How Lynnwood Handles Accessory Structures: A Practical Guide

Lynnwood maintains 26 local ordinances across all categories, and 3 of those deal specifically with accessory structures. Here is a breakdown of what the city actually requires, what is prohibited, and where Lynnwood falls on the strict-to-permissive spectrum compared to other cities.

Shed Rules

Sheds and accessory structures in Lynnwood must comply with LMC zoning setback requirements and the Washington State Building Code (WAC 51-50). Small sheds under 200 sq ft may be exempt from a full building permit but must still meet setback requirements. Contact the building division to confirm.

Key details: Code: LMC Title 21; WAC 51-50. Permit Exemption: Possible under 200 sq ft (confirm with building dept.). Setbacks: Must comply with residential zone requirements. Contact: Building Division: 425-670-5410.

Unpermitted structures receive a notice to either obtain a retroactive permit (with double fees) or remove the structure within 60 days. Fines of $100–$500 apply for non-compliance.

Garage Conversions

Garage conversions to habitable space or ADUs require a building permit under WAC 51-50. Conversions must meet habitability, energy code, and zoning requirements. HB 1337 (2023) facilitates ADU conversions with reduced design and impact fee restrictions.

Key details: Permit Required: Yes — building permit (WAC 51-50). ADU Conversion: Facilitated by HB 1337 (2023). Standards: Energy code, habitability, setbacks. Contact: Building Division: 425-670-5410.

Unpermitted garage conversions face fines of $500–$2,000, mandatory permit acquisition (double fees), and may need to be restored to garage use if code requirements cannot be met.

ADU Rules

Washington State HB 1337 (2023) requires Lynnwood to allow up to 2 ADUs per single-family lot. Detached ADUs in Lynnwood can be up to 1,200 sq ft and 16 ft tall; above-garage ADUs may reach 18–20 ft. No owner-occupancy requirement under HB 1337 (effective for Snohomish County cities ~May 31, 2025). Building permit required.

Key details: State Mandate: HB 1337 (2023) — RCW 36.70A.680. Max Detached ADU: 1,200 sq ft, 16 ft tall. Above-Garage ADU: Up to 18–20 ft. No Owner-Occupancy: Required (HB 1337 preempts).

Unpermitted ADUs face stop-work orders and removal or legalization requirements. Fines of $500–$2,000 apply for unpermitted construction. Properties with illegal ADUs may face title issues at sale.

The Bottom Line

Lynnwood's accessory structures rules are a mixed bag. Some areas are strict, others are relaxed, and the details matter. The best approach is to check the specific rule that applies to your situation rather than assuming Lynnwood is broadly strict or permissive.

This guide is based on Lynnwood's current municipal code. Local rules can and do change, so check the individual ordinance pages for the latest details, penalties, and FAQs.