Garage Remodel Mega-Guide

This is a guide to help homeowners understand their options – and the complexities – of remodeling a garage in Portland.

Remodeling your garage in Portland offers a unique opportunity to expand your living space, enhance property value, and adapt your home to evolving needs. However, navigating the complexities of such a project—from understanding local regulations to making design decisions—can be daunting. Our comprehensive guide demystifies the process, providing you with the insights needed to transform your garage effectively.

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What Defines an ADU in Portland?

• ADU, as legally recognized by the city: An Accessory Dwelling Unit, or “ADU” (also commonly referred to as “mother-in-law unit”), is a small secondary dwelling unit constructed on the same property as an existing primary dwelling unit. To qualify as an ADU, it must have a fully functional kitchen, a full bathroom, and a living space. You must also get an independent water/sewer supply and an independent electric supply. 99% of the time our clients say they want an ADU – but they don’t actually mean the legal definition of an ADU.
• Converting a garage to living space and adding a bedroom and a bathroom: this is what most clients are looking for. Your space that is non-livable now considered a “garage” now becomes habitable space and this square footage is added to your house and is recorded for tax assessment purposes. You could have an office in this space, you could sleep in this space. It is not an ADU because… it does not have a kitchen.
• Converting garage to living space as recognized by the city (no plumbing): A space that is non livable now considered a “garage” now becomes habitable space and this square footage is added to the house and is recorded for tax assessment purposes. You could have an office in this space, you could sleep in this space. This would be the most cost effective and easiest option.

You most likely want to “add a Bedroom and a Bathroom” – not create a legally designated ADU.

So now you might be thinking that you want just a finished space, with a bathroom, shower, sink where a guest or in-law could stay – someone could live there. This is now a new bedroom (or office), and a new full (or half) bathroom added to your existing single family residence. This is NOT an ADU – instead this is a new bed/bath added to your primary residence. Remember: no kitchen = no ADU.

Your tax records, Zillow/Redfin listing and MLS listing will now show an additional bedroom and additional bathroom. That means more value and a higher priced asset! It also means more taxes however.

Structural Permits (also called Building Permits) and “Change of Use” 

When you are changing the use of an area from X to Y and you want that change to be recognized by the city, then the city wants a permit for that change and the tax assesor wants to tax it!

Q: Are you adding new walls, removing old walls or enclosing a new space or area? 

You may or may not need a building permit, but it might be worth trying to execute without one. If it is needed, you can rest assured that Portland will let us know during the permit process. We can advise you and prepare those docs before submitting.

Q: Are you changing openings to doors and windows? 

If the openings are getting bigger or moving – meaning the structural headers engineered for those openings are moving – then you will need a structural/building permit.

Q: Are you changing any exterior walls or interior load bearing walls? 

Not only do you need a building permit, you need engineering calculations to account for these changes. That means your permit needs an engineers stamp to accompany your plan set.

Understanding Building Permits

Building permits are all about changes to the structure itself, is it legal, is it engineered properly, is it to code, is the work being done being performed by a licensed professional. You pay the permit fee to compensate Portland for their additional scrutiny over your project.

Non-Structural Remodeling Tips

Some “non structural” remodeling that should be fine without a building permit: Adding insulation, drywall, paint; Removing/replacing an existing window/door (like for like); Finishing flooring of any kind; Base, trim, etc as well as sheeting and siding; Most electrical: Adding lights, outlets, electrical, heating (Portland may ask, why are you heating it?); Limited plumbing: Modifying existing, adding a hose bib.

If the “use” of the space is changing, then a permit is required, but if the structure isn’t changing, and the “loads” are not changing then an engineer’s stamp is not required!

Trade Permits: Plumbing, Electrical, Mechanical

Ok, now that you have decided on building permit or no building permit – as well as structural or no structural (engineering) we can look at the trade permits you likely need depending on your circumstance.

In contracting we call this MEP: Mechanical, Electrical and Plumbing.

Plumbing Considerations for Your Remodel

What is your water meter size? Can you even add more fixtures? See the w3 worksheet to answer this question.

When you fill this worksheet out with your existing fixtures, it will show you how many new fixtures Portland will allow on your existing meter. If you end up going over, then Portland will require you to upgrade your meter. That isn’t something a contractor can do, but rather a service Portland will execute for you, for a fee, as part of your permit requirements.

How do you avoid this fee or change? Can you remove a hose bib, or remove a garage sink? Do you need a shower or can you do without? Each fixture adds up and you need to have a sufficient meter in order to accomodate those additional fixtures.

• Is there a water source close to the location of the proposed project? If not, we need to access via your house/basement/crawlspace and dig/trench a line to bring cold (and hot) out there.
• Do you know your water meter size? 1″ or 3/4″ or 1/2″. Depending on that meter size you might not be able to add another “fixture” on to it. Usually this is not an issue, but it does happen.
• Most important: the water and waste will need to drain somewhere. That means we need to trench back to your house, cut into the foundation, and connect to the existing soil stack. No way around this.

Finishing a garage is no problem at all, but adding the plumbing for the bathroom is usually the biggest challenge.

Everything is ultimately possible, and we do full showers/baths in garages, but it adds complexity and cost.

Side note: If you are pursuing the ADU designation, you will be required to include a “common area” shut off for the water service. This can be internal or external but each residence needs to be able to access their own water shut off.

Electrical Considerations for Your Additional Living Space

Can your electrical panel support more circuits or do you need to add a sub panel? It almost always makes sense to have a second panel because the orignial pannel likely doesn’t have the room to include the new circuits necessary.

If you are going for the ADU designation, you will need to have a “common area” shut off on the exterior of the home. Both the main residence AND the secondary residence (the ADU) need to be able to get to their own electrical shut off.

Furthermore, ADU’s will require a separate sub panel for all of the electrical work and circuits which serve the ADU.

Side note: how much power do you have going to your primary residence – meaning, what is the service level you are paying for from PGE? If its 100-200 amps, it likely won’t be enough to power this new living space and your electrical service may need to be upgraded. This isn’t something your contractor can do, but rather something that needs to be requested directly from PGE. More power needs = higher electric bill.

Mechanical Considerations:

When adding a mechanical system to an Accessory Dwelling Unit (ADU) in Portland, mechanical permits are required for all heating, cooling, and ventilation installations. This includes systems such as ductless heat pumps, furnaces, water heaters, and bathroom exhaust fans. Because ADUs are considered independent living spaces, they must have their own mechanical systems or approved extensions of the main home’s system, and all work must be performed by licensed contractors. The City of Portland enforces strict code compliance for ADUs, especially regarding energy efficiency and indoor air quality, making it essential to obtain the proper permits and ensure the systems are appropriately sized and vented.

For garages being converted into standard bedrooms or bathrooms (not classified as ADUs), mechanical permit requirements are still applicable for any new or relocated heating or ventilation components. If you’re adding a new HVAC duct, bath fan, or electric heater, a mechanical permit is typically required. However, these spaces are not subject to the same independent utility standards as ADUs, so the systems may be directly tied into the main home’s existing HVAC infrastructure. Even though the requirements are slightly less stringent, all mechanical installations must still meet Oregon Residential Specialty Code standards to ensure safety and efficiency. It’s always a best practice to work with a licensed contractor who understands local permitting rules and can coordinate inspections smoothly.

Navigating Legalities and Transparency

In the end, anything that is legally possible in your jurisdiction is physically possible to execute. The correct path forward in your garage remodel project is a spectrum of your intended use and level of transparency with the city of Portland.

Dealing with Non-Compliance

What happens if you make a modification that Portland doesn’t like or permit? You have to fix it, if you don’t you will be assessed a fine – however, everyone’s goal is to achieve “to code” construction and not assess fines. Portland will work with you in good faith to rectify the issue.

• If you didn’t pull permits, then you have to do everything in reverse and “prove” to Portland that it is up to code.
• Framing/Structural:
  • Removing finished drywall (ouch)
  • Showing insulation and vapor protection
  • Fire blocking between floors
  • Headers around doors and windows
• MEP:
  • Electrical runs have nail plates
  • Plumbing has sufficient fall
  • Mechanical is venting properly

Want to Avoid the Permitting Scrutiny?

200 square feet, less than 15 ft high, do not require a building permit. However, if you are wanting to change the use of that space it will require a building permit.

Unfortunately, it is very unlikely that a permit is not required – proceed with caution.

If your contractor keeps telling you that permits are not needed for a major rennovation like this it is a big red flag.

Are You Modifying Your Openings?

When you change the size or location of windows and doors you often need a building permit. You can close off and remove existing openings like removing a door or window without a structural permit. You can make openings smaller. You can swap doors and windows like for like.

Are You Modifying Existing Walls or Roofing?

If you are moving or removing walls, you will likely need a building permit. If you are adding walls, you quite often do not need a building permit – but Portland ultimately decides what they require.

You Decided. An Accessory Dwelling Units (ADU) is Necessary!

Step 0: Evaluate Your Existing Space You Intend to Convert:

Unfinished areas may not meet current building code requirements for living space. This includes:

• Ceiling height
• Emergency egress windows (emergency exit windows)
• Insulation and ventilation
• Stairs

These conditions could make it expensive, difficult, or even impossible for you to convert into an ADU. Learn more about how to research your property below.

Most things can be overcome, but if your ceiling height is insufficient it must be raised to 6’8″ or greater in order to be eligible. 

Check the permit history for a house

Depending on the age of your house, we may have inspection cards or microfilmed plans that show the permit history for your house. It is important to verify the permit records, not rely on the tax information from the county assessor’s office. If an “existing” finished attic or basement was not permitted, it will need to be legalized through the new permit as if the work was not already done.

Some records are available online. Visit our How to Request Public Property Records webpage.

Find out about the zoning standards for an ADU

There are a variety of design and use standards in the zoning code which apply to the creation of an ADU. These include:

• Restrictions on short term rentals and home occupations
• Limits on the size of the ADU
• Design requirements for new detached ADUs over 15 feet tall

For detailed information on the zoning code standards such as visibility and height allowances, click here.

City Utility Connections

The ADU and the primary dwelling unit shall have separate and independent water supply and sanitary sewer systems, except as allowed by Water and Environmental Services.

Get more information on water and sewer requirements such as decommissioning a septic tank or cesspool, numbers of allowable fixtures, and shared and separate meters.

Construction Standards

Construction of new accessory dwelling units and additions to existing single-family dwellings to create an accessory dwelling unit must comply with the requirements of the Oregon Residential Specialty Code (ORSC) for one- and two-family dwellings.  Alternative construction standards, listed in the Accessory Dwelling Unit Code Guide, apply when an accessory dwelling unit is created within an existing single-family dwelling unit or within an existing detached accessory structure such as a garage.

Accessory dwelling units may be added to townhouses, which are considered a single-family dwelling unit, if the townhouse structure meets the requirements of Code Guide: Additional Dwelling Units and Common Spaces within Townhouse Structures (202.43 Kb).  Accessory dwelling units may not be added within an existing two-family dwelling unit unless the structure is modified to meet the requirements of the Oregon Structural Specialty Code (OSSC) or unless the existing dwelling units are redesigned to meet the requirements of townhouses. Note: The Accessory Dwelling Unit Code Guide does not apply to structures reviewed under the OSSC.

Who Can Do the Work?

Contractors must have a license to work in Oregon. The Oregon Construction Contractors Board (CCB) issues licenses to contractors. The permit application and their company materials must list the license number. Need help finding a contractor? The CCB website has good tips on how to search for one. Plumbing and Electrical contractors have additional license requirements.

If you are a homeowner doing the work yourself, then you can sign the trade permit applications. You cannot do the electrical work yourself for an ADU. You must hire a licensed electrical contractor to do the electrical work on an ADU. The State of Oregon has some helpful information for homeowners:

ADU SDC Waiver Program

You may be eligible to apply for an SDC waiver. Learn more about this program.

Fees and System Development Charges

The development of an ADU requires building permit fees, water service fees and System Development Charges (SDCs).  In some instances, fees or SDCs can be substantial. Fees and SDC charges are based on the information below.

Building Permit Fees

Permit fees are based on the type of permit, the work proposed, the valuation of the work, and the staff that needs to review the work. When you create a new dwelling unit, system development charges are usually charged.

System Development Charges

The construction of ADUs or the conversion of existing structures to ADUs is typically subject to System Development Charges (SDCs) that are levied by the Portland Parks and Recreation, Environmental Services, Transportation, and Water Bureaus.

Transportation SDCs

For ADUs where the SDC is not waived, the Bureau of Transportation charges an SDC. Rates are updated annually on July 1.

Environmental Services SDCs

For ADUs where the SDC is not waived, the Bureau of Environmental Services charges an SDC.  The amount of the SDC will be based on fees that were paid previously and the addition of an ADU based on the current sewer connection charge. Rates are updated annually on July 1.

In some cases, it may be necessary to increase the size of the sewer or wastewater line or to provide the ADU with a separate connection to the sanitary sewer system.  In these cases, additional fees will be required even if SDC charges are waived.

Parks and Recreation SDCs

For ADUs where the SDC is not waived, Portland Parks and Recreation charges an SDC for the creation of any ADU. The fee changes annually on July 1. Please call Parks and Recreation for the current rate.

Water Bureau SDCs

The Water Bureau does not automatically charge an SDC when an ADU is constructed. If the ADU can be added without changing the size of the existing water service, there is no charge. Click here for more information about connecting to city utilities. Upon request, the Water Bureau can verify the existing water service size. If an increase in water service is required, then there is a charge for increasing the service along with the differential cost increase for the larger service. Please contact the Water Bureau for more information.

Step 1: Schedule a 15-minute appointment

This is an optional step. If you still need help, we are here for you if you have questions about the information and materials you need to apply. You can schedule a free 15-minute appointment with any of these reviewers:

• Meet with a City Planner to receive information about planning and Zoning and Tree Code requirements that apply to your property.
• Meet with a Building Code and Engineering Reviewer to get help with building code and engineering requirements.
• Meet with a Permit Technician if you have questions about the permit process or if you need help with application requirements.
• Meet with a Water expert tofind out if your project requires you to increase the size of your existing water meter.
• Meet with a Transportation expert to find out if your project will trigger right-of-way improvements.

Contact Environmental Services if you have questions about sanitary or stormwater sewer lines: 503-823-7761.

If you need help, these are experts we recommend you meet with for this project. Not all review groups are listed. The groups listed above will help get you started.

Step 2: Complete an ADU building permit application and required forms and documents

If you plan to build a new detached ADU, follow the New Single Family Residence guidelines.

If you plan to convert existing space to an ADU, you need to have completed building permit application, a site plan, and architectural plans. For a complete list of submittal requirements for conversions of an existing space see “Submittal Requirements – 1 & 2 Family Residential.” You might also want to read our step-by-step guide for completing a building permit application.

If your project qualifies as a Major Residential Alteration and Addition (MRAA), there are additional requirements including a delay period and notification to neighbors and neighborhood associations. Review the MRAA webpage for more about these requirements.

Step 3: Apply for an ADU permit online or in person

If you plan to build a new detached ADU, please follow the New Single Family Residence guidelines. The steps listed here are for converting an existing space to an ADU.

You can submit your ADU permit application request online using Development Hub PDX. Read step-by-step instructions for submitting a permit application request online or in person.

For most projects, electronic plans are submitted through the Single PDF process. Large projects such as commercial new construction are submitted through PDX E-plans and ProjectDox.

If you need to submit paper plans, you can set up an appointment to pick up plans or drop off plans in person. Or, please call us and we will work with you.

Step 4: Check plan review status and make corrections to an application

You can check the status of a permit review on Portland Maps permit/case search. Many people might review a single permit. The Permit Review Process webpage has more information about the groups that review permits.

Checksheets: 

A checksheet is sent to the applicant when a reviewer needs additional information, or a correction must be made to the plans. When you have gathered the additional information or made the corrections, you will need to send us a checksheet response with corrections. Reviewers will be notified that a checksheet response has been received and the review will continue.

Keep in mind that many departments and many people will be reviewing your application. Each of those people and departments have their own “checksheet” and hoops they make you jump through. Overcoming these requirments one by one is often the phase of the project which takes the longest. 

Step 5: Get Your ADU Permit

You will be contacted when your permit is ready and notified of your final fee total. Instructions will be given on how to get your approved permit and pay your fees. Your permit is not issued until all fees are paid. Read more about the pre-issuance process.

Step 6: Start Construction and Schedule Inspections

The inspection card lists all the inspections you will likely need during your ADU construction project, and what work needs to be done first.

Once your building permit is issued, erosion control measures and sometimes tree protection measures must be installed, inspected and approved prior to beginning any further ground-disturbing activities. All permits need a final approval inspection to be complete.

Step 7: Schedule an Inspection, and Make Corrections

To schedule an inspection, call the automated inspection request line. You will need your IVR or permit number and the three-digit code for the inspection.

Get the results of the inspection on Portland Maps permit/case search the next day. Read more about why work does not get approved and how to schedule a reinspection.

If you have questions before or after your inspection, you can talk with an inspector.

Other Considerations

Trees: Ground disturbance or construction staging that impacts a root protection zone of an existing tree may trigger tree preservation requirements for trees located on private property and/or in the public right-of-way. The value of a project may also trigger tree planting requirements for private property and/or in the public right-of-way. More information may be found at the Portland Trees website.

Temporary Street Use Permits: To reserve on-street parking, close sidewalks, travel or bike lanes, or to close streets to facilitate construction, contact the Temporary Street Use Permit (TSPU) Office (see “Contact Information” at the end of the ADU Code Guide) for information and requirements or apply for permits online at www.tsup.info.

Addresses: Addresses for sites with one or more ADUs will be assigned as follows:

• A single street address (number) will be assigned to the site, with letters used to designate each separate dwelling unit regardless of the orientation of the front door of the unit.
• The Unit letters (A, B, C, D, etc.) will be assigned to all dwelling units, including those on corner lots.
• The address of the ADU must be permanently affixed on the main entrance of the dwelling unit and be legible from the public way that provides access to the primary unit. When the address posted at the unit entrance is not visible from the public way, a duplicate address must be permanently affixed to a permanent structure at the entrance to the site from the primary public way.

Existing “Accessory Rental Units”: Existing Accessory Rental Units (ARUs), which were created by permit under previous zoning regulations, will be considered ADUs under the new regulations. Because of the change in some standards, these pre-existing ADUs may be nonconforming to one or more Zoning Code standards. For additional information, please contact Planning and Zoning.

Discontinuance of Accessory Dwelling Units or Accessory Rental Units: To discontinue using an existing ADU or ARU as an independent living unit, a building permit is required. The purpose of the permit is to document that the accessory unit no longer exists as a separate legal living unit.

Permanent cooking facilities in the ADU or ARU must be abandoned by removing the appliance (and exhaust hood) and permanently capping the exhaust duct serving the hood. If a gas range is being abandoned, the gas piping branch serving that appliance must be abandoned and permanently capped at the point where it originated at the trunk line. If an electric range is being abandoned, the circuit breaker(s) and receptacle serving the range must be removed, with the electrical wiring cut flush with the side of the service panel or subpanel, so that it cannot be easily reconnected. The wiring at the receptacle must be cut flush with the side of the outlet box and a blank cover plate installed.

“Illegal” Accessory Units: Property owners must obtain a building permit to legalize existing ADUs that were constructed without a building permit. Verification of the compliance of concealed building components that were covered without inspection will be at the discretion of the building inspector.

More Information and Common Questions

QUESTION: Can a single-family dwelling have more than one kitchen?

RESPONSE: The Oregon Residential Specialty Code doesn’t limit the number of kitchens in a single-family dwelling. However, the 2017 ORSC defines a dwelling unit as, “A single unit providing complete independent living facilities for one or more persons, including provisions for living, sleeping, eating, cooking and sanitation.” (ORSC R202). BDS seeks to avoid illegal conversions of single-family dwellings into duplexes or multi-family structures. Such conversions create fire and life safety issues for the residents because the structures do not comply with the ORSC requirements for multiple dwelling units in a single structure or attached structures. In order to accomplish this goal, BDS will require a building permit to install a new kitchen within a single-family dwelling and will impose certain conditions outlined in this document. In order to install an additional kitchen:

• The accessory kitchen may be located in a portion of the building that would meet the definition of a dwelling unit only if that portion of the building is not and will not be separated from the rest of the building by walls or closing a door.
• The accessory kitchen may not be located in a detached structure with a bathroom.
• Any additional accessory kitchen installed in a single-family dwelling must comply with all of the same Electrical, Plumbing and Mechanical Code requirements as the main kitchen.
• The home owner must complete and record an “Additional Accessory Kitchen Covenant” as part of the building permit process. That Covenant is the property owner’s acknowledgement that the structure will remain a single-family dwelling and that the accessory kitchen will not become part of an additional dwelling unit without obtaining a building permit for the creation of the additional dwelling unit. The covenant must have the permit number listed (available after the permit has been set up) and be signed by a City Plans Examiner before it is recorded. Once it is recorded, a copy of the recorded Covenant must be provided to BDS as a condition of permit Issuance.

Follow this link Accessory Kitchens in Single Family Dwellings to find the forms you will need if you will be adding a kitchen.

QUESTION: What building code modifications are allowed for accessory dwelling units?

RESPONSE: ADUs must comply with the requirements of the Oregon Residential Specialty Code (ORSC) for two-family dwellings as modified by the alternative standards listed in this Code Guide…

A. Electrical System

1. Electrical panels. ADUs must have electrical circuits completely independent of, and share no loads with, the main dwelling unit…
2. Electrical license. All new electrical work shall be conducted by a licensed electrical contractor…

B. Heating System

1. Mechanical Closets. For conversions or additions, the furnace that supplies heat to the primary dwelling unit may remain…
2. Ductwork. For conversions and additions, existing ductwork…
   • Permanently sealed and terminated at the point where the ductwork enters the ADU; and
   • All exposed ductwork for the primary dwelling unit located below the ceiling line of the ADU is wrapped with one layer of 5/8” Type X gypsum board.
3. Radiant Systems. Radiant systems may be used or extended to the ADU…

C. Plumbing System

1. Water Heater. Dwelling units may share a water heater…
2. Water Supply. If a single water supply line has been approved through the Water Bureau…
   • Conversions or additions. Each individual fixture has a shut-off valve, or a whole dwelling shut-off valve is installed, accessible from both units.
   • New construction. Each unit is supplied with a control valve accessible from that unit.
   • The water supply line downstream from the meter may also need to be upsized…
3. Sewer. The ADU and the primary dwelling may use a common building sewer line provided:
   • No more than five water closets (toilets) are on a single 3-inch line, and
   • New Fixtures. When the floor level of the ADU is lower than the next uphill manhole cover in the street…
     • A backwater valve(s) for the drain piping serving each new plumbing fixture in the ADU is required…
     • When a backwater valve(s) is installed, it must remain accessible for maintenance and replacement within the ADU.

D. Fire and Life Safety

1. Occupant Designation. Submittal drawings used to permit ADUs shall have clearly labeled rooms…
2. Separation Between Dwellings and between a Dwelling and Common Space.
   • New Construction. Where a new wall or floor/ceiling is constructed…
   • Existing conditions. This code guide allows the following reductions…
     1. Separation walls. Existing stud-framed walls which serve as separation walls shall be covered on both sides with:
        • Existing lath and plaster in sound condition; or
        • Existing half-inch (minimum) gypsum wallboard in sound condition
     2. Floor / Ceiling Separations. Existing floor framing with existing subfloor…
        • Existing lath and plaster in sound condition; or
        • Existing half-inch (minimum) gypsum wallboard in sound condition
        • Prescriptive option:
          • Existing floor structure with existing finish (any joist size and spacing)
          • Resilient Channels
          • 3-inch-thick glass fiber insulation
          • Minimum half-inch Type X gypsum wallboard
     3. Openings.
        • A door between a dwelling unit and common space must be…
        • A door between dwelling units in newly constructed buildings…
        • Openings between dwelling units in existing construction…
     4. Supporting Construction. The beams, columns, and bearing walls…
        • Exposed wood columns not less than 6-inch nominal thickness.
        • Existing exposed wood beams not less than 4 inches nominal thickness
        • Existing bearing walls with at least half-inch gypsum wallboard protection
3. Ceiling height, stairs, light, ventilation, emergency egress, and energy conservation.
   • Hallways. Existing hallways shall be at least 2 feet 6 inches wide…
   • Doors
     • Dwelling Entrance Doors. All interior and exterior doors…
   • Stairs. Stairways shall have at least 6 feet 4 inches of headroom…

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