Roofing Guide to the International Residential Code (IRC)

By Roof Online Staff Updated October 2, 2022

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Roofing Guide to the International Residential Code

Table of Contents

Introduction

This page references the 2018 International Residential Code. Although it’s not the latest version, the 2018 version of the code is currently the most commonly used.

Sections of the code which reference roofing or roof-adjacent aspects of construction are presented on this page. We also provide links to the building code for every chapter below so you can see the actual language of the sections you’re interested in.

You may be looking for the Roofing Guide to the International Building Code.

For a good guide to the entire IRC, consider getting DEWALT 2018 Residential Construction Codes: Complete Handbook. (Link goes to the book’s Amazon page.)

Search this page: This is a pretty long page. We highly recommend using CTRL+F to search for the exact words you’re looking for. Here’s how you do it on desktop and tablet. Here’s how you do it on mobile. If you don’t know this one simple trick, click that link, read the article, and learn how to do it. It will save you a lot of time in the future if you learn how. It’s easy.

Note on Amendments to the Building Code

Always check with your local building inspector’s office or website to be certain which version of the building code is in effect in your area.

New versions of the model IRC are produced every 3 years, but they are not adopted or put into effect by local authorities every 3 years. In fact, they are not adopted with any consistency from country to country, state to state, or even city to city.

An important thing to be aware of is the fact that the majority of the governing authorities which adopt the codes do so with amendments.

The codes produced by the International Code Council are model codes, which means that they are simply standardized templates that the authorities in each actual jurisdiction can use as a foundation for their building codes. Some places will adopt the codes as they are, without amendments, but this is not very common.

Local authorities can (and they do!) add things, remove things, change the language, and make exceptions to the model code, so it’s not enough to simply know which version of the model code has been adopted.

Please see our page Building Codes & Roofing 101 • Important Facts & Guidelines for more information.

Chapter 1 Scope and Administration

See the full code for Chapter 1 on the ICC website.

See the full code for Chapter 1 on the UpCodes website.

Section R104 Duties and Powers of the Building Official

  • R104.10 Modifications (Roof Online Note: This section gives the building inspector leeway when it comes to enforcing the code. It allows you to present reasonable requests for code requirement modification if strictly following the code is impractical but the intent and purpose of the code will still be satisfied.)
  • R104.11 Alternative materials, design and methods of construction and equipment

Section R105 Permits

  • R105.2 Work exempt from permit
  • R105.2.2 Repairs

Section R106 Construction Documents

Chapter 3 Building Planning

See the full code for Chapter 3 on the ICC website.

See the full code for Chapter 3 on the UpCodes website.

Section R301 Design Criteria

(Roof Online Note: This section mentions roofs over 100 times.)

  • R301.2 Climatic and geographic design criteria
  • R301.2.1 Wind design criteria
  • R301.2.2.2 Weights of materials
  • R301.6 Roof load

Section R302 Fire-Resistant Construction

  • R302.2.4 Parapets for townhouses
  • R302.2.5 Parapet construction
  • R302.2.6 Structural independence

Section R308 Glazing

  • R308.6 Skylights and sloped glazing
  • R308.6.8 Curbs for skylights

Section R316 Foam Plastic

  • R316.5 Specific requirements
  • R316.5.2 Roofing
  • R316.5.3 Attics

Section R324 Solar Energy Systems

  • R324.4 Rooftop-mounted photovoltaic systems
  • R324.5 Building-integrated photovoltaic systems
  • R324.6 Roof access and pathways

Chapter 4 Foundations

See the full code for Chapter 4 on the ICC website.

See the full code for Chapter 4 on the UpCodes website.

Section R406 Foundation Waterproofing and Dampproofing

Chapter 6 Wall Construction

See the full code for Chapter 6 on the ICC website.

See the full code for Chapter 6 on the UpCodes website.

(Roof Online Note: This chapter mentions roofs over 200 times, mostly having to do with wall construction requirements which ensure that the walls can support the loads imposed on them.)

Chapter 7 Wall Covering

See the full code for Chapter 7 on the ICC website.

See the full code for Chapter 7 on the UpCodes website.

Section R703 Exterior Covering

  • R703.3 Wall covering nominal thickness and attachments
  • R703.3.1 Soffit installation
  • R703.3.3 Fasteners
  • R703.4 Flashing (Roof Online Note: Flashing requirements at wall and roof intersections, chimneys.)
  • R703.8 Anchored stone and masonry veneer, general
  • R703.8.2 Exterior veneer support
  • R703.8.2.2 Support by roof construction

Chapter 8 Roof-Ceiling Construction

See the full code for Chapter 8 on the ICC website.

See the full code for Chapter 8 on the UpCodes website.

(Roof Online Note: This chapter covers rafters, among other things. It mentions rafters over 200 times and includes rafter span tables. Also covers wood panel (plywood, OSB) roof sheathing requirements.)

Section R801 General

Section R802 Wood Roof Framing

Section R803 Roof Sheathing

  • R803.2 Wood Structural Panel Sheathing (Roof Online Note: This subsection covers plywood and OSB sheathing. See Table R503.2.1.1 for minimum allowable panel thickness by span and load.)

Section R804 Cold-Formed Steel Roof Framing

Section R806 Roof Ventilation

Section R807 Attic Access

Chapter 9 Roof Assemblies

See the full code for Chapter 9 on the ICC website.

See the full code for Chapter 9 on the UpCodes website.

(Roof Online Note: This is the main roofing chapter of the code. In particular, note that the Section R905 subsections for each different type of roofing material cover deck requirements, slope, fasteners, underlayment, and flashing for that specific roof type.)

Section R902 Fire Classification

Section R903 Weather Protection

  • R903.2 FlashingR903.2.2 Crickets and Saddles
  • R903.3 Coping
  • R903.4 Roof drainage

Section R904 Materials

Section R905 Requirements for Roof Coverings

  • R905.1 Roof covering application
  • R905.1.1 Underlayment
  • R905.1.2 Ice barriers (Roof Online Note: “Ice Barriers” covers the installation requirements for ice and water shield.)
  • R905.2 Asphalt shingles R905.2.8 Flashing R905.2.8.2 Valleys R905.2.8.5 Drip Edge
  • R905.3 Clay and concrete tile
  • R905.4 Metal roof shingles
  • R905.5 Mineral-surfaced roll roofing
  • R905.6 Slate shingles
  • R905.7 Wood shingles
  • R905.8 Wood shakes
  • R905.9 Built-up roofs
  • R905.10 Metal roof panels
  • R905.11 Modified bitumen roofing
  • R905.12 Thermoset single-ply roofing (Roof Online Note: This section covers EPDM roofing.)
  • R905.13 Thermoplastic single-ply roofing (Roof Online Note: This section covers PVC and TPO roofing.)
  • R905.14 Sprayed polyurethane foam roofing
  • R905.15 Liquid-applied roofing
  • R905.16 Photovoltaic shingles
  • R905.17 Building-integrated Photovoltaic (BIPV) roof panels applied directly to the roof deck

Section R906 Roof Insulation

Section R907 Rooftop-Mounted Photovoltaic Panel Systems

Section R908 Reroofing

(Roof Online Note: This section covers the requirements for replacing an existing roof or installing a new roof over an old roof. It also tells you how many roofs (how many layers of roofing) you can put down on top of one another on a building and under what conditions.)

Chapter 10 Chimneys and Fireplaces

See the full code for Chapter 10 on the ICC website.

See the full code for Chapter 10 on the UpCodes website.

Section R1003 Masonry Chimneys

Section R1005 Factory-Built Chimneys

Chapter 11 [RE] Energy Efficiency

See the full code for Chapter 11 on the ICC website.

See the full code for Chapter 11 on the UpCodes website.

Section N1101 General

  • N1101.6 (R202) Defined terms (Roof Online Note: We recommend reading this subsection first.)
  • N1101.7 (R301.1) Climate zones
  • TABLE N1101.7 (R301.1)
  • CLIMATE ZONES, MOISTURE REGIMES, AND WARM-HUMID DESIGNATIONS BY STATE, COUNTY AND TERRITORY
  • N1101.10 (R303.1) Identification

Section N1102 (R402) Building Thermal Envelope

  • N1102.1 (R402.1) General (Prescriptive)
  • N1102.1.2 (R402.1.2) Insulation and fenestration criteria
  • N1102.1.3 (R402.1.3) R -value computation
  • N1102.1.4 (R402.1.4) U- factor alternative
  • N1102.2 (R402.2) Specific insulation requirements (Prescriptive)

Section N1109 (R503) Alterations

  • N1109.1.1 (R503.1.1) Building envelope

Chapter 18 Chimneys and Vents

See the full code for Chapter 18 on the ICC website.

See the full code for Chapter 18 on the UpCodes website.

Section M1804 Vents

  • M1804.2 Termination
  • M1804.2.1 Through the roof

Section M1805 Masonry and Factory-Built Chimneys

Chapter 23 Solar Thermal Energy Systems

See the full code for Chapter 23 on the ICC website.

See the full code for Chapter 23 on the UpCodes website.

Section M2301 Solar Thermal Energy Systems

  • M2301.2 Design and installation
  • M2301.2.1 Access
  • M2301.2.2 Collectors and panels
  • M2301.2.2.1 Roof-mounted collectors
  • M2301.2.9 Roof and wall penetrations

Chapter 24 Fuel Gas

See the full code for Chapter 24 on the ICC website.

See the full code for Chapter 24 on the UpCodes website.

Section G2415 (404) Piping System Installation

  • G2415.9 (404.9) Above-ground piping outdoors

Section G2427 (503) Venting of Appliances

  • G2427.5 (503.5) Masonry, metal and factory-built chimneys
  • G2427.5.3 (503.5.4) Chimney termination
  • G2427.6 (503.6) Gas vents
  • G2427.6.4 (503.6.5) Gas vent terminations
  • G2427.6.6 (503.6.7) Roof terminations
  • G2427.7 (503.7) Single-wall metal pipe
  • G2427.7.3 (503.7.3) Termination
  • G2427.7.5 (503.7.5) Roof penetrations

Chapter 26 General Plumbing Requirements

See the full code for Chapter 26 on the ICC website.

See the full code for Chapter 26 on the UpCodes website.

Section P2607 Waterproofing of Openings

  • P2607.1 Pipes penetrating roofs

Chapter 29 Water Supply and Distribution

See the full code for Chapter 29 on the ICC website.

See the full code for Chapter 29 on the UpCodes website.

Chapter 31 Vents

See the full code for Chapter 31 on the ICC website.

See the full code for Chapter 31 on the UpCodes website.

Section P3103 Vent Terminals

  • P3103.1 Vent pipes terminating outdoors
  • P3103.3 Flashings and sealing

Chapter 44 Referenced Standards

See the full code for Chapter 44 on the ICC website.

See the full code for Chapter 44 on the UpCodes website.

(Roof Online Note: This chapter includes around 50 standards relevant to roofing.)

Appendix H – Patio Covers

See Appendix H on the ICC website.

See Appendix H on the UpCodes website.