Three Common ADU Mistakes New England Homeowners Make — and How to Avoid Them

Short answer? Yes, ADUs can be a huge win. They add space, flexibility, and real value. But only if you avoid the mistakes that trip most people up. And trust me, I’m seeing the same three problems over and over.

Here’s what to watch out for—and how to keep your ADU project smooth instead of stressful.

1. Assuming the New State Law Overrides Local Rules

A lot of homeowners hear “by-right ADUs” and think that means anything goes. Not quite.

Yes, the state now requires towns to allow at least one ADU. But each town still controls the details:

• Size limits

• Setbacks

• Parking

• Where it can be located

• Whether it can be detached

• Height restrictions

  
  

This is where people get blindsided—because every town is a little different.

🔥 What to do instead: Before you start drawing plans or calling builders, get clear on your town’s exact rules. A five-minute check can save you thousands of dollars and weeks of headaches.

2. Underestimating the Real Cost

This one is huge. Many homeowners go into an ADU project thinking it’s a $60K job. But remember—an ADU is a fully functioning home:

• Plumbing

• Electrical

• HVAC

• Proper foundation

• Insulation

• Fire and safety code considerations

  
  

Depending on size and layout, real costs often land closer to $150K–300K. And the fastest way to blow the budget? Overbuilding the ADU with high-end finishes that don’t add meaningful value.

🔥 What to do instead: Get multiple bids from builders who actually specialize in ADUs. Keep finishes simple and functional unless you’re targeting a premium rental.

3. Designing for “Right Now” Instead of the Next 10–20 Years

Today you might be building an ADU for a parent. Next year, you might want rental income. Five years later, a buyer may want it for an adult child, a nanny, or downsizing.

Most ADU regrets come from designing too narrowly:

• Units that are too small

• Layouts that don’t age well

• No storage

• Too many stairs

• Odd floorplans that turn off buyers

  
  

🔥 What to do instead: Plan a flexible layout. Include aging-friendly features. Think long-term usability. A smart design today increases your resale value tomorrow.

Thinking About an ADU on the South Shore?

If you’re curious whether your property qualifies—or you want the right connections to trusted ADU builders—reach out anytime. The new Massachusetts rules are creating real opportunities for homeowners, and the right plan makes all the difference.