What's Included in the Price of a BuildX ADU?

By Buz Artiano, BuildX | January 2026

When a Massachusetts homeowner starts thinking about building an ADU, one of their first questions is: what's actually included in the price? It is a fair question, but one that rarely get a straight answer. ADU price quotes can vary dramatically between builders due to scope differences, not just quality differences. One builder might include site prep while another leaves it out. One quote includes appliances while another does not.

At BuildX, we believe transparency builds trust. We have constructed dozens of ADUs in Massachusetts and we've heard every version of "I thought that was included" from homeowners who worked with other builders. This article outlines exactly what's included in our pricing, what costs extra and why, and how to read any builder's quote so you can compare apples to apples.

What's Included in Our Base ADU Price?

Our ADU packages range from $284,301 to $525,861 based on their size and how they are configured and will include everything needed to give the homeowner a complete, code-compliant ADU accessory dwelling unit that is move-in-ready.

Architectural Plans and Design

Naturally, everything starts with the architectural plans because every ADU starts with a design. With the base price are the full architectural plans for your specific lot and requirements, including complete architectural drawings, structural engineering, interior layout and finish specifications, and compliance documentation for building codes.

In our experience, good architectural plans include not just code information but also structural drawings that ensure the ADU can actually be framed correctly.

Permits & Engineering

The permitting process is where many ADU projects can get stalled. Our base price includes all standard building permits and the engineering work that is necessary to get them.

In our experience, permitting, site work, and utility coordination are the most common items excluded from base ADU pricing.

• The building permit application process and all included fees
• The zoning compliance review
• Standard structural engineering
• Compliance to the energy code (stretch code where applicable)

Foundation

Foundation types will vary depending on the ADU design and the different site conditions. Our base price will include a standard foundation that is suited to your chosen type of unit.

Proper foundation prep is critical. The walls need to be ground, holes patched, and everything scraped clean. Skipping this step can lead to major leaks and mold issues years later.

• Slab-on-grade, crawl space, or a full basement depending on the model chosen
• Concrete work and reinforcement
• Waterproofing and vapor barrier
• Installation of foundation drainage system

Framing & Structural Work

The framing and structural work is the actual skeleton of your ADU: walls, roof, and everything that makes it stand up.

• The exterior and interior wall framing
• Framing and sheathing of the roof
• Installation of window and door rough openings
• Sheathing and house wrap

Electrical Rough-In & Finish

Electrical work is one of the most important and strictly regulated aspects of any ADU.

In our experience, you want to work with someone who understands the bigger picture, including energy usage incentives and utility interconnection requirements.

• A 200-amp panel (or sub-panel as appropriate)
• All the wiring, outlets, and switches
• All light fixtures (builder-grade standard)
• Smoke and CO detectors
• The bathroom exhaust fans

Plumbing Rough-In & Finish

Plumbing connects your ADU to the necessary water and waste systems. Decades of valuable expertise go into new construction plumbing to ensure everything is done right.

• All supply and drain lines
• A tankless or standard water heater
• Hookups for the kitchen sink, faucet and dishwasher
• Toilet, vanity, shower/tub fixtures for the bathroom
• Hookups for the washer and dryer

HVAC (Heating & Cooling)

Climate control is an important feature of every ADU.

• A mini-split heat pump system for heating and cooling
• The proper sizing for the size of your unit
• All the ductwork or line sets
• A thermostat

Insulation

The energy codes in Massachusetts are strict and getting stricter. So proper insulation is essential for both comfort and to maintain compliance to code.

• The wall cavity insulation
• The attic/ceiling insulation
• Insulation for floors (if applicable)
• Air sealing

Drywall & Interior Finishes

Once the rough work has been completed, we will finish the interior.

Color trends have shifted over the last couple of years, with blues and greens becoming popular choices for interior paint.

• Installation and finishing of drywall
• Painting the interior walls and ceiling of the ADU
• Addition of all trim and moldings
• Installation of interior doors and hardware

Flooring, Cabinets & Countertops

Every ADU is a custom piece. Even with the same layout, the specific finish selections make each one unique.

• Laying LVP or tile flooring (standard selections)
• Installation of the kitchen cabinets
• Installation of either laminate or entry level grade quartz countertops
• Installation of the bathroom vanity

Exterior Finishes

• Vinyl, fiber cement or 'per design' siding
• Architectural shingled roof
• Windows and exterior doors
• Installation of all gutters and downspouts
• Installation of outside light fixtures

What's Not Included In The Standard Price? What's Additional And Why

There are certain items that are not included in the base pricing because they can change a great deal depending on the property. Including them in a "standard" price would either raise the base prices unrealistically or leave the homeowner with unexpected costs later.

Included vs. Additional: Quick Reference

Site Work & Excavation

Every prospective ADU site is going to be different. Some lots are flat and ready to build on, but others need lots of leveling, tree removal, or retaining walls.

Site work involves permitting for construction projects, working with regulations like Title V, zoning, and planning board requirements.

Utility Connections

The process of connecting your ADU to water, sewer, and electricity will involve trenching, permits, and sometimes additional fees from the utility company. The cost depends on the distance from your existing connections and also whether your lot already has municipal sewer or septic.

Septic System Upgrades

If your property is on a septic system, this is often the factor with the biggest cost variable.

If your system is functioning and meets current Title V regulations, that is the best scenario because modifications are possible. If it is non-conforming or non-functioning, that is the worst scenario and you basically have to start over.

Premium Finish Selections

Our base price will include quality, builder-grade finishes but upgrades are available to quartz countertops, hardwood floors, custom cabinetry, or high-end fixtures at an additional cost.

Why Do ADU Builder Quotes Differ So Much?

When you're comparing ADU quotes, sometimes you end up comparing apples to oranges even if the actual square footage seems to be the same. This is the reason why:

1. Different scope definitions. One builder includes appliances; another doesn't. One covers utility connections; another lists them as "by owner."
2. Variations in quality. For instance "Windows" might mean different things: single-pane vinyl or triple-pane fiberglass. "Cabinets" can mean RTA boxes or custom solid wood.
3. Hidden allowances. Some quotes can seem to show a very low cost but might include "allowances" that rarely cover actual costs.
4. Permit assumptions. One quote might be for just a simple permit process and another one may have included extra for possible variances.

How to Read Any ADU Quote

Before signing anything, always ask the following questions:

• What's the complete scope of work? Make sure you get a detailed line-item breakdown.
• What's explicitly excluded? Get a list of everything that is not included in your quote, such as site work, utilities, appliances and permits.
• What are the finish specifications? Investigate the brand names, materials and quality levels of what will be included in the base quote.
• What's the permit strategy? Find out who handles permits and what happens if there is a delay.
• What's the timeline? How long is the process likely to take, from start to finish.
• What's the warranty? Check all warranties carefully for the structure itself, systems and finishes.

Frequently Asked Questions

What Should You Expect in Your BuildX Quote?

When you choose to work with us, you'll always know exactly what's included, what's additional, and why.

Have questions about your specific property? Give us a call at (781) 627-7000 or request a free consultation.