jurisdictional requirements invites fines or rejected permits.
prevent-remove-ice-dams-roof-winter 1

Documentation

The Ice & Water Shield Evidence Report

The OneClick Code IWS report doesn’t just output numbers and dimensions. You will be armed with a complete compliance record.

Property-Specific Data

Each report includes the property address, date generated, and a unique report ID for easy tracking.
Property Specific Data

Jurisdictional Confirmation

Identifies the Authority Having Jurisdiction (AHJ), for example, Arapahoe County, along with municipal contact details for verification.

Jurisdictional Confirmation-1

Code Compliance Evidence

Each report includes the property address, date generated, and a unique report ID for easy tracking.
Code Compliance

Watch

See It in Action

Watch how OneClick Code’s IWS Calculator provides a clear report in minutes.

Frequently Asked Questions

What is the difference between an Ice & Water Shield and standard underlayment?

An Ice & Water Shield is a self-adhered, waterproof membrane designed for eaves, valleys, and roof penetrations—areas most prone to leaks from ice dams or heavy rain. Standard underlayment is water-resistant, not waterproof.

How do building codes determine if IWS is required?

Per IRC R905.1.2, an ice barrier is required in areas where the average daily temperature in January is 25°F or less. Many jurisdictions amend this rule to expand protection zones. The calculator automatically references both IRC and local amendments.

Can I use this calculator for commercial buildings?

This tool is optimized for residential roofing codes under the IRC. For commercial projects governed by the IBC, OneClick Code’s paid reports provide equivalent compliance guidance.

Does the calculator include cost estimates?

The public calculator focuses on coverage and code requirements. Subscribed users in the full OneClick Code platform can access cost integrations and exportable estimates.

How accurate is the data in OneClick Code reports?

Every jurisdictional requirement is verified directly with local building departments and updated regularly, ensuring your reports are accurate, auditable, and defensible in claims.

Is the calculator free to use?

A preview version is free via a free trial. For full functionality, including downloadable reports, cost data, and integrations, you can access it through a paid OneClick Code subscription.

Where can I learn more about Ice & Water Shield requirements?

You can view details in IRC R905.1.2 / R905.2.7, or simply create an account with OneClick Code to see how these standards apply to your ZIP code.

Calculate Your Ice & Water Shield Report Now

Get started

Don’t leave compliance to chance. Generate a code-verified Ice & Water Shield report to protect your bid, margins, and reputation. Start Your Free Preview or Book a Demo to unlock full access to OneClick Code’s suite of roofing compliance tools.

Try for Free Book a Demo
occ_backgrounds_standoff_2