Single-Family Homes IRC Summary Relating to Construction Documents
March 29, 2002The following is a summary of the SBCCI comparison on the differences between current building codes and the new IRC code. The items in bold will have an immediate effect to new and existing construction documents. Included are codes that have not necessarily changed, but with the IRC's interpretation may still require changes to the construction documents. Please be aware that this list may not be complete and only affects the drawings. There are numerous items that may affect the builder that are not covered in this venue.
Chapter 3: Building Planning
R301 – Basic wind speeds have been revised, high wind construction is addressed, requirements added for glazing protection for buildings located in wind borne debris regions.
R301.4 – The minimum uniformly distributed live load shall be as provided in Table 301.4.
R303.4 – Stairway illumination.
R304 – The minimum habitable room size has been changed from 150 square feet to 120 square feet.
R305 – The minimum ceiling height for habitable rooms has been changed from 7'-6" to 7'-0".
R308.4 – Panels in sliding and bifold closet door assemblies are considered hazardous glazing locations. Requirements added for hazardous glazing location in walls enclosing stairway landings.
R308.5 – Windows, other than site built, must meet the wind load requirements of Sections R301.2.1 and R301.2.1.2.
R308.6.2 – The IRC permits laminated glass for skylights with 0.015-inch PVB interlayer, but limits size and height above walking surface.
R310.1 – The IRC requires basements with habitable space to have an emergency escape opening. Requirements added for bulkhead enclosures and window wells.
R310.1.2 – The minimum net clear opening height has been changed from 22 inches to 24 inches. (5 sq. ft. total on the 1st floor, 5.7 sq. ft. total on the remaining floors.)
R310.2 – This section adds the requirements for window wells for emergency openings with sill height below grade.
R311.5 – This section adds the requirements for positively anchoring exterior decks, balconies, stairs and similar exit facilities to the primary structure.
R312 – The IRC exempts landings from the exterior side of sliding doors and changes the maximum elevation height of a landing at an exterior doorway from 8-1/4 inches to 8 inches.
R314.4 – The continuous handrail required by Section R315.1 shall be located on the side where the tread is narrower.
R314.5 – Spiral stairways shall have a minimum tread depth of 7-1/2" at 12" from the narrow edge and a maximum rise of 9-1/2". Minimum headroom is 6'-6".
R314.6 – Circular stairways shall have a minimum tread depth of 11" at a point 12" from the side where the treads are narrower.
R315.1 – Handrails having minimum and maximum heights of 34" and 38" from the nosing of the treads, shall be continuous the full length of the stairs with two or more risers. Exceptions: Handrails may be interrupted by a newel post at a turn.
R315.2 – The handgrip portion of handrails shall have a width of 1-1/4" minimum to 2-5/8" maximum.
R316.1 – Porches, balconies or raised floor surfaces more than 30" above the floor or grade shall have guards not less than 36" high. Open sides of stairs with a total rise of more than 30" shall have guards not less than 34" high.
R317.1 – The IRC requires smoke alarms to be installed in accordance with NFPA 72. (Actuation of any one smoke alarm shall activate all alarms in the unit.)
R323.1.4 – The IRC reduces the metal pedestals or piers supporting wood columns projecting above the floor from 2" to 1".
R325 – This new section adds the requirement for premises identification (site address).
Chapter 4: Foundations
R403.1.7 – The IRC restricts placing buildings or footings on or adjacent to slopes steeper than 1:3.
R403.1.7.1 – Building clearances are required from ascending slopes. The IRC contains provisions requiring buildings to be set back from adjacent slopes to avoid drainage and erosion.
R403.1.8 – The IRC contains provisions for constructing foundations on expansive soils.
R403.1.8.1 – Soil must comply with four provisions in the IRC to be classified as Expansive Soils.
Chapter 5: Floors
R502.3 – Allowable joists spans. The IRC contains different joist span tables. CABO Tables 502.3.1c and 502.3.1d are not used in the IRC.
R502.2.1 – The IRC contains specific requirements regarding the attachment of wood framed decks to wood framed construction.
R502.3.1 – The IRC contains provisions for determining joist spans in sleeping areas.
R502.5 – Allowable header and girder spans. Span tables in the IRC are expanded and contain more detailed information than is found in CABO.
R502.6.1 – Floor systems. The IRC maintains the requirement for overlapping the ends of floor joists, but the provisions are different.
R502.10 – Framing of openings. The IRC includes requirements for framing tail joists into headers at framed openings.
R502.11.2 – The IRC requires bracing to prevent rotation and provide lateral stability.
R502.11.3 – Alterations to trusses shall not be made without approval of a registered design professional.
Chapter 6: Wall Construction
R602.3.1 – Stud spacing. The IRC contains provisions for studs more than 10 feet in length in bearing walls. Table R602.3.1 is new in the IRC.
R602.7 – The IRC contains new span tables for determining required header sizes: Table R502.5(1) and Table R502.5(2).
R602.8 – Firestopping required. "Firestopping" is new terminology in the IRC. Add to plans as note.
Chapter 8: Roof-Ceiling Construction
Rafter span tables have been expanded in the 2000 IRC to include 70 psf and 50psf of ground snow load.
Chapter 10: Chimneys and Fireplaces
R1001.2 – This section has been revised to change the maximum amount of corbeling from 6" to one-half of the chimney's wall thickness.
R1002 – The IRC has expanded the factory-built chimney section to include prescriptive requirements for decorative shrouds, solid fuel appliances, and medium-heat appliances.
R1002.12 – The IRC increases the clearance of combustibles from the back face of masonry fireplaces from 2" to 4".
R1004 – The IRC has deleted the six provisions and requires factory built fireplaces to be listed and labeled and installed in accordance with the listing. The IRC addresses decorative shrouds and unvented gas log heaters.
Chapter 11: Energy Efficiency
N1102 – Simplified prescribed thermal performance criteria are provided for the building envelope (walls, ceilings, floors) in Table N1102.1. This table is applicable where:
- Type A-1 residential buildings have glazing which does not exceed 15% of the gross area of the exterior walls.
- The building is located in an area where the heating degree days (HDD) are less than 13,000. (See Table N1101.2 for climate zone values and Table N1102.1.1.1(1) for corresponding HDD values).
Any residential building which does not meet these criteria must meet the energy conservation requirements of the IECC.
Chapters 13, 15, 16: Mechanical
M1305 – Access requirements for central furnaces and attic installations are new in the IRC. Electrical outlet and lighting requirements are also new.
M1501.1 – An allowance for a single length of flexible transition clothes dryer exhaust duct, listed in accordance with UL 2158A, not to exceed 8 feet is new in the IRC.
M1602.3 – Several new prohibited sources of return air and new exceptions to the prohibitions have been included.
Chapter 24: Fuel Gas
G2437.5.1 – The maximum length of a clothes dryer exhaust duct shall not exceed 25 feet from the dryer location to the outlet terminal. The maximum length of the duct shall be reduced 2-1/2 feet for each 45 degree bend and 5 feet for each 90 degree bend.
Chapter 28: Water Heaters
P2801.5 – Drain pan requirements are new in the IRC.
P2801.6 – The 18 inch minimum elevation requirement for water heaters with an ignition source which are installed in the garage is new in the IRC.
Chapter 38: Power and Lighting Distribution
E3801.2.1 – Receptacles shall be installed so that no point along the floor line in any wall space is more than 6 feet. (Doors to be in closed position.)
E3801.2.2 – Wall space. Any space that is 2 feet or more in width, or space occupied by fixed panels in exterior walls, excluding sliding panels.
E3801.4.1 – Wall counter space. A receptacle outlet shall be installed at each wall counter space 12 inches or wider. Receptacle outlets shall be installed so that no point along the wall line is more than 24 inches, measured horizontally, from a receptacle outlet in that space.
E3801.4.2 – Island counter spaces. At least one receptacle outlet shall be installed at each island counter space with a long dimension of 24 inches or greater.
E3801.4.3 – Peninsular counter space. At least one receptacle outlet shall be installed at each peninsular counter space with a long dimension of 24 inches or greater.
E3801.10 – Hallways of 10 feet or more in length shall have at least one receptacle outlet.
E3802.6 – Kitchen receptacles. All 125-volt, single-phase, 15-and 20-ampere receptacles that serve countertop surfaces shall have ground-fault circuit-interrupter protection for personnel.
E3802.7 – Bar sink receptacles. All 125-volt, single-phase, 15- and 20-ampere receptacles that serve a countertop surface, and are located within 6 feet of the outside edge of a wet bar sink shall have ground-fault circuit-interrupter protection for personnel.
E3803.3 – Additional locations. Where lighting outlets are installed in interior stairways, there shall be a wall switch at each floor level to control the lighting outlet where the stairway has 6 or more risers.
E3803.4 – Storage. In attics, at least one lighting outlet shall be installed where these spaces are used for storage. Such lighting outlet shall be controlled by a wall switch or shall have an integral switch.
International Energy Conservation
The I.E.C.C. requires glazing percentages and minimum insulation values included in the construction documents. The state and county that the house is being built in will determine the minimum R values based on the glazing percentage of the house's exterior. An example would be Galveston County - Zone 3B, with 25% glazing would require Chart 1. Whereas Denton County - Zone 6B, with the same house would require Chart 2.
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The question the builder will need to address when they build a house with multiple elevations in multiple counties is… Do you use the worst case situation to determine R-values or do you figure each case separately? It is our understanding that the construction documents are required to include minimum R-values specific to that house, so multiple generic charts may not work.
Please be aware that there are also additional items in the I.E.C.C. not pertaining to the construction documents that will probably affect the builder.
On a final note, the "Windstorm Resistant Construction Guide" and the "Standard for Hurricane Resistant Residential Construction" suggest construction practices (i.e. window location) that the builder may wish to address. Kipp*Flores Architects can address these items with the builders to determine cost feasibility. Please let us know if you wish to make adjustments to the plans in this area.