What are the requirements to build ADU in San Mateo City?
Constructing an ADU in San Mateo enables you to expand your living space and support multigenerational living or provide a separate area for aging in-laws. For a successful project, it's crucial to understand San Mateo's specific local regulations and thoroughly evaluate the financial aspects of construction. This guide provides comprehensive insights into San Mateo's ADU regulations and critical financial considerations, aiding you in effectively planning and executing your project.
Number of ADUs on a property
How many ADUs can you build in San Mateo?
In San Mateo, properties with an existing or proposed single-family residence can only construct 1 ADU.
How many ADUs does San Mateo allow for multifamily properties?
Multifamily properties in San Mateo are allowed to have a maximum of two detached ADUs. Additionally, within existing multifamily structures, non-livable spaces can be converted into one or more ADUs, provided these conversions do not surpass 25% of the total units.
Setbacks for an ADU
What are the setbacks required for an ADU in San Mateo?
San Mateo requires a minimum 4-foot setback from the side and rear lot lines for all new ADU construction. Additionally, the setback from the front lot line should meet the requirements of the lot's underlying zone district.
What is the minimum distance the ADU must be from existing structures?
In San Mateo, there is no specific minimum distance set by the city that ADUs should be from existing buildings. However, it is common for cities to require a minimum distance of 6 feet between ADUs and existing structures.
Are setbacks required if converting existing structures into ADU?
No setbacks are necessary when converting existing structures into ADUs in San Mateo.
Find out FREE if the zoning designation for your property allows you to build an ADU
The size of ADU for properties with a single-family home
How big can an attached ADU be in San Mateo?
The size of an attached ADU in San Mateo is determined by the floor area maximum imposed by the underlying zoning district and the remaining floor area allowance on the lot. If the lot's floor area allowance is fully applied, only a state-exempted "by right" ADU of up to 800 square feet is allowed.
How big can a detached ADU be in San Mateo?
The size of a detached ADU in San Mateo is subject to the same conditions as attached ADUs.
Is there a minimum size of an ADU?
There is no minimum size requirement for ADUs in San Mateo.
Can you convert existing space to an ADU?
Yes, converting existing space into an ADU is allowed in San Mateo.
The size of ADU for properties with a multi-family home
How big can an attached ADU for a multifamily building be in San Mateo?
In multifamily properties, the dimensions of an attached ADU in San Mateo are based on the maximum floor area allowed by zoning rules and the remaining space on the lot. If the lot is fully used, only a state-exempted "by right" ADU of up to 800 square feet is allowed.
How big can a detached ADU for a multifamily building be in San Mateo?
For multifamily buildings, the size of a detached ADU in San Mateo follows the same regulations as attached ADUs.
Can you stack detached ADUs on top of each other?
No, stacking detached ADUs on top of each other is not allowed. The regulation allows for adding an ADU above an existing detached structure, such as a garage, but it does not permit stacking one detached ADU on top of another.
Can you attach two ADUs to each other?
No, attaching two ADUs together is not acceptable in San Mateo. While regulations allow for up to two ADUs on a property with an existing multifamily building, they cannot be attached to each other according to current regulations.
Can you convert existing space to an ADU?
Yes, in San Mateo, converting existing space within a multifamily dwelling into an ADU is allowed.
The height for ADU
What is the max height for an ADU on a property with a single family house?
The tallest an attached ADU can be on a single-family property is 24 feet to the top plateline and 32 feet to the roof peak, measured from existing ground level. For a detached ADU, the height limit is 16 feet to the top plateline and 24 feet to the roof peak, measured from the existing ground level as well.
What is the max height for an ADU on a property with a multifamily building?
The maximum height for an ADU in San Mateo on a property with a multifamily building follows the same requirements as those for a single-family property.
Can you build a 2-story ADU in San Mateo?
Yes, you can build a 2-story ADU in San Mateo.
The parking requirements for ADU
What is the parking requirement for an ADU in San Mateo?
Each ADU in San Mateo should have a minimum of 1 off-street parking space, following specific size and location criteria. Exemptions from this requirement apply if the ADU is within walking distance of public transit, situated in a historically significant district, integrated into an existing primary residence or accessory structure, located in an area with required on-street parking permits unavailable to ADU occupants, or within one block of a car share location. Additionally, if no parking space is required, one off-street parking space per ADU may be voluntarily provided.
Where can a parking space be located?
Parking for the ADU in San Mateo can be set within the required setbacks in the front, side, and rear yard areas. Moreover, if a garage, carport, or covered parking structure is removed or converted into an ADU, replacement off-street parking is not necessary.
Design requirements for ADU
How many bedrooms can an ADU have in San Mateo?
San Mateo does not provide specific guidelines regarding the number of bedrooms for ADUs. However, in many cities within California, ADUs typically have at least 1 bedroom unless they are proposed as studio units.
Does an ADU need a kitchen in San Mateo?
In San Mateo, ADUs typically require a full kitchen, unlike JADUs, which may have an efficiency kitchen.
Does an ADU require independent utility meters?
It depends. If an ADU is built within existing space, independent water, sewer, or power connections may not be necessary. However, if the ADU is built outside of existing space, the city may require new or independent utility connections.
What is the minimum ceiling height?
In San Mateo, habitable spaces such as ADUs should meet the minimum ceiling height requirement of 7 feet, as required by the California Building Code.
Get the size of the ADU possible to build on your property after applying all these regulations
Permits for ADU
How long does it take to get an ADU permit in San Mateo?
Getting an ADU permit in San Mateo usually takes about 8 weeks, involving a plan check process before the permit is issued. This timeline is similar to that of many other cities in California.
When do you need a licensed professional to design an ADU in San Mateo?
In San Mateo, it's advisable to engage a licensed professional, like an architect or engineer, to design an ADU, especially if exploring unconventional construction methods.
Does San Mateo require in-person submission of plans for an ADU?
In San Mateo, in-person submission of plans for an ADU is not required. Instead, applicants can securely submit building permit and planning applications online through the Customer Self-Service Portal (CSS) on the city's Online Permit Center.
Does San Mateo require coastal development permits?
Yes, San Mateo requires coastal development permits.
Economics of ADU
How much does it cost to build an ADU in San Mateo?
Building an ADU in San Mateo typically costs around $380 per square foot, covering expenses such as permits, architectural design, and engineering services. For instance, constructing a 900-square-foot ADU would amount to about $390,000, including both soft and hard costs.
Is it profitable to build an ADU in San Mateo?
To determine the profitability of constructing an ADU in San Mateo, it's essential to compare construction costs with local real estate market values. For example, a 900-square-foot ADU could potentially have a market value of around $700,000. Given the construction cost of $390,000, this suggests a potential return on investment of about 80%.
Additionally, factors influencing profitability may include potential rental income or the advantages of accommodating family members on the same property.
Can you sell an ADU in San Mateo?
In San Mateo, the sale of an ADU may be feasible under state regulations like AB 1033, which also allows for conversions into condominiums, potentially requiring the establishment of a Homeowner Association (HOA) for management.
Are ADUs rent controlled in San Mateo?
Rent control isn't imposed on ADUs in San Mateo. Landlords can annually adjust ADU rents in line with regulations like AB 1482, which typically apply to properties aged 15 years or older.
How to get money to build an ADU in San Mateo?
To acquire funding for building an ADU in San Mateo, individuals may consider utilizing resources like the CalHFA’s ADU Grant Program. This initiative offers grants of up to $40,000, which can cover expenses such as architectural designs, permits, and site preparation. These funds aim to support the establishment of ADUs as an affordable housing solution in the area.