IRC2021Ch. 3

Building Planning

Design criteria, light, ventilation, room dimensions, and means of egress

Sections

R301.2

Climatic and Geographic Design Criteria

Establishes climatic and geographic design criteria including wind speed, seismic design category, weathering, frost line depth, termite infestation probability, and winter design temperature for building design.

R301.2.1

Wind Design Criteria

VIRGINIA WIND DESIGN: Inland areas (incl. Front Royal/Warren County): 105 mph. Coastal areas: up to 130 mph. Wind speed affects: fastener schedules, sheathing attachment, window/door ratings, roof tie-downs. Higher wind speeds require more fasteners and may require engineering review.

R301.2.1-MD

Wind Design Requirements - Maryland

Maryland wind speeds: Western 105-110 mph, Central 110-115 mph, Coastal/Eastern Shore 115-130 mph. Enhanced requirements near Bay.

R302.1

Exterior Walls

Specifies fire-resistance ratings and fire separation distances for exterior walls, projections, openings, and penetrations based on proximity to property lines.

R308

Glazing

Parent section for safety glazing requirements.

R308.3

Human Impact Loads

SAFETY GLAZING REQUIRED in hazardous locations per CPSC 16 CFR 1201.

R308.4

Hazardous Locations

HAZARDOUS LOCATIONS - Safety glazing required in doors, near stairs, wet areas, and other specific locations.

R308.4-MD

Safety Glazing Requirements - Maryland

Safety glazing (tempered/laminated) required in doors, sidelites within 24", bathrooms, and stairways.

R308.6

Skylights and Sloped Glazing

SKYLIGHT REQUIREMENTS: Must be listed/labeled per AAMA/WDMA/CSA 101. Safety glazing required (tempered, laminated, or approved plastic). ENERGY: Zone 4A max U-factor 0.55, SHGC 0.40. Proper curb construction and flashing critical - use manufacturer flashing kits. Fall protection may be required for low-slope skylights.

R308.6-MD

Skylight Safety Glazing - Maryland

Skylight glazing: laminated (0.015" PVB) or tempered glass required. Must meet AAMA/WDMA/CSA 101 standards.

R308-AL

Glazing and Windows - Birmingham

Birmingham window requirements include safety glazing per IRC R308 and energy performance per 2015 IECC Zone 3A (U-0.35, SHGC 0.25). Historic districts require matching window styles.

R308-AR

Windows and Glazing - Arkansas (AFPC 2021 + 2014 AR Energy Code)

Window requirements combine AFPC 2021 safety glazing with 2014 AR Energy Code performance. Zone 3A: U-factor 0.50 max, SHGC 0.30 max. SHGC is critical for reducing cooling loads in hot-humid climate.

R310

Emergency Escape and Rescue Openings

Basements and every sleeping room shall have at least one operable emergency escape and rescue opening. Minimum opening: 5.7 sq ft (5.0 sq ft at grade floor), minimum width 20 inches, minimum height 24 inches. Maximum sill height 44 inches above floor. COLORADO NOTE: Window wells required where egress windows are below grade. Wells must have ladder/steps if over 44 inches deep.

R310.1

Emergency Escape and Rescue Openings

EGRESS WINDOWS REQUIRED in ALL sleeping rooms. MINIMUMS: 5.7 sq ft net clear opening (5.0 sq ft at grade), 24" height, 20" width, sill max 44" from floor. When replacing windows in bedrooms, new windows must meet egress requirements. Casement and awning windows typically provide better egress than double-hung.

R310.1-MD

Emergency Escape and Rescue Openings - Maryland

Egress windows required in all bedrooms: 5.7 sq ft minimum (5.0 at grade), 24" min height, 20" min width, 44" max sill height.

R311.2

Egress Door

EGRESS DOOR - Min one per dwelling unit. 32" clear width, 78" min height. Side-hinged.

R311.2-MD

Egress Door Requirements - Maryland

Egress door requirements: side-hinged, minimum 32"x78" clear opening. Landings required both sides.

R311.3

Landings at Doors

DOOR LANDINGS - Required each side of exterior doors. 36" min in direction of travel.

R311-AR

Doors and Egress - Arkansas (AFPC 2021 Vol III)

Door requirements per AFPC 2021 Vol III (IRC R311). Egress doors, landing requirements, and energy performance for Zone 3A. Seismic considerations for door frame anchorage in SDC C/D.

R322.1

Flood Hazard Areas - General

FLOOD ZONE CONSTRUCTION: Verify flood zone on FEMA FIRM maps before construction. Zone A: Lowest floor at/above BFE. Zone V (coastal): Bottom of lowest structural member at/above BFE. Substantial improvement (>50% value) triggers full compliance. Chesapeake Bay and Shenandoah River areas have flood zones. Check with local floodplain administrator.

R322.1-MD

Flood Hazard Areas - Maryland

Flood zone construction per FEMA requirements. Chesapeake Bay Critical Area rules apply. Freeboard of 1-2 ft above BFE typically required.

R327

Wildfire Hazard Mitigation (Local Adoption)

Where adopted by local jurisdiction, construction in designated wildfire hazard zones must comply with fire-resistant requirements. Class A roof assemblies required. Fire-resistant exterior wall coverings. Ember-resistant vents. Tempered glass windows. Defensible space. COLORADO NOTE: Many mountain and foothill communities have adopted WUI codes. Post-Marshall Fire (2021), Boulder County has strictest requirements. Colorado State Forest Service provides defensible space guidance.