ADU Construction Planning in Shoreline, WA

Shoreline’s fresh Maps results were unusually sparse for one principal query, which supports a dedicated location page. The page still needs to solve a local planning job rather than simply attract a city keyword.

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

What does Shoreline say about ADUs?

The City’s permit FAQ says the zoning code allows two ADUs on each lot and that they may be attached or detached. It also says zoning affects the number of houses, including ADUs, that can be placed on a property.

Shoreline’s Permit Applications page says a building permit is required to construct an ADU or convert existing space. The page links an ADU handout and directs applicants to 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:

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

Shoreline’s FAQ warns owners to contact the City before tree removal and links private-property tree regulations. A tree decision can affect the ADU footprint, access and construction method. Do not clear a site based only on a concept plan.

Use the feasibility guide to record the lot evidence and unresolved questions.

Which ADU type fits Shoreline properties?

A detached backyard unit can preserve independence but needs a complete structure and utility path. An attached addition may reduce some trenching while directly affecting the main home. A basement or garage conversion can reuse space if height, moisture, fire, access and building systems support legal occupancy.

Compare all realistic paths before treating the smallest apparent construction area as the cheapest. The detached ADU, attached ADU and conversion guides use the same decision framework.

What permit and design work belongs in the scope?

The provider or design team should identify the site plan, existing and proposed drawings, structural work, energy documents, mechanical and plumbing information, tree material and other required reviews. Ask who submits, answers corrections and updates the issued construction set.

If a standard plan is proposed, 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 responsibility table.

What utilities and access should be investigated?

Map the side sewer, water service, electrical panel and stormwater path. Determine whether work will cross driveways, landscaped areas or tree-root zones. Ask who coordinates service upgrades and restores the property after trenching.

Tight residential access can affect equipment, hauling and material delivery. An alley may help, but its condition, grade and right-of-way rules still need review. Include 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 feasibility, survey, design, permits, site protection, foundation, building work, utilities, finishes, restoration and contingency. A Shoreline-specific total depends on the lot and proposal.

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

How should Shoreline builders be compared?

Verify the legal contracting entity through Washington L&I and request recent Shoreline ADU or comparable infill projects. A nearby Seattle project may be useful construction proof, but it does not prove familiarity with Shoreline’s forms and tree review.

Give providers the same property facts, plan basis and finish schedule. Use the builder comparison guide to normalize design, permits, site work, utility work, exclusions, schedule, payments and written warranty documents.

Prepare a Shoreline tree-and-access sketch

Mark the main house, proposed ADU, significant trees, root-protection assumptions, driveway or alley, equipment route, material staging and utility trenches on one current sketch. Add known grades, retaining features and drainage direction. The sketch does not replace a survey or arborist work, but it lets the City, designer and builder discuss the same physical constraints.

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

What should be closed before accepting a Shoreline total?

Require written responsibility for zoning confirmation, tree material, site plan, structure, energy documents, trade permits and City corrections. The proposal should identify sewer, water, electrical and stormwater assumptions and state who pays fees and restoration.

Use a dated drawing and allowance schedule for every bidder. Resolve any difference between the selected plan and the issued permit set before construction begins.

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