The floor plan is the single most important design decision for your ADU. It determines how the space feels to live in, how much rent it commands, how efficiently it builds, and how well it fits your lot. A well-designed 550 sqft one-bedroom can feel more spacious and livable than a poorly laid out 800 sqft unit — and it costs significantly less to build.
This guide walks through the most popular ADU floor plan types for Bellingham properties, from compact studios to full two-bedroom layouts. Each section includes room dimensions, layout concepts, and guidance on which Whatcom County lots they work best for.
Every lot is different, which is why we design custom plans rather than using templates. Start with a free feasibility study to find out which layouts work on your property, or explore our ADU design process to learn how we approach custom planning.
Studio Layouts: 300–500 Sq Ft
Best for: small lots, budget builds, short-term rental, single occupants
Studio ADUs combine sleeping, living, and kitchen areas into one open space with a separate bathroom. They're the most efficient use of square footage and the least expensive to build. In Bellingham, studios rent for $1,200–$1,500/month and work particularly well on smaller lots where setback constraints limit the footprint.
The Compact Square (20' x 16' — 320 sqft)
The most space-efficient layout. A galley kitchen runs along one wall (8' of counter + appliances), with the bathroom accessed from the entry hall. The main living/sleeping area is roughly 14' x 16' — enough for a queen bed, a small sofa, and a dining table for two. A large window or sliding glass door on the far wall brings in natural light and creates visual depth.
Key dimensions: Kitchen wall 8' long, bathroom 5' x 8', main living area 14' x 16'. Entry closet for coats/storage.
The Open Loft (18' x 22' — 396 sqft)
A slightly longer rectangular layout that uses a partial wall or bookshelf to define the sleeping nook from the living area. The L-shaped kitchen occupies the front corner with a breakfast bar that doubles as a dining surface. The bathroom is centrally located, and a stackable washer/dryer fits in a closet adjacent to it. The elongated shape allows for windows on three sides.
Key dimensions: Kitchen L-shape 8' x 6', bathroom 5' x 7', sleeping nook 10' x 11', living area 11' x 14'. Breakfast bar seats 2.
The Garden Studio (24' x 20' — 480 sqft)
A more generous studio for lots that can accommodate a larger footprint. The wider floor plan allows a dedicated entry vestibule with coat closet and shoe storage — a PNW essential. The full-width kitchen includes an island with seating for two. A sliding barn door separates the sleeping area for privacy. French doors open to a small deck, blending indoor/outdoor living.
Key dimensions: Kitchen with island 10' x 12', bathroom 6' x 8', sleeping area 12' x 12', living area 12' x 14'. Entry vestibule 4' x 6'.
One-Bedroom Layouts: 500–700 Sq Ft
Best for: long-term rental, couples, single professionals, maximum ROI
One-bedroom ADUs are the most popular layout in Bellingham — and for good reason. They offer a dedicated, closable bedroom (a major upgrade over studios for tenant retention), a full kitchen and living room, and enough space to feel like a real home. Current rental rates for 1BR ADUs in Bellingham range from $1,400–$1,800/month, making them the sweet spot for rental ROI.
The Efficient Rectangle (22' x 26' — 572 sqft)
The workhorse one-bedroom layout. The front door opens to a combined living/dining room with the kitchen along the side wall. A short hallway leads to the bedroom (11' x 12') and a full bathroom with a tub/shower combo. The bedroom has a full closet with sliding doors. This layout minimizes hallway space and puts every square foot to work. The rectangular footprint is cost-effective to frame and easy to site on most lots.
Key dimensions: Living/dining 12' x 16', kitchen 8' x 10', bedroom 11' x 12', bathroom 5' x 8'. Hall closet + bedroom closet.
The Split Layout (24' x 26' — 624 sqft)
Separates the bedroom from living areas with the bathroom and laundry closet acting as a sound buffer in between. The front half of the unit contains an open-plan kitchen and living room with plenty of natural light. The rear half houses the bedroom with windows on two walls for cross-ventilation. A small covered entry porch provides weather protection and defines the entrance. This layout excels for privacy and noise separation.
Key dimensions: Open kitchen/living 14' x 18', bedroom 12' x 13', bathroom 6' x 8', laundry closet 3' x 4'. Covered porch 6' x 8'.
The Open-Plan Cottage (20' x 34' — 680 sqft)
A longer, narrower layout perfect for narrow lots or deep backyards. The front section is a generous open kitchen/dining/living area that spans the full 20-foot width. The rear section contains the bedroom, bathroom, and a walk-in closet. A peninsula kitchen counter defines the cooking area while maintaining the open feel. This plan works especially well oriented east–west with the living area facing south for maximum natural light.
Key dimensions: Kitchen/dining/living 20' x 18', bedroom 12' x 14', bathroom 6' x 9', walk-in closet 5' x 6'. Peninsula bar seats 3.
Two-Bedroom Layouts: 700–1,000 Sq Ft
Best for: families, roommates, maximum rental income, multigenerational housing
Two-bedroom ADUs command the highest total rent in Bellingham ($1,800–$2,200/month) and appeal to a broader tenant pool: small families, couples with a home office, and roommates. They approach Bellingham's 1,000 sqft limit, so every square foot needs to be carefully allocated. These layouts require larger lots due to the bigger footprint and setback constraints.
The Side-by-Side (28' x 28' — 784 sqft)
Both bedrooms are on one side of the unit, separated from the living area by a central hallway. The shared bathroom sits between the two bedrooms for easy access from either room. The open-plan kitchen/living/dining area occupies the other half with a full-size kitchen and room for a dining table and sofa. A stacked washer/dryer fits in a hall closet. This layout is ideal for roommates because both bedrooms are roughly equal in size.
Key dimensions: Primary bedroom 11' x 12', second bedroom 10' x 11', bathroom 6' x 9', kitchen/living/dining 14' x 20'. Hall closet + two bedroom closets.
The Primary Suite (26' x 34' — 884 sqft)
A longer layout that separates the primary bedroom suite from the second bedroom with the living area in between. The primary bedroom has its own en-suite bathroom (shower only) and a walk-in closet. The second bedroom shares a hall bathroom near the entry. This plan works beautifully for couples renting to a single roommate, or for a parent and child. The separated bedrooms provide genuine privacy for both occupants.
Key dimensions: Primary bedroom 12' x 14' with en-suite 5' x 7', second bedroom 10' x 12', hall bathroom 5' x 8', kitchen/living 16' x 18'. Total two full baths.
The L-Shape (varies — 950 sqft)
An L-shaped footprint solves a common problem on Bellingham lots: the buildable area isn't a clean rectangle due to setbacks, existing structures, or lot shape. By wrapping the floor plan around a corner, you can maximize square footage while respecting site constraints. The L-shape also creates a natural courtyard space between the two wings — perfect for a small patio. One wing contains the bedrooms and bathroom; the other holds the kitchen, living, and dining areas.
Key dimensions: Each wing approximately 16' x 30'. Primary bedroom 12' x 14', second bedroom 11' x 12', bathroom 6' x 9', kitchen/living/dining 16' x 22'. Protected courtyard between wings.
Design for Your Lot
Every lot in Bellingham presents a unique puzzle. Setbacks, lot shape, slope, utility locations, existing structures, and orientation all constrain and inform floor plan choices. Here are the key site factors that determine which layouts work for your property:
Setback Requirements
Bellingham requires minimum setbacks from property lines: typically 5 feet on the side and rear for detached ADUs. After subtracting setbacks from your lot dimensions and the footprint of your main house, the remaining buildable area determines your maximum ADU footprint. Narrow lots often call for long, narrow plans (16–20' wide); wider lots allow for more square floor plans.
Lot Shape & Slope
Irregular lot shapes (pie-shaped, flag lots, corner lots) require creative floor plan solutions. Sloped lots may benefit from a split-level design that uses the grade change as a design feature. Our team uses GIS data and site visits to map the buildable area and design a floor plan that takes advantage of your lot's unique characteristics rather than fighting them.
Solar Orientation
In the Pacific Northwest, maximizing south-facing windows is critical for natural light and passive solar heating. We orient the living room and primary windows toward the south whenever the lot allows it. On north-facing lots, clerestory windows, skylights, and light-colored interiors help compensate. Proper orientation can significantly reduce heating costs and improve livability.
Relationship to Main Home
Where the ADU sits relative to your main house affects privacy, views, yard usability, and access. We consider sightlines from both homes, entry paths, shared outdoor areas, and how the ADU's placement affects your existing outdoor living space. The goal is a layout that enhances your property rather than making it feel crowded.
Bellingham-Specific Floor Plan Considerations
1,000 sqft maximum: Without a conditional use permit, your ADU cannot exceed 1,000 square feet of heated living space. This is measured to the exterior walls, so actual interior space is roughly 50–80 sqft less depending on wall thickness. Plan accordingly — a well-designed 950 sqft two-bedroom is better than an awkwardly cramped 999 sqft plan.
Setback constraints: In most Bellingham residential zones, detached ADUs require 5-foot side and rear setbacks. Corner lots have additional front/street-side setback requirements. The buildable area after setbacks determines your maximum footprint. We map this precisely during the feasibility study.
North vs. south orientation: Bellingham's latitude means the sun is low in the sky for much of the year. South-facing windows are critical for daylighting and passive solar gain. Our floor plans place primary living spaces on the south side whenever possible and minimize north-facing glazing to reduce heat loss.
Rain and entry design: With 35+ inches of rain per year, covered entries and mud rooms aren't luxuries — they're necessities. Our plans include a covered entry porch or vestibule for shedding wet layers before coming inside. This small addition (30–50 sqft) makes a huge livability difference.
Features That Maximize Rental Value
Beyond the basic layout, specific features can meaningfully increase what tenants will pay — and how long they stay. These features cost relatively little to include during construction but add significant rental value:
In-Unit Laundry
Stacked washer/dryer in a closet. The #1 amenity tenants look for. Adds $50–$100/month in rental value.
Ample Storage
Entry closet, bedroom closet, kitchen pantry, and at least one linen closet. Small units feel bigger with good storage.
Private Outdoor Space
A small deck, patio, or covered porch. Even 60 sqft of outdoor space significantly improves livability and tenant satisfaction.
Natural Light
Windows on multiple walls, south-facing glazing, and light-colored finishes. Especially important in the PNW's overcast climate.
Dishwasher
A standard 24” dishwasher or 18” compact model. Surprisingly few rental units have one, making it a strong differentiator.
Sound Insulation
Extra insulation in walls, quality windows, and solid-core interior doors. Quiet living space is a premium feature for tenants.
Our Custom Design Process
We don't sell pre-made plans. Every ADU we build starts with your specific lot, your goals, and your budget. Cookie-cutter plans lead to compromised layouts, missed opportunities, and expensive site modifications. Our process ensures the floor plan is optimized for your property from day one:
Free Feasibility Study
We evaluate your lot using GIS data, zoning maps, and setback calculations. You'll learn the maximum buildable footprint, which layout types fit, and estimated costs — before you commit to anything.
Site Assessment
An on-site visit to verify GIS data, check utility locations, assess drainage and slope, evaluate solar orientation, and understand the relationship between the main home and the proposed ADU location.
Custom Floor Plan Design
Based on the feasibility study and site assessment, we develop a custom floor plan optimized for your lot, your goals (rental income, family living, home office), and your budget. You review and refine the plan before permitting begins.
Permit-Ready Drawings
Our plans are stamped by a licensed architect and include everything needed for the city permit application: floor plans, elevations, structural details, mechanical layout, and site plan. See our permitting services for details.
Frequently Asked Questions
What is the maximum size for an ADU in Bellingham?
In Bellingham, ADUs can be up to 1,000 square feet without a conditional use permit (CUP). With a CUP, you may be able to go larger depending on your lot size and zoning district. For most homeowners, the 1,000 sqft limit is more than adequate for a comfortable one- or two-bedroom layout. Our designs maximize livable space within this limit through efficient floor planning and smart storage solutions.
What floor plan gets the best rental income?
In the Bellingham rental market, a one-bedroom layout in the 550-700 sqft range offers the best return per square foot. Current rents for 1BR ADUs range from $1,400-$1,800/month, while studios (300-500 sqft) rent for $1,200-$1,500 and two-bedrooms (700-1,000 sqft) rent for $1,800-$2,200. The one-bedroom hits the sweet spot: it costs significantly less to build than a two-bedroom but commands nearly as much per square foot in rent.
How do setback requirements affect my floor plan options?
Setbacks determine how close your ADU can be to property lines, which directly affects the maximum footprint. In Bellingham, detached ADUs typically require 5-foot side and rear setbacks. On a standard 50x100-foot lot, this leaves a buildable area of about 40x90 feet (minus the main house footprint). For smaller lots or lots with unusual shapes, we design compact footprints — sometimes as narrow as 16 feet wide — and use vertical space or L-shaped layouts to maximize square footage within the available area.
Can I customize a floor plan to fit my specific lot?
Absolutely — that is exactly what we do. Every lot in Bellingham has unique characteristics: dimensions, slope, orientation, setback constraints, utility locations, and relationship to the main house. We design custom floor plans optimized for your specific property rather than using generic templates. Our feasibility study evaluates your lot and identifies the best floor plan approach before any design work begins.
Find the Right Floor Plan for Your Lot
Our free feasibility study maps your buildable area and recommends floor plan types that work for your specific property.
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