International Residential Code

Product Requirements (IRC R703)

Products must be certified and labeled to show they conform to their established ASTM standard:

Installation Requirements

CLADDING — IRC R703 provides prescriptive and performance installation requirements:

• In general, vinyl and insulated vinyl siding are installed 16" on center using roofing nails, although variations are allowable including other approved fasteners like staples and screws.
• Polypropylene siding panels range in size and are unique. Manufacturer’s installation instructions should be reviewed and in many cases it may be less than 16" on center. It must be installed over some type of wood sheathing.

SOFFIT — IRC Section R704 provides specific requirements for the installation of vinyl soffit panels:

• According to Section R704.1 in high wind areas, the soffit panels must be designed to meet the appropriate design pressure.
• R704.2.1 requires that each soffit panel be fastened at both the fascia and wall and that there be no unsupported spans greater than 16" without the use of an intermediate nailing strip.
• Where soffit is being used in high-wind areas, it must comply with Section R704.3.

Considerations and Conditions for use in High-density Developments

• In general, vinyl siding, polypropylene siding and insulated vinyl siding are not limited in their application with homes built under the IRC.
• In two instances, performance measures related to high density construction and fire will apply:
  • IRC R302 General
  • IRC Table R302.1 (1) place requirements of a 1-hour tested assembly according to ASTM E119 on exterior walls that are 5' or closer to the property line
• Vinyl siding is a part of many E119-rated assemblies.

Polypropylene Siding

IRC R703.14.2 limits the use of polypropylene siding on walls that are closer than 5' to the property line (separation distance) and on walls 10' or closer to walls of other buildings on another lot unless a certification of flame spread index is provided in accordance with R703.14.3. Note, this provision does not apply to walls that are perpendicular to the line used to determine the separation distance (example: front and rear elevations of townhouse construction).