Attic, basement, or garage conversion
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Source: Attic, basement, or garage conversion ↗ Last modified: Sun, 19 Apr 2026 19:59:57 GMT
Portland Permitting & Development (PP&D) is happy to work with you on your project. This page gives you information on what's required with your permit application. You can also schedule an appointment to discuss your conversion project.
You'll need a building permit for this project
You need to get a building permit when you convert an attic, basement, or garage to a living space (also called a habitable space). Your project might also need electrical, plumbing, or mechanical permits ↗. If you're increasing the size of a structure, see Residential Additions ↗.
Learn about ADU permits
If you plan to use the converted space as an accessory dwelling unit (ADU), visit the ADU permit page ↗.
What you need for a completed conversion application
To begin the permitting process for your conversion project, you'll need three things:
- A completed building permit application
- A site plan ↗
- Architectural plans
Please carefully read the submittal requirements below. They explain what you must include in a completed application. You can also find links to other forms like the building permit application.
Review the submittal requirements to learn more about what's required with your application:
Review the plan drawings requirements:
- Drawings, drawn to scale, to verify compliance with code.
- Drawings may be handwritten or drawn if they're clear and legible. Text or notes need to be in print handwriting.
- Minimum drawing size: 11x17. All required information needs to be clear and legible. Minimum printed text is to be 3/32” or the equivalent 12-point font.
- Applicants can't use professional drawings without the permission of the professional. For example, you can't use an architect’s stamped plan without their permission.
Depending on the scope of work, you may also need structural calculations.
Here's an example of a floor plan for converting a basement into living space. It shows most of the information you need for an average conversion:
Your project might qualify as a Major Residential Alteration and Addition (MRAA) ↗. If so, there are more requirements. These include a delay period and notification to neighbors and neighborhood associations. See the MRAA webpage ↗ for more detail on these requirements.
A combination permit allows you to request all inspections at once. You can also pay for all the permits at one time. If you're applying for a combination permit, submit these trade permit applications:
Each project is unique, so we might need to ask you for more information.