Maryland ADU Cost Breakdown: Where the Project Budget Actually Goes

Last researched: September 19, 2026. A Maryland ADU budget is easier to understand when you stop treating it as one number. A contractor’s total can contain design, site work, structure, utilities, interiors and closeout in very different proportions depending on the property and delivery method.

This page does not publish one “correct” cost split for every ADU. Instead, it gives homeowners a practical way to break a written proposal into comparable cost buckets, then test how much each bucket contributes to the total.

If you only need a total planning range, use the Maryland ADU Costs & Budget Calculator. If you are trying to understand why a quote grows, use the Cost Escalation Guide. This page focuses on the anatomy of the bid itself.

The 12 cost buckets worth separating

Build your own cost anatomy

What Maryland pricing evidence tells us

Published Maryland pricing confirms why a component view is more useful than a statewide average. UP Craftsmen currently says an ADU in Montgomery County or Washington, DC can average about $250,000–$300,000. Our September 2026 review of Maryland builder-published ranges found much lower starting figures for some interior conversions and substantially higher figures for detached or high-finish work.

Makara’s Maryland cost material, as reviewed in our current cost guide, describes hard construction costs as roughly 70–80% and soft costs as roughly 20–30% in its own planning framework. That is useful as a builder-published reference, but it should not be treated as a universal Maryland rule. A difficult site can push site/utility costs much higher; a conversion can shift more money into correcting the existing structure.

For that reason, the safest workflow is:

1. Get the written total.
2. Break it into cost buckets.
3. Mark every bucket as fixed price, allowance, excluded or unresolved.
4. Compare bids only after the buckets match.

Which components change the most from property to property?

Ask contractors for these numbers separately

• Preconstruction/design fee
• Survey and engineering
• Permit management vs actual government fees
• Site work and grading
• Foundation
• Framing/exterior shell
• Plumbing
• Electrical
• HVAC
• Interior finishes
• Kitchen and bathroom allowances
• Utility connections
• Septic/well work, if applicable
• Landscaping/site restoration
• Contingency or unknown-condition allowance
• Final closeout and warranty scope

A proposal does not need to expose the contractor’s internal profit or every subcontractor invoice. It does need enough scope detail for you to know what work your price actually buys.

Three bid traps this breakdown exposes

“Turnkey” without a written definition

One company may use “turnkey” to mean design through final inspection. Another may exclude utility-company charges, landscaping, permit fees or septic work. The word itself is not a scope.

Very low finish allowances

A contractor can present a low total while carrying minimal allowances for cabinets, counters, plumbing fixtures, lighting or flooring. Ask for the actual allowance values before comparing totals.

Site work hidden behind allowances

Site and utility unknowns are sometimes carried as allowances rather than fixed prices. That may be reasonable before excavation, but the contract should clearly state the assumption and how overages are handled.

How this fits with the rest of your Maryland ADU budget

Use the tools in this order:

1. Find the reviewing jurisdiction.
2. Check basic feasibility.
3. Map the site constraints.
4. Build the total planning budget.
5. Use this page to break the total into components.
6. Check what is missing from the quote.
7. Compare written contractor bids on the same scope.

Maryland ADU cost breakdown FAQs

What is the largest cost component of an ADU?

There is no single answer for every Maryland property. The building shell and interior construction can dominate a straightforward detached project, while site work, utilities or corrections to an existing garage/basement can dominate another project.

What percentage of an ADU budget should be design and permits?

Do not use one percentage as a rule. Makara’s Maryland cost material describes soft costs broadly as about 20–30% in its planning framework, but project-specific design, engineering, permit and agency costs can differ materially.

Should contractor bids show every component separately?

They do not need to reveal the contractor’s internal cost accounting, but the written scope should be detailed enough to identify major inclusions, exclusions, allowances and unresolved items.

Are utilities part of construction cost?

Sometimes yes, sometimes partly, and sometimes no. Confirm whether water, sewer, electric service, trenching, meters, panels and utility-company charges are included in the quoted scope.

Why can two similar-size ADUs have very different budgets?

Site conditions, utility distance, foundation type, existing-structure conditions, finish level, permitting scope, contractor delivery model and private well/septic requirements can all change the project cost independently of floor area.

Sources checked

• City of Annapolis — ADU Costs FAQ
• UP Craftsmen — ADU Design & Build Process and Cost FAQ
• Maryland ADU Guide — published Maryland builder pricing review

Maryland ADU Guide is an independent research publication, not a contractor, estimator, architect, engineer or permitting agency. The calculator’s default percentages are illustrative placeholders, not Maryland averages. Replace them with written project-specific figures before making financial decisions.