Retaining Walls & Rockeries
See also: See also: Decks, Fences, Grading Permit, Sheds
What Is It?
A retaining wall is a structure designed to support soil at a steeper angle than the soil could stand on its own; it may or may not be attached to a building. A rockery consists of placed rocks used to control soil erosion.
What Permits Do You Need?
You don’t need a construction permit if you meet all of the following three conditions:
- The rockery or retaining wall will be 4 feet or lower in height as measured from the bottom of the footing (even if under grade) to the top of the wall.
- The wall is not located in a parcel with an environmentally critical area (ECA).
- You will not damage adjoining properties or structures during or after construction of the wall.
If you don’t meet these three conditions, you need a new construction permit. For example, if you are building a wall at the property line, the potential for damage may exist and you need a construction permit.
- Tip 103, Site Plan Requirements
You may also need a grading permit depending on the amount of soil you plan to move or the area you plan to disturb.
Research the Code
- Rockeries and retaining walls don’t contribute toward your lot coverage limit. This limit is the percentage of your lot that can be covered by a house and other buildings, such as garages, or impervious surfaces, such as paving.
- You cannot build a rockery or retaining wall of any height on a parcel with an ECA unless you meet very specific requirements or obtain an exemption. Rockeries and retains walls are not eligible for small project waivers.
- Rockery designs must be prepared by a geotechnical engineer or comply with the prescriptive rockery installation design standards.
- You need a side sewer permit if you plan to install drainage behind your wall and connect it to a side sewer. See the Subsurface Drainage Systems section of Director's Rule 4-2011, Requirements for Design & Construction of Side Sewers (Drainage & Wastewater Discharges).
- If building near a property line or public right-of-way, you must ensure the retaining wall or rockery is built on your property. If you build within the right-of-way, you must follow additional requirements. See the Seattle Right-of-Way Improvement Manual for more information.
- Tip 321, Rockeries: Prescriptive Design and Installation Standards
- Tip 327A, Environmentally Critical Areas Exemptions, Relief from Prohibition on Steep Slope Development, and Modifications to Submittal Requirements
- Tip 508, Grading and Retaining Wall Construction Near or Adjacent to Property Lines
Should You Hire a Professional?
- Rockery and retaining wall drawings commonly require a professional stamp (indicating they were designed by an architect or engineer). If your rockery or retaining wall does not require a professional stamp, you can prepare the drawings yourself or hire a professional.