Multnomah County, OR Noise Ordinances: Aircraft Noise (2026)
Key Facts
- Interior noise standard
- 45 dBA day/night average
- Trigger contour
- 65 Ldn noise contour
- Certification required
- Oregon-registered acoustical engineer
- Permit condition
- Recorded noise easement to Port of Portland
- Contour appeals
- County Building Code Board of Appeals
Summary
Homes built within the 65 Ldn noise contour near Portland International Airport must include sound insulation to hold interior noise to 45 decibels, plus a recorded noise easement and buyer disclosure.
On land within the 65 Ldn noise contour, All new or replacement structures, additions (when the addition is a minimum of 105 of the size of the original structure), and reconstructed structures (when the cost of reconstruction exceeds 75% of the value of the original structure) shall be constructed with sound insulation or other means to achieve a day/night average interior noise level of 45 dBA.
(B) An Oregon registered engineer knowledgeable in acoustical engineering shall certify that the building plans comply with the standard set forth in Subsection (A) of this Section.
(1) The engineer must take into account the construction materials, type of foundation, soil type and other physical factors of the site in their evaluation.
(2) The engineer must use the ANSI, ISO, ASTM or other nationally accepted standard for the transmission coefficients of various materials. Assume all openings (doors and windows) are closed for calculation purposes.
(3) Certification may also be accomplished by a study of existing structures located within the same Ldn Noise Contour and vicinity (block, subdivision, park or moorage) to determine the expected noise level of a proposed structure(s).
(S-1 2022)
Full Breakdown
Multnomah County's Noise Impact (NI) overlay covers only land mapped within the 65 Ldn contour around Portland International Airport, not the whole unincorporated county and not Portland itself, which enforces its own building code. Within the mapped area, new or replacement structures, qualifying additions, and major reconstructions must be built with sound insulation achieving a 45 dBA interior day/night average noise level, certified by an Oregon-registered acoustical engineer using ANSI, ISO, or ASTM transmission-coefficient standards. Building and land-use permits also require the applicant to record a noise easement to the Port of Portland and a disclosure statement warning buyers or tenants of airport noise before permit issuance.
Violations & Fines
Permits for land inside the mapped NI overlay are withheld until the applicant records the noise easement and disclosure statement and provides the engineer's sound insulation certification; the County will not issue a building or land-use permit without them.
Frequently Asked Questions
Does this noise overlay apply to homes in Portland?
What triggers the sound insulation requirement?
Sources & Official References
Other rules in Multnomah County
Compare Multnomah County to another location·View the Oregon noise ordinances overview
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