Why Does a 100-Day ADU Build Depend on Picking Everything Up Front?

By Buz Artiano, BuildX | November 2026

Watch: Behind the Build: ADU Construction Walkthrough

Your builder tells you he can build your ADU quickly, then hands you a list of decisions about rooms you haven't designed yet. Locking in a whole bunch of decisions before anything has even been built feels rushed and unnecessary. So most families just end up deciding everything about the structure, and put off deciding about finishes until they can really get a good view of the space. Not too long after that, the schedule they were quoted starts getting stretched longer and longer, and they can't figure out why that's happening.

My name is Buz Artiano, founder of BuildX. We have built dozens of ADUs across Massachusetts, concentrated on the South Shore and Plymouth County, and we do all of the design, permitting, and construction. So we're the ones ordering the materials, coordinating different contractors, and working through the Massachusetts rules about septic evaluation, lot coverage limits, and reviews. When decisions aren't made, we are responsible for that.

We'll explain a little better. The 100-day build isn't a number that we throw out and then hope that we can really finish in that time. We are able to hold to that 100 days because of the work we do before anything starts being built. Once you see how that determines the schedule, you'll have a much better understanding of how a builder's timeline works.

Why Does the 100-Day Build Depend on Decisions Made Before Day One?

The secret to the 100-day build is to pick everything right at the beginning. Choose all your finishes, have your plan with all the details worked out before the construction even starts. That's not just the way we like to work, it's essential to the 100-day build guarantee.

Once we break ground, we guarantee completion in 100 days. Having final decisions isn't the only thing that makes that possible. It also comes down to permits, site prep, and making sure we've fully evaluated and mapped out your property. But your selections are a big part of what the schedule depends on, because we order everything before we even start digging so there are no slow downs because we're waiting for materials. Our plans are designed and all the choices are settled up front so we can give you accurate pricing and timeline, that's what the schedule is built on.

The way we describe it on site is simple. You don't fly the plane while you're building it. You obviously build the plane first. The 100 days depends on everything being finalized before construction starts.

When Does the 100-Day Clock Actually Start?

The guarantee starts on the day we start digging and ends when the ADU is move-in ready. But that starts after your permits, selections, site prep, and construction contract all finalized. Pre-construction, the phase where design, budget, and selections are finished before any digging starts, doesn't count towards the 100-days, and town permitting doesn't either. And as a reminder, we handle all that for you, you never have to deal with permitting yourself. You can take all the time you need coming up with a finished plan, the 100 days only starts once everything is final and we start digging.

Everything is written down before you sign anything, and that only happens after you've approved the full budget and selections, and the contract price is fixed. Some properties make a 100-day build impractical though. If we find ledge or other site conditions during pre-construction, we tell you before you sign that because of the conditions of your lot, your build will take 110, 120, or even 130 days, and we put that number in your quoted timeline from the very beginning, you'll never be surprised. The full terms are laid out in BuildX's 100-Day ADU Build Guarantee: What It Covers and What Can Extend It.

Measuring the timeline from when we start digging also explains why we are often able to finish in less than 100 days. We measure the timeline for all of our jobs the same way, from digging to move-in day.

What Does One Open Decision Do to the Schedule?

Windows are the most clear example of this. We order windows the day you sign the construction agreement, because the lead time starts when the order is placed, not when we start building. If a crew frames the shell of an ADU in a week and then has to wait six weeks for windows, that's five weeks of progress you've lost. Until the windows are in, the building is not weather-tight, which means we can't put in the insulation or drywall, and all the trades like plumbing and electrical can't come in and do what they need to do either. If you haven't decided on all the windows you want, including whether the bedroom gets a slider, then we can't put in the order.

Kitchens work the same way. Cabinet boxes are built around a drawing, and the drawing is built around the appliance that was drawn into it. An appliance picked during pre-construction has plenty of time to be delivered on time. But if you order late or change your mind about an appliance after the cabinets are ordered, then the cabinets have to be changed and that takes quite a bit of time.

That's why a decision that's made too late or changed part way through costs the schedule weeks. The cost of a late decision comes from everything that comes after it that's being held up.

Am I Rushing If I Lock Every Selection Before Construction Starts?

We understand why you would feel that way. Choosing finishes for a room that doesn't exist yet feels like you're just guessing and hoping for the best, which feels worse than just waiting. But rushing a decision and locking a selection early are two completely different things, and it actually works the opposite way than you might think.

Before construction starts, revisiting a decision is still cost effective even though a change at that stage can still cost money for extra design time or a re-done drawing, the difference is, construction hasn't started, so no crew is standing around waiting on you to make a decision. Once the frame is up, if you change your mind you'll be holding up crews and trades. The rush that people don't want is created by deferring decisions until later, not by deciding before construction.

During pre-construction we work through cabinets, flooring, siding, roofing, windows, doors, plumbing fixtures, and finishes with you. Insulation and plasterboard quantities are finalized after we measure everything on site, everything else gets ordered ahead of time. When the build starts, we've made a solid plan with you and materials have been ordered so everything runs smoothly and on schedule. You're sure about what you are getting, down to the price when we start digging.

What Did Picking Everything Up Front Look Like on a Real Build?

George is a BuildX client. We built his 900-square-foot ADU with a two-car garage underneath in Plymouth, and we did a walk through with a camera with him when we were about half-way through construction. That's the point in time where people have the hardest time seeing the vision of the finished project and when they will usually have questions or complaints, so we asked him directly at this time whether there was anything we could have done better.

His answer: "Honestly, no. Everything, like I said before, was so smooth. You know, all the process, you know, we had no idea what we were getting into as far as construction goes. I mean, no one in our family is in construction."

If you've never built anything, that last line applies to you as well. The reason his build went smoothly wasn't because he had construction experience, we already know he didn't. They had a smooth build because all the decisions were made before construction started. His ADU was finished in 98 days from digging to move-in. That is the secret to a happy project, and that's how we end up with happy customers.

When Is Locking Everything Up Front the Wrong Call?

You should expect us to argue for the way we do things, but we'll tell you when it's not the right fit. Locking in all the selections before we start construction is how we are able to stay on a tight schedule, but that's not necessarily the right process for everyone.

If you are not ready to decide on certain things, don't do it just to stay on a scheduled start date. If you're still working out whether a parent is moving in or not, or you haven't decided how many bedrooms you want, you should spend some more time in the design phase and not rush things and start a little later. Beginning construction when decisions aren't all settled only gives you the worst of both worlds: a rushed decision and a stalled build.

Some homeowners also want to think about their choices over a few months so that they're really sure about what they want. They want to see the framed space, and decide on things while they are standing in it. That is a legitimate way to build, and it can produce a beautiful home just like our method does, but it just won't be a 100-day build, and a builder who tells you that you can have it both ways is not being truthful with you.

How Do You Get Your Plan Ready Before the Clock Starts?

The choice isn't about fast vs slow, it's about when you make your decisions. On paper a change costs very little, and the timing is yours to set. Once framing starts, you have no control over the timing anymore.

If you want a schedule you can plan a family around, the work that earns it happens before anyone breaks ground, and that is the part we can start with you now.

What Would It Take to Lock Your Plan Before Ground Breaks?

We will walk your property, work through your plan and every selection with you, and tell you before we break ground whether your build fits inside 100 days.