Building a separate living space inside an underused bedroom or basement corner has become very popular in Portland, Oregon. Property owners in Portland who are looking at a junior ADU, also known as a JADU, want to avoid the high costs of building a brand-new detached structure. Mighty ADU Company has worked on many older homes across neighborhoods like Cully and Woodstock. Carving out existing square footage is a very effective way to add functional space or rental income without pouring a new foundation.
Junior ADU projects in the Portland metro area typically cost between $80,000 and $140,000. Projects with a straightforward layout where plumbing is already close by and only require an efficiency kitchen, minor framing, and a separate exterior door will stay on the lower end of that range. Upgrading an old electrical panel, removing old lath-and-plaster walls, or upgrading insulation to meet modern energy codes will push the total cost toward the higher figure.
What Actually Drives the Price Up?
Square footage is not the primary factor when working inside an existing thermal envelope. The total budget is influenced by a few specific site conditions:
- Plumbing distance from the main house stack
- The current capacity of your electrical panel
- Asbestos or lead paint remediation in older homes
- Fire-separation walls required between the primary dwelling and the new unit
The damp Pacific Northwest winters mean that moisture management and proper ventilation are very important. Spaces being converted that have damp-proofing issues or poor subfloor drainage require structural repairs before the interior is finished to keep the project on budget.
What is Included in a Standard Quote?
A reputable contractor provides a detailed line-item estimate rather than vague lump sums. A standard quote covers architectural drawings, structural engineering stamps if load-bearing walls are shifting, city plan-check fees, and all rough-in through finished trades for electrical, plumbing, and mechanical systems. The estimate also includes drywall, flooring, basic cabinetry for the efficiency kitchen, and final finishes. Property owners should always check whether appliance packages and light fixtures are part of the deal or if they need to purchase those separately.
How to Avoid Overpaying
Changing your mind halfway through framing will increase costs during a Junior ADU project. Altering layouts after rough-in work is complete triggers costly change orders. Designs should be locked down before the construction work begins. Property owners should also pay close attention to utility tie-ins. Reusing existing lines wherever possible saves thousands of dollars, so make sure to let your designer know upfront that you want to minimize new trenching or core drilling through older concrete slabs.