Significant Changes to the 2015 IRC and IECC

Contact: Gary Ehrlich
(202) 266-8545

In collaboration with the National Multifamily Housing Council, National Apartment Association and BOMA International, NAHB released a report regarding the significant changes to the 2015 ICC model codes. Download the report 2015 ICC Model Codes: Summary of Important Changes for more details. Here is a summary:

Beneficial Changes to the IRC Building Planning and Construction Provisions

  • Section 301.2.1.2 Protection of openings. This change replaces the two-story limit on the use of wood structural panels for windborne debris protection with a limit based on a 33-foot meanroof height. (RB41)
  • Section R308.4.7 Glazing adjacent to bottom stair landing. This change limits the requirement for glazing at the bottom of a landing by excluding windows greater than 180 degrees from the bottom face of the landing. (RB115)
  • R310.6 Alterations or repairs of existing basements. This change includes clarification when an emergency escape and rescue opening is required in existing dwellings and additions. (RB124)
  • Section R315 Carbon Monoxide Alarms. This change is a complete rewrite of the section to match the format for smoke alarms. It also introduces exceptions from requiring carbon monoxide detectors, based on the same exceptions found under smoke alarms. (RB161)
  • Section R316.4 Thermal Barrier. This change adds 23/32 wood structural panels as an acceptable alternative for thermal barrier protection. (RB172)
  • R403.1.1 Minimum size. The existing table of minimum footing widths, Table R403.1, is replaced with a new, expanded, engineering-based table that reduces the minimum footing width for many common one- and two-story dwelling foundations. (RB211)
  • Section R404.1.1 Design required. Revises the retaining wall definition and provision and requires a foundation wall to be supported at both the top and bottom prior to backfilling. (RB228)
  • Section R507.1 Decks. Changes include new floor joist and beam span tables, allowable post sizes and other construction details. (RB264)
  • Section R507.2.4 Deck lateral load connection. Adds alternative to deck lateral connection. (RB262)
  • Table R602.3 (1) Fastening schedule for structural members. Changes the minimum fastener schedule and is significantly revised, including the addition of common nails and other nail types. In most cases, the minimum number of box nails previously required is increased by one. (RB278)
  • Table R602.10.3 (1) Bracing requirements based on wind speed. Allows using the average of the two spaces between a braced wall line and the next adjacent braced wall line on each side as the spacing used to enter the wind table. (RB293)
  • Table R602.10.5 Minimum length of braced wall panels. Allows segments of continuously-sheathed portal frames to contribute more towards required bracing. (RB310)
  • Section R602.10.8.2 Connections to roof framing. Adds the option to use wood structural panel sheathing to provide high-heel blocking and allows truss supplier to provide truss blocks without requiring engineer's stamp. (RB319)
  • Section R703.3 Nominal thickness and attachments. Limits use of the prescriptive siding attachment table based on wind speed, exposure category and mean roof height. (RB367) Adds provisions for attachment of siding through foam sheathing over cold-formed steel framing. (RB390) Adds provisions for attachment of siding through foam sheathing over concrete and masonry walls.(RB391)
  • Section R703.6 Wood Shakes and Shingles. Updates requirements for the attachment of wood shakes and shingles as exterior wall and roof cladding. (RB369)
  • R905.1.1 Underlayment. Provides a new table summarizing underlayment requirements, including high-wind requirements. Adds alternative for using 4-inch strips of self-adhered membrane at panel joints. (RB435)

Be Aware of These Changes to the IRC Building Planning and Construction Provisions

  • Section R322.1 General. The section is revised to recognize Coastal A Zones where established by FEMA or the jurisdiction and require foundations of dwellings in Coastal A Zones to be constructed using pier and pile foundations similar to Zone V structures, with the exception that backfilled stem walls are permitted. (RB180)
  • Section R322.2.1 Elevation requirements. The section is revised to require a minimum one foot of freeboard for dwellings in Zone A flood hazard areas. (RB188)
  • New Section R322.3.5.1 Protection of building envelope. A section is added requiring an exterior door be provided at the top of stairs enclosed with breakaway walls and providing access to the dwelling. (RB198)
  • Section 602.7.5 Supports for headers. The section is revised to require at least one king stud is needed each end of a header in addition to required jack studs. A table is added providing the minimum number of king studs based on the opening size. (RB286)

Beneficial Changes to the IRC Energy Conservation Provisions

  • Table N1102.1.4 Equivalent U-Factors. U-factor wall corrections for walls in all climate zones. (RE50)
  • Section N1102.2.4 Access hatches and doors. Vertical doors allowed to meet exterior door requirements. (RE58)
  • Section N1102.2.8 Floors. Adds option to have floor insulation not against the underside of floor. (RE60)
  • Section N1103.3 Ducts. The proposal changes the duct leakage requirements from mandatory to prescriptive, while retaining the testing requirement and duct construction specifications. (RE109)
  • Section N1103.3.2 Sealing (mandatory). Removed exception for sealing longitudinal joints (RE111) and introduced an additional alternative for duct leakage testing to the outdoors. (RE112)
  • SectionN1103.5.3 Hot water pipe insulation. Eliminates pipe insulation to kitchen and eliminates table. It also limits insulation to all pipe 3/4 inch or larger. (RE132)
  • New Appendix T Recommended procedure for Worst-case testing of atmospheric venting systems. Introduces new definitions for Combustion Appliance Zone and additional requirements for the required testing of combustion appliances. (RE193)
  • New Appendix U Solar Ready Provision. Adds an appendix that contains requirements for areas on the roof to be dedicated for future installations. (RE9)

Be Aware of Changes to the IRC Energy Conservation Provisions

  • Table N1102.4.1.1 Air Barrier and Insulation installation. Cavities within corners and headers shall be insulated by completely filling the cavity with a material having a thermal resistance of R3 per inch minimum. (RE83)
  • Section N1103.5.1 Heated water circulation and Temperature maintenance systems. Requires limited water temperature increase to 10F (RE125.1) and adds a pointer in a new IRC Plumbing section back to section N1103.4.1 (RE125.3)
  • Section N1105.4.2 Compliance Report. Details compliance report requirements. (RE163)
  • Section N1106 Energy Rating Index Compliance Alternative. Introduces a HERS-like alternate compliance path. (RE188)

Beneficial Changes to the IRC Mechanical and Plumbing Provisions

  • Section M1503.4 Makeup air required. The section was revised to explicitly permit the use of gravity dampers for the kitchen makeup air system and clarify that natural ventilation (rather than fans) can be used to provide the required makeup air. (RM34)
  • M1601.4.1 Joints, seams and connections. The section is revised to require longitudinal joints to be sealed or gasketed on snap-lock and button-lock type ducts. (RM53)
  • P2603.2.1 Protection against physical damage. The section is revised to reduce the dimension for requiring strike plates from 1-1/2 inches to 1-1/4 inches, thus reducing the number of strike plates required. (RP14)
  • Table P2903.1 Required capacities at point of outlet discharge. The table was revised to reduce the required minimum flow rate capacities for lavatory, sink and shower fixtures, thus effectively reducing the required size of piping. (RP79)
  • Section R3201.2 Trap seals.. Revises section to allow more options for traps subject to evaporation, such as barrier-type trap seal protection devices. (RP150)

Be Aware of These Changes to the IRC Mechanical and Plumbing Provisions

  • New Section M1411.4 Condensate pumps. Added a new section requiring an automatic shut-off be provided on condensate lines serving appliances in attics and crawl spaces in case the condensate pump fails. (RM22)
  • Section M1506.2 Duct length. The section was revised to incorporate a new exhaust duct length table based on ASHRAE 62.2 that specifies very stringent maximum limits on duct lengths. (RM36)