Happy Valley ADU Builder

The real work of a Happy Valley ADU happens before the build

An ADU is a real building with its own kitchen, bath, and utilities, which is why the site work and connections drive as much of the cost as the walls do. JDI Construction is a family-owned, Vancouver-based design-build remodeler, and we treat an accessory dwelling unit as exactly that — a full second home that has to work on your particular lot — so we confirm what your specific Happy Valley property allows before we design to it. In a fast-growing area of newer, large hillside subdivisions, that groundwork often turns on grade and utilities as much as on square footage.

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 what decides what's possible, along with what to expect on cost and timeline.

What decides what you can build

An ADU lives or dies on a few factors, and every one of them is set by your lot rather than by the plan you have in mind:

A few decisions worth making early

The choices that make or break an ADU come well before design. The first is feasibility: Oregon is broadly ADU-friendly, but the details — size caps, setbacks, height, parking, and fees — are decided locally, and what Happy Valley permits differs from unincorporated Clackamas County or the City of Portland. We confirm what your specific lot allows before drawing anything, and on Happy Valley's newer hillside lots that means reading the slope, the drainage, and how a unit fits within a subdivision's layout and any HOA considerations. The second decision is type and use: a detached cottage, an attached addition, a garage conversion, and a basement unit carry very different costs and site demands, and whether you're building for rental income, family, or a workspace shapes the plan. The third is budgeting for the parts you can't see — the sewer, water, and power connections and the system development charges that come with adding a dwelling.

What Happy Valley homeowners build ADUs for

Most Happy Valley ADUs we're asked about serve one of a few purposes: a rental for income, a private and independent space for aging parents or adult children, or a studio or home office set apart from the main house. Each one steers the design differently — a rental favors durability and its own entrance, while a multigenerational unit favors single-level, step-free living.

Because so much of Happy Valley is newer construction on larger hillside lots, there's often room for a detached cottage — though the slope and grading are usually the deciding factors, and an attached unit can sometimes make better sense on a steep parcel. Whatever the use, we design a compact footprint to live larger than its square footage, using light, storage, and ceiling height to keep a small home from feeling small.

What does an ADU cost in Happy Valley?

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 it's size, finish level, and — the part homeowners often underestimate — the site and utility work. On Happy Valley's sloped hillside lots, grading, access, retaining, and running sewer, water, and power to a new dwelling can be a real share of the budget, on top of the connection and system development charges. That's exactly why we scope those items 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 can take longer than a straightforward 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 moves faster than a ground-up cottage, and a sloped hillside site can add site-prep time. 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 Happy Valley 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 the first wall goes up. As a single accountable design-build team, we handle the feasibility, the design, the utility connections, and the build under one roof, so nothing gets lost 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. Happy Valley is a short drive from our Vancouver home base, close enough for us to stay responsive throughout a project this involved.

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