Accessory Dwelling Unit is now legal by Right in MA (MA ADU Law 2025)

Accessory Dwelling Unit is now legal by Right in MA (MA ADU Law 2025)

Accessory Dwelling Units Are now legal by Right in MA, as of February 2 2025. Under the new law, here are the major factors:
    1) An ADU can be
        a. no more than half of the gross floor area of the principal dwelling, or 900 square feet, whichever is smaller.
        b. internal within an existing primary residence
        c. attached to a primary residence as a new construction addition 
        d. completely detached
        e. must maintain a separate entrance

Next, municipalities are not permitted to set unreasonable restrictions on the development ADUs, like:
    a. Requiring owner-occupancy for either the ADU or the principal dwelling
    b. Imposing any minimum parking requirements that exceed:
        i. One space if the lot is outside 0.5 miles of a transit station
        ii. No additional spaces if within 0.5 miles of a transit station
    c. Limiting the number of ADUs allowed in a zoning district
    d. Requiring that ADUs only be attached or only detached from the main dwelling

Municipalities also:
    a. cannot impose stricter design, size, or zoning standards than those for single family homes
    b. cannot mandate separate utility connections
    c. cannot enforce more restrictive environmental or safety rules than state standards
    
Municipalities can:
    a. set stricter design rules in historic districts
    b. regulate or prevent ADU’s from being used as short-term rentals

Here is a more detailed list of specific unreasonable regulations:   

    I. Design Standards 
            Municipalities cannot be stricter than those applied to single-family homes.
            Regulations that increase costs excessively or make ADU construction impractical are not allowed. 
    II. Dimensional Standards 
            Setback, lot coverage, open space, bulk, height, and story limits must be equal to or more permissive than those for single-family homes.
            No minimum lot size can be required for ADU construction.
    III. Utilities, Safety, and Emergency Access 
            There can be no requirement for a separate water, sewer, or electric connection unless mandated by state law or a utility provider.
            Local emergency access rules cannot be stricter than state fire code. 
    IV. Environmental Regulations 
            Rules regarding environmental protection (e.g., wastewater treatment, stormwater management) cannot be stricter than those applied to single-family homes in the same zoning district.
            Must comply with state environmental regulations (Title 5 septic standards, etc.). 
    V. Site Plan Review 
            The process must be clear, objective, and fair.
            Municipalities cannot impose subjective conditions or discretionary reviews that hinder ADU approval. 
    VI. Impact Analysis, Studies, and Fees 
            Municipalities cannot require extra studies, reports, or fees for ADUs if these are not also required for single-family homes. 
    VII. Modular Dwelling Units 
            Prefab or modular homes used as ADUs must be allowed if they comply with the Massachusetts Building Code.
            Cities cannot impose additional restrictions just because an ADU is modular. 
    VIII. Historic Districts 
            Municipalities MAY impose stricter design and dimensional standards on ADUs in historic districts.
            However, these standards must still be reasonable and cannot outright prevent ADU construction. 
    IX. Pre-existing Nonconforming Structures 
            If a principal dwelling, existing structure, or lot is already nonconforming with zoning rules (e.g., due to setback violations), a Protected Use ADU cannot be prohibited solely for this reason, and the ADU must be allowed if it complies with the Building Code and state law.

Here is the link to the Final MA ADU regulations as of 2-2-25 in pdf form
            
Do you think these new options will hurt or enhance existing properties?

Will this allow second home owners to create staff/caretaker housing where the is none now?

What do you see happening?

Best, Heath