What Construction Shortcuts Do Most ADU Builders Take (And How to Avoid Them)?

By Buz Artiano, BuildX | April 2026

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You are about to spend $250,000 or more on an ADU, but you realize you have no way of knowing if the company building it is even doing it right. You're not a contractor, so how in the world would you know what proper soil compaction looks like, whether insulation was installed behind the shower wall, or if the HVAC is put in the ideal place. Being unsure about all this stuff can keep people stuck because they are afraid of making mistakes that will cost them later, so they just stay stuck.

My name is Buz Artiano, and I am the founder of BuildX. We've built dozens of ADU projects across Massachusetts, mostly around the South Shore and Plymouth County areas. We are the only team you need, we handle design, permitting, and construction. So we see every phase of a project from the first site visit up until you move in. We deal with septic constraints, zoning issues, and the state's new ADU laws. After building this many units, you develop a list of things that other builders tend to skip. This article will be all about those shortcuts and what you need to know about them.

Every builder has pet peeves. Ours happen to be the construction shortcuts that cost people comfort and safety and make their new home lower quality and less durable. The shortcuts we're going to talk about aren't something we made up. They come from walking jobsites, looking at other builders' work, and seeing the same failures over and over that could have easily been prevented. This article gives you a specific checklist of things you can use to evaluate any ADU builder, whether you hire us or not.

What Are the Most Common Shortcuts ADU Builders Take?

Construction shortcuts fall into two categories: structural corners that compromise the building's long-term integrity, and finish-level omissions that reduce livability. Both matter, but structural shortcuts are harder to detect and more expensive to fix after the fact.

The structural shortcuts are things like not compacting the soil under concrete slabs and garage floors, and skipping insulation behind showers. The livability shortcuts are more things like not installing bathroom windows, leaving out linen closets, skipping closet lighting, installing doors that are too small, and using unvented microwaves. Every one of these issues just keeps showing up in ADU construction across Massachusetts, and they're all avoidable if the builder plans for them from the start.

The rest of this article breaks each shortcut down, explains why builders skip it, and tells you exactly what to ask so you can spot it before you sign a contract.

Why Do So Many ADU Garage Floors and Slabs Crack?

If you've ever walked into a garage or basement and seen a long crack running down the middle of the floor, or noticed the slab has sagged to one side, that's actually from not compacting the soil enough. This is one of the most common and one of the worst construction shortcuts in residential building, and you can't see it during construction.

The standard method to compact soil is to backfill the excavated area and run a plate compactor over the soil. Many contractors believe that compacting in six-inch to twelve-inch lifts with a plate compactor gets plenty of compaction, but it doesn't. The soil will probably feel firm on the surface, but air pockets and loose material are all trapped underneath, and over time, natural settling occurs, and the concrete slab above starts to sag and then crack.

At BuildX, we use a two-step compaction method that gets rid of this issue completely. After we compact the soil, we build a dam around the outside of the slab area and flood the whole thing with water. The water forces soil particles into the remaining air pockets and causes everything to settle while the dirt is still exposed. Then we run a concrete vibrator through the fill, poking it down every six to eight inches across the entire area. On recent projects, we've measured up to eight or nine inches of additional settling after the water-and-vibrate step, even on soil that was already compacted using heavy equipment. That's a huge amount of sag and cracking that we make sure never happens.

The only way to achieve 98 to 100 percent compaction is to use the water and vibrate trick. If your builder's compaction process doesn't include those things, ask them how they can prevent the slab from cracking five years from now. You want a builder who plans for the long term, not someone who just gets the job done, but it fails a few years down the road.

What Happens When a Builder Skips Insulation Behind the Shower?

Pre-fabricated shower units are standard and very common in ADU construction. They're efficient, cheap, and available in accessible forms. The problem is what happens behind them.

The correct order to do things in is to install spray foam insulation on the outside wall before the shower unit goes in. Once the foam cures, the shower unit can be installed up against a fully insulated wall with no gaps or leaks. Unfortunately it's more common to do it the wrong way, which is to install the shower unit first, bolt it to the framing, and then try to spray the foam insulation behind it after the fact.

Doing it that way really doesn't work well at all. When you bolt a shower unit to the wall and try to spray behind it, the foam can't get into and seal all the holes and gaps. As a result, those holes and gaps become cold spots in winter, and they trap condensation as well, which makes the whole place less energy efficient. We've seen this failure on enough projects to guarantee that if the shower goes in before the insulation, there will be gaps.

Ask your builder whether they pre-insulate exterior walls behind shower units before installation. If they tell you they spray after the unit is set, that's not a good sign.

Which Livability Features Do Most ADU Builders Leave Out?

Structural shortcuts compromise the building. Livability shortcuts compromise your everyday life in a big way. We're talking about the things that you'll notice every single day, and they're too easy for builders to shortcut them.

No bathroom window. A bathroom without a window relies on only a fan for ventilation and moisture control. In a 900-square-foot ADU where the bathroom is probably being used by an aging parent or a disabled family member, natural light and ventilation are absolutely necessary. They affect comfort, air quality, and how long your finishes like paint and cabinets will last in a room that has such high humidity.

No linen closet in the bathroom. This is a small design decision but it has a huge impact on your daily life. Without a linen closet or cabinet in the bathroom, the person living there has to walk to another room to get a towel before or after showering. When you live in a normal sized house with lots of closets, it's only a small inconvenience, but in a small ADU where every square foot of space counts, it's really more of a design fail. We install a linen closet or linen cabinet in every ADU bathroom we build. No matter what.

No closet lights. This one surprises people. If you go walk through some expensive homes in Massachusetts and check the closets, most of them don't have any lights in them. In an ADU, where the closet is probably the only storage for a person's entire wardrobe, a dark closet is the worst. Closet lights are cheap and only take a few minutes to wire during rough-in. There's absolutely no reason to skip them.

Undersized doors. Standard interior doors in most homes are 2 feet 6 inches wide. But that's too narrow for a wheelchair, a walker, or even a large piece of furniture. We install 3-foot doors in every ADU we build. The cost difference is next to nothing, but the difference it makes for accessibility is huge. If the ADU is being built for an aging parent or a family member who might need a wheelchair or walker in the future, you don't want to install 2-foot-6-inch doors because eventually you'll have to take the door off and cut into the wall with a saw to make it wide enough for a wheelchair. Plan for 3-foot doors from the start.

Unvented microwaves. An over-the-range microwave needs to be vented to the outside so it can double as a range hood. When the microwave isn't vented, the fan just recirculates cooking grease, moisture, and unpleasant smells right back into your kitchen. You turn on the fan and you can feel air blowing right back into the room from around the edges of the microwave. In a compact ADU kitchen, that's not just annoying, it affects air quality and how clean the surfaces in your kitchen are. Venting a microwave to the outside adds very little cost during construction and is almost impossible to try and add later after all the walls are closed up.

Does HVAC Placement Count as a Construction Shortcut?

HVAC placement is not exactly considered a shortcut, but putting it in the wrong place creates problems that are expensive to fix. In ADU construction, the three best places to put HVAC equipment is in the garage or basement when possible, a crawlspace, and the attic.

Placing HVAC equipment against the ceiling of a garage seems logical enough, but think about this. By installing it against the ceiling you lose height in a space that's already compact, and you have to do a bunch of special fireproofing to meet code when it's inside a garage. Moving the system to an unvented attic setup (which is sometimes called a hot roof) keeps the equipment in cooled space, doesn't sacrifice ceiling height in the garage, and it means you don't have to do extra work by fireproofing everything.

Make the decisions about where to put your HVAC equipment during the design, not later during the framing. If your builder hasn't talked to you about the placement of your HVAC stuff before construction starts, make sure you ask where the equipment is going and why. Where it goes can affect ceiling height, energy efficiency, and maintenance access.

What Should You Ask Your Builder Before Signing a Contract?

You don't need a construction background to evaluate builder quality. All you need to do is ask the right questions. All of the shortcuts we talked about give you a way to evaluate a builder by giving you the right questions to ask.

On compaction: "What is your compaction process for slab-on-grade and garage floors? Do you water and vibrate after compaction?" A builder who uses water and vibration will be happy to describe the process for you. But if they don't use this method, they will just distract from the question or they will assure you that basic soil compaction using heavy equipment is enough, but it's not.

On insulation sequencing: "Do you install spray foam behind shower units before or after you put it in?" They should say before. Any other answer means you will have an insulation void behind your shower wall.

On livability features: "What is the size of the doors you install? Do your ADUs include bathroom linen closets, closet lighting, and vented microwaves?" These should all be easy yes-or-no questions. If the builder hesitates or tells you that he can but there will be an upgrade charge, that tells you what their standard for quality is.

On HVAC: "Where do you plan on putting the HVAC equipment and why?" A builder who has thought through HVAC placement will explain their methods and what they think is best. You don't want the builder who just says they'll figure it out during construction.

You should never feel bad about asking all these questions. They're the same questions we answer for every single family we work with at BuildX. A builder who takes quality seriously will be more than happy to answer them all for you.

Are These Standards Realistic for Every ADU Budget?

Not every family has the same budget. Some of the features we talked about, like bathroom windows and linen closets, require us to add them into the design from the beginning. Others, like proper compaction, are decisions we make because they don't add much to the cost. The water-and-vibrate compaction method only takes a few hours of labor, it doesn't cost thousands of dollars. Pre-insulating behind shower units is just a question of what order we do things in, it's not a paid upgrade.

We are a design-build company, and we build to all these standards on every project we do. That means our pricing shows our level of quality. If you are comparing our quote to a builder who doesn't include this stuff, you're not comparing apples to apples. We're not trying to criticize other builders, we're just reminding you to compare everything side by side, not just the overall price. The cheapest ADU is almost never the best value if you end up having to go back later and fix cracked slabs, cut in wider doors, or add ventilation.

If your budget means you have to make sacrifices, make them on finishes, not on structural stuff. Choose a less expensive countertop before you skip good soil compaction. Choose a simpler cabinet style before you get rid of the linen closet. The features that give you comfort and durability should be the last items you get rid of, not the first thing.

Build the Checklist Before You Build the ADU

The difference between a quality ADU and a shortcut-filled one isn't always something you can see from the outside. It's under the slab, behind the shower wall, inside the closet, and at the exhaust vent above the stove. Now you know what to look for. Take these questions to every builder you interview, and let their answers guide your decision.