Accessory Dwelling Units

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New Regulations Approved

Regulations for accessory dwelling units were approved by City Council on Sept. 5, 2023. Detached accessory dwelling units (ADUs) were historically only allowed in the Old Town Residential zone district. The new regulations permit ADUs in most zone districts that allow single family dwellings and expand the types of ADUs to also include attached/interior units. Some basic design standards are required. No changes are proposed for the underlying standards for accessory buildings or accessory dwelling units (e.g., height, setbacks). The ordinance approving the regulations may be found in the document library to the right.

Access a handout of the new regulations in the document library to the right.

Need more information? Please feel free to contact staff or schedule a meeting with City staff by selecting a date and time through our online scheduler (External link).

Summary of New Regulations

  • Expanding Beyond Old Town: The new regulations expand the availability of ADUs to most zones that currently permit single-family dwellings.
  • Expanding the Palette of ADUs: The new regulations allow different types of ADUs, including detached ADUs (which were already allowed in Old Town), units that are attached to the main home (“attached”), and units within the main home (“interior”).
  • Design Standards: Basic design standards are established.
  • Allowing Under Existing Rules: No changes are made to the underlying standards for accessory buildings or accessory dwelling units (e.g., height, setbacks).

What is an Accessory Dwelling Unit?

An Accessory Dwelling Unit (or "ADU"), is a small independent living space on the same lot as a primary residence. It typically includes a kitchen and bathroom. These are sometimes referred to as mother-in-law suites or carriage houses. Detached ADUs are currently allowed in the Old Town Residential zone district.

What is the Accessory Dwelling Unit Project?

This project takes a fresh look at the appropriateness and potential locations for different types of accessory dwelling units in Lafayette. It is a temporary step taken in anticipation of a comprehensive revamp of the Land Use Code in 2024. The proposed regulations, if implemented, would give certain homeowners the option to construct an ADU on their property, as long as they meet existing standards related to size, location, lot coverage, and other factors.

New Regulations Approved

Regulations for accessory dwelling units were approved by City Council on Sept. 5, 2023. Detached accessory dwelling units (ADUs) were historically only allowed in the Old Town Residential zone district. The new regulations permit ADUs in most zone districts that allow single family dwellings and expand the types of ADUs to also include attached/interior units. Some basic design standards are required. No changes are proposed for the underlying standards for accessory buildings or accessory dwelling units (e.g., height, setbacks). The ordinance approving the regulations may be found in the document library to the right.

Access a handout of the new regulations in the document library to the right.

Need more information? Please feel free to contact staff or schedule a meeting with City staff by selecting a date and time through our online scheduler (External link).

Summary of New Regulations

  • Expanding Beyond Old Town: The new regulations expand the availability of ADUs to most zones that currently permit single-family dwellings.
  • Expanding the Palette of ADUs: The new regulations allow different types of ADUs, including detached ADUs (which were already allowed in Old Town), units that are attached to the main home (“attached”), and units within the main home (“interior”).
  • Design Standards: Basic design standards are established.
  • Allowing Under Existing Rules: No changes are made to the underlying standards for accessory buildings or accessory dwelling units (e.g., height, setbacks).

What is an Accessory Dwelling Unit?

An Accessory Dwelling Unit (or "ADU"), is a small independent living space on the same lot as a primary residence. It typically includes a kitchen and bathroom. These are sometimes referred to as mother-in-law suites or carriage houses. Detached ADUs are currently allowed in the Old Town Residential zone district.

What is the Accessory Dwelling Unit Project?

This project takes a fresh look at the appropriateness and potential locations for different types of accessory dwelling units in Lafayette. It is a temporary step taken in anticipation of a comprehensive revamp of the Land Use Code in 2024. The proposed regulations, if implemented, would give certain homeowners the option to construct an ADU on their property, as long as they meet existing standards related to size, location, lot coverage, and other factors.

Q&A

Please share any questions you may have and City staff will reply in about two business days. Note that both the question and answer will be posted on this page for others to view.

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  • Share The non-old height seems really low. at 16' for the ADU unit it means the unit cannot be placed on top of a garage. Is that the correct height for an non- oldtown ADU unit? Is that average of all corners to corner eves or to peak? on Facebook Share The non-old height seems really low. at 16' for the ADU unit it means the unit cannot be placed on top of a garage. Is that the correct height for an non- oldtown ADU unit? Is that average of all corners to corner eves or to peak? on Twitter Share The non-old height seems really low. at 16' for the ADU unit it means the unit cannot be placed on top of a garage. Is that the correct height for an non- oldtown ADU unit? Is that average of all corners to corner eves or to peak? on Linkedin Email The non-old height seems really low. at 16' for the ADU unit it means the unit cannot be placed on top of a garage. Is that the correct height for an non- oldtown ADU unit? Is that average of all corners to corner eves or to peak? link

    The non-old height seems really low. at 16' for the ADU unit it means the unit cannot be placed on top of a garage. Is that the correct height for an non- oldtown ADU unit? Is that average of all corners to corner eves or to peak?

    mtstarr asked 8 months ago

    Thank you for the question. Yes, the height limit for detached ADUs was kept at 16' outside of the Old Town Residential zone district. We did expand the types of ADUs to also include interior and attached units, which would fall under the primary structure height limit (likely 27' depending on your location). Descriptions of those can be found in the handout under the "documents library" above. 

    The method for measuring building height may be found here under "b". Please don't hesitate to reach out to us any time if you have questions or need additional information. 

    Phil Kleisler

    303-661-1265

  • Share I'm planning a detached ADU in my back yard in Old Town. The existing sewer line goes from my house straight back to the main city sewer line that is buried within a 10' easement that crosses the back of my property. I actually got to see the line when the neighbor whose property backs onto mine replaced their sewer line and had it all dug out within my easement. My existing line is 3", which is big enough for my house but will need to be upgraded to 4" from where the new ADU drain joins it to the city sewer line, about 25 feet. I have done a sewer line replacement in the past in Boulder (with inspection), so I'm planning to install as much of the new line as possible. I will have it all dug out around the main sewer connection, if allowed. What part of the final connection do city personnel do, and what is the cost? Of course this will all be with proper permits for the ADU work. on Facebook Share I'm planning a detached ADU in my back yard in Old Town. The existing sewer line goes from my house straight back to the main city sewer line that is buried within a 10' easement that crosses the back of my property. I actually got to see the line when the neighbor whose property backs onto mine replaced their sewer line and had it all dug out within my easement. My existing line is 3", which is big enough for my house but will need to be upgraded to 4" from where the new ADU drain joins it to the city sewer line, about 25 feet. I have done a sewer line replacement in the past in Boulder (with inspection), so I'm planning to install as much of the new line as possible. I will have it all dug out around the main sewer connection, if allowed. What part of the final connection do city personnel do, and what is the cost? Of course this will all be with proper permits for the ADU work. on Twitter Share I'm planning a detached ADU in my back yard in Old Town. The existing sewer line goes from my house straight back to the main city sewer line that is buried within a 10' easement that crosses the back of my property. I actually got to see the line when the neighbor whose property backs onto mine replaced their sewer line and had it all dug out within my easement. My existing line is 3", which is big enough for my house but will need to be upgraded to 4" from where the new ADU drain joins it to the city sewer line, about 25 feet. I have done a sewer line replacement in the past in Boulder (with inspection), so I'm planning to install as much of the new line as possible. I will have it all dug out around the main sewer connection, if allowed. What part of the final connection do city personnel do, and what is the cost? Of course this will all be with proper permits for the ADU work. on Linkedin Email I'm planning a detached ADU in my back yard in Old Town. The existing sewer line goes from my house straight back to the main city sewer line that is buried within a 10' easement that crosses the back of my property. I actually got to see the line when the neighbor whose property backs onto mine replaced their sewer line and had it all dug out within my easement. My existing line is 3", which is big enough for my house but will need to be upgraded to 4" from where the new ADU drain joins it to the city sewer line, about 25 feet. I have done a sewer line replacement in the past in Boulder (with inspection), so I'm planning to install as much of the new line as possible. I will have it all dug out around the main sewer connection, if allowed. What part of the final connection do city personnel do, and what is the cost? Of course this will all be with proper permits for the ADU work. link

    I'm planning a detached ADU in my back yard in Old Town. The existing sewer line goes from my house straight back to the main city sewer line that is buried within a 10' easement that crosses the back of my property. I actually got to see the line when the neighbor whose property backs onto mine replaced their sewer line and had it all dug out within my easement. My existing line is 3", which is big enough for my house but will need to be upgraded to 4" from where the new ADU drain joins it to the city sewer line, about 25 feet. I have done a sewer line replacement in the past in Boulder (with inspection), so I'm planning to install as much of the new line as possible. I will have it all dug out around the main sewer connection, if allowed. What part of the final connection do city personnel do, and what is the cost? Of course this will all be with proper permits for the ADU work.

    William asked 11 months ago

    Hello,

    Thank you for the question. All work for a sewer line replacement back to the main and a new ADU on your property is required to be completed by contractors that are licensed with the City of Lafayette. A permit will be required for both for the sewer line (including a Building Permit and a Right of Way Permit) and for the new ADU.  

    Here’s the process in a nutshell. The contractors will complete the replacement of the sewer line, including the connection to the City main. Upon completion, the contractors will schedule an inspection for the Building Permit and Right-of-Way Permit. The Building Permit includes the replacement of the sewer line from the property line to the connection with the existing house line and can include a branch to the new ADU if it is being completed at the same time as the ADU. The Right-of-Way Permit includes the replacement of the sewer line from the property line to the connection with the City main line, or simply the connection to the City main line if the main is on your property.

    Typically, your contractors will take care of obtaining permits and they can reach out to buildingpermits@lafayetteco.gov for more information.

  • Share It appears that a detached ADU requires the same extensive building permit application as, for instance, an addition. Your staff have told me that a soil test is not necessary if the addition uses the same type of foundation as the existing house (and that it is performing adequately). Would the same waiver term apply to detached ADU? It's significant since I've been quoted a price of $2000 to soil testing. Also, I assume that structural plans must be stamped by an architect or structural engineer, as with other building permits? on Facebook Share It appears that a detached ADU requires the same extensive building permit application as, for instance, an addition. Your staff have told me that a soil test is not necessary if the addition uses the same type of foundation as the existing house (and that it is performing adequately). Would the same waiver term apply to detached ADU? It's significant since I've been quoted a price of $2000 to soil testing. Also, I assume that structural plans must be stamped by an architect or structural engineer, as with other building permits? on Twitter Share It appears that a detached ADU requires the same extensive building permit application as, for instance, an addition. Your staff have told me that a soil test is not necessary if the addition uses the same type of foundation as the existing house (and that it is performing adequately). Would the same waiver term apply to detached ADU? It's significant since I've been quoted a price of $2000 to soil testing. Also, I assume that structural plans must be stamped by an architect or structural engineer, as with other building permits? on Linkedin Email It appears that a detached ADU requires the same extensive building permit application as, for instance, an addition. Your staff have told me that a soil test is not necessary if the addition uses the same type of foundation as the existing house (and that it is performing adequately). Would the same waiver term apply to detached ADU? It's significant since I've been quoted a price of $2000 to soil testing. Also, I assume that structural plans must be stamped by an architect or structural engineer, as with other building permits? link

    It appears that a detached ADU requires the same extensive building permit application as, for instance, an addition. Your staff have told me that a soil test is not necessary if the addition uses the same type of foundation as the existing house (and that it is performing adequately). Would the same waiver term apply to detached ADU? It's significant since I've been quoted a price of $2000 to soil testing. Also, I assume that structural plans must be stamped by an architect or structural engineer, as with other building permits?

    Bill asked about 1 year ago

    Thank you for the question.  A soil report will not be required for an attached ADU, provided that:

    • the portion of the attached foundation is the same type as the existing foundation, 
    • the existing foundation is determined by the Structural Engineer to be performing adequately, and 
    • the engineer provides a letter certifying that the existing foundation is performing adequately.  

    Detached ADUs need to include a soil report if there is a new foundation that is not replacing another. 

    All structural plans are required to be stamped by a structural engineer. All architectural plans need to be designed and stamped by an architect or other similarly qualified professional. Please also ensure that the plans include details for the fire rated separation walls as well as the independent climate control systems.

    You are welcome to contact Michael Stitt at Michael.stitt@lafayetteco.gov or Linda Lee at buildingpermits@lafayetteco.gov directly with any more questions and they will be happy to help you with the permit and inspection process. Thank you for your interest in building in Lafayette.

Page last updated: 13 Mar 2024, 10:07 AM