ADU Construction Planning in Shoreline, WA

Shoreline has its own ADU, tree and permit rules. Owners need a local planning guide rather than a Seattle page with the city name changed.

This independent guide is not the City of Shoreline or a contractor. Confirm current code, checklists and site conditions with Planning and Community Development.

What does Shoreline say about ADUs?

The City’s permit FAQ says the code allows two attached or detached ADUs on each lot. It also says zoning controls the total number of homes, including ADUs, on a property.

Shoreline’s Permit Applications page says new ADUs and conversions need a building permit. It links an ADU handout and the building-permit checklist.

Use the live pages and current handout when preparing the project. Rules and forms can change.

How should the Shoreline lot be checked?

Prepare parcel, zoning, lot and existing-house facts. Then evaluate:

• planned number and type of units.
• yards, coverage, height and building placement.
• trees and possible removal or protection rules.
• slope, drainage and retaining conditions.
• driveway, alley and side-yard access.
• sewer, water and electrical routes.
• parking and household circulation.
• easements or title conditions.

Shoreline tells owners to contact the City before removing trees and links its private-property tree rules. A tree can affect the unit’s location, access and building method. Do not clear the site from a concept plan alone.

Use the early site-check guide to record the lot evidence and unresolved questions.

Which ADU type fits Shoreline properties?

A detached backyard unit offers privacy but needs a full building and utility path. An attached unit may reduce trenches but affect the main home. A basement or garage may work. Its height, moisture, fire safety, access and systems must support legal living space.

Compare all practical paths before assuming the smallest unit is cheapest. Use the same questions from the detached ADU, attached ADU and conversion guides.

What permit and design work belongs in the quote?

The team should list the site plan, current and planned drawings, structure and energy records. Add mechanical, plumbing and tree details and other reviews. Ask who files, answers City comments and updates the issued plans.

If a standard plan is planned, confirm whether Shoreline recognizes any prior review and which site-specific documents remain. Do not describe a Seattle ADUniverse plan as Shoreline-approved without direct confirmation.

The design and permits guide supplies a duty table.

What utilities and access should be investigated?

Map the side sewer, water, power panel and rainwater path. Check whether work crosses driveways, plants or tree roots. Ask who plans service upgrades and repairs the site after trenching.

Tight access can affect machines, hauling and deliveries. An alley may help, but its condition, slope and street rules still need review. Put the access assumptions in the estimate.

Read the utilities and site-work guide before comparing “turnkey” totals.

How much should be budgeted?

Use the Seattle-area cost guide to separate site checks, survey, design and permits. Add site protection, foundation, construction, utilities, finishes, repairs and money for surprises. The Shoreline total depends on the lot and quote.

Require realistic allowances and a statement of owner-supplied items. Ask what concealed conditions or City choices would move the price. A price without tree, drainage, access or service assumptions is not a complete comparison.

How should Shoreline builders be compared?

Check the legal builder through Washington L&I and ask for recent Shoreline ADUs or similar projects. Nearby Seattle work may show building skill. It does not prove knowledge of Shoreline’s forms and tree rules.

Give companies the same site facts, plans and finish list. Use the builder comparison guide to compare design, permits, site work, utilities, exclusions, timing, payments and warranties.

Prepare a Shoreline tree-and-access sketch

On one sketch, mark the main home, ADU, large trees, driveway or alley and machine path. Add storage, utility trenches, slopes, retaining walls and drainage. This does not replace a survey or tree report. It gives the City, designer and builder the same site to discuss.

Ask whether work access or trenching affects a protected tree and whether tree review must precede final placement. If an alley is planned for access, confirm right-of-way conditions and the equipment actually assumed in the price.

What should be closed before accepting a Shoreline total?

Assign zoning, tree records, site plans, structure, energy records, trade permits and City comments in writing. The quote should list sewer, water, power and rainwater assumptions. State who pays fees and repairs.

Give every bidder the same dated plans and allowances. Resolve any difference between the selected plan and issued permit set before work begins.

Keep the tree choice, utility confirmations and access sketch with the final permit documents. Those records help the site supervisor protect the assumptions that supported approval and pricing.