INTERNATIONAL RESIDENTIAL CODE

CHAPTER 3 PLANNING

TABLE R301.4 IRC Interpretation No. 11-04 2000 Edition Issued: 12-20-04

R301.4 Live load. The minimum uniformly distributed live load shall be as provided in Table R301.4.

TABLE R301.4 MINIMUM UNIFORMLY DISTRIBUTED LIVE LOADS (in pounds per square foot) USE LIVE LOAD

Exterior 60

Decksf 40

Fire escapes 40

Passenger vehicle garagesa 50a

Attics without storageb,e 10

Attics with storageb,e 20

Rooms other than sleeping 40

Sleeping rooms 30

Stairs 40c

Guardrails and handrailsd 200 For SI: 1 pound per square foot = 0.0479 kN/m2, 1 square inch = 645 mm2, 1 pound = 4.45 N. a. Elevated shall be capable of supporting a 2,000- pound load applied over a 20-square-inch area. b. No storage with slope not over 3 units in 12 units. c. Individual stair treads shall be designed for the uniformly distributed live load or a 300-pound concentrated load acting over an area of 4 square inches, whichever produces the greater stresses. d. A single concentrated load applied in any direction at any point along the top. e. Attics constructed with wood trusses shall be designed in accordance with SectionR802.10.1. f. See Section R502.2.1 for decks attached to exterior . ! ! ! ! ! ! ! ! ! ! Q1: Is the loading criteria for attics constructed with wood trusses governed by Note e of Table 301.4 which states that attics constructed with wood trusses shall be designed in accordance with Section R802.10.1?

A1: No. The minimum live loads provided in Table R301.4 are the minimum loads which must be applied in the design of each of the elem ents listed. Attics constructed to include storage space must be designed for 20 psf live load. The loads in the Table includes roofs/attics constructed using conventional and framing or wood truss framing. The provisions in Section R802.10.1, as referenced in Note e, are specific requirements for the design and fabrication of wood trusses, and does not provide live loads specific to wood trusses.

Q2: Is there a minimum height requirement for attics with storage?

A2: Yes. There are two basic design parameters that must be employed when establishing the minimum height requirement for attics with storage; 1) the minimum allowable roof slope, and 2) the minimum clearance required for INTERNATIONAL RESIDENTIAL CODE attic access. The minimum allowable roof slope over an attic containing storage space must be greater than 3 units vertical in 12 units horizontal (3:12), see Note b. W here access is provided to the attic, the minimum vertical height permitted is 30 inches (see Section R807.1).

Q3: Is the 20 psf live load for attics with storage required to be applied concurrent with other required live loads?

A3: Yes. ______