The best ADU builder for your household is the one whose documented scope, design and delivery process fit your property and budget. Before comparing advertised prices, ask every company for the same evidence and the same cost breakdown.
Published by Lumara, a Massachusetts ADU builder. This is a practical comparison framework—not an independent ranking or an endorsement of any company.
01 / Verify before comparing
Match the builder’s claims to real evidence.
Check the company and the responsible people.
Ask for the contracting entity’s legal name, the person supervising construction, relevant registration and license numbers, and current insurance documentation. A Home Improvement Contractor registration and a Construction Supervisor License are different credentials; one does not replace the other.
Separate completed homes from plans and renderings.
Request examples comparable to your proposed ADU: location, construction method, scope, completion status and the builder’s actual role. Ask whether photographs show that company’s completed work, another project type, or an architectural visualization.
With the owner’s permission, speak to a previous client about communication, allowances, changes and closeout—not only the finish quality. A project under design can demonstrate planning work, but it is not evidence of a completed home. Lumara identifies those stages separately in its Massachusetts work-in-progress examples.
02 / Put every proposal on the same basis
A lower starting price is not necessarily a lower project cost.
Ask each builder to mark every item below Included, Allowance, Excluded or Unknown. Record the responsible party and the document supporting the number. An excluded item still belongs in your total budget.
The home
Structure, insulation and enclosure; roofing; windows and doors; kitchen and bathroom; interior finishes; appliances; and internal plumbing, electrical, heating, cooling and ventilation.
The foundation and site
Survey and layout; excavation; rock or unsuitable soil; foundation; drainage; tree work; access; grading; and restoration. Confirm whether foundation is inside or outside the advertised model price.
The utility connections
Water, electrical service and trenching; sewer connection or septic work; utility-company charges; and work inside the principal house. Ask what distance and capacity assumptions support each allowance.
The preparation
Architectural and engineering documents; energy-code coordination; septic design; wetlands or other investigations; permit applications; authority fees; revisions; and project management.
The delivery and finish
Transport, cranes or lifting equipment where needed; staging; assembly; weather protection; site connections; decks, steps or ramps; inspections; and the final path to occupancy.
The remaining risk
What is fixed, estimated or not yet investigated? How are allowances reconciled? Who approves changes? Keep a separate household contingency rather than treating an incomplete quote as a guaranteed total.
A useful comparison: home price + preparation + foundation and site + external utilities + delivery and installation + other agreed scope = the project budget before your contingency. Include each item once; different builders group them differently.
Compare like-for-like finish and scope assumptions—not only dollars per square foot. Lumara’s Massachusetts ADU cost guide separates the starting home price from property-specific additional work.
03 / Ask what has actually been checked
The property should shape the proposal.
Placement is more than a shape on a map.
Ask what supports the proposed position: approximate GIS information, a survey, a zoning review or an approved plan. Discuss access, privacy, grades, drainage, trees, flood conditions and wetlands where relevant. A preliminary placement is not a survey or approval.
Ask who will resolve the remaining questions, what each investigation costs and which decisions depend on its results. Review the state’s ADU FAQs and the requirements for your municipality rather than relying on a blanket promise that every yard qualifies.
Make wastewater and utilities explicit.
For a property on septic, ask who will review existing records, system capacity and the proposed bedroom count, and who coordinates with the Board of Health. Do not treat an assumed tie-in as an engineered solution. For sewer and other utilities, confirm connection routes, capacity and the responsible utility or authority.
Construction labels do not replace accountability.
Get a clear division of responsibility.
Whether a proposal is panelized, modular or site-built, ask what happens off site, what happens on your property, and who is accountable for the interfaces. Identify the designer, engineer, foundation contractor, installer, licensed trades, permit coordinator and day-to-day construction contact.
Ask who checks foundation dimensions before delivery, protects unfinished assemblies from weather, coordinates inspections and resolves a mismatch between the plans and field conditions. A single point of contact is useful only when the written scope supports it.
Review the design for the person living there.
Compare furnished plans with dimensions, not just exterior renderings. Check usable living area versus footprint, storage, laundry, entry access, circulation and bathroom layout. Ask which finishes and adjustments are standard and which are additional.
For an aging parent or a household with mobility needs, discuss the actual route from parking to the home and specific door, turning and bathroom requirements. Do not assume a general “accessible” label means a layout fits the individual. Explore Lumara’s Studio and One Bedroom starting models, then resolve the household’s needs through design.
05 / Compare the complete schedule
Ask when the clock starts—and what stops it.
A quoted construction duration may begin after investigations, design, permits, utility coordination and procurement. Ask for those stages separately, plus the conditions that must be satisfied before the advertised build period begins.
Request milestone assumptions.
Review expected dates or ranges for site investigations, design decisions, applications, approvals, procurement, foundation readiness, assembly, utility completion, inspections and occupancy. Identify dependencies controlled by the builder, homeowner, utility and public authorities.
Plan around the household’s real deadline.
Explain lease expirations, care arrangements or other move-in needs early. Ask what a delay would change and what contingency is realistic. Compare the full project process, not only the days spent building the structure.
06 / Before signing or paying
Make the next commitment specific.
Know what this agreement authorizes.
An initial property review, a paid investigation, a design agreement and a construction contract are different commitments. Confirm the deliverables, fees, ownership or use of documents, exclusions, cancellation provisions and next decision at each stage.
For construction, review the drawings and specifications referenced by the contract, payment milestones, allowance treatment, written change process, insurance, responsibility for approvals and the handling of delays or disputes. Get independent legal advice for contract-specific questions; the applicability of HIC protections depends on the work and property.
Define completion and aftercare.
Ask what must be finished for each payment and for final completion. Clarify the punch list, required inspection and occupancy records, manuals, warranties, lien-related documentation where applicable, site restoration and who responds to a later service issue.
Compare the duration, exclusions and claim process of written warranties rather than assuming every component has the same coverage. For financing, check that lender draws and contractor payment milestones are compatible before committing to the build.
This guide is general planning information, not legal, engineering or property-specific approval advice. Verify current requirements with the responsible authority and appropriately qualified professionals.
Put the questions to your property
A clearer decision starts with your address.
Explore Lumara’s homes, pricing and current Massachusetts work. Then request a no-cost initial Property Review to discuss placement, access, utilities and the next step. Onsite is recommended; Phone/Zoom is available.
