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POL Government Elected Officials Auditor Griffin-Valade Charter, Code & Policies City Code & Charter Online Code & Charter Title 24 Building Regulat Chapter 24.85 Seismic Design Requirements for Existing Buildings
Chapter 24.85 Seismic Design Requirements for Existing Buildings

- Note
(Added by Ordinance No. 168627, effective Mar. 22, 1995.)

24.85.010 General.
(Amended by Ordinance No. 178831, effective November 20, 2004.)
 
A. The provisions of this chapter prescribe the seismic design requirements for existing buildings undergoing changes of occupancy, additions, alterations, catastrophic damage, fire, or earthquake repair, or mandatory or voluntary seismic strengthening. The requirements of this chapter only apply to buildings for which a building permit has been applied for to change the occupancy classification, add square footage to the building, alter or repair the building.
 
B. Under the authority provided by State law, the provisions of this chapter prescribing seismic rehabilitation standards for existing buildings can be used in lieu of meeting the requirements of the current edition of the State of Oregon Structural Specialty Code.

24.85.015 Structural Design Meeting.
(Added by Ordinance No. 178831, effective November 20, 2004.) Upon request, BDS engineering staff is available to meet with an owners design engineer to review proposed seismic strengthening plans in a pre-design meeting. A written record of the meeting discussion and determinations will be placed in the permit record.

24.85.020 Seismic Related Definitions.
 
(Amended by Ordinance Nos. 169427, 170997, 178831 and 180917, effective May 26, 2007.) The definitions contained in this Section relate to seismic design requirements for existing buildings outlined in this Chapter.
 
A.  ASCE 31 means the Seismic Evaluation of Existing Buildings ASCE/SEI 31-03 published by the American Society of Civil Engineers and the Structural Engineering Institute.
 
B.  ASCE 31 Evaluation means the process of evaluating an existing building for the potential earthquake-related risk to human life posed by that building, or building component, and the documentation of that evaluation, performed and written according to the provisions of ASCE 31.  ASCE 31 Evaluation is divided into two categories:
1.  Non-essential facilities evaluation means a Tier 1 and a Deficiency-Only Tier 2 analysis to the Life Safety (LS) performance level as defined by ASCE 31 unless a complete Tier 2 analysis is required by ASCE 31.
 
2.  Essential facilities evaluation means a Tier 2 analysis to the Immediate Occupancy (IO) performance level as defined by ASCE 31.
C.  ASCE 31Improvement Standard means the Tier 1 and Tier 2 Life Safety Performance Level Criteria of ASCE 31.
 
D.  ATC 20 means the 1989 Edition of the manual on “Procedures for Post Earthquake Safety Evaluation of Buildings” published by Applied Technology Council.
 
E.  BDSmeans the City of Portland’s Bureau of Development Services.
 
F.  Building Addition means an extension or increase in floor area or height of a building or structure.
 
G.  Building Alteration means any change, addition or modification in construction.
 
H.  Catastrophic Damage means damage to a building that causes an unsafe structural condition from fire, vehicle collision, explosion, or other events of similar nature.
 
I.  Essential Facility has the same meaning as defined in the OSSC.
 
J.  Fire and Life-safety for Existing Buildings (FLEx) Guide means a code guide published by the Bureau of Development Services, outlining alternative materials and methods of construction that are allowed for existing buildings in Portland.
 
K.  FM 41 Agreement means a joint agreement between Portland Fire & Rescue, the Bureau of Development Services and a building owner to schedule improvements to the building following a determination of the fire and life safety hazards posed by the existing condition of the building as provided under Oregon law.
 
L.  Live/Work Space means a combination working space and dwelling unit.  A live/work space includes a room or suite of rooms on one or more floors designed for and occupied by not more than one family and including adequate working space reserved for the resident’s occupancy. A live/work space is individually equipped with an enclosed bathroom containing a lavatory, water closet, shower/and or bathtub and appropriate venting.
 
M.  Net Floor Area means the entire area of a structurally independent building, including an occupied basement, measured from the inside of the permanent outer building walls, excluding any major vertical penetrations of the floor, such as elevator and mechanical shafts.
 
N.  Oregon Structural Specialty Code (OSSC) means the provisions of the State of Oregon Structural Specialty Code as adopted by Section 24.10.040 A.
 
O.  Reinforced Masonry means masonry having both vertical and horizontal reinforcement as follows:
1.  Vertical reinforcement of at least 0.20 in2 in cross-section at each corner or end, at each side of each opening, and at a maximum spacing of 4 feet throughout. One or two story buildings may have vertical reinforcing spaced at greater than 4 feet throughout provided that a rational engineering analysis is submitted which shows that existing reinforcing and spacing provides adequate resistance to all required design forces without net tension occurring in the wall.
 
2.  Horizontal reinforcement of at least 0.20 in2 in cross-section at the top of the wall, at the top and bottom of wall openings, at structurally connected roof and floor openings, and at a maximum spacing of 10 feet throughout.
 
3.  The sum of the areas of horizontal and vertical reinforcement shall be at least 0.0005 times the gross cross-sectional area of the element.
 
4.  The minimum area of reinforcement in either direction shall not be less than 0.000175 times the gross cross-sectional area of the element.
P.  Roof Covering Repair or Replacement means the installation of a new roof covering following the removal of an area of the building’s roof covering exceeding 50% or more of the total roof area within the previous five year period.

Q.  Unreinforced Masonry (URM) means adobe, burned clay, concrete or sand-lime brick, hollow clay or concrete block, hollow clay tile, rubble and cut stone and unburned clay masonry that does not satisfy the definition of reinforced masonry as defined herein. Plain unreinforced concrete shall not be considered unreinforced masonry for the purpose of this Chapter.
 
R.  Unreinforced Masonry Bearing Wall means a URM wall that provides vertical support for a floor or roof for which the total superimposed vertical load exceeds 200 pounds per lineal foot of wall.
 
S.  Unreinforced Masonry Bearing Wall Building means a building that contains at least one URM bearing wall.

24.85.030 Seismic Improvement Standards.
(Amended by Ordinance Nos. 170997 and 178831, effective November 20, 2004.) For changes of occupancy structural additions, building alterations and catastrophic or earthquake damage repair, the design standard shall be the current edition of the OSSC unless otherwise noted by this Chapter.

24.85.040 Change of Occupancy or Use.
(Amended by Ordinance Nos. 169905, 170997 and 178831, effective November 20, 2004.) The following table shall be used to classify the relative hazard of all building occupancies:
 
 TABLE 24.85-A
 Relative
Hazard Classification
 OSSC Occupancy Classification
 Seismic
Improvement
Standard
 5 (Highest)
 A, E, I-2, I-3, H-1, H-2, H-3, H-4, H-5
 OSSC
 4
 R-1, R-2, SR, I-1, I-4
OSSC
 3
 B,M
 ASCE 31
 2
 F-1, F-2, S-1, S-2
ASCE 31
 1 (Lowest)
 R-3, U
ASCE 31
 
A. Occupancy Change to a Higher Relative Hazard Classification. An occupancy change to a higher relative hazard classification will require seismic improvements based upon the factors of changes in the net floor area and the occupant load increases as indicated in Table 24.85-B below. All improvements to either the OSSC or ASCE 31 improvement standard shall be made such that the entire building conforms to the appropriate standard indicated in Table 24.85-B.
 
TABLE 24.85-B
 Percentage of Building Net Floor Area Changed
Occupant Load Increase 
Required Improvement Standard  
 Relative Hazard Classification
 1/3 of area or less and
 Less than 150
 None
 1 through 5
 More than 1/3 of area or
 150 and above
 ASCE 31
 1, 2, and 3
 More than 1/3 of area or
 150 and above
OSSC
 4 and 5
 
Multiple occupancy changes to a single building may be made under this section without triggering a seismic upgrade provided the cumulative changes do not exceed 1/3 of the building net floor area or add more than 149 occupants with respect to the legal building occupancy as of October 1, 2004.
 
B. Occupancy Change to Same or Lower Relative Hazard Classification. An occupancy change to the same or a lower relative hazard classification or a change in use within any occupancy classification will require seismic improvements using either the OSSC or ASCE 31 improvement standard, as identified in Table 24.85-A above, where the change results in an increase in occupant load of more than 149 people as defined by the OSSC. Where seismic improvement is required, the entire building shall be improved to conform to the appropriate improvement standard identified in Table 24.85-A.
 
Multiple occupancy changes to a single building may be made under this section without triggering a seismic upgrade provided the cumulative changes do not result in the addition of more than 149 occupants with respect to the legal building occupancy as of October 1, 2004.
 
C. Occupancy Change to Live Work Space. Any building occupancy classified as relative hazard category 1, 2, or 3 may undergo a change of occupancy to live/work space provided that:
1. The building shall be improved such that the entire building conforms to the ASCE 31 improvement standard; and
 
2. The building meets the fire and life safety standards of either the FLEx Guide or the current OSSC.
 
3. Any Unreinforced Masonry bearing wall building converted to live/work space, regardless of construction costs, shall be improved such that the entire building conforms to the ASCE 31 improvement standard.
D. Occupancy Change to Essential Facilities. All structures which are being converted to essential facilities, as defined in the OSSC, shall comply with current state code seismic requirements, regardless of other requirements in this section.

24.85.050 Building Additions or Structural Alterations.
(Amended by Ordinance No. 178831, effective November 20, 2004.) An addition that is not structurally independent from an existing building shall be designed and constructed such that the entire building conforms to the seismic force resistance requirements for new buildings unless the three conditions listed below are met. Furthermore, structural alterations to an existing building or its structural elements shall also meet the following three conditions:
 
A. The addition or structural alteration shall comply with the requirements for new buildings;
 
B. The addition or structural alteration shall not increase the seismic forces in any structural element of the building by more than 5 percent unless the capacity of the element subject to the increased forces is equal to or greater than that required for new buildings. Multiple force increases on an element are allowed provided the cumulative force increase does not exceed 5 percent of the force on the element from its original, unaltered state; and
 
C. The addition or structural alteration shall not decrease the seismic resistance of any structural element of the existing building unless the reduced seismic resistance of the element is equal to or greater than that required for new buildings.

24.85.051 Mezzanine Additions.
(Added by Ordinance No. 178831, effective November 20, 2004.) A mezzanine addition shall not require seismic strengthening of the entire building when all of the following conditions are met:
 
A. Entire building strengthening is not required by any other provision contained in this Title;
 
B. The net floor area of the of the proposed mezzanine addition is less than 1/3 of the net floor area of the building;
 
C. The mezzanine addition does not result in an occupant load increase, as defined by the OSSC, of more than 149 people; and
 
D. Subsections 24.85.050 A. - C. shall also apply to mezzanine additions.

24.85.055 Structural Systems Damaged by Catastrophic Events.
(Added by Ordinance No. 170997; amended by 178831, effective November 20, 2004.)
 
A. Building structural systems damaged less than or equal to 50%.
1. If a building is damaged by a catastrophic event such that the area of the resulting structural damage is less than or equal to 50 percent of the building's net area, all damaged lateral load resisting components of the building’s structural system must be designed and constructed to current provisions of the OSSC. These components must also be connected to the balance of the undamaged lateral load resisting system in conformance with current code provisions. Undamaged components need not be upgraded to current lateral load provisions of the current code, unless required by other provisions of this title.
 
2. New lateral system vertical elements must be compatible with any existing lateral system elements, including foundations. In multistory buildings, the engineer shall confirm that the new lateral system vertical elements do not introduce soft or weak story seismic deficiencies, as defined by ASCE 31, where they did not previously exist, or make existing conditions more hazardous.
B. Building structural systems damaged more than 50%. Where a building is damaged by a catastrophic event such that the area of the resulting structural damage is greater than 50 percent of the building’s net floor area, all lateral load resisting components of the entire building’s structural system must be designed and constructed to the current provisions of the OSSC.

24.85.056 Structural Systems Damaged by an Earthquake.
(Added by Ordinance No. 178831, effective November 20, 2004.) As a result of an earthquake, the Director may determine through either an ATC 20 procedure or through subsequent discovery any structure or portion thereof to be in an unsafe condition as defined by State law. As a result of making this determination, the Director may declare the structure or portion thereof to be a public nuisance and to be repaired or rehabilitation as provided in Subsections 24.85.056 A.-C., or abated by demolition or removal in accordance with Title 29. For the purposes of this Section, an "unsafe condition" includes, but is not limited to any portion, member or appurtenance of a building that has become detached or dislodged or appears likely to fail or collapse and thereby injure persons or damage property; or any portion of a building or structure that has been damaged to the extent that the structural strength or stability of the building is substantially less than it was prior to the damaging event.
 
A. Buildings built prior to January 1, 1974 with lateral support systems that have unsafe conditions shall be repaired or improved to resist seismic forces such that the repaired lateral system conforms to the ASCE 31 improvement standard.
1. Where less than 50% of the lateral support system has been damaged, only the damaged elements must be repaired.
 
2. Where 50% or more of the lateral support system has been damaged, then the entire lateral support system must be repaired to resist seismic forces such that the repaired system conforms to the ASCE 31 improvement standard.
B. Buildings built on or after January 1, 1974 with lateral support systems that have unsafe conditions shall be repaired or improved to resist seismic forces such that the repaired lateral system conforms to the code to which the building was originally designed, but not less than that required to conform to the ASCE 31 improvement standard.
1. Where less than 50% of the lateral support system has been damaged, only the damaged elements must be repaired.
 
2. Where 50% or more of the lateral support system has been damaged, then the entire lateral support system must be repaired to resist seismic forces such that the repaired system conforms to the code to which the building was originally designed, but not less than that required to conform to the ASCE 31 improvement standard.
C. New lateral system vertical elements must be compatible with any existing lateral system elements, including foundations. In multistory buildings, the engineer shall confirm that the new lateral system vertical elements do not introduce soft or weak story seismic deficiencies, as defined by ASCE 31, where they did not previously exist, or make existing conditions more hazardous.

24.85.060 Required Seismic Evaluation.
(Added by Ordinance No. 169427; amended by 178831, effective November 20, 2004). When an alteration for which a building permit is required has a value (not including costs of mechanical, electrical, plumbing, permanent equipment, painting, fire extinguishing systems, site improvements, eco-roofs and finish works) of more than $175,000, an ASCE 31 evaluation is required. This value of $175,000 shall be modified each year after 2004 by the percent change in the R.S Means Construction Index for Portland on file with the Director. A letter of intent to have an ASCE 31 evaluation performed may be submitted along with the permit application. The evaluation must be completed before any future permits will be issued. The following shall be exempted from this requirement:
 
A. Buildings constructed or renovated to seismic zone 2, 2b or 3 under a permit issued after January 1, 1974.
 
B. Detached One- and two-family dwellings, and their accessory structures.
 
C. Single story, light frame metal and light wood frame buildings, not more than 20 feet in height from the top surface of the lowest floor to the highest interior overhead finish and ground area of 4,000 square feet or less.
 
A previously prepared seismic study may be submitted for consideration by the Director as equivalent to an ASCE 31 evaluation.

24.85.065 Seismic Strengthening of Unreinforced Masonry Bearing Wall Buildings.
(Added by Ordinance No. 169427; amended by 170997 and 178831, effective November 20, 2004). When any building alterations or repairs occur at an Unreinforced Masonry Bearing Wall Building, all seismic hazards shall be mitigated as set forth in Subsections 24.85.065 A. and B. A previously permitted seismic strengthening scheme designed in accordance with FEMA 178/310 may be submitted for consideration by the Bureau Director as equivalent to the ASCE 31 improvement standard:
 
A. Roof Repair or Replacement. When a roof covering is repaired or replaced, as defined in 24.85.020, the building structural roof system, anchorage, and parapets shall be repaired or rehabilitated such that, at a minimum, the wall anchorage for both in-plane and out-of-plane forces at the roof and parapet bracing conform to the ASCE 31 improvement standard. In-plane brick shear tests are not required as part of the ASCE evaluation under this subsection.
 
B. Additional Triggers.
1. Building alterations or repair. When the cost of alteration or repair work which requires a building permit in a 2 year period exceeds the following criteria, then the building shall be improved to resist seismic forces such that the entire building conforms to the ASCE 31 improvement standard.
 
 TABLE 24.85-C 
 Building Description  Cost of Alteration or Repair
     Single Story Building      $40 per square foot
     Buildings Two Stories or Greater      $30 per square foot
 
2. Special building hazards. Where an Unreinforced Masonry Building of any size contains any of the following hazards, the building shall be seismically improved if the cost of alteration or repair exceeds $30 per square foot:
a. The Building possesses an Occupancy Classification listed within the Relative Hazard Category 5 as determined in Section 24.85.040 of this Chapter; or
 
b. The building is classified as possessing either vertical or plan irregularities as defined in the OSSC.
3. Exclusions from cost calculations. Costs for site improvements, eco-roofs, mandated FM41 agreements, mandated ADA improvements, mandated non-conforming upgrades under Title 33, mandated elevator improvements and mandated or voluntary seismic improvements or work exempted from permit as described in Chapter 1 of the OSSC will not be included in the dollar amounts listed in Subsections 24.85.065 B.1. and 2.
 
4. Live/Work spaces in Unreinforced Masonry buildings. See Section 24.85.040 B for requirements when a Unreinforced Masonry building is converted to contain live/work spaces.
 
5. Automatic cost increase. The dollar amounts listed in Subsections 24.85.065 B.1. and 2. shall be modified each year after 2004 by the percent change in the R.S. Means of Construction Cost Index for Portland, Oregon. The revised dollar amounts will be made available at the Development Services Center.

24.85.067 Voluntary Seismic Strengthening.
(Added by Ordinance No. 178831, effective November 20, 2004.) Subject to permit approval, a building may be strengthened to resist seismic forces on a voluntary basis provided all of the following conditions are met:
 
A. Mandatory seismic strengthening is not required by other provisions of this Title;
 
B. The overall seismic resistance of the building or elements shall not be decreased such that the building is more hazardous;
 
C. Testing and special inspection are in accordance with the OSSC and the City of Portland Administrative Rules;
 
D. The standard used for the seismic strengthening is clearly noted on the drawings along with the pertinent design parameters; and
 
E. A written narrative shall be clearly noted on the drawings summarizing the building lateral system, seismic strengthening and known remaining deficiencies. The summary information shall reflect the level of analysis that was performed on the building.

24.85.070 Phasing of Improvements.
(Amended by Ordinance No. 178831, effective November 20, 2004.)
 
A. The Director may approve a multi-year phased program of seismic improvements when the improvements are pre-designed and an improvement/implementation plan is approved by the Director. The maximum total time allowed for completion of phased improvements shall be ten years. A legal agreement between the building owner and the City of Portland shall be formulated outlining the phased seismic improvements and shall be recorded with the property deed at the County.
 
B. Upon review, the Director may extend the maximum time for the phased improvements. The Director shall adopt rules under Section 3.30.035 describing the process for granting an extension.

24.85.075 Egress Through Existing Buildings.
(Added by Ordinance No. 178831, effective November 20, 2004.) The building structure and seismic resistance of an egress path through, under or over an existing building must meet the required seismic improvement standard specified in Section 24.85.040, Table 24.85-A, under any of the following conditions:
 
A. The egress path is from an adjacent new building or addition and the new building or addition area equals 1/3 or more of the existing building area; or,
 
B. The egress path is from an adjacent existing building that undergoes alterations or a change of occupancy requiring its egress path(s) meet the seismic improvement standards as required by this Chapter; or
 
C. The additional occupant load, as determined by the OSSC, using the egress path through the existing building is 150 people or more.

24.85.080 Application of Other Requirements.
(Amended by Ordinance No. 178831, effective November 20, 2004.) Building permit applications to improve the seismic capability of a building shall not trigger: accessibility improvements so long as the seismic improvement does not lessen accessibility; fire life safety improvements so long as the seismic improvement does not lessen the buildings fire resistance or exiting capability; landscape improvements required by Chapter 33; street tree improvements required by Section 20.40.070.
 
Conformance with these regulations may not exempt buildings from future seismic regulations.

24.85.090 Fee Reductions.
(Amended by Ordinance No. 178831, effective November 20, 2004.) Building permit, plan review and fire life safety review fees for structural work related to seismic strengthening covered by this Chapter will be waived when such fees total less than $2,500, and will be and reduced by 50% when such fees would total $2,500 or more.

24.85.095 Appeals.
(Amended by Ordinance No. 178831, effective November 20, 2004.) Because unanticipated circumstances may arise in the enforcement of these requirements for existing buildings, consideration as to the reasonable application of this Chapter may be addressed through the Board of Appeals as provided in Section 24.10.080.
 

Title 24 Building Regulat
Chapter 24.10 Administration and Enforcement
Chapter 24.15 Definitions
Chapter 24.20 Special Inspections
Chapter 24.25 Movings of Buildings
Chapter 24.30 Home Occupations
Chapter 24.35 Historical Buildings
Chapter 24.40 Use of and Projections Over Public Streets and Property
Chapter 24.45 Parking and Driveway Surfaces
Chapter 24.50 Flood Hazard Areas
Chapter 24.51 Wildfire Hazard Zones
Chapter 24.55 Building Demolition
Chapter 24.60 Fences
Chapter 24.65 Sidewalk Vault Openings
Chapter 24.70 Clearing, Grading and Erosion Control
Chapter 24.75 Uniform Building Address System
Chapter 24.80 (Repealed)
Chapter 24.85 Seismic Design Requirements for Existing Buildings
Chapter 24.90 Manufactured Dwelling Installation and Accessory Structures, Manufactured Dwelling Parks, Recreation Parks, Recreational Park Trailer Installation and Accessory Structures
Chapter 24.95 (Repealed)