Accessory Dwelling Units (ADUs) - Quick Guide

Small ADU Tiny Home Unit with Green Trees in Background

Worcester has adopted zoning provisions to allow Accessory Dwelling Units ("ADUs") as of January 9, 2024! The purpose of allowing ADUs is to enable the creation and expansion of new, diverse housing opportunities intended to increase the supply of healthy, accessible, affordable and sustainable living spaces that address varied housing needs. ADUs provide flexibility for diverse housing types and enable more opportunities for intergenerational living environments and provide rental income for homeowners while encouraging the efficient use of existing housing stock.

What is an ADU? As defined by the Ordinance, an Accessory Dwelling Unit is "a self-contained housing unit which provides complete, independent living facilities for one or more persons located on the same lot as an existing dwelling unit(s), that is clearly subordinate in use, size and design to the largest existing dwelling unit(s) or principle building, and maintains separate entrances, either directly from the outside or through an entry hall or corridor shared with the principal dwelling."

Overview of Accessory Dwelling Unit (ADU) Ordinance

ADU Ordinance Adopted January 9, 2024

Use/Occupancy Restrictions

  • ADUs are allowed on all properties with one lawfully existing single-, two- or three-family residential dwelling.
  • A maximum of 1 ADU is permitted per property.
  • The owner is required to live on the property that has an ADU.
    • No more than 3 unrelated people may live in any dwelling unit in the City; except for in a lodging house.
    • The owner must record an ADU Owner's Affidavit against the property's title at the Worcester District Registry of Deeds.
  • ADUs require a certificate of occupancy to be issued.
  • The principal building and the ADU must remain in common ownership. An ADU may not be sold separately from the principal building to which it is an accessory use.
  • For any property with an ADU, dwelling units may not be rented for less than 28 days.
  • Adding an ADU to a property will not change that property's zoning classification. However, the property will need to meet the building and fire code requirements to comply with the increased number of dwelling units.

Dimensional Regulations for ADUs

  • ADUs can be in an existing building (including accessory structures - like garages), a new detached building or an addition to an existing dwelling.
  • ADUs are limited to 900 SF and up to 2 bedrooms.
  • ADUs cannot be located in the front yard. If added to the side of an existing building, the ADU must be setback 5' from the front elevation of the main building.
  • If an addition to/expansion of an existing building is proposed to accommodate an ADU, the changes must comply with the dimensional regulations for the existing use.
  • No additional parking is required for an ADU; however, existing parking may not be removed in order to create an ADU if the existing parking is needed to meet zoning requirements.
  • If a proposed ADU cannot meet these dimensional requirements, it may be permitted by  Special Permit from the Planning Board. Special Permits typically take about 3 months to obtain approval. Special permits are discretionary, meaning that there is no guarantee that a request will be approved.

Process Highlights

  • It is recommended that applicants select and hire a design professional (to draw plans that meet the relevant building and fire codes), and a contractor (to oversee the construction project).
    • You can check the credentials of your contractor or design professional online using the Massachusetts licensed professionals state licensing credentials, which can be found online at - Professional Licenses & Permits (most professionals will be listed under "Building & Trades")
    • Ask your contractors for a valid "Certificate of Insurance" before they begin any work!
  • Inspectional Services requires that the following be submitted as part of any application for an ADU building permit:
    • A to-scale architectural plan, depicting the location and gross square footage of the existing dwelling unit(s), the location and square footage of the proposed ADU and the location of all ingress and egress points from the ADU and the principal building.
    • A to-scale site plan, prepared and stamped by a MA registered professional land surveyor, depicting the required setbacks.
  • The Inspectional Services Department may require additional documentation as necessary during the permitting process.
  • If the proposed ADU exceeds the dimensional requirements, you will need a Special Permit from the Planning Board prior to permitting with the Inspectional Services Department.
  • ADUs are expensive. We encourage you to try to secure financing before starting the building permit process.
    • Contact your local bank to learn more about ADU financing options. Not all banks have a financing product that is specific to ADUs, but some do! There are several local banks with financing products that do not require you to re-finance your existing mortgage and that let you anticipate the income from the ADU unit in projecting your ability to carry the loan. Ask your bank for more information!
    • The City is exploring opportunities to provide future financial and/or technical assistance for ADUs.

If you'd like to propose an ADU, your first step is to obtain plans that show where the ADU will be located on the property in relationship to the existing dwelling. Check out our "Have a Question" section below to see if we've already answered your questions and it not, help us by Submitting Your Questions Online!

Creating an ADU Checklist

  • Submit a New/Change Street Numbering request.
  • This process takes time, so it is recommended to request a new address as soon as possible.
  • You must provide a plan that shows the location of the proposed ADU relative to the existing structure and/or floor plans showing the relationship of the proposed unit to the existing unit(s) in the building, on a plot plan.
  • All ADUs need an address to ensure emergency responders will know where the ADU is located should you ever need emergency assistance – during or after construction.
  • A special permit is needed if your ADU will not meet the setback requirements, height requirements, etc.
  • The Special Permitting process could take appoximately three months, so please plan accordingly.
  • For Water/Sewer Connections, reach out to DPW engineering at
    • You may need to upgrade your existing system or add a new connection for an ADU.
    • ADUs in detached buildings (new or existing) are likely to have a sewer connection fee of $1,650/bedroom.
  • For properties served by a septic system, you will need to provide information regarding your existing system at the time of your building permit application. Request a copy of your septic plan from Inspectional Services via email:
    • A new septic plan may need to be approved by Inspectional Services to serve any additional living space.
  • For Electric/Gas connections, you or your contractor should contact your local utility provider to place a Work Request for what is proposed (e.g., request separate metering or a new service).

Check if your property is near a wetland/stream/river/pond, in a floodplain or is the building a historic structure or in a Local Historic District. There may be additional permits from the Conservation Commission or Historical Commission that are needed before you can begin work or obtain a building permit. Contact us at to check with a planner if you are not sure.

  • A Certificate of Occupancy is the last part of a building permit process and would be generated following a successful final inspection in association with your building permit application.
  • All ADUs must have a Certificate of Occupancy - indicating the property has an ADU - in order to be considered "legal."
  • If you're not sure if an ADU is legal, contact Inspectional Services by emailing with the address for the property.
  • Visit the OpenGov Portal
  • Create a log in/account
  • Choose Building and zoning and then building permit
  • There is information about ADU's and requesting the building permit on the next page.
  • You will be required to record a copy of a notarized owner's affidavit against your title/deed to alert future purchasers that there is an ADU and that the owner is required to live on the premises.
  • Submit to-scale architectural plans and a survey/plot plan for your planned ADU
    • Your plan should show the location of the ADU relative to the existing structure on a plot plan.
    • This includes internal units and additions to existing structures and should provide a floorplan that shows the new unit in relationship to the existing unit.
  • Submit a signed Owner's Affidavit, which is required to be recorded at the Registry of Deeds (cost is $105).

Have a Question?

Note: this section is still being developed! Help us by Submitting Your Questions Online.

  • Yes, all ADUs will require a new address! If you apply for a building permit under your current address, the building permit will be put on hold and require you to create a street numbering request (SNCA) before we're able to issue a building permit for the project. To apply for a street numbering slip, you must provide a plan that shows the location of the ADU relative to the existing structure, and/or floor plans showing the relationship to other unit(s) in the building, on a plot plan. Please note that adding an ADU to your property will increase its assessed value but the property record card through the Assessor's Office will not be updated to reflect the ADU's address.

    You can Apply for a Street Numbering Slip online.

  • ADUs require a certificate of occupancy prior to use. You can obtain a copy of the certificate of occupancy for any property from Inspectional Services by emailing with the address for the property. If you don't have an occupancy certificate indicating the property has an ADU, the space that is being thought of as an ADU is not yet "legal."

  • It really depends. Adding an ADU may change the classification of a property under the building code and introduce new requirements that impact the new unit, or the entire structure related to things like life-safety including, but not limited to, egress, sprinklers and fire alarms. For example, if your proposed ADU constitutes a third unit to an existing structure, it will require Fire Protection Systems. However, each situation is unique; you should contact Inspectional Services by emailing to discuss your specific proposal.

  • It depends. While Worcester is a specialized stretch code community, the specialized stretch energy code does not automatically apply to every project. The specialized stretch energy code requirements will apply to new construction or larger renovation projects. However, each situation is unique; you should contact Inspectional Services by emailing to discuss your specific proposal.

  • It depends. ADUs located in existing dwellings with utilities may rely on their existing plumbing (water/sewer) connections. If you propose to modify your existing utilities outside of your house (e.g. upgrade the size of your water line, install a new line, etc.) you will need a permit from DPW&P Engineering. However, ADUs in detached structures will require a permit from DPW&P Engineering as you will need to make changes to the sewer outside of your house and the associated trenching for water and sewer. A plumbing permit will be required to connect the water from the primary dwelling to the ADU. Utility changes to allow ADUs - especially for detached structures require interconnection with your existing utilities and may dictate the location of your new utilities, so it's important to plan for this early in your design process.

    We recommend starting this process by contacting DPW&P Engineering to get a copy of your property's sewer connection record by emailing: Your licensed drainlayer can then Apply for a Permit from DPW&P Engineering for work online.

    Note: If you'd like your tenants to pay for their share of utilities, you can ask your licensed contractor to install a sub-meter for you to monitor their usage - but the City will continue to monitor only the existing meter and issue one bill to you as the owner for whatever units are/will be on the property.

  • Not at this time. The City is exploring opportunities to provide future financial and/or technical assistance for ADUs.

Evolution of the Zoning Amendment

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