Building Codes

Minimum roof snow load

The minimum design roof snow load for all structures in Oregon is 20 pounds per square foot (psf). This may not be reduced for slope or any other conversion factor and may be only modified where applicable by a rain-on-snow surcharge. (Oregon Structural Specialty Code (OSSC), Section 1608.1)

Rain-on-snow surcharge

A 5 psf rain-on-snow surcharge will be added to the minimum design roof snow load if either of the following conditions exist:

• All roofs with a slope of less than 4.76 degrees (1 on 12 pitch)
  
  or
• Roofs of any slope that constrain runoff, e.g., any roof where the drainage system is impeded by parapets or any other physical obstructions capable of accumulating more than 1 inch of standing water on any part of the roof when the primary or the secondary (drains or scuppers) means of drainage is blocked by debris, snow or ice. (Structures with a continuous gutter at the low point eave or a comparable system are not be considered as having constrained runoff.)

Snow Load Analysis for Oregon, Structural Engineers Association of Oregon

Ground snow load

To find the ground snow load used to determine the design snow loads for buildings and other structures, refer to the online lookup tool or the online map published by the Structural Engineers Association of Oregon (SEAO). The design roof snow load may not be less than 20 psf with rain-on-snow surcharge as applicable.

For more information

Design snow loads for buildings and other structures are determined based on the American Society of Civil Engineers 7-16 Standard, Minimum Design Loads for Buildings and Other Structures, Chapter 7.

Based on the 2019 Oregon Structural Specialty Code

"Prefabricated structure" means a building or sub-assembly that has been in whole or substantial part manufactured or assembled using closed construction at an off-site location to be wholly or partially assembled on site; but does not include a manufactured structure. [ORS 455.010(6)]

1. Clackamas County submittal requirements
   1. Provide two 8-1/2" x 11" or 8-1/2" x 14" plot plans of the building site.
   2. Complete and submit a Building Permit Application.
   3. Provide one copy of design plans approved by the State of Oregon.
   4. Provide two sets of foundation plans for review and inspection. Engineering may be required.
2. Insignia of Compliance
   All prefabricated structures shall bear an Insignia of Compliance, also known as the "goldtag." "Insignia of Compliance" means the plate affixed to a structure by the Department of Consumer and Business Services or a third party to signify compliance with all state building code requirements for which the structure was inspected [ORS 455.705(7)]. An insignia shall be permanently attached to each unit in a visible location during transportation and after installation.
3. Clackamas County's site enforcement and inspection responsibility
   1. Plumbing Permits, Electrical Permits and Mechanical Permits are required. Clackamas County will perform a utility connection inspection prior to approving electrical, plumbing, gas and sewage connections to the structure. See OSSC Section 1704.5 for Site Enforcement Agency Responsibility.
   2. Inspect every device and every connection of component assembly to assure that such assembly is capable of developing a complete load path as required by code.
   3. Inspect incomplete structures during on-site construction.
   4. Inspect and approve the installation of prefabricated structures.
   5. Inspect connections at marriage lines between modular units of prefabricated permanent and relocatable buildings to assure that such connections are capable of developing a complete load path as required by the approved plans approved by the State of Oregon.
   6. Issue a Certificate of Occupancy as provided in Section 109 of the OSSC.
4. Permits for transporting modular units
   Permits for transporting modular units are issued to the mover. No transportation permit or driveway permit will be issued by the Engineering Department without approval of the applicable placement permits.

You must obtain both building and electrical permits when installing solar photovoltaic (PV) systems. Electrical permits require inspections, but do not include plan review.

For the building permit, we review construction documents and inspect the installation. This review is meant to protect life and property from hazards and to facilitate safety in emergency situations.

Building permits for PV systems are divided into two categories:

• prescriptive
• non-prescriptive

Use the checklist to find out what qualifies as prescriptive.

Zoning

Solar systems that qualify as an Accessory Use are allowed in all land use zones in Clackamas County when the annual power-generating capacity of the system is limited to power consumed by the property. Solar energy systems that exceed an Accessory Use are subject to land use review.

Fees

All fees include State surcharge.

Permit applications

• Building Permit Application
• Renewable Electrical Energy Application
• Solar Prescriptive Checklist

Other resources

• Plot Plan Requirements
• Zoning and Development Ordinance 1017
• Oregon Structural Specialty Code (OSSC), Section 3111
• Online Permits
• Electrical Diagram Template
• Oregon Residential Energy Tax Credits
• Federal Energy Tax Credit

Additional information

Prescriptive installations as defined by the Oregon Structural Specialty Code (OSSC), Section 3111 are roof installations on conventional light-frame construction (such as a wood-framed house) which comply with specific criteria and do not require an engineered design. The permit fees are flat rate and permits are typically issued 2–3 business days after submittal.

Non-prescriptive installations are those that do not qualify as prescriptive. They include ground-mounted systems, systems installed on roofs that are not conventional light-frame construction, installations in high wind or ground snow load areas and flood hazard areas, or installations where the combined weight of the equipment and racking exceeds 4.5 pounds per square foot. These types of installations require an engineered design and can take up to 4 weeks for review depending on the complexity of the project. The fees are variable based on value (excluding panel and inverter costs).

Accessory use is defined as a subordinate use — the function of which is clearly incidental to that of the main building or use on the same lot. Where solar systems exceed an accessory use, a pre-application meeting ($400) and conditional use application ($3,945) are required prior to applying for building permits. There is also a Transportation System Development Charge (TSDC) applied to these types of systems. The TSDC varies by location. For an estimate contact Lori Phillips at loriphi@clackamas.us with the site address.

In order to provide a timely but comprehensive code compliance review, complete construction plans and specifications are needed. Incomplete plans and specifications may delay permit processing. Please see the One- and Two-Family Dwelling Building Permit Application Checklist for a list of requirements.

We will review your submittal plans for completeness at the time of permit application and give you a Residential Plan Submittal Checklist.

Seismic Design

OSSC 1613

• Seismic Design Category – D

Wind Design

OSSC 1609
Wind Exposure is site specific and it is the design professional's responsibility to determine the exposure category selected for the area of construction.

* Sites located within a special wind region shall be verified online.

Soil Load-Bearing Values

OSSC 1806
These presumptive design soil load-bearing values shall be used if a geotechnical report is unavailable for the project.

Soil Lateral Loads

OSSC 1610
These presumptive design soil lateral loads shall be used if a geotechnical report is unavailable for the project.

Snow Loads

OSSC 1608

• Reference Clackamas County's snow load design criteria.

Foundation Frost Protection

OSSC 1809.5

To protect foundations from frost, they must be installed below the determined frost depth. The table below provides the minimum top of footing depth from grade based upon the elevation where the project is located.

Design criteria for residential structures

Seismic Design

ORSC Figure R301.2.2.1

Wind Design

ORSC Table R301.2(1)

• Basic Design Wind Speed – 98 mph

ORSC Table R301.2(1) 

• Special Wind Region,
  Basic Design Wind Speed - 120 mph

Soil Load-Bearing Values

ORSC Table 401.4.1
The design load-bearing values shall be used if a geotechnical report is unavailable for the project.

• Class of Soil Material – ML, Inorganic Silts and Clayey Silts
• Vertical Foundation Pressure – 1,500 psf

Snow Loads

OSSC 1608

• Reference Clackamas County's snow load design criteria

Foundation Frost Protection

OSSC 1809.5

To protect foundations from frost, they must be installed below the determined frost depth. The table below provides the minimum bottom of footing depth from grade based upon the elevation where the project is located.

Current Adopted Codes