Typical Lot Size
3,500–6,000
sq ft
Max ADUs
2
per lot
Permit Type
type_i
Timeline
4-6 weeks
Median Home Price
$500,000–$700,000
Est. ADU Rent
$1,400–$1,900/month
Neighborhood Overview
The Lettered Streets neighborhood sits between downtown Bellingham and Western Washington University, making it one of the city's strongest rental markets. Dense urban lots and established housing stock make basement and attached ADUs particularly attractive here.
Dense, urban, walkable neighborhood with a mix of historic homes, apartment buildings, and student housing. Close to downtown, WWU, and multiple transit routes. Active street life.
ADU Construction Allowed
Lettered Streets qualifies for ADU construction under Bellingham's updated ordinance (BMC 20.10.036) and Washington's HB 1337.
- Detached ADUs (DADUs) allowed
- Attached ADUs allowed (basement, addition, above-garage)
- Up to 2 ADUs per lot
- Parking exempt (near transit)
Transit routes: Multiple WTA routes — downtown transit center nearby
Why Build an ADU in Lettered Streets
- Prime rental location between downtown and WWU — strong year-round demand
- Walkable to shops, restaurants, and employers — no car needed for tenants
- Multiple transit routes provide parking exemptions for ADU construction
- Older homes often have spacious basements eligible for the 5-year size exemption
- Established rental market with proven ADU demand
Special Considerations
Some of the smallest lots in Bellingham — detached ADU placement can be challenging
Tight setbacks on narrow lots may limit options to attached or basement conversions
Student rental market means seasonal vacancy patterns (lower demand in summer)
On-street parking is competitive — transit exemption is a significant advantage
Learn more about ADU regulations: Review Bellingham ADU laws, understand the permitting process, or see the complete cost breakdown for Whatcom County.
Ready to get started? Our free feasibility study analyzes your specific parcel in 48 hours.
Frequently Asked Questions
What ADU type works best in the Lettered Streets?
Due to compact lot sizes (3,500–6,000 sq ft), basement conversions and attached ADUs are the most popular choices in the Lettered Streets. Many older homes have generous basements that qualify for the 5-year size exemption, allowing conversions over 1,000 sq ft without a conditional use permit.
How much rental income can I expect from a Lettered Streets ADU?
Lettered Streets ADUs typically rent for $1,400–$1,900/month depending on size and finishes. The proximity to WWU and downtown ensures strong demand, though you may see slightly lower occupancy during summer months when students leave.
Do I need to provide parking for my ADU?
No. The Lettered Streets neighborhood is well within the ½-mile transit proximity zone, so no off-street parking is required for ADU construction. This is a major advantage on compact lots where every square foot counts.
Can I build a detached ADU on a small Lettered Streets lot?
It depends on your specific lot dimensions and setbacks. While challenging on lots under 4,500 sq ft, it's possible on larger or corner lots. Our feasibility study measures your exact buildable area and recommends the best ADU type for your parcel.
