Hillsboro Home Additions

The best additions are the ones you can't point to

A well-built addition disappears — you can't tell where the old house ends and the new one begins. JDI Construction is a family-owned, Vancouver-based design-build remodeler, and on an addition our job is really two jobs at once: building the new space, and marrying it to the existing foundation, roofline, and walls. Hillsboro spans a wide range of that work — the older homes near downtown that predate the Silicon Forest boom, and the newer developments that filled in as the tech corridor grew — and an addition behaves differently on each. Unlike an ADU, which stands off as a separate unit, an addition expands the home you already own, sharing its roof, systems, and foundation.

Our designers and trades work as one team, so the addition you approve is drawn to tie into the house that's actually there — we don't hand a set of plans to a separate crew and hope the new roof and foundation line up. Below is how additions are built, the decisions that come first, and what drives cost and schedule.

The parts that matter most

An addition is really a set of connections between new construction and an existing house. These are the parts we plan around before anything gets framed:

1. 1
   

   Structure & loadNew load paths, beams, and headers where we cut into the existing house.
2. 2
   

   Tying inFoundation, roofline, and siding matched so new and old read as one home.
3. 3
   

   SystemsExtending HVAC, electrical, and plumbing to serve the added space.
4. 4
   

   Setbacks & permitsWhat your lot allows for expansion, and the engineering and permits that go with it.

A few decisions worth making early

An addition turns on a handful of decisions that come before design. The first is up or out: building out is generally simpler and cheaper when the lot has room, while adding a second story keeps your yard but requires verifying that the existing foundation and framing can carry the added weight. The second is capacity — whether the current foundation, electrical panel, and heating and cooling system can serve the new square footage or need upgrading along the way. The third is what the parcel permits: setbacks, lot-coverage limits, and height rules that vary by jurisdiction, and in Hillsboro's newer developments often by HOA as well. We check all of it against your specific lot before we draw, so the plan fits the house and the property from the start.

What Hillsboro homeowners add on for

Most Hillsboro additions come from wanting more of a home that already suits you: a primary suite, an extra bedroom, a larger family room, or a real home office — the kind of space a growing household or a work-from-home routine keeps demanding. Because an addition is attached and shares the roof, systems, and foundation, it expands the house you have instead of creating a separate building the way an ADU would.

The matching challenge depends on the vintage. On the older homes near downtown, the work is matching siding, trim, and rooflines that have weathered for decades so the new part doesn't stand out. In the newer developments around the Silicon Forest, the materials are easier to source but the design usually has to satisfy HOA guidelines and tighter lot-coverage rules. In both cases we treat the seams — foundation, roofline, exterior skin, and interior transitions — as the work that decides whether the addition reads as original or added on.

What does a home addition cost in Hillsboro?

Cost starts with the type of addition: a bump-out that leans on the existing structure sits well below a second-story addition that requires reinforcing the foundation and framing beneath it. From there it's size, how much structural work the tie-in demands, how hard the existing materials are to match, and whether the systems need extending or upgrading. Because our design and our trades are both in-house, we can price the structural realities honestly up front and give you an itemized estimate once the addition is drawn, so the number reflects your house and your lot rather than a generic per-square-foot figure.

How long does a home addition take?

An addition is a months-long project more than a weeks-long one, because it runs through design and engineering, permitting, foundation and framing, tying into the existing structure, and then finishes. Second-story and structural additions take longer than a simple bump-out. We give you a realistic schedule before demolition, handle the engineering and permits the work requires, and sequence it to keep the existing home weather-tight and livable while the new space goes up.

Why homeowners in Hillsboro choose JDI

An addition is where design-build earns its keep, because the design, the structural engineering, and the construction all have to agree for new and old to meet cleanly. As a single accountable team, we handle the plans, the load paths, the tie-in, and the finishes under one roof, so nothing falls through the gap between an architect and a separate builder. We manage the permitting, keep you updated through our client portal, and stand behind the work with a five-year workmanship warranty. JDI is just across the river in Vancouver, a short drive from Hillsboro, so we're close enough to be on-site and responsive throughout a project this involved.

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