Lake Oswego ADU Builder

In Lake Oswego, confirming what your lot allows is the real first step

The hardest part of building an ADU usually isn't the construction — it's confirming what your specific lot actually allows. JDI Construction is a family-owned design-build remodeler, and we begin every accessory dwelling unit there: it's a second, independent home on your property, and the zoning and utilities settle what's buildable long before a design does. The Portland metro is generally very ADU-friendly, which tends to help Lake Oswego homeowners, but rules still vary by city and jurisdiction and every lot is its own case — so we confirm what your specific property allows before drawing anything. Lake Oswego's larger, custom lots around Oswego Lake often carry more room to work with, along with the slopes, mature trees, and utility runs that make a careful feasibility read essential.

Our designers and trades work as one team, so the unit you approve is grounded in what the site and the code actually permit — we don't hand a hopeful floor plan to a separate crew and find out later it won't pass. Here's the range of ADUs we build, what decides what's possible, and what to expect on cost and timeline.

What decides what you can build

Before a design means anything, a few factors set the boundaries of what your lot can hold. These are the ones we confirm first:

A few decisions worth making early

The choices that make or break an ADU come well before design. First is feasibility. Lake Oswego benefits from the metro's ADU-friendly climate, but its rules are the city's, not automatically Portland's, and no two lots are alike once slope, tree cover, access, and utility lines enter the picture — so we confirm what your parcel permits before drawing. Second is type and use: a garage conversion, a basement unit, an attached addition, and a detached cottage differ widely in cost and in what the site must support, and building for rental income, family, or a home office shapes the layout. Third is budgeting for the parts you can't see — the sewer, water, and power connections and the system development charges that a new dwelling brings. On larger, sloped lots those connection runs can be longer than expected, so we scope the site and utility work up front.

What Lake Oswego homeowners build ADUs for

The ADUs we're asked about in Lake Oswego tend to serve one of a few purposes: a private space for aging parents or adult children who want independence while staying close, a rental unit that draws on the region's steady housing demand, or a home office, studio, or guest quarters set apart from the main house. Each points the design somewhere different — a multigenerational unit favors single-level, step-free living, while a rental leans toward durability and a separate entrance.

Lake Oswego's larger custom lots often leave real room for a detached cottage, and homes with existing garages or lower levels can suit a conversion just as well. Whatever the use, we design a compact footprint to live larger than its square footage — and to sit comfortably alongside a well-kept main house — using light, storage, and ceiling height to keep a small home from feeling small.

What does an ADU cost in Lake Oswego?

ADU cost is driven first by type: a garage or basement conversion that reuses an existing structure generally costs less than a detached cottage built from the ground up. After that come size, finish level, and — the part homeowners most often underestimate — the site and utility work. Extending sewer, water, and power to a new dwelling, handling grading and access on a sloped or wooded lot, and covering connection fees can take a meaningful share of the budget, which is why we scope it early. With design and trades both in-house, we give you an itemized estimate once we know what your lot allows and which type fits, so the number reflects your project rather than a generic per-square-foot figure.

How long does an ADU take to build?

An ADU runs on three clocks: feasibility and design, permitting, and construction. Permitting for a second dwelling generally takes longer than a remodel because it involves zoning and utility review, so we build that time into the plan rather than promising a quick turnaround. Once permits are in hand, construction depends on the type — a conversion is faster than a ground-up cottage. We give you a realistic schedule after the feasibility check, handle the permitting, and keep you updated through our client portal as the unit comes together.

Why homeowners in Lake Oswego choose JDI

An ADU rewards a builder who understands the rules as well as the construction, because the project can stall at the permit counter long before framing begins. As a single accountable design-build team, we handle the feasibility, the design, the utility connections, and the build under one roof, so nothing slips between a zoning question and the crew on site. We manage the permitting, keep you informed through our client portal, and stand behind the work with a five-year workmanship warranty. We're based across the river in Vancouver, a short drive away, close enough to stay responsive through a project this involved.

JDI Construction — "Built by family. Trusted by neighbors." Design-build remodeling and ADU construction based in downtown Vancouver, WA, serving Lake Oswego and the greater Portland–Vancouver metro since 2007.