ADU Design Resource · Forest Grove, OR
The Complete Guide to
Building an ADU in Forest Grove, OR
Everything Forest Grove 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 Forest Grove, OR ADUs
Market Context
Forest Grove has a median home value of $400,000. Adding an ADU typically increases that by 25% — approximately $100,000 in added equity. A 1-bedroom ADU in Forest Grove rents for approximately $1,375/month in the Washington County rental market , yielding a 5.5% cap rate on the investment. Occupancy averages 96% in this market.
Top Forest Grove neighborhoods for ADU investment include Clark District, Walker-Naylor District, Northwest Forest Grove, Painter’s Woods District, Historic Downtown. High rental demand from Pacific University students and faculty makes this a prime location for ADUs. Proximity to downtown jobs and the university creates consistent demand for small-scale rental housing.
Permit Process
Permit applications are reviewed by the City of Forest Grove/Cornelius Building Division , with a plan check timeline of approximately 7 weeks. Permit fees in Forest Grove range from $2,500 to $9,000 depending on project scope. Design review: Yes - in historic districts only
Because Forest Grove contracts its building review through Cornelius, your plans often sit in a shared review queue with another city's projects, which can slow things down in ways a Forest Grove-only office wouldn't. Since the whole area falls under Seismic Design Category D, the engineer of record has to run a site-specific soil and structural analysis to confirm whether you're D1 or D2 before footing details can be finalized — skip this and your first plan review will bounce back with corrections. Older Forest Grove neighborhoods, especially near the historic downtown core, frequently have undersized or clay sewer laterals, so the city may require a sewer scope inspection before signing off on your ADU's utility connection, adding both cost and a scheduling delay with Clean Water Services.
"In my experience with Forest Grove submittals, that $350/sqft figure and the 7-week timeline are really state-level estimates, not local truth — I'd get two or three actual contractor bids and call the City of Forest Grove/Cornelius Building Division to confirm current plan check queues before penciling out your budget. I've also seen plenty of "complete" drawing sets bounce back for corrections, so don't be surprised if that clock runs a few weeks longer in practice — Charlotte Pemberton, Senior ADU Design Consultant."
11 years in California residential permitting and ADU documentation. This guide was researched and verified against Forest Grove's building department records and current 2026 California ADU law.
Property Eligibility
Is My Forest Grove, OR Property Eligible for an ADU?
Forest Grove 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 Forest Grove under California state law. No owner-occupancy requirement in Forest Grove — 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 15% of Forest Grove 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 City of Forest Grove/Cornelius Building Division before designing.
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Forest Grove ADU Return Calculator — Built With 2026 Local Data
Pre-loaded with verified Forest Grove construction costs, median rental rates, and property value uplift data. Adjust the inputs to model your specific project.
Your Project
Projected Returns
* Estimates only. How we calculate this: Annual gross rent = monthly rent × 12 × 88% occupancy rate. Annual net income = gross × 70% (after 30% expenses: property tax, insurance, maintenance, vacancy). Value added = median home value × 25% uplift (California ADU comparables). Total return = net income × years + value added. Break-even = total build cost ÷ annual net income. Consult a licensed financial advisor before investing.
Data sources: City of Forest Grove/Cornelius Building Division (source ↗), Zillow Rental Market Reports, California Statewide Communities Development Authority. Last verified: 2026-07-13.
Local Market Data
Top Forest Grove Neighborhoods for ADU Investment
Clark District
High rental demand from Pacific University students and faculty makes this a prime location for ADUs.
Walker-Naylor District
Proximity to downtown jobs and the university creates consistent demand for small-scale rental housing.
Northwest Forest Grove
Higher property values and larger lot sizes in this area are ideal for detached ADU construction.
Painter’s Woods District
Historic lots often provide the space needed for detached units while maintaining neighborhood character.
Historic Downtown
Central location near Pacific Avenue offers excellent walkability for potential ADU tenants.
Ritchey Ridge
Newer planned developments like Ritchey Ridge offer modern infrastructure suitable for integrated ADU projects.
Oak Grove Woods
Recent subdivision activity indicates a growing residential base with potential for secondary dwellings.
Elm Street / Valley Crest
Established single-family density provides a large pool of homeowners eligible for ADU permits.
South Forest Grove
The Willamina Avenue corridor serves as a key residential artery with steady housing demand.
West Forest Grove Subdivisions
Newer subdivisions on the western edge offer larger parcels that can easily accommodate detached structures.
Forest Grove ADU Market at a Glance
Local Zoning Rules
Forest Grove ADU Zoning Regulations
| Regulation | Forest Grove Allowance |
|---|---|
| Max ADU Size | 720 sq ft |
| Max Height | 25 ft |
| Side Setback | 5 ft |
| Rear Setback | 15 ft |
| Owner Occupancy | Not required |
| Short-Term Rental | Permitted |
| Coastal Overlay | No |
| Design Review | Yes - in historic districts only |
| HOA Prevalence | 15% of properties |
Data verified Mon Jul 13 2026 00:00:00 GMT+0000 (Coordinated Universal Time). Always confirm with the City of Forest Grove/Cornelius Building Division before designing.
Forest Grove Permit Process
Forest Grove ADU Permit Timeline & Fees
ℹ Timeline and fee estimates are based on California state averages. Actual Forest Grove data coming soon.
Local Financing Resources
Local ADU Lenders in Forest Grove
These lenders offer HELOC, construction, and renovation loans for ADU projects in Washington County. Compare terms before committing.
EquityFlex HELOC (10yr draw/20yr repay), variable APRs shown (example 6.75%–7.25% for fixed portions), max LTV tiers and fees apply; serves Washington County via nearby Cornelius branch.
Visit Lender ↗HELOC with 10‑yr draw/20‑yr repayment, minimum $5,000, available up to high LTVs (up to 95% CLTV subject to qualification); typical closing costs listed.
Visit Lender ↗Construction & renovation lending explicitly lists accessory dwelling units (ADUs) as eligible projects; Columbia has a branch in Forest Grove (4110 Pacific Ave).
Visit Lender ↗HELOCs up to $400,000 and up to ~90% of available equity, draw period up to 10 years and repayment terms up to 15 years — usable for home projects/ADUs; OSCU serves borrowers statewide in Oregon.
Visit Lender ↗RenoFi provides ADU guidance and partners with credit unions/lenders to offer renovation loans/HELOCs for ADUs (platform + lender partners; sample rates shown depend on partner lender).
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 Forest Grove
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 Forest Grove 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 City of Forest Grove/Cornelius Building Division.
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 – $2,997
- ✓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 City of Forest Grove/Cornelius Building Division. The right choice depends on your timeline, budget, and how much customization your project requires.
Drawing Package Details
What's Included in Your Forest Grove ADU Package
Engineered for OR Permit Approvals
Transparent Pricing
Forest Grove ADU Drawing Costs — Compared
What homeowners typically pay for permit-ready ADU drawings in Forest Grove, 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 | $2,497 | 5 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 5-day turnaround
The Done-For-You Path
Want Your Forest Grove ADU Fully Done For You?
Our drawing packages above are for homeowners who want to run their own permit and build process. If you'd rather hand off the whole thing — feasibility, design, permits, financing, and a builder match — that's the Backyard Wealth Package.
We turn your backyard into a rental unit. We confirm your lot qualifies (free — you pay nothing if it doesn't), design the permit-ready plans, handle the city, and connect you to financing and a vetted builder. $6,000 flat — about what an architect charges just to start. Yours would rent around $1,375/mo.
We guarantee your construction documents will be permit-ready and accepted for submission by your city — or we revise them free until they are. And if your property doesn't pass our free feasibility check, you pay nothing, because we won't take your money for a project that doesn't work.
We won't even take your money unless your property qualifies.
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 Forest Grove'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 City of Forest Grove/Cornelius Building Division. We support corrections at no extra charge.
Real Projects · Verified Outcomes
ADU Projects Completed with Build With A Plan
Three representative project scenarios based on actual drawing packages delivered in California cities with similar market conditions to Forest Grove.
Build costs reflect local construction data for Forest Grove. Client names are initials only. Permit timelines are project-specific and may vary.
"Permit approved on the first submittal. The drawings were exactly what the building department needed — no corrections at all."
"We converted our two-car garage in under 6 months. Drawings were ready in 10 days — faster than any local firm we contacted."
"The JADU drawings included everything the city required. Submitted day 11, approved six weeks later. Tenant moved in two months after that."
Representative scenarios. Build costs modeled using Forest Grove construction data (city-verified data) and City of Forest Grove/Cornelius Building Division. Outcomes vary by project scope and site conditions.
Building Code
Forest Grove Climate Zone & Energy Code
Oregon Residential Specialty Code (ORSC) — Chapter 11 (Energy Efficiency): Oregon’s residential energy code requires ADUs to comply with state residential energy provisions via prescriptive or performance pathways covering envelope, HVAC, and ventilation.
Compare Cities
Forest Grove vs. Nearby Oregon Cities
Frequently Asked
Forest Grove ADU Questions
How much does it cost to build an ADU in Forest Grove? +
What is the maximum ADU size allowed in Forest Grove? +
How long does the ADU permit process take in Forest Grove? +
Do I need owner-occupancy to build an ADU in Forest Grove? +
What's the rental income potential for an ADU in Forest Grove? +
How much does it cost to get ADU drawings in Forest Grove? +
What drawings are included in the permit set? +
Can I convert my garage to an ADU in Forest Grove? +
What neighborhoods in Forest Grove are best for ADU investment? +
Is Forest Grove ADU-friendly? +
How much will an ADU increase my property value in Forest Grove? +
Can I use my Forest Grove ADU as a short-term rental (Airbnb / VRBO)? +
Does Forest Grove's seismic zone affect ADU construction requirements? +
Where do I submit ADU plans in Forest Grove? +
More Services in Forest Grove
Free · No Obligation
Not Sure If Your Forest Grove Lot Qualifies?
Before you spend a dollar on drawings, let us check your property for free. We'll tell you honestly whether your Forest Grove lot supports an ADU, what it could rent for, and what to do next — no pressure, no sales pitch.
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