ADU Builder on Cape Cod

Cottages, garage apartments and in-law suites, built by John Murray

Murray Construction is an owner-operated ADU builder on Cape Cod, based in Sandwich. John Murray is a master carpenter with more than 20 years in the trades, and he is personally on every project, from the first site walk to the final walkthrough.

An accessory dwelling unit is a small, complete home on the same lot as your house, with room for a parent, an adult child or a long-term tenant. This page covers the ADU types John builds, what to check first, how a project runs and what drives the cost.

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ADUs we build on Cape Cod

Most Cape properties suit one of four approaches, depending on your lot, your septic system and how the space will be used.

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Detached cottage: A separate small house in the yard with the most privacy. It needs its own foundation and utility runs and must fit your lot’s setbacks.
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Above-garage apartment: A unit over a new or existing garage. A new garage can be framed to carry living space above; see our garage builder services on Cape Cod.
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Attached addition: An apartment built onto the side or back of your house, sharing a wall but with its own entrance. It often reuses existing utility connections.
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Interior conversion: Turning a basement, attic or wing of the house into a self-contained unit. It changes the least outside, but headroom, egress and light have to work.

ADU construction on Cape Cod: what to check first

Since February 2, 2025, Massachusetts allows one “protected use” ADU by right in single-family zoning districts in every community except Boston. By right means you don’t need a special permit for that unit, and your town can’t require that the owner live on the property.

There are limits. A protected-use ADU can be no larger than 900 square feet or half the gross floor area of your main home, whichever is smaller. Towns can still apply reasonable rules such as setbacks and site plan review, and they may restrict short-term rental of an ADU, so plan on long-term or family use unless your town clearly allows otherwise. Your town’s building department and zoning office have the local details.

On the Cape, the real limit is often Title 5 septic capacity. Septic systems are sized by bedroom count, and a new bedroom in an ADU can push a property past what its system is approved for. Any septic upgrade is designed by a septic designer or engineer and approved by your board of health. John checks this before design money is spent. Lots near wetlands or the shore may also need Conservation Commission review.

How an ADU project with John works

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Consultation and site visit: John walks the property with you, looks at where a unit could go and flags septic, setback and access questions on the spot.
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Feasibility and design: The septic and zoning picture is confirmed first, then plans are drawn to fit the size cap, your lot and your budget.
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Written quote: You get a written quote that spells out the scope, materials and what is included.
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Permits: John handles the building permit application and coordinates with the septic designer, board of health and any other reviews your project needs.
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Build: John does the framing and carpentry himself and coordinates the licensed electricians, plumbers, HVAC installers and septic contractors the project requires.
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Final walkthrough: After inspections, you walk the finished unit with John and go over anything that needs attention.

What affects the cost of an ADU

Every ADU is priced from its own site and plan. These factors matter most:

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Type of unit: A detached cottage needs a new foundation and utility runs; a conversion uses structure you already have.
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Septic work: Whether your system can take the added bedroom or needs an upgrade designed and approved first.
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Size and layout: Square footage, number of bedrooms and whether the unit has a full kitchen and bath.
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Site conditions: Slope, ledge, access for equipment and distance to existing water, sewer or power.
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Finishes: Windows, siding, flooring, cabinets and fixtures, and whether they match the main house.

Where we build ADUs

As an accessory dwelling unit builder on Cape Cod, John works in Sandwich, Bourne, Falmouth, Mashpee, Barnstable, Dennis and nearby towns. If an ADU isn’t the right fit for your lot, adding space to the main house may be; see our home additions on Cape Cod.

Frequently asked questions

Can I build an ADU on my property?

If you are in a single-family zoning district, state law allows one protected-use ADU by right, within the size cap and your town’s reasonable rules. On Cape Cod the deciding question is often septic capacity. John looks at both during the first site visit and tells you what needs confirming before any design work.

Do you handle permits?

Yes. John prepares and files the building permit and coordinates with the septic designer or engineer, the board of health and any other review your project needs, such as Conservation Commission review near wetlands. You stay informed at each step while he handles the paperwork.

Do I have to live on the property to build an ADU?

For a protected-use ADU, Massachusetts towns can’t require the owner to live in either the main house or the ADU. Towns may still set other reasonable rules, and they may restrict short-term rental, so check your town’s current rules before planning around rental income.

Who does the septic, electrical and plumbing work?

Licensed trades. Septic work is designed by a septic designer or engineer and approved by your board of health, and electrical, plumbing and HVAC are done by licensed contractors. As the general contractor, John schedules and coordinates them so the work fits together, and he does the framing and carpentry himself.

Can the ADU match my existing house?

Yes. Matching rooflines, trim, siding and window styles is part of the design conversation from the start. As a master carpenter, John can make a cottage or garage apartment look like it has always belonged on the property, or give it its own character if you prefer.

How do I get an estimate?

Call John at (508) 648-3215 or send a note through our contact page with your town, the type of ADU you have in mind and anything you know about your septic system. He will set up a time to walk the property before preparing a written quote.

Related guides

Plan your ADU with John

Call (508) 648-3215 or send a message, and John will walk your property and talk through what it can support.

Request an Estimate Call (508) 648-3215