Commercial & Multi-Family Rooftop Solar Power Permitting

Rooftop solar installations on commercial and multi-family structures are routed through a detailed plan review process and are not eligible for over the counter permitting. Submittals require Design Review approval by our Land Use Planning Department, Electrical and Structural Plan Review, as well as review by the Fire Marshal’s Office.

Prepare

Discuss required applications, associated fees and, review timelines with the Customer Service Team at the Permit Counter. The Permit Services Team can be reached at 206-275-7605 or by emailing epermit.tech@mercerisland.gov. 

Select a contractor, and make sure that they have a Mercer Island Business License. 

Required Permits & Approvals

The following permits and approvals are required prior to work beginning on the project. 

1. Design Review Approval
2. Building Permit
3. Electrical Permit
4. Fire Permit

Required Forms

1. Development Application - 
   This is the application form associated with the Design Review Approval. Select "Design Review (Code Official)". See fee associated with this Land Use application here.
2. Building Permit Application
3. Electrical Permit Application
4. Fire Permit Application

Required Documents

1. Project Narrative - The project narrative should describe the proposed development and briefly describe how the project complies with the applicable Design Standards in the Land Use Code. (See Additional Information section below for more information about Design Standards.)
2. A Construction Plan Set, including:
   1. Site plan: Show the proposed structure where the system will be installed; boundary lines of the property, required setbacks from property lines and exterior edges of buildings, etc.
   2. Plan view layout of proposed photovoltaic system
   3. Sections and details of code compliant layout of panels, roof attachment and panel installation.
   4. Structural design and existing roof plan information, as needed to demonstrate structural compliance with the International Building Code.
   5. Electrical system design and layout

Formatting Requirements for the Plan Set - Submit electronic plan sheets formatted to print to scale on 11”x17” (or larger) paper.  Drawings should be to a scale that is legible and easily reviewed.  Plan sheets should be merged into a single PDF document, with each sheet bookmarked with Sheet Number and Description.  Click here to learn how to add bookmarks using Adobe Acrobat DC.

1. Supplemental Information and Spec Sheets
   1. Electrical Specifications
   2. Equipment Specifications
   3. Structural Reports or Calculations, as needed to demonstrate structural compliance with the International Building Code

Submit these documents as individual PDF files. You do not need to bookmark these documents.

How to Apply

Submit your plans, forms and supplemental documents to the Mercer Island Permit Submittal Portal.

Additional Information

1. Building-Mounted solar installations are Appurtenances regulated by Design Standards in Title 19 of the Mercer Island City Code (MICC).
   1. For projects within the Town Center, see MICC 19.11.030 (A.5)
   2. For projects outside of the Town Center, see MICC 19.12.060 (B.2)
2. Installations on existing buildings are subject to the International Existing Building Code. New installations on existing buildings are typically a Level 2 Alteration under IEBC 2015 Section 504. All relevant requirements of a Level 2 Alteration should be met, including Section 807 in its entirety. Section 807 requires, in part, that "Existing structural elements supporting any additional gravity loads as a result of the alterations... shall comply with the International Building Code. For the purpose of investigating the exceptions to 807.4 and 807.5 respectively, note that the 5 and 10% respective increases are to any "element," and not to the building overall.
3. Submittal items related to the solar array and existing building structures must be prepared and stamped by a WA state registered design professional. If this structure is a "significant structure" per RCW 18.43.020, that design professional must be a registered Structural Engineer per RCW 18.43.040.
4. Learn more about connecting to the electrical grid and net metering at this PSE webpage.