Everything You Need to Know Before Buying an ADU in Massachusetts
Everything you'll want to know before you add a second home to your property, from the South Shore team that designs, permits, and builds ADU homes start to finish, including the first approved under Plymouth's 2024 bylaw.
Home of the 100-day build guarantee
Once BuildX breaks ground, your ADU is finished in 100 days* or less. Guaranteed, in writing.
We handle the town, you don't
Permitting, planning board, zoning, even the letters to your neighbors. BuildX manages every approval for you.
Real, stick-built homes
Every BuildX ADU is a custom home built on site. Nothing modular, nothing prefab.
Is building an ADU right for you?
Maybe you have a parent who shouldn't live alone anymore, but assisted living feels wrong. Maybe your adult kid is back home, or you want a private guest suite, or you just want to downsize without leaving the neighborhood you love.
If any of that sounds like you, an accessory dwelling unit, a second small home on your property, might be the best move you make this decade. This guide walks you through all of it: the 4 types of ADUs, the costs, the rules, and exactly how it works, in plain English.
I'm Buz Artiano, founder of BuildX, the South Shore team that designs, permits, and builds ADU homes start to finish. I have spent 40 years building homes here, and I wrote every word of this guide myself. One thing I want to be clear about from the start: we build these as homes for the people you love, not as investor units. That focus shapes every decision we make.
Why families choose BuildX
- The #1 recommended ADU builder on the South Shore
- 5.0 stars on Google reviews
- Home of the 100-day* build guarantee
- You never deal with the town. We handle every permit.
- Built Plymouth's first ADU under the 2024 bylaw
Want to know if an ADU could work on your property? Two easy ways to find out, no pressure.
If you only read one thing
- Most BuildX ADU builds take about 6 to 9 months start to finish, depending mostly on permitting, site conditions, and how quickly decisions get made.
- BuildX ADUs typically cost $284,301 to $525,861, plus site work, based on which floor plan you choose. Site work is priced after a free lot review.
- Massachusetts allows compliant ADUs by right, and BuildX handles the permitting and town approvals for you.
- BuildX designs, permits, and builds your ADU. We have a 100-day* build guarantee from the time we break ground on your project, after permitting and site prep are complete.
- BuildX builds these as homes for family, not investor units, for people who own property on the South Shore and want a real home, handled start to finish.
- BuildX is probably not your builder if you want the cheapest possible structure, or you'd rather manage permits and subcontractors yourself. We'll say so honestly.
That's the gist. Now the whole story, one piece at a time.
What's covered in this buyer's guide
Five short parts. Read it straight through, or jump to whatever you need.
Part 2 · Will an ADU work for you?
03Is a BuildX ADU right for you? 04How big can it be? 05Will my land carry it? 06We handle the town 07Matching your homePart 4 · You're in good hands
10Meet Buz Artiano 11Why BuildX 12The 100-day guarantee 13Built for life 14By the numbers 15Real families, real ADUsPart 5 · The BuildX process
16Your 10-step path 17What to expect 18Are you ready? 19Additional questions 20Let's talk 21Keep exploringThis could be you
Picture it first. The rest is just details, and we handle the hard ones.
The 4 types of ADUs
An ADU is simply a second, smaller home on your lot. It comes in 4 shapes, and we build all of them. Don't worry about picking the "right" one yet, that's what we figure out together.
Detached
A standalone little home in your yard. The most private and flexible option, and the most popular. Best when you have the space.
Attached
Shares one wall with your existing home. Often a little less expensive, one fewer exterior wall and an easier tie-in, and great on tighter lots.
Basement conversion
Turn a walk-out or full-height basement into a complete, separate living space, with its own entrance, kitchen, and bath.
Interior conversion
Carve a self-contained unit out of space you already have, such as over a garage or in an underused part of the house.
Every ADU BuildX builds is a real, stick-built home, never modular or prefab.
So which one is right for your family?
Reasons people choose to build an ADU
The reason matters, because it shapes the size, the layout, and the finishes.
Care for aging parents
Keep Mom or Dad close, independent, and safe, without the cost or distance of assisted living.
Future flexibility
A private home that adapts with your life over the years. Whatever your household needs next, the room is already there.
Room for adult kids
A landing spot for a college grad or a family member who wants to stay close while keeping their own front door.
Guest suite or home office
Space for visitors, a quiet studio, or a work-from-home setup that's genuinely separate from the main house.
Downsize, keep your land
Move into a right-sized home and pass the main house to family, or sell it, all without leaving your neighborhood.
Add long-term value
A well-built ADU adds usable square footage and flexibility that pays off whether you stay or sell.
Tell us who it's for, and we'll design it for them:
- For a parent: no-step entry, wider doorways, laundry on the same floor, and a layout that still works years from now.
- For an adult child: privacy, parking, storage, and real separation from the main house.
- For downsizing: comfort, storage, a porch or outdoor space, and accessibility features built in for later.
The real reason most people build?
To keep the people they love close.
Near enough to see every day, not just on holidays.
Will an ADU work on your property and for your lifestyle?
The honest answers to the two questions behind every ADU: will it work for me, and will it work on my property?
Is a BuildX ADU right for you?
If you saw your reason in the last section, you're already a strong candidate. A BuildX ADU is a great fit when you want a real, permanent, well-built home that adds room and value to property you already own, and you'd rather have it handled for you than wrestle with contractors and the town yourself, including planning and permitting.
And we might not be the right fit. Here's when we'll say so.
- You need space in the next few weeks. A custom ADU is a real home, about 6 to 9 months start to finish. If you need room right now, we aren't the fast option.
- You want to expand your existing home, not add a separate one. That's an addition, not an ADU, and we build those too, sometimes on the same project.
- You just need basic covered storage. If you don't need a kitchen, a bath, and a second address, a garage or outbuilding may be a better, lower-cost option.
- You want a pure rental investment. We build homes for the people you love, not investor units. That family focus is core to who we are, so an investor build isn't a good fit for BuildX.
We'd rather point you to the right answer than sell you the wrong one.
If none of those describe you, then the only real questions left are how big can it be, will my land carry it, and what will it cost. That's exactly what comes next.
How big can my ADU be?
In Massachusetts the limit is 900 sq ft or 50% of your home's gross floor area, whichever is smaller. Our minimum build is 550 sq ft. Some towns, including Plympton, Norwell and Bourne, allow larger with a variance, and we handle that conversation for you.
Big enough. Now, will your land carry it?
Will my land carry it?
This is the question people worry about most, and it's almost always a solved problem. Here's the comfortable overview, wastewater first, because that's the one that matters.
If you're on town sewer, you're in great shape, it's the simplest path and often the fastest to permit. If you're on septic, capacity is measured in bedrooms, not bathrooms, so a right-sized ADU usually fits within what your system already supports. Systems installed since the 1995 Title 5 update are usually in good shape. An older system may need an update, which is simply part of the plan we price up front, and if your tank happens to sit where the ADU would go, it can usually be relocated.
Want us to look at your lot? Book a free Project Clarity Call.
Land sorted. What about the town?
We handle the town, you don't
One of the best parts families consistently tell us about working with BuildX: you never have to deal with the town yourself. We do that. Permitting, the planning board, the zoning board of appeals and any variance, the surveying, even the letters to your neighbors, all of it is ours to manage. We prepare the permit package, respond to the town's comments, and manage every revision, so you're never stuck in the back-and-forth. By Massachusetts law a compliant ADU is generally allowed by right, and we run the entire approval process so you never chase the building department.
No paperwork on your plate. Now let's make sure it looks like it belongs.
It'll look like it belongs with your home
A good ADU doesn't look bolted on. It looks like it grew up alongside your house. A few easy ways we make it blend with your home and your property:
- Matching materials. Siding, shingles, color, and trim chosen to match your existing home.
- The right roofline. A roof pitch and style that echoes the main house.
- Windows that agree. Window shapes and proportions that feel like the same family.
- Smart placement and scale. Sited and sized so it sits naturally on the lot, not crowding it.
- Finishing touches. Walkways, plantings, and details that tie the two buildings together.
Looks handled. So what does it actually cost?
What it costs, honestly
Two numbers, both shown up front. No fairy tales, and a price that doesn't move on you.
Two numbers, no fairy tales
The question we hear most is "what's actually included?" Here's the honest answer, in two parts, so the price never moves on you.
That's the full span of our 14 floor plans. Prices include the complete building package, foundation through move-in-ready finishes. Site work is priced separately after a free lot review, so your final price is always Plan Price plus Site Work.
Your complete home, foundation to finish: design, engineering, permitting, project management, and construction. Once you sign, it does not change.
Only what your lot needs: septic or sewer tie-in, water, electric, excavation, the driveway, tree clearing. Carried at a worst-case allowance, then credited back if unused.
That's the whole formula. No surprise change orders, and we're never financially ahead of you. We give you a firm number only after we've seen your lot, at no cost, because a low number that climbs later isn't a real number.
Here's what that range looks like: 3 of our floor plans, at different starting price points
Every BuildX home starts from a floor plan like these. The plan you choose sets your Plan Price; site work is added after your free lot review.
These are 3 of our 14 floor plans; every plan is 100% customizable. Plan prices are point-in-time estimates and are updated regularly; your final price is confirmed with a current quote after your free lot review. Your site work (septic or sewer, grading, water, electric, driveway, clearing) is quoted after your free lot review and credited back if unused.
What moves the cost of your site work up or down?
| If your lot has | It usually means |
|---|---|
| An easy sewer tie-in | Lower site work |
| A septic evaluation or update | More planning, sometimes an upgrade |
| A long run to water or power | More excavation and electrical |
| Trees, slope, or a new driveway | Added site prep |
No dollar figures until we've seen your lot, but this is the shape of it, so site work feels knowable, not scary.
Want to know where your lot lands? Start with a free lot review.
How people pay
There's no single right way, and you don't need it all figured out before we talk. Most families use cash, a home equity line of credit (HELOC), a construction loan, or a blend, and some bridge the gap by selling another property after move-in.
You've seen what an ADU could be for you. Now, who makes it real?
You're in good hands
You've pictured it, and you know it fits. Here's the team that builds it, and the families who already trusted us.
The builder you'll actually work with
Buz Artiano
BuildX is more than a home builder. Building is what we do, but the relationships we create along the way are what drive us. Buz listens to your vision first, then earns your trust with a home designed around your life, not a quote pulled off a shelf.
He started framing houses in 1984, and BuildX is his third and most focused company. When Plymouth passed its ADU bylaw in 2024, BuildX built the very first ADU under the new law. Today Buz keeps 6 ADUs in progress at a time and has sat down with 160+ South Shore families. He also writes every article in our Learning Center, on one rule: if a homeowner asks, they deserve an honest answer, even the uncomfortable ones.
- 40+ years and 800+ homes built
- 18,000+ repair projects completed
- HIC licensed and GAF-certified roofer
- Built Plymouth's first ADU (2024 bylaw)
- 5.0 stars on Google
- 3-year warranty on every build
Built around you, not around a quote
The things South Shore homeowners tell us matter most, and the reasons they choose BuildX.
We handle the town, you don't.
Permitting, the planning board, the zoning board of appeals (and any variance), surveying, architecture, even the letters to your neighbors. We do all of it. By Massachusetts law a compliant ADU is generally allowed by right, and we manage the entire approval process so you never chase the building department.
A fixed price before we start
You sign a fixed-price contract, then pay only for work that's already done. No surprise change orders, and we're never financially ahead of you.
The 100-day build guarantee
About 6 to 9 months start to finish. Once we break ground, your ADU is finished in 100 days* or less, and you live in your main home the whole time.
Real, stick-built homes
Every BuildX ADU is a custom home built on site. Nothing modular, nothing prefab, full-house quality at a smaller footprint.
Built for life
Every plan includes 36-inch doorways, zero-entry showers, and single-floor living as standard, ready for a walker or wheelchair whether you need it today or years from now.
One project manager, full visibility
One dedicated project manager start to finish, with their direct number, plus live site cameras so you always know exactly where your build stands.
Designed around you
Our floor plans are starting points. Buz does all the architecture in-house, so walls move and rooms grow until it's yours. Bring your own plans and we'll build from those, too.
Not an estimate. A guarantee.
The promise families ask about most, spelled out plainly: what it covers, when the clock starts, and why BuildX can put it in writing.
How the guarantee works
Once we break ground, your ADU is move-in ready within 100 days* of the first shovel, guaranteed in writing, not aspirational marketing. We can promise it because of everything that happens before the build: by the time we break ground, your design, budget, selections, and permits are all locked. No mid-project scrambling. And you stay in your own home the whole time.
When the clock starts
Day one is the day we break ground, once your permits, selections, site prep, and construction contract are set. Town permitting (usually 90 to 120+ days) runs before that, and BuildX handles all of it.
Why we can promise it
By the first shovel, every decision is already locked: design, budget, selections, and permits. Tight sequencing, subcontractors who respect the schedule, and one project manager who keeps it moving.
What backs it
Every BuildX build carries a 3-year warranty and an 11-month check-in, well beyond the industry-standard one year.
Read exactly what the guarantee covers (and what can extend it) →
*The 100-day build clock starts at the first shovel, after design, budget, selections, permitting, and site prep are complete. If your build is going to run longer than 100 days, we will tell you the day we finish pre-construction, before we break ground, and explain exactly why. The reasons are almost always site-driven: ledge, difficult soil or grade, unusual lot conditions, or other things we can only confirm once your property work is fully scoped.
Comfortable today, adaptable for tomorrow
Every BuildX ADU is built to provide comfortable living as a standard, not as an upgrade. We do that with a few non-negotiables on every build: 36-inch doorways, zero-entry showers instead of tubs, and single-floor living, so the home works whether you need accessibility today or years from now.
That's the standard behind every build. Here's the track record behind the standard.
Built on four decades, not a sales script
A quick gut-check on who you'd be trusting with your home. These numbers reflect Buz's and BuildX's full building career across the South Shore, not ADUs alone.
South Shore homeowners, in their own words
Not stock photos and slogans, actual families who built with BuildX.
Here's exactly how the BuildX build process goes
The path from first call to move-in day, what to expect on timing, and how to take the first step.
A clear path, built around you
Project Clarity Conversation
Day one (~30 min)A real conversation, not a sales pitch: who you're building for, what you're trying to solve, and whether an ADU is even the right move. If it isn't, we'll tell you.
See a Finished ADU in Person
Within 1–2 weeksWalk through a completed BuildX ADU, touch the finishes, ask the hard questions. Most clients say this is the moment it stops feeling like a dream and starts feeling real.
Project Discovery Call
~30 min, scheduled within daysNow we get specific: your site, feasibility, budget ranges, and design ideas, making sure the vision, budget, and reality all line up. If something doesn't, we'll say so.
Site Visit
~1 hour on-siteOur builder walks your property, reading the lot, utilities, access, and setbacks, to catch anything that could blow up a budget before any money changes hands.
Proposal Review
~1 hour, in personWe sit down and walk every line, full scope, timeline, and budget guidance, with no vague items and no surprises buried in the fine print. Hard questions welcome.
Design Kickoff Agreement
Kicks off the design phaseThis launches design and engineering, your designer, engineers, and permit team get to work. It isn't the construction contract, just the green light to plan your project properly.
Budget Review & Selections
Runs through design & permittingWe review all pricing and selections together, so you see where every dollar goes, and work through anything over budget here, before you sign a construction contract.
Construction Contract
Permitting ~90 to 120+ daysWith your approved budget and selections, we sign and break ground. By now you know us, you've seen our work, and you know exactly what to expect.
100-Day Guaranteed Build
100 days or less*Move-in ready within 100 days* of the first shovel, in writing, not a goal. Tight sequencing, subcontractors who respect the schedule, a project manager who keeps it moving.
Move In Day!
The whole pointYour parent has their own space. Your adult child is out of the spare room. Your family is together, with room to breathe. This is why we do what we do.
How long it really takes
Plan on roughly 6 to 9 months start to finish. Town permitting usually runs 90 to 120+ days and we handle all of it, and once we break ground, your home is finished in 100 days* or less, guaranteed.
That's the whole path. So, where are you right now?
Are you ADU-ready?
Not a test, just a way to see where you are. The more you can check, the more ground we'll cover on your Project Clarity Conversation.
The more boxes you can check before your Project Clarity Conversation, the more ground we cover together. Don't know a few yet? Note them down, those are exactly the things we'll sort out on the call.
Additional questions people have about building an ADU
The rest of the common ones, in one place.
What if site work makes the project too expensive?
That's exactly why we review your lot before giving you a final number. If site conditions would push the project past your comfort zone, we'll tell you before you spend serious money, not after.
When do I actually have to commit money?
Steps 1 through 5 of our process, the clarity call, the in-person showing, the discovery call, the site visit, and the proposal review, cost you nothing. The first dollar changes hands at the Design Kickoff Agreement, and even that isn't the construction contract; it funds the design, engineering, and permitting work so your project can be planned properly. You sign the construction contract only after you've approved the full budget and every selection.
What does the 100-day guarantee actually cover?
The guarantee covers the construction phase: from the first shovel to move-in ready, after your design, selections, and permits are complete. Town permitting (usually 90 to 120+ days) runs separately, and we handle all of it. If pre-construction scoping shows your build will run longer than 100 days, for site-driven reasons like ledge, difficult soil, or unusual lot conditions, we tell you before we break ground and explain exactly why. Read the full guarantee details here.
Are these stick-built or modular?
Every BuildX ADU is a traditional, stick-built home, built on site. Nothing modular or prefab.
Can I customize the plans, or bring my own?
The plans on our site are starting points. Buz does all the architecture in-house, so rooms move, walls shift, and porches get added until it's right. If you already have your own plans, we can build from those.
What's the difference between an ADU and an addition?
An ADU is a self-contained living space with its own entrance, kitchen, and bath, capped at 900 sq ft / 50%. An addition expands your existing home and isn't bound by that cap. We do both, and can combine them on one project.
Can I rent it out?
We build ADUs as homes for the people you love, not as investor units, and that focus is a big part of what makes a BuildX home feel like home. Massachusetts protects long-term rental of a compliant ADU statewide. Short-term, Airbnb-style rental is different: state law lets each town restrict or prohibit it, and some towns, including Plymouth, do. Either way, rentals aren't what we design or build for.
Does an ADU add value to my property?
Yes. A finished ADU adds real, lasting value, and even an ADU-ready lot is increasingly sought after across the South Shore.
What foundation options are there?
Three: a standard 44-inch crawl space; an oversized 6 ft 7 in crawl space (tall enough to stand in for storage, but just under the height that would count against your square footage); or a full basement where the town allows it.
Ready to take the first step?
Start wherever feels right: see one in person, or just have a low-key conversation about your property. No pressure, any time.
No pitch and no obligation, either way. A tour shows you the space and a real sense of cost; a call walks through your property, who it's for, your timeline, and how you'd pay.
Real Families · Real Reviews · Real ADUs
This guide is a starting point, not the whole story
We've covered the big questions here. When you want to go deeper, it's all a click away, at your pace, no pressure, no pitch.