Multnomah County's permitting is genuinely layered. Depending on where your property sits, you could be dealing with the county land use office, the City of Portland, the City of Gresham, or the City of Troutdale. And Portland in particular has some of the most environmentally and architecturally specific permit requirements in the Pacific Northwest.
The good news: Oregon law allows anyone to draw residential plans. The challenge: those plans must meet a specific set of environmental and formatting requirements that most people don't know about until their application is rejected.
Do You Need a Site Plan for a Small Permit in Multnomah County?
Yes—and in Multnomah County, this is true even for primarily interior projects. A site plan is required.
Depending on your jurisdiction, the site plan must include:
- Property lines with accurate dimensions and total lot area.
- Setbacks (front, rear, and side per Title 33 for Portland, or Chapter 39 for unincorporated).
- Existing and proposed structures clearly differentiated.
- Easements and driveway locations.
- Lot coverage and FAR (Floor Area Ratio) calculations.
- Tree survey (Title 11) — documenting all trees 12 inches or larger in diameter.
- Stormwater management notation (if the project adds 500+ sq ft of impervious surface).
- An indicated scale (minimum 1" = 10') and a North arrow.
- A Multnomah County Tax Lot Number.
Formatting rule: For Portland submittals, drawings must be in permanent black ink—no color, no pencil.
Who Runs Into This in Multnomah County
- Gresham homeowners who try to pull a county permit, only to be directed to the City of Gresham's building department.
- Portland residents who add a large concrete patio to their backyard, not realizing that adding 600 square feet of impervious surface triggers a mandatory Oregon-licensed Engineer stormwater management review.
- DIY shed builders who erect a 200-square-foot shed without realizing it sits exactly on the 200 sq ft exemption limit, and that any utilities whatsoever push it into permit territory.
- Homeowners near trees who submit a deck permit application for Portland without a Title 11 tree survey, causing an immediate rejection.
What Needs a Site Plan in Multnomah County
- Fence permit site plan — Front yard fences limited to 3.5 feet; side and rear fences up to 7 feet are permit-exempt. Fences over 7 feet require a permit.
- Shed permit site plan — Required for sheds over 200 sq ft or over 10 ft tall in unincorporated areas. (Sheds 200 sq ft or less and under 10 ft tall are exempt from structural building permits).
- Deck permit site plan — Required for decks attached to the house or for raised freestanding decks.
- Patio permit site plan — Required if adding 500+ sq ft of impervious surface (triggers stormwater review).
- Pool permit site plan — Required. Must show barriers and setbacks.
- Addition permit site plan — Required. Full site plan showing existing and new footprints, lot coverage, and FAR calculations.
- ADU (Accessory Dwelling Unit) — Required. Under HB 2001, ADUs are allowed on all residential lots in Portland's residential zones.
Why This Trips People Up in Multnomah County
The Land Use Approval Step. For properties in unincorporated Multnomah County, you cannot simply apply for a building permit. You must first obtain land use approval from the County Land Use Planning Division (1600 SE 190th Ave, Suite 116, Portland, OR 97233). Only after that approval do you take your plans to the building department, which contracts with Portland, Gresham, or Troutdale to review them. Five sets of plans are needed for final sign-off.
Portland's Title 11 Tree Survey. Portland's tree code (Title 11) requires that for most permit applications, you survey and document all trees on your property that are 12 inches or larger in diameter at breast height (DBH). You cannot simply draw a deck 5 feet from a large oak; you must document it, and you may be required to take protective measures.
The 500 Sq Ft Stormwater Trigger. If your project adds 500 or more square feet of new impervious surface (concrete, asphalt, roofing), your site plan must include a stormwater management plan reviewed by an Oregon-licensed Professional Engineer. Many homeowners building large patios or driveways are blindsided by this.
The 200 Sq Ft + 10 Ft Height Exemption. Oregon exempts sheds from structural building permits if they are 200 square feet or less and under 10 feet in height. Both conditions must be met. Adding any electrical or plumbing voids the exemption.
Zoning and Setbacks in Multnomah County
Portland Residential Setbacks (Title 33):
- R5 (5,000 sq ft): Front 10 ft / Side 5 ft / Rear 5 ft
- R7 (7,000 sq ft): Front 15 ft / Side 5 ft / Rear 5 ft
- R10 (10,000 sq ft): Front 20 ft / Side 10 ft / Rear 10 ft
HB 2001 Middle Housing: Duplexes through fourplexes are now allowed in all Portland residential zones. Modified lot coverage and height limits may apply.
How the Tool Handles This — 5 Steps
SitePlans.ai loads Multnomah County parcel data so you can generate the black-ink, scaled site plan required for Portland's DevHub portal or for county land use sign-off:
- Enter your address — Lot lines load from county GIS or PortlandMaps data.
- Place your project — Add your deck, ADU, or addition.
- Annotate your trees — Use the tool's annotation features to mark trees 12 inches or larger in diameter near the project.
- Calculate impervious surface — Determine if you cross the 500 sq ft stormwater threshold.
- Export a clean PDF — Download a professional plan ready for DevHub upload or for the five-set county land use sign-off.
Where This Tool Fits — and Where It Doesn't
| Situation | Best path |
|---|---|
| Deck, shed, or addition in Portland | SitePlans.ai for the required scaled site plan |
| Unincorporated county — land use approval phase | SitePlans.ai can generate the concept plan for land use review |
| Adding 500+ sq ft of impervious surface | SitePlans.ai for layout + licensed OR Engineer for stormwater plan |
| New home construction | Licensed OR Architect/Engineer required |
| Disputed property lines | Licensed OR Land Surveyor required |
What This Doesn't Replace
Our site plan generator online tool helps create preliminary, conceptual site plans for residential projects. It is not a licensed land survey, a stormwater management plan, or a Title 11 certified tree survey. If your project adds 500 or more square feet of impervious surface, an Oregon-licensed Professional Engineer must prepare the stormwater management component.
Comparison: Your Options for a Multnomah County Site Plan
| Method | Cost | Time | Stamp | Notes |
|---|---|---|---|---|
| Hand sketch | Free | 1–2 hrs | ✗ | Must be in permanent black ink; no color; minimum 1"=10' scale |
| SitePlans.ai | Free first plan | Minutes | ✗ | Generates the correctly formatted, scaled black-ink PDF |
| CAD drafter | $300–$800+ | 1–2 weeks | Sometimes | Useful for complex ADU or multi-unit projects |
| Licensed OR Engineer/Surveyor | $800–$2,500+ | 2–4 weeks | ✅ | Required for stormwater management, new homes |
| SitePlans.us (done-for-you) | Custom | 1–3 days | ✗ | Best if your DevHub or county land use submittal was rejected |
Common Mistakes That Delay Multnomah County Permits
- Skipping land use approval — Applying for a building permit in unincorporated Multnomah County before getting county land use sign-off.
- Missing the tree survey — Submitting a Portland deck permit without the Title 11 documentation of trees 12" or larger.
- Using color on plans — Portland requires plans in permanent black ink only.
- Ignoring the stormwater threshold — Adding 600 sq ft of patio without an engineer stormwater review.
- Wrong portal — Applying for a Portland property permit through the county system instead of Portland's DevHub.
Support and Local Resources
- Portland PP&D DevHub — portland.gov/bds (for properties in Portland city limits).
- Multnomah County Land Use Planning — 1600 SE 190th Ave, Suite 116, Portland, OR 97233 | (503) 988-3043 (for unincorporated areas).
- PortlandMaps — portlandmaps.com — CRITICAL for zoning, tree canopy, and past permits.
- FEMA Flood Maps — msc.fema.gov
Nearby Counties
Frequently Asked Questions
1. Do I need county land use approval before getting a building permit?
For properties in unincorporated Multnomah County, yes. You must get land use approval from the County Land Use Planning Division before building permit sign-off. Five sets of plans are needed at the sign-off stage.
2. What is the Title 11 tree survey?
Portland's Title 11 (Tree Code) requires that all trees 12 inches or larger in diameter be documented and protected during construction. Your site plan must show their location for most permit applications.
3. Do I need a permit for a shed?
In unincorporated Multnomah County, sheds under 200 square feet and under 10 feet in height are exempt from structural building permits. Adding electrical or plumbing voids the exemption.
4. What triggers the stormwater management requirement?
Any project adding 500 or more square feet of new impervious surface (patio, driveway, roof) must be reviewed by an Oregon-licensed Professional Engineer for stormwater management.
5. Can anyone draw residential plans?
Yes. Oregon allows anyone to draw and submit residential plans—you do not need to be a licensed architect or engineer for standard residential projects.
6. Can I use SitePlans.ai for a Portland permit?
Yes. SitePlans.ai generates a correctly scaled site plan in the proper format (black ink, minimum 1" = 10' scale) with tree survey annotations ready for Portland's DevHub.
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Start Your Multnomah County Site Plan
Verify your jurisdiction on PortlandMaps first. Then enter your address below to pull your property lines, place your project, annotate your trees, calculate your impervious surface, and download the formatted PDF you need for DevHub or county land use approval.
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Got a correction from PP&D or the county land use office? Send the comments to SitePlans.us and we'll draft the revision for you.
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