Aberdeen sits at the east end of Grays Harbor, where the Chehalis and the Wishkah meet the tide. It’s a working port city, and the permit picture is split. City of Aberdeen is one reviewer. Grays Harbor County is another. Hoquiam, next door, is a third with its own limits, and Cosmopolis, south across the Chehalis, is a fourth. Your mailing address doesn’t tell you which one you’re dealing with.
Our factory is in Battle Ground, near Vancouver, WA, so an Aberdeen set is a long haul: I-5 north, then US-12 west through Centralia, Elma, and Montesano. That distance shows up in the quote, and warranty visits are scheduled trips rather than same-day stops.
We have set a two-story multi-unit building here, with stacked modular pieces on one foundation. More on that job below.
City of Aberdeen, Grays Harbor County, or Hoquiam first
Look up the parcel before you sketch anything. If the lot is inside Aberdeen city limits, Aberdeen Community Development and the building department own the file. If it isn’t, you’re in unincorporated Grays Harbor County, even when the mail says Aberdeen. Lots in Hoquiam or Cosmopolis go to those cities’ counters instead.
Washington law allows two ADUs on qualifying properties in urban growth areas. The available space, utility capacity, and any protected areas still affect what you can build. Read the Washington ADU laws guide and the Grays Harbor County ADU rules guide. The city or county reviews the site plan and issues the permits. We coordinate that process for your project.
Older published city ADU language (AMC 17.47.020 in circulating zoning text) described one ADU per residential building and a size cap around 800 square feet of habitable area, with a director exception for some single-floor conversions. Inside the UGA, state law requires two ADUs on qualifying lots and prevents a local size cap below 1,000 square feet, and the statute preempts conflicting local rules. Check the current Aberdeen Municipal Code and the city’s ADU handout the week you file. A printout from before the comprehensive-plan update may be out of date.
Unincorporated county lots go through the Grays Harbor County Building Division. Zoning, septic, and environmental review vary by parcel, so there isn’t one countywide size number to quote. Well and septic limits are common west of the I-5 corridor. Don’t apply an Aberdeen city number to a county acreage lot, or county septic rules to a sewered city lot.
Setbacks depend on the zone, so we don’t quote a citywide number. Floodplain and shoreline overlays can also take a big bite out of a backyard that looks generous on the zoning map.
Flood, harbor, and the Chehalis
After jurisdiction, flood is the first site question. Aberdeen’s flood chapter (AMC 15.55) ties to the FEMA Flood Insurance Study for Grays Harbor County and incorporated areas. It covers special flood hazard areas, Zone AE along the Chehalis and Wishkah, floodway limits, and coastal flooding. Any encroachment in the floodway needs an engineer’s no-rise analysis, and new residential construction in the floodway is tightly limited.
Harbor and river-adjacent lots need a flood-map check before anyone orders a module. We don’t publish base-flood elevations. If you know your lot is in a flood overlay, mention it on the evaluation. Elevation, flood openings, and foundation type all go in the local permit packet.
Soils change from one part of town to the next. Wishkah-side lots, Chehalis-side lots, and the older downtown grid each bring their own mix of saturated silts, high groundwater, and old fill. That affects excavation and whether a crawlspace or a stem wall makes sense. Expect a geotech report more often here than on a typical suburban plat.
How Aberdeen takes a permit
Harbor files stall on flood notes more often than on design. Incomplete flood information, stormwater, and access comments are the usual reasons a file comes back. Here’s the order we work in:
- Confirm the zone allows the dwelling, using city maps and the current Aberdeen ADU materials, and confirm the lot isn’t in Hoquiam or the county.
- Plot plan: existing house, proposed cottage, the zone’s setbacks, utilities, flood information if the lot is in or near the SFHA, and a truck or crane path that works with downtown parking or a harbor-side driveway.
- Engineered modular plan set. These are modular homes under the Washington State Building Code, inspected by L&I in the factory. They ship with an L&I factory insignia and are not HUD (the federal standard for manufactured homes) manufactured homes. Aberdeen still reviews the foundation, placement, and utilities.
- Submit to the City of Aberdeen (or Grays Harbor County if unincorporated) with utility connection plans. Site prep, including grading, foundation, and sometimes flood-related elevation, is part of the job.
- Inspections as called, then occupancy. Keep the approved drawings on site.
A typical city submittal includes the application forms, a plot plan with existing and proposed structures, the engineered modular set, foundation and connection drawings, and utility letters. If the lot is in a flood or shoreline overlay, those reports go in the same packet. Aberdeen’s counter is smaller than Vancouver’s, but staff still expect a complete file.
County lots add septic design, well adequacy, and environmental review. On those parcels, the health department sign-off can decide the project before the floor plan does.
Lots we see
Downtown and the older river-town blocks can be tight, with short lots, on-street parking, and a street grid that wasn’t laid out for modules. North of the Chehalis and along the Wishkah you add grade, retaining walls, and driveways built for a passenger car. West toward Hoquiam the two cities run together on the ground but stay separate on paper. South toward Cosmopolis, the river is the line.
Harbor-adjacent and low parcels raise floodplain and geotech questions first. Upland lots still come down to sewer laterals, panel capacity, and a truck path.
Getting modules to Aberdeen
Delivery from the factory runs I-5 to US-12, then the last miles on US-101 or city arterials. Oversize timing matters, and a 12-foot-wide Model K is an easier street-use permit than a 14-foot Model E. School traffic, on-street parking, and a narrow approach off Wishkah or Heron all come up on evaluations. Downtown event days go on the schedule early so they don’t surprise anyone on delivery day.
Overhead lines, firs, and a 24-foot street with parking on both sides are the usual in-town delivery puzzle. A single-module home is a morning’s work when the path is clear. A two-piece home on a dead-end street near a school needs a different plan.
Because this is a long trip, punch list and warranty visits are scheduled in advance. We take Aberdeen jobs when the route, the pad, and the permit file make the haul worthwhile. Centralia is on the way, and Ocean Shores, farther west, is a different last mile on sand.
The multi-unit lift on the harbor
Our Aberdeen job so far was a two-story multi-unit building: four stacked modules, metal straps instead of nylon because the boxes sit tight, and a crane on a harbor-side foundation. The video is in our public library, and it shows we can lift and stack here.
A backyard cottage is a smaller file: one or two accessory units, a residential plot plan, and a last mile that may be tighter than a multi-unit pad. We point to the harbor lift as proof of crane capability, not as an ADU case study.
Models
These are modular homes, not HUD manufactured.
- Model K (~432 sq ft). Guest or rental one-bedroom on a typical residential lot.
- Model E / Model F (~616 sq ft). Two bedrooms when the zone, the flood overlay, and the slope or grid all allow it.
Inside the UGA, state law prevents a local size cap below 1,000 square feet on covered lots. That doesn’t mean every downtown lot can take a larger cottage, so measure the pad, the truck path, and the flood map first. Model L makes sense only when coverage, height, and the current size cap allow it.
ADU, tiny home, or guest house
If it has a kitchen and bath, Aberdeen treats it as a dwelling. Family use, long-term rental, and short-term lodging are separate use questions. Inside the UGA, state law dropped owner-occupancy mandates, which is why a rental ADU is an option for many owners. Short-term rental rules are still local, so don’t assume an ADU permit covers a vacation rental.
Cost and timeline
The model sets the starting home price. Trench length, flood or soils work, electrical capacity, foundation work, and the long haul set the rest. Building indoors keeps the home out of the harbor rain, but city review and site prep still drive the schedule.
The Model K starts at $85,500 for the home itself. Permitting, delivery, installation, and site work are listed separately in your property-specific proposal. A US-12 haul runs well past the 20 miles the flat delivery rate covers, so the delivery line is priced after a property evaluation. See the Washington ADU cost guide.
Utilities
Most in-city Aberdeen lots are on city water and sewer. You still need to check lateral length, cleanout location, and whether the electrical service can carry a second dwelling without a panel upgrade. Outside the city you’re often on well and septic, and county rules plus septic design usually decide those parcels. If you don’t know which you have, that’s the first thing we check.
Site work and weather
The harbor is wet most of the year. The house is built indoors, but on the lot, saturated soils, tidal influence, and winter water affect excavation and erosion control. Summer is the easier set window. Winter sets happen with tighter site controls and an eye on US-12 conditions.
Foundation excavation, trenching, grading, and minor tree work are part of a normal Aberdeen job. If the flood map requires elevation, that’s why we pull the FIRM early. We bring a standard delivery trailer, and a crane when the swing needs it. We weather-seal the same day when we can, then finish mechanical and plumbing tie-ins. Two-piece plans add a day to join the halves.
Financing is usually a HELOC, cash-out refinance, or a construction-to-permanent lender who has worked with factory-built ADUs. See financing.
What to send
An address is enough to start. Useful extras: a survey, tax-lot and zoning printout, flood-map or elevation certificate if you have one, prior building permits, photos of the backyard and the street approach, and whether the unit is for family, long-term rental, or a cottage you might live in. We check jurisdiction, zone, flood overlays, utilities, and whether a truck or crane can reach the pad.
If you already picked a model, tell us. We’ll still check it against coverage, height, the current size cap, and the flood map before treating it as the plan.
After the set
Inspections, walk-through, punch list, keys, and the warranty packet. Aberdeen inspectors sign off on occupancy for city lots, so keep the approved drawings on site until they do.
Send the address. Tell us whether the lot is in the city, the county, or Hoquiam if you know, where the building would sit, and whether it’s for family, rental, or you. We’ll match a model to your lot.
