How Long Does It Really Take to Build an ADU? (A Plymouth Family's 8-Week Build)

By Buz Artiano, BuildX | March 2026

Watch: Plymouth's First ADU | Our Life-Changing Journey with BuildX

We're sure you've heard plenty of construction horror stories. A neighbor starts an addition and it ends up dragging on for nine months, or someone's contractor just disappears for three weeks right in the middle of the project. When you search "how long does it take to build an ADU," every answer basically just says "it depends." None of that is going to help you plan your ADU. You need a real price, backed by a real project, so you can tell your parents when they can move in or figure out when your family's situation actually changes.

My name is Buz Artiano, and at BuildX we have completed dozens of ADU projects across Massachusetts, mostly around the South Shore and Plymouth County areas. We personally handle all the design, permitting, and construction ourselves. That means we control the timeline from the first drawing to the day you move in. We also effectively deal with the big things that slow other builders down, like septic evaluation under Title V, lot coverage limits, and the state's by-right ADU laws. When we give you a timeline, we've already figured in the extra time for those big variables. Most builders don't even discover those potential issues until they've already started the build.

Pam and John Myette are BuildX clients. We built their 900-square-foot, two-bedroom detached ADU at 72 Jordan Road in Plymouth for their son William. That was actually Plymouth's very first ADU, which was built before the Affordable Homes Act. We broke ground in October, and they were moving in before Christmas. The entire construction phase took 8 to 10 weeks.

You should expect a builder to want to share projects that went well. We are sharing the Myettes' story because it's the norm for our customers. Their timeline matches what we see with most of our builds, and their honesty about their experience is more useful to you than anything we could say about ourselves.

How Long Does ADU Construction Actually Take?

The construction phase for a detached ADU, from the day the excavator breaks ground to the day you receive a certificate of occupancy, typically runs 8 to 12 weeks on a BuildX project. That's the window of time where contractors are on your property, equipment is running, and your ADU turns from a hole in the ground into a beautiful finished home.

John Myette described his family's experience for us. He said "they broke ground the first week of October, and the reality of actual construction was probably 8 to 10 weeks." He said it was right on Buz's target. They were really hoping to get in by Christmas, and we were able to make that happen.

That's not the only story. On the Bartlet family's ADU in Plympton, Sherie Bartlet said that they broke ground on May 19th and moved in on August 11th. That's 84 days from excavation to move-in. Two different families, two different towns, two different seasons, and both projects were finished in about the same amount of time.

John told us that he has a lot of friends who build houses, and they couldn't believe the Myettes built one in three months.

Watch: Why This Family Built an ADU for Their Autistic Son | Plymouth's 1st ADU

Why Do Most ADU Projects Take So Much Longer?

When homeowners search for ADU construction timelines online, the results they usually get say it takes from 6 months to a year or more. That's because most of those timelines include everything like design meetings, permitting delays, septic engineering, site prep, and then the actual building. That also includes projects where contractors aren't coordinated, the builder doesn't control the schedule, or details and scope were not finalized before breaking ground.

The difference between an 8-week build and a 9-month build almost always comes down to three main things. First, whether the design was actually done and finalized before the permits were pulled. Second, whether contractors and trade work was planned out in advance. And third, whether one company owns the entire process or whether you will be working with multiple people or companies. When a homeowner hires an architect, then a permit expediter, then a general contractor, then subcontractors, there's gaps of time between all these processes and that time adds up really fast.

Pam Myette said the BuildX schedule was aggressive. She said they just got it done. John says that's because every trade flowed right into the other one. One person is done, the next one comes in immediately. That doesn't happen by accident. It requires a good team managing every phase.

What Does the Construction Phase Look Like Week by Week?

While every site has its own variables, the typical BuildX ADU construction follows a pretty consistent pattern. The Myette project in Plymouth shows how this plays out in real life.

The timeline below is what we see across our detached ADU projects on standard lots in southeastern Massachusetts. Site conditions, septic requirements, and weather can change the timeline of some of the individual phases by a few days in either direction, but the overall pattern is the same.

We compress what other builders spread across six months because we have a finalized plan in place before we start building. By the time the excavator shows up, all your materials are ordered, all the trade work is scheduled, and every inspection is on the calendar. We've been doing this a long time and we know that the number one cause of construction delays is not weather or material shortages, it's indecision. When the homeowner is still picking finishes while the framer is waiting for direction, that slows everything down. We lock in your selections during design so the construction phase keeps moving without any stops.

John Myette said "Kevin, our project manager, was on site every day." John said that every morning Kevin gave him a rundown of what they would be doing that day. The subcontractors were always on time and always very professional. All that coordination is what makes an 8-week build possible. It has nothing to do with working faster, it's all about eliminating dead time between phases.

What Happens Before Construction Starts?

The 8 to 12 week window is for the construction only. Before we even start digging, there's a whole pre-construction phase to things that includes design, engineering, permitting, and site evaluation. For most BuildX projects, all the pre-construction stuff adds several months to the total project time.

The Myettes said they were breaking ground in September to clear trees, and the actual foundation work started the first week of October. That means their pre-construction work, including design, permitting through Plymouth's local bylaw process, and site prep, was all done before October. The total time from our first conversation with them to the time they moved in was longer than 8 weeks, but the part that disrupts your daily life with trucks and equipment and workers on your property takes weeks, not months.

This makes a big difference when it comes to planning. If you are moving someone out of a nursing facility, you need to know when the ADU will be ready to move into. If you have a lease that's ending, you need a reliable move-in date. The construction timeline is the piece you can plan around most accurately, because it is the phase we control directly.