Code Related FAQs

What is the difference between the International Building Code (IBC) and the International Residential Code (IRC)?

The main difference between these two codes is that the International Building Code can be used to design any building or structure. In fact, the scope of the IBC states that its provisions apply to the "construction, alteration, movement, enlargement, replacement, repair, equipment, use and occupancy, location, maintenance, removal and demolition of every building or structure or any appurtenances connected or attached to such buildings or structures."

The International Residential Code has a scope that is limited to one- and two-family dwellings and multiple single-family dwellings (townhouses) not more than three stories in height with a separate means of egress and their accessory structures.

What are the Building Codes used in the City of Redmond?

The City of Redmond does not have its own Building Code. The Washington State Building Code Council determines, through legislative action, which building codes will be used by the local jurisdictions throughout the State of Washington. See our page on Codes In Use for a list of the current applicable construction codes, regulations, and local amendments.

What are the Climatic & Geographic Design Criteria, IRC Table R301.2(1), for the International Residential Code (IRC) in Redmond?


IRC Table R301.2(1) 
Ground Snow Load 15 pounds per square foot
Wind Speed 85 miles per hour
Seismic Design Category D2
Winter Design Temo 27º F
Ice Shield Underlayment Required No
Flood Hazards FEMA Flood Hazard Map = FIRM 1999
Air Freezing Index 113
Mean Annual Temperature 52º F

Subject to Damage From:

Weathering  Moderate
Frost Line Depth 12 inches
Termite Slight to Moderate

What are the IBC design criteria and are there any additional IRC design criteria?


Additional IBC & IRC Design Information
Ground Snow Load                                    15 pounds per square foot (IBC Figure 1608.2) 
Rain On Snow Surcharge 5 pounds per square foot added to flat roofs if slope is <1/2" per foot. (IBC 1608.3.4 & ASCE 7-02 Section 7-10)
Wind Speed 85 miles per hour (IBC Figure 1609)
Seismic Design Category This is site specific for buildings designed under the IBC.
(IBC 1615 & 1616)
Minimum Roof "Live Load" Design Refer to IRC Table R301.6 & IBC 1607.11.2
Rainfall 2 inches per hour for roof drainage design.
Soil Bearing Capacity 1,500 pounds per square foot, unless a Geo-Technical Report is provided.
(IBC Table 1804.2 & IRC Table R401.4.1)
Geo-Technical Report A soils report from a geo-technical engineer is required for commercial construction and may be required for residential construction on steep or difficult lots. (IBC 1802)
Frost Line Depth 12 inches