Start with the space you need. Price follows the selected home and a defined scope.
Massachusetts ADU cost guide · 2026
A clear ADU budget starts with the property.
Understand the home, professional services, site work and utilities together. Lumara uses the property review to identify the scope needed for a complete project budget.
Survey, septic or wetland work is scoped for the property and authorized before it begins.
Review the required design work, professional services and fee before moving forward.
The cost stack
One project. Four different kinds of cost.
A model price alone cannot describe a buildable Massachusetts ADU. Lumara separates the home, professional services, site work, and utilities so each decision stays visible.
The ADU
The selected building structure, systems, windows, fixtures, code package and interior finish direction.
Professional services
Survey, architectural drawings, structural engineering, energy/code coordination, and permit-ready documentation as required.
Site + installation
Delivery access, foundation, excavation, grading, drainage, crane or set conditions, restoration, and other lot-specific work.
Utilities + approvals
Electric, water, sewer or septic routes; capacity upgrades; permit fees; inspections; and requirements identified during local review.
Decision gates
Spend in sequence—not all at once.
The purpose of feasibility is to avoid committing to full design or construction before the property, delivery route, utility path, and likely permit approach make sense.
Property review
Address, likely placement, setbacks, access, utilities, and major constraints.
Investigations, if needed
Resolve the septic, survey or wetland questions needed to advance this property.
Plans
Architectural and structural work begins only after scope and authorization are clear.
Build scope
Model, site work, utilities, installation, schedule, and contract are finalized.
What the figures mean
Allowance, estimate, and contract price are not interchangeable.
Clear labels protect the homeowner and the project team. Each figure becomes more precise as the property and technical scope become known.
LabelScopeMeaning
Starting priceSelected homeA model entry point. It is not a universal installed price for every property.
AllowanceIdentified site workA planning amount reserved for an identified scope; reconciled to the actual service and written terms.
EstimatePlans and engineeringAn early budget expectation for architectural and structural work, refined before authorization.
Contract priceProject-specificThe agreed price for a defined scope after the site, selections, exclusions, and responsibilities are documented.
Important: This page explains how the budget is developed; it is not an offer or final construction quote. Property conditions, design, utility capacity, permitting, material selections, and third-party requirements can change the total.
Cost questions
The useful answer is specific to the lot.
These are the questions Lumara resolves before recommending a configuration or next paid step.
What belongs in the complete project budget?
The budget should account for the home, plans and engineering, permits, foundation, utility connections, site work and applicable delivery or installation. Lumara defines inclusions, exclusions and property-dependent items in the written scope.
Is preconstruction one phase or two?
It depends on the property. Septic, survey or wetland investigations may need a separate early scope before full plans and engineering. Lumara explains the required work and fees before each phase is authorized.
Why can’t Lumara give one installed price for every property?
Two identical ADUs can require very different foundations, access plans, utility runs, drainage work, septic coordination, or electrical upgrades. A property review identifies those variables before they become surprises.
What can increase the site-work cost?
Long utility runs, limited delivery access, ledge, slopes, drainage conditions, tree work, electrical capacity, septic requirements, difficult excavation, and restoration needs are common cost drivers.
When does construction pricing become reliable?
Pricing becomes substantially more reliable after the property review, required site investigations, selected model, utility strategy, permit path, and design scope are known. Lumara can then organize a defined project scope and exclusions.
Start with the lot
Start with a property-specific budget.
Start with your Massachusetts address and request a property review. Lumara reviews fit, access, utilities and major cost drivers, then follows up with a written recommendation.