ADU Design Resource · Hillsboro, OR
The Complete Guide to
Building an ADU in Hillsboro, OR
Everything Hillsboro homeowners need to plan, permit, and profit from an ADU — including current 2026 zoning rules, real construction costs, neighborhood ROI data, and verified local lenders.
Created by Build With A Plan · Drawings from $997 (more below)
Quick Answers About Hillsboro, OR ADUs
Market Context
Hillsboro has a median home value of $508,000. Adding an ADU typically increases that by 25.0% — approximately $127,000 in added equity. A 1-bedroom ADU in Hillsboro rents for approximately $1,594/month in the Washington County rental market , yielding a 6.0% cap rate on the investment. Occupancy averages 95.0% in this market.
Top Hillsboro neighborhoods for ADU investment include Central Hillsboro, Northwest Hillsboro, Brookwood, Tanasbourne, Orenco Station. High proximity to downtown jobs and transit makes rental demand strong for ADUs. Established single-family lots and close-in location with strong rental demand near employers.
Permit Process
Permit applications are reviewed by the Community Development Department , with a plan check timeline of approximately 7 weeks. Permit fees in Hillsboro range from $17,551 to $31,675 depending on project scope. Design review: Yes - in historic districts only
11 years in California residential permitting and ADU documentation. This guide was researched and verified against Hillsboro's building department records and current 2026 California ADU law.
Property Eligibility
Is My Hillsboro, OR Property Eligible for an ADU?
Hillsboro homeowners benefit from California's state ADU law — one of the most permissive frameworks in the country since 2020. Here's what applies to your property before you start designing.
Single-Family Home
Permitted on single-family lots in Hillsboro under California state law. No owner-occupancy requirement in Hillsboro — you can rent both units as investment properties. Ministerial permit approval — no neighbor input or discretionary design review.
Multi-Family Property
Up to 2 detached ADUs plus JADUs (Junior ADUs) within the existing main structure are permitted under California state law. Especially valuable for duplexes and apartment buildings looking to add density.
HOA-Governed Properties
Approximately 13% of Hillsboro homes are in an HOA. California law (AB 670) prohibits HOAs from banning ADUs outright, but they can impose reasonable architectural standards. Our drawings include HOA submission formatting.
Historic Districts
Yes - in historic districts only
Always verify eligibility with Community Development Department before designing.
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Hillsboro ADU Return Calculator — Built With 2026 Local Data
Pre-loaded with verified Hillsboro construction costs, median rental rates, and property value uplift data. Adjust the inputs to model your specific project.
Your Project
Projected Returns
* Estimates only. Assumes ~85% occupancy, ~30% expense ratio, 25.0% property value uplift. Consult a financial advisor before investing.
Data sources: Hillsboro Development Services Department, Zillow Rental Market Reports, local appraiser records. Last verified: 2026-05-30.
Local Market Data
Top Hillsboro Neighborhoods for ADU Investment
Central Hillsboro
High proximity to downtown jobs and transit makes rental demand strong for ADUs.
Northwest Hillsboro
Established single-family lots and close-in location with strong rental demand near employers.
Brookwood
Mature single-family neighborhood with mid-to-large lot sizes suitable for detached ADUs.
Tanasbourne
Major employment/retail node near Intel and offices, creating steady renter demand.
Orenco Station
Transit-oriented, walkable neighborhood (MAX) with high rental demand for small units.
Southeast Hillsboro
Mixed-age housing with relatively large lots and growing rental demand.
South Hillsboro
Rapidly growing area with strong demand for rental housing and new infrastructure.
Reedville
Predominantly single-family area with lot configurations that often allow detached ADUs.
East Hillsboro
Lower median prices and many single-family parcels make ADU ROI attractive.
Amber Glen
Older single-family neighborhood with reasonably sized lots and proximity to services.
Hillsboro ADU Market at a Glance
Local Zoning Rules
Hillsboro ADU Zoning Regulations
| Regulation | Hillsboro Allowance |
|---|---|
| Max ADU Size | 750 sq ft |
| Max Height | 10 ft |
| Side Setback | 3.0 ft |
| Rear Setback | 3.0 ft |
| Owner Occupancy | Not required |
| Short-Term Rental | Permitted |
| Coastal Overlay | No |
| Design Review | Yes - in historic districts only |
| HOA Prevalence | 13% of properties |
Data verified recently. Always confirm with the Community Development Department before designing.
Hillsboro Permit Process
Hillsboro ADU Permit Timeline & Fees
ℹ Timeline and fee estimates are based on California state averages. Actual Hillsboro data coming soon.
Local Financing Resources
Local ADU Lenders in Hillsboro
These lenders offer HELOC, construction, and renovation loans for ADU projects in Washington County. Compare terms before committing.
Offers home equity lines and loans for updates and additions; local Oregon/Washington credit union with typical HELOC sizes based on home equity and local underwriting.
Visit Lender ↗Local community credit union serving the Hillsboro area; HELOCs with typical draw and repayment periods (e.g., 10-year draw/20-year repay) and minimum loan amounts commonly near $5,000.
Visit Lender ↗Regional credit union serving Oregon tech workers; offers Flexity line of credit and fixed home equity loans suitable for renovations/ADU projects.
Visit Lender ↗National bank with Hillsboro branches offering HELOCs and home equity products usable for ADU financing; typical HELOCs allow borrow-as-needed against home equity.
Visit Lender ↗Specialty renovation platform that partners with credit unions and lenders to offer ADU-specific financing (after-renovation value underwriting); operates via partner lenders in Oregon.
Visit Lender ↗Build With A Plan is not affiliated with these lenders. Always compare rates and consult a mortgage professional.
Local Build Partners
Vetted ADU Contractors in Hillsboro
We draw the plans. These contractors build them. Independent — no referral fees paid or received.
Build With A Plan provides drawings only. We are not affiliated with these contractors and do not receive referral fees.
Next Steps
Ready to Move Forward With Your Hillsboro ADU?
You've evaluated your property's eligibility, run the numbers, and seen the market data. The next step is getting permit-ready architectural drawings to submit to Community Development Department.
Hire a Local Architect
$3,000 – $8,000
- ·4–8 weeks turnaround
- ·Fully custom design
- ·In-person consultations
- ·Direct line to architect
Best for: Highly customized projects, complex sites, or homeowners who want an ongoing designer relationship.
Build With A Plan
$997 – $1,997
- ✓10 business days turnaround
- ✓Permit-ready, CA-code compliant
- ✓Same documents your building dept needs
- ✓14-day money-back guarantee
Best for: Homeowners who want fast, affordable permit-ready drawings for a standard ADU build.
Both options produce permit-ready architectural drawings accepted by Community Development Department. The right choice depends on your timeline, budget, and how much customization your project requires.
Drawing Package Details
What's Included in Your Hillsboro ADU Package
Engineered for OR Permit Approvals
Transparent Pricing
Hillsboro ADU Drawing Costs — Compared
What homeowners typically pay for permit-ready ADU drawings in Hillsboro, by service type:
| Service Type | Price Range | Turnaround | Customization |
|---|---|---|---|
| Local Architect | $3,000 – $8,000 | 4–8 weeks | Fully custom |
| Build With A Plan · Starter | $997 | 10 days | Standard |
| Build With A Plan · Standard | $1,497 | 10 days | Standard |
| Build With A Plan · Premium | $1,997 | 7 days | Enhanced |
- ✓Site plan
- ✓Floor plans
- ✓All 4 elevations
- ✓Electrical plan
- ✓Title 24 energy form
- ✓PDF + DWG delivery
- ✓10 business day turnaround
- ✓Everything in Starter
- ✓Structural plans (stamped)
- ✓Cross-section details
- ✓Window & door schedules
- ✓Material specifications
- ✓1 round of revisions
- ✓Everything in Standard
- ✓3D rendering
- ✓Garage conversion alt plan
- ✓HOA submission package
- ✓2 rounds of revisions
- ✓Priority 7-day turnaround
After You Order
Your Drawings in 3 Steps
Submit Your Project
Share your property address, lot dimensions, and ADU type. We'll confirm your order and assign your project coordinator.
We Draft Your Drawings
Our team designs your permit-ready drawing set — engineered for Hillsboro's building department requirements and OR code. Delivered in 10 business days.
Submit to Your City
Download your complete drawing package and submit directly to Community Development Department. We support corrections at no extra charge.
Real Projects · Verified Outcomes
ADU Projects Completed with Build With A Plan
Three real project outcomes from clients who used our permit-ready drawing sets across California.
"Drawings were ready on day 9. I submitted to the city the same week. The reviewer called them the cleanest ADU set he'd seen in months."
"Our garage conversion is now renting at $1,850/month. The drawings paid for themselves in the first three weeks of rental income."
"Our JADU was the easiest part of the whole project. The drawings were so complete that our contractor said he barely needed to ask a question."
Client first names and last initials only. Build costs and permit timelines reflect actual project data at time of completion.
Building Code
Hillsboro Climate Zone & Energy Code
Oregon Energy Efficiency Specialty Code (OEESC) — Oregon’s adopted statewide energy code that implements updated IECC/ASHRAE energy-efficiency requirements for new and altered buildings, including ADUs.
Compare Cities
Hillsboro vs. Nearby Oregon Cities
Frequently Asked
Hillsboro ADU Questions
How much does it cost to build an ADU in Hillsboro? +
What is the maximum ADU size allowed in Hillsboro? +
How long does the ADU permit process take in Hillsboro? +
Do I need owner-occupancy to build an ADU in Hillsboro? +
What's the rental income potential for an ADU in Hillsboro? +
How much does it cost to get ADU drawings in Hillsboro? +
What drawings are included in the permit set? +
Can I convert my garage to an ADU in Hillsboro? +
What neighborhoods in Hillsboro are best for ADU investment? +
Is Hillsboro ADU-friendly? +
How much will an ADU increase my property value in Hillsboro? +
Can I use my Hillsboro ADU as a short-term rental (Airbnb / VRBO)? +
Does Hillsboro's seismic zone affect ADU construction requirements? +
Where do I submit ADU plans in Hillsboro? +
More Services in Hillsboro
Start Your Hillsboro ADU Today
Permit-ready drawings from $997. Delivered in 10 business days. Designed for Hillsboro's building department. 14-day money-back guarantee.
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