How Long Does It Take to Build an ADU? Timeline From Deposit to Move-In

By Buz Artiano, BuildX | January 2026

One of the main things homeowners want to know when they are considering an ADU is how long the entire process takes. Which makes sense, of course you want to know when your parents can move in, when the rental income starts, or simply when the disruption and construction on your property ends.

After all the ADUs we have built throughout Massachusetts, we have refined our process to deliver very predictable timelines. At BuildX we offer a 100-day build guarantee from the day we break ground. That is not some lame marketing promise either. It is a commitment we track on every project, and the majority of our builds actually finish in around 80 to 85 days.

What Is the Total Timeline From Start to Move-In?

The complete ADU timeline from your first deposit to being move-in ready is usually 6 to 8 months. As you now know, there are 2 separate phases to building an ADU.

So for example, if you signed a pre-construction agreement in January 2026, you would likely move in somewhere between June and August 2026. The exact timing can vary a little, depending on timing on permit processing in your town or area, whether you need septic work, and how complex your project is.

What Happens During the Pre-Construction Phase?

Pre-construction is where we do all the planning before any construction can start. This phase typically takes 60 to 120 days and includes several different processes.

How Does the 100-Day Build Guarantee Work?

Our 100-day guarantee starts the day we begin digging your foundation, so when construction actually begins. From that moment, you have a firm commitment from us: 100 days to move-in. But it IS important to remember that if your project will take longer than 100 days, we tell you before you sign the construction contract. We might say your job will be 110 or 120 days because of a complicated driveway, or ledge in the ground, or maybe a tie-in to your existing home. Bottom line is, you will know the timeline before committing. But for the most part, most of our builds finish faster than 100 days. Our recent Freetown project was completed in 82 days. The longest build we have ever done was 120 days, and we communicated that timeline upfront.

What Makes a 100-Day Build Possible?

The secret to a fast, predictable build is having everything planned and ordered before construction starts.

During pre-construction, we sit down and go over and finalize every detail such as cabinets, flooring, siding, roofing, windows, and doors. Everything is figured out before we ever break ground. We are never going to come to you mid-project asking what roof color you want when roofers arrive the next day.

The day you sign the construction contract, we order everything right away. Windows, doors, framing, electrical wiring, plumbing fixtures, roofing, siding, all of it. Our suppliers know they need to hold materials until we need them. The only two things we cannot pre-order are insulation and drywall.

Doing it this way serves two purposes. It locks in pricing because material costs fluctuate, and it eliminates the delays that plague other builders who order materials after construction starts.

What Are the Construction Milestones?

Construction follows a pretty standard set of milestones. Here is the usual order of things.

After framing, each phase typically takes one to two weeks. We work consistently, there is no stopping and starting. The only time we pause is when we are waiting for inspections.

How Can You Track Progress During Construction?

Once we sign the construction contract, you receive access to our Job Tread portal. You get a login and can install the app, which lets you track all our progress right from your phone.

You also have a dedicated project manager. This person stays with your project from planning stages all the way through the final walkthrough. They attend site meetings, get to know your family, and understand all the details of your build. There is never an awkward handoff where a stranger shows up to manage your job.

How Does the Payment Schedule Align With the Timeline?

Payments are only made after work is completed. You can look at your project and verify the work is done before paying. The structure works like this:

What Can Extend the Timeline?

While we control construction timing tightly, there are still certain things for the pre-construction that are outside our control:

Ready to Lock In Your ADU Timeline?

The sooner you start pre-construction, the sooner we can reserve your spot on our calendar. Right now, we typically have openings a few months out, but those slots fill quickly as other homeowners move through their pre-construction phases.

If you want to discuss your property and get a realistic timeline for your project, reach out to schedule a site visit. We will walk your lot, talk through any complications, and give you a clear picture of when you could be handing keys to your tenant or welcoming your parents home.