360-932-0505
Home Additions2026-09-11T11:38:58-07:00

More house without moving

Room additions, second-story additions, ADUs, and garage conversions across Bellingham and Whatcom County. Turn extra square footage into everyday living space.

When you love the neighborhood but need more room

Moving isn’t always the answer. If you like where you live but need more space, an addition is almost always cheaper than a new house — and you keep the yard, the commute, and the community you’re already in.

We build room additions, second-story additions when the footprint is fixed, detached ADUs where zoning allows, and garage conversions. Every project is engineered for the existing structure, permitted through Whatcom County or your city, and finished to match the original home.

What's included

Room Additions

Family rooms, primary suites, home offices, and sunrooms.

Second Stories & ADUs

Add up when you can’t add out. Detached ADUs where zoning allows.

Conversions

Garage-to-living-space and existing-structure conversions.

What we offer

Room Additions

A room addition is the most common Whatcom County home addition — a new family room, primary suite, home office, sunroom, or mudroom bumped out from the existing footprint. We handle foundation, framing, envelope, and finish so the addition feels original.

Second Story Additions

When you can’t add out — narrow lot, tight setbacks, mature landscaping — you add up. Second-story additions require structural analysis of the existing foundation and walls and careful sequencing to weatherproof during construction. We coordinate all of it.

ADUs and DADUs (Detached Accessory Dwelling Units)

Bellingham and Whatcom County both allow accessory dwelling units in most residential zones — attached to the main house or as a separate structure. ADUs work as family housing, rental income, or a home office with a bathroom. We handle design, permit, and build.

Garage Conversions

Converting an attached or detached garage into livable space is often the fastest and least expensive way to add a bedroom, office, or ADU. We insulate the slab, upgrade windows and doors, and finish to habitable-space code across Whatcom County.

Sunrooms and Four-Season Rooms

Whatcom County weather rewards a well-built sunroom. We build fully insulated four-season rooms that function like any other room in the house, and lighter three-season sunrooms for spring-through-fall use. Both integrate cleanly into the existing structure.

How the project runs

01

Feasibility

On-site assessment of structure, setbacks, and zoning.

02

Design

Coordinated drawings, structural engineering, permit set.

03

Build

Foundation to finish, matched to existing home’s aesthetic.

04

Integration

Seamless tie-ins so the addition looks original, not added.

Frequently Asked Questions

What does an addition cost?2026-09-09T13:30:56-07:00

Room additions in Whatcom County typically run $350 to $550 per square foot depending on complexity. ADUs and second-story additions vary more widely with structural scope.

Will the addition look like it belongs?2026-09-09T13:30:48-07:00

Yes. Matching siding, trim, and rooflines to the existing home is one of the hardest parts of an addition, and it’s a detail we prioritize.

Can you build an ADU on my property?2026-09-09T13:30:40-07:00

Depends on zoning and setbacks. Whatcom County and Bellingham both allow ADUs in most residential zones, but there are size and placement rules. First conversation includes a feasibility check.

How long does a room addition take?2026-09-09T13:30:25-07:00

From signed contract to move-in, a typical room addition runs 4 to 7 months, depending on scope and permit turnaround. Second-story additions and ADUs run longer.

Can you add an ADU or rental in the basement?2026-09-09T13:30:17-07:00

Sometimes, depending on zoning and separate-entry requirements. Bellingham and Whatcom County both allow basement ADUs in most residential zones. We check feasibility as part of the first conversation.

Ready to start your project?

Free estimates for Whatcom County residential projects. No obligation, no pressure.

© 2026 LGC Construction, LLC · Licensed & Insured in Washington State · Whatcom County