US ProPaint & Renovation handles the accessory dwelling unit ADU Cohasset MA homeowners are requesting. That includes detached backyard cottages, attached in-law suites, and garage conversions, from design and permitting through final inspection. Based in Hingham and working across Norfolk County, we deliver a code-compliant, move-in-ready unit. Every build is backed by a 2-year workmanship warranty and over 23 years on the South Shore.
By JR Reis, Owner, US ProPaint & Renovation · Last updated July 2026
Clients ask what an accessory dwelling unit is before anything else, and the answer shapes every decision that follows. An ADU is a fully self-contained residential unit with its own kitchen, bathroom, and separate entrance. It sits on the same lot as a primary single-family home. There are three main forms. These are internal conversions, attached additions that share a wall with the main house, and fully detached structures like a backyard cottage. Our ADU service page covers each type in detail, including when one form fits your lot better than another.
In Cohasset, many properties are large Colonial and Cape-style homes on generous lots, so all three types are viable. The right choice depends on a few things. Specifically, these include your existing utility access, your setbacks, how much the primary residence can support structurally, and how much separation the future residents want.
Yes, and they are easier to build now than ever. Under the Massachusetts Affordable Homes Act (Chapter 150 of the Acts of 2024), the rules changed on February 2, 2025. ADUs up to 900 square feet are now allowed by right in single-family zones statewide. As a result, Cohasset homeowners no longer need a special permit or variance for a standard ADU. The Building Department now processes the application administratively.
Cohasset has also adopted ADU-L (Large) provisions under its own local zoning amendments, which allow units up to 1,250 square feet on qualifying lots. That is a meaningful jump above the state’s 900 sq ft baseline, so it opens more design options for homeowners who need extra space. A few local rules matter upfront. First, no ADU in Cohasset may serve as a short-term rental. Second, every unit needs a separate entrance that meets state egress code.
However, on smaller in-town lots, particularly near the Beechwood neighborhood and along Jerusalem Road, your lot may still be undersized against setback or coverage limits. In that case, you may need a variance. We assess that at the initial site visit before any money changes hands. For projects that don’t meet the ADU definition, our home additions service follows a different permitting track. We handle permits ourselves and have worked through the Cohasset process on multiple South Shore projects.
Clients want to know how much it costs to build an ADU before they commit to a site visit. In practice, a realistic answer depends on the type. Here is the current South Shore market pricing by category.
Several South Shore factors also affect cost beyond those averages. For example, Cohasset properties outside the municipal sewer zone need a Title V septic evaluation. As a result, if the existing system cannot support another bedroom, upgrades typically add $15,000–$35,000. Rocky ledge is common along this coast too, so hitting granite during excavation adds cost and schedule time. Finally, the Massachusetts Stretch Energy Code adds roughly 5 to 8% to insulation and HVAC costs, though it lowers long-term utility bills on a rental unit. We include all of these variables in our written estimates. Contact us for a free site evaluation and an itemized breakdown with no obligation.
How long it takes to build an ADU in Cohasset depends mostly on which phase runs longest. In Massachusetts, that is almost always permitting. A straightforward detached ADU typically runs 6 to 10 months from first site visit to certificate of occupancy. Here is how our process breaks down.
Attached and internal ADUs typically run 4 to 7 months because site work is far lighter. In addition, we provide a written project schedule at contract signing, so there are no surprises about where the time goes.
US ProPaint & Renovation is an ADU builder South Shore MA contractors know. That is because JR Reis has run projects on this coast for over 23 years. So when clients search for the best ADU builder on the South Shore MA, our record is what they find. It includes over 2,500 completed projects and a 4.8-star Google rating across 157 reviews. As one South Shore homeowner, Kevin Caravella, put it, we are “much more than a painting contractor.”
As an in-law suite contractor Norfolk County families rely on, we understand what multi-generational builds require. A basement ADU for an aging parent needs more than code compliance. For example, it needs proper ceiling height, step-free entry where the lot allows, and noise separation from the main living space. We build to those standards by default. In addition, every ADU includes a 2-year workmanship warranty. We also offer a financing program for qualified homeowners, so the investment does not have to be all cash.
We hold Massachusetts Contractor License #186517 and comply with the Stretch Energy Code and all applicable state and local requirements. Our own crews handle foundation and framing, because we do not subcontract structural work.
When you search for ADU construction near me around Cohasset, you are already in our primary service area. Our Hingham base also means we can reach detached or attached ADU projects across Norfolk County quickly, often the same day you call.
We serve Cohasset, including North Cohasset, Beechwood, and the Sandy Beach area. Beyond that, we cover Hingham, Scituate, Norwell, Marshfield, Duxbury, Hull, Kingston, and Plymouth. Some homeowners have already worked with us on deck construction or deck repair. For them, ADU work follows the same approach: upfront scope, a written schedule, and no surprises at the invoice. You can also read our home addition guide to see how ADU projects compare to a standard addition before your consultation.
An ADU is a self-contained residential unit with its own kitchen, bathroom, and separate entrance, located on the same property as a primary single-family home. ADUs come in three forms. They can be detached, attached as an addition sharing a wall, or internal, like a converted basement or in-law suite.
Yes. As of February 2, 2025, ADUs up to 900 square feet are allowed by right in single-family zones under the Massachusetts Affordable Homes Act. Cohasset also permits ADU-L units up to 1,250 square feet. All units need a separate entrance and cannot be short-term rentals. In addition, setbacks, coverage limits, and septic capacity may affect feasibility on a specific property.
Generally, costs run roughly $100,000 to $200,000 for internal conversions, $150,000 to $250,000 for attached ADUs, and $225,000 to $375,000 for detached builds. South Shore factors like Title V septic, ledge removal, and Stretch Energy Code compliance affect the final number. We provide free estimates with a full written breakdown.
Most ADU projects in Cohasset take 6 to 10 months from site evaluation to certificate of occupancy. The three main phases are design and permitting (8–14 weeks), foundation and framing (4–8 weeks), and interior build-out (6–10 weeks). Internal conversions typically run 4 to 7 months because site prep is minimal.
Yes, as a long-term rental under a standard lease of 30 or more days. Cohasset’s bylaws prohibit ADU use as a short-term rental such as Airbnb or VRBO. Under current state law there is no owner-occupancy requirement, so you do not need to live on the property to rent the ADU to a tenant.
US ProPaint & Renovation, Inc. 175 Derby St STE 4 Hingham, MA 02043 Phone: (617) 922-6305 Toll Free: (800) 964-0717 Hours: Mon–Fri 8:00 AM–5:00 PM | Sat 8:00 AM–3:00 PM Serving Cohasset, Hingham, Scituate, Norwell, Marshfield, Duxbury, Hull, Kingston, Plymouth, and surrounding Norfolk County and Plymouth County communities.
