Millbrae Share Retaining Walls: When Is A Building Permit Required?

Millbrae CA

01 March, 2021

5:25 AM

Description

Press release from the City of Millbrae: February 27, 2021 Some of the most important projects for homeowners are landscaping their front and back yards. Often in Millbrae, this landscaping requires the use of retaining walls, especially in cases where homeowners want to cut back sloping grade in their rear or side yards. The City of Millbrae has some requirements based on State building codes that property owners should consider when installing a retaining wall. The main purpose of building permits and State and local building code compliance are to protect the health, safety, and general welfare of the public. Non-compliant construction can lead to property damage or other potential adverse impacts caused by structural collapse, improper shoring, landslides, and general deterioration. What is a retaining wall? A retaining wall is a structure that is designed to uphold soil behind it. This allows for changes in the grade of a plot and flat areas to be used for building structures or backyard features. Several factors must be considered in order to build a safe and the proper retaining wall. For example, property owners will need to determine the properties of the soil, the elevation and slope of the ground, and what the height of the wall needs to be. These factors will determine what type of wall is needed and how it should be designed. A variety of wall types, such as poured concrete walls, concrete or masonry block walls, sheet pile walls, and others, can then be designed and built to achieve the desired outcome. For taller walls, it is necessary to utilize a soil engineer or geologist to ensure the surcharge of the soil is retained by the proper type of retaining wall and built within standard engineering practices. Is a permit necessary? When remodeling a home or property, a permit is usually required when additions, alterations or new construction is involved. If property owners are considering building a retaining wall, a permit will be needed if the wall is over 48" tall. In some cases, an engineering plan will be required for the project, so please check with the City's Building Division before starting work. Specific to building a retaining wall, there are several key features property owners should note, that will always require permitting: If the total height of the wall and footing exceeds four feet measured from the bottom of the footing to the top of the retaining wall; If there is any back slope adjacent to the retaining wall; If surcharge load conditions exist (buildings, roads, vehicle loads or sloped conditions); and/or, If solid fences are attached or adjacent to the proposed retaining wall. What are tiered retaining walls? Use of tiered walls is a special condition where two or more short walls, horizontally offset from one another, are used in lieu of a single tall retaining wall. When tiered walls are not properly offset from each other, the upper wall may impose a surcharge condition on the lower wall. In order for the walls to be treated as a separate retaining wall, a general guideline is that the tiered walls need to be horizontally offset by a minimum distance of two times the exposed wall height of the lower wall. For example, two tiered retaining walls, each with an exposed wall height of three feet and level backfill, that are horizontally offset by a distance of two feet would be treated as a single six-foot tall wall. As a result, a building permit would be required This press release was produced by the City of Millbrae. The views expressed here are the author's own.