Why would a routine deck addition near Roberts Field suddenly need a letter from an acoustical engineer before the county will issue a permit? Nothing got louder. No new flight was added. The runway hasn't changed length yet. What changed is a line on a map, and it changed almost two years before most property owners near the airport noticed.
That's the part worth sitting with if you're buying, selling, or planning to build anywhere near Redmond Municipal Airport. The friction here isn't about aircraft noise getting worse. It's about a 2024 zoning boundary redraw that quietly pulled roughly 125 properties into a set of rules that most listing agents, and more than a few homeowners, don't know to check for until a permit application stalls.
A Line on a Map Moved, Not a Flight Path
Deschutes County's Airport Safety (AS) Combining Zone exists to keep incompatible building heights and uses out of the airspace and noise footprint around the airport. Layered inside it is a 55 DNL noise contour, the boundary the county uses to decide which structures need noise mitigation.
In 2024, the county updated both boundaries as part of the Redmond Airport Master Plan, a document last revised in 2018. The application was filed in April 2023, went through a hearings officer in November of that year, and the Board of County Commissioners approved the final text amendment on June 26, 2024. It became effective that September. The change wasn't triggered by more air traffic today. It was triggered by planned changes to the length of the primary runway and a future parallel runway, which shifted where the county's mapped "imaginary surfaces," approach corridors, and noise contour actually sit. Move the planned runway geometry, and the protected footprint around it moves too, even before a single foot of new pavement gets poured.
The county's own filing puts a number on the result: approximately 125 properties that weren't inside the AS Combining Zone or the 55 DNL contour before now are. If your parcel is one of them, the rules that apply to it changed on paper in 2024, whether or not anyone told you.
What the New Boundary Actually Requires
Two separate obligations live inside that redrawn boundary, and they trigger at different moments.
Inside the AS Combining Zone generally, height limits apply to prevent new structures from penetrating the imaginary surfaces around approach and departure paths. That matters for anyone planning a second story, a detached shop, or anything taller than what's already there.
Inside the 55 DNL noise contour specifically, new noise-sensitive construction or additions require the property owner to submit a letter from a licensed acoustical engineer certifying that interior sound levels meet the county's required decibel limits before the county will sign off. That's a real cost and a real scheduling dependency that most remodel timelines don't budget for, because most homeowners don't know their parcel is inside the line until the permit reviewer flags it.
For context, the federal threshold that guides residential compatibility around airports is an average of 65 decibels or lower over a 24-hour period, the standard the FAA uses nationally and the one Redmond's own noise abatement program points to when explaining its contour maps.
Two Noise Rules With the Same Name, Different Teeth
Redmond actually has two distinct sets of noise-related development rules, and conflating them is an easy mistake. One governs land near the airport. The other governs land near industrial and business park uses on the city's southeast side, and it has nothing to do with aircraft.
| AS Combining Zone / 55 DNL Contour | Southeast Redmond Noise Overlay | |
|---|---|---|
| Governed by | Deschutes County, tied to Roberts Field's master plan | City of Redmond zoning code |
| What it addresses | Aircraft noise and building height near the airport | Industrial and manufacturing noise near residential areas |
| Trigger | New construction or additions inside the mapped contour | New or expanding industrial, manufacturing, or business park development |
| What's required | Acoustical engineer's letter for interior sound compliance | Berms, buffers, or vegetated open space between uses |
| Width | Defined by the mapped contour around the airport | 350 feet, centered on the relevant right-of-way or zone boundary |
If a seller's disclosure or a title report mentions a "noise overlay," it's worth confirming which one applies to the parcel in question. They're administered by different governments for entirely different reasons.
Why the Line Moved This Year, Not Some Other Year
The timing makes more sense once you look at what's happening at the airport itself. Redmond Municipal Airport broke ground in 2025 on an $180 million terminal expansion, funded through airport bonds and revenue, federal grants, and airport cash rather than local property taxes. Construction crews finished the expansion's foundation and first-floor slab by late March 2026, and the project is on track for a terminal opening in late 2027, adding seven new jet bridges and enough concourse space to more than double seating.
The master plan update that redrew the noise and safety boundaries is the paperwork twin of that construction project. Runway length changes tied to the same master plan shifted where the protected surfaces sit, and the county adjusted its zoning maps to match. That's why a property owner can find themselves newly inside the 55 DNL contour without a single additional flight having taken off yet. The boundary reflects where the airport's infrastructure is heading, not just where it stands today.
What This Means If You're Under Contract Near Roberts Field
For anyone with a parcel near the airport, three things are worth doing before you close, list, or pull a permit.
Ask to see the recorded noise disclosure and contour map, which the city has filed with the county recorder's office, and confirm whether the specific parcel fell inside the 2024 boundary or stayed outside it. Build extra time and budget into any remodel or addition plan if the parcel is inside the 55 DNL contour, since the acoustical engineer's letter is a real line item, not a formality. And if you're the seller of a home where an addition or new structure went up after September 2024, keep the compliance documentation on hand. A buyer's lender or inspector asking about it during a transaction is a much worse moment to discover it's missing than during a routine remodel.
Three Questions Worth Asking Before You Waive Inspection
Does this affect homes that aren't planning to build anything? The height and acoustic requirements attach to new construction and additions, not to owning or reselling an existing structure as is. But the boundary itself is a matter of public record, and a buyer's lender or title company may still ask about it.
Is this the same map buyers sign off on in a standard noise disclosure? It can overlap, but the recorded contour map tied to the 2024 amendment is the authoritative version for permitting purposes. A generic noise disclosure form isn't a substitute for checking the actual boundary.
Could the line move again? Airport master plans get revisited on a roughly decade-long cycle, and the last one ran from 2018 to 2024. Given the runway work now underway, a future update tied to the parallel runway construction itself is plausible, though no new boundary change has been filed as of this writing.
None of this is a reason to avoid a home near Roberts Field. It's a reason to ask the right question at the right point in the process, rather than finding out from a permit reviewer three weeks before your contractor was supposed to start.
If you're weighing a purchase, sale, or remodel near the airport and want someone who checks the county's actual filings before you write an offer, The Agency Bend works this market daily. Request a Premium Market Consultation and get a straight answer before you're locked into a contingency deadline.
