Home Additions in Marysville

Permit applications for room additions and DADUs in Marysville go through Snohomish County PDS — not the city, not Seattle SDCI. Most housing in 98270 and 98271 was built between the mid-1990s and mid-2000s during Marysville's growth surge. Those homes are hitting their limits — three bedrooms, one bath, no dedicated home office, no real space for a multigenerational household. Plenty of those lots qualify for a detached ADU under WA HB 1337, which statewide now allows two ADUs per single-family lot. Getting the site plan right on first submission matters because a bounce-back from Snohomish County PDS resets the plan review clock entirely, adding weeks before framing even starts. A Mitsubishi mini-split handles heating and cooling in a new addition without extending ductwork through finished walls.

The older blocks around Comeford Park and the State Avenue downtown corridor hold housing from the 1940s through the 1960s — post-and-pier foundations, smaller lots, some original galvanized plumbing still in service. Those homes need a structural and foundation assessment before any second-story addition reaches the drawing stage. Vertical loads change everything when the original framing was spec'd for single-story living, and a structural engineer needs to sign off on supplemental footing pads and LVL beam sizing before Snohomish County PDS opens a plan review file. East Marysville in 98271 is a different story. Out there, housing shifts to 1990s and 2000s ramblers on larger parcels: slab-on-grade construction, builder-grade framing, more room on the lot for a DADU footprint. Setback and FAR calculations still apply — PDS enforces those regardless of HB 1337 — but the structural approach is simpler when you're adding horizontal square footage rather than going vertical on a foundation that was never designed for it.