ADU Construction in Hillsboro, OR
Global Home Views takes accessory dwelling units, garage conversions and in-law suites requests for Hillsboro, OR on one national line - scoped and quoted without the runaround. Accessory dwelling units built to code - detached builds, garage conversions and basement suites - from feasibility and zoning through final occupancy. Hillsboro has a mixed housing stock: 47% detached houses, 13% attached or townhouse units and 32% in buildings of five or more units.
- Licensed and insured contractors only
- Written scope before work starts
- No obligation on quotes
- Local permit knowledge
ADU Construction cost in Hillsboro
Typical Hillsboro range: $100,300 - $365,800 per unit. Reflects Oregon labor and material costs. Estimate for planning, not a quote - call (844) 624-3161 for a written scope.
An ADU is a zoning project before it is a construction project. Setbacks, lot coverage, parking relief, owner-occupancy rules and utility capacity decide what can legally go on your lot, and they vary street by street.
Months of persistent damp with little drying time make ventilation and drainage planes the difference between a sound assembly and rot.
Utilities are the line item that surprises people: whether your existing panel and sewer lateral can carry a second dwelling, or whether you are trenching to the main.
What the job includes
- Zoning and feasibility review
- Plan sets and permit submittal
- Detached, attached and garage conversions
- Separate utility metering
- Kitchen and bath rough-in
- Final inspection and occupancy sign-off
Homes in Hillsboro and adu construction work
Public figures for the city of Hillsboro in Washington County, not the metro, and the general practice that follows.
Hillsboro has a mixed housing stock: 47% detached houses, 13% attached or townhouse units and 32% in buildings of five or more units.1 On a mixed stock, feasibility turns on the individual lot - detached houses on larger parcels are the usual candidates; attached homes rarely qualify. Building permits in Hillsboro are normally issued by the city building department.2,3 ADU plan review and permits go through the city building department; the contractor prepares the plan set and submits it.
Owners and renters are roughly balanced in Hillsboro, with 50% of occupied homes owner-occupied (63% statewide).1 Most of Hillsboro's housing is recent: only 24% of units predate 1980 (U.S. 50%) and 19% were built since 2010.1 Newer subdivisions often carry HOA covenants that affect ADUs separately from zoning - check the CC&Rs before design spend. Hillsboro sits in IECC climate zone 4C (Marine).4 In this climate zone the energy code sets wall and ceiling insulation levels that a conversion must meet.
The median owner-occupied home in Hillsboro is valued at $521,100 (ACS), above the Oregon median of $477,600.1 Home values above the state median tend to support fuller scopes; the written scope should still separate must-do from nice-to-have. Heating dominates the year: about 4,830 heating degree days against 275 cooling degree days (base 65°F).5,6 In a heating-led climate, insulation and air sealing carry most of the energy-code weight for any work that opens the envelope.
| Before 1940 | 2.9% |
|---|---|
| 1940-1959 | 5.1% |
| 1960-1979 | 16.4% |
| 1980-1999 | 31.8% |
| 2000-2009 | 24.9% |
| 2010 or later | 18.9% |
Sources and notes (6)
- U.S. Census Bureau, American Community Survey 5-year estimates (ACS 2020-2024 5-year (released 2026-01))
- U.S. Census Bureau population estimates (Vintage 2024)
- U.S. Census Bureau geographic code files (2020)
- Guide to Determining Climate Zones by County: Building America and IECC 2021 Updates (PNNL-33270) (September 2022 (IECC 2021 county map))
- NOAA NCEI U.S. Climate Normals, nearest station (1991-2020 normals (published 2021))
- NOAA NCEI normals station inventory (1991-2020)
- Climate figures are for NOAA station Portland-Hillsboro Ap, 1.1 miles from the place center; housing figures are ACS ACS 2020-2024 5-year with 90% margins of error in the source tables.
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Hillsboro and nearby
Requests for Hillsboro go through our national line, (844) 624-3161; we confirm whether a contractor can take the job. How a referral works.
ADU Construction nearby
Straight-line distances between place centers, not drive times. All ADU Construction in Oregon
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Open Hillsboro, OR in Google MapsADU Construction questions in Hillsboro
How much does adu construction cost in Hillsboro, OR?
Most adu construction projects in Hillsboro, OR land between $100,300 and $365,800, depending on scope, access and material grade. That is an estimated range for planning, not a quote - call (844) 624-3161 and we will scope your job properly.
Can I legally build an ADU on my lot?
That depends on your zoning, setbacks, lot coverage and utility capacity. Feasibility review comes first, before any design spend.
What kind of housing does Hillsboro have?
Hillsboro has a mixed housing stock: 47% detached houses, 13% attached or townhouse units and 32% in buildings of five or more units. Owners and renters are roughly balanced in Hillsboro, with 50% of occupied homes owner-occupied (63% statewide). Census figures for the place itself, not the metro.
Who issues building permits in Hillsboro?
Building permits in Hillsboro are normally issued by the city building department. Whether a specific job needs one is decided by that office; the contractor confirms it before work starts.
Other services in Hillsboro
Get a free Hillsboro ADU Construction quote
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