35+ Years Building in Maryland
Add Space, Add Income, Add Home — Now Legal in Every Maryland County
The ADU Builder is the accessory-dwelling-unit division of Madrid’s Contracting — 35 years of Maryland construction experience, now focused on detached, attached, and conversion ADUs across Anne Arundel, Howard, Prince George’s, and Baltimore counties.
What Is an ADU, and Is It Legal in Maryland?
An accessory dwelling unit (ADU) — also known as an in-law suite, granny flat, or carriage house — is a smaller, independent living space built on the same lot as a single-family home. ADUs have their own entrance, kitchen, and bathroom, and can be detached, attached, or converted from existing spaces such as a garage, attic, or basement.
Yes — as of October 1, 2026, Maryland law requires every county to allow at least one ADU by right. Anne Arundel County got there first, passing its own ordinance back in 2023; Howard, Prince George’s, and Baltimore counties are now required to meet that same baseline. As the ADU division of Madrid’s Contracting, we’ve been helping homeowners build compliant, quality ADUs since Anne Arundel’s ordinance passed, and we’re ready to do the same under each county’s new rules.
How It Works
Three Steps From Idea to Move-In
Free Consultation
We walk your property and talk through goals, budget, and zoning — no cost, no obligation.
Design & Permitting
Our team draws the plans and handles your county's ADU permitting from start to finish.
Build & Move In
Our own crews build it — the same team that's built Maryland homes for 35 years.
ADU Types
Find the Right ADU for Your Property
Detached ADU
A detached ADU is a fully separate backyard structure — the most popular accessory dwelling unit in Maryland for homeowners who want maximum privacy and long-term rental flexibility. Anne Arundel County’s 2023 ADU ordinance allows detached units on nearly every residential lot with no minimum lot size required, and the other Maryland counties we serve each have their own version of that same by-right standard.
Fastest Turnaround
Garage Conversion
A garage conversion ADU is the fastest, lowest-cost path to a livable accessory dwelling unit in Maryland — no new foundation, no site excavation, and often a lighter permitting lift than a detached build. We handle the full permitting process for garage-to-ADU conversions from start to finish, whichever Maryland county you’re in.
Fastest Turnaround
Attic Conversion
An attic conversion ADU makes use of space you already have, turning unfinished upper-floor square footage into a fully permitted accessory dwelling unit. Maryland counties still require proper egress windows and structural review for attic ADUs, which our team manages as part of your permitting package.
Fastest Turnaround
Basement Conversion
A basement conversion ADU is often the lightest permitting lift of any accessory dwelling unit type in Maryland, since the structure and foundation already exist. Egress windows are still required by code, and our team handles that compliance work as part of every basement ADU conversion.
Local Expertise & Trust
The ADU Builder is the accessory dwelling unit division of Madrid’s Contracting — 35 years of licensed, insured remodeling and construction across Anne Arundel County and the surrounding Maryland counties we now serve. Same crews, same accountability, new focus: helping local homeowners navigate their county’s ADU ordinance and build detached, attached, and conversion ADUs the right way, the first time.
Transparent Pricing
No lowball teaser quotes. Every ADU project starts with a free, on-site consultation where we walk your property, review your zoning district, and give you a real number — in writing — before any work begins. Most ADU projects in our area run $120K–$300K+ depending on type, size, and finishes.
Full-Service Permitting
Anne Arundel County led the way, requiring ADU permits since its 2023 ordinance, Bill 6-23 — well ahead of Maryland’s statewide ADU law, which now requires every county to meet that same baseline. We handle permitting from drawings to final inspection across Anne Arundel, Howard, Prince George’s, and Baltimore counties (plus Baltimore City), so you don’t deal with the county at all. See our full guide to Maryland ADU law and Bill 6-23 for the details.
Transparent Pricing
Most ADU Projects Run $120K – $300K+
Exact cost depends on ADU type, size, and finishes — we give you a real number after a free on-site consultation, not a lowball estimate.
Why Build an ADU
Reasons to Build an ADU
Rental Income
Turn unused yard or garage space into steady monthly income.
Aging Parents
Keep family close with a private, accessible space of their own.
Guests & Family
A comfortable place for visitors without giving up your main home.
Adult Children
Give grown kids independence while staying close to home.
Service Areas
Serving Anne Arundel County & Beyond
- Severna Park
- Annapolis
- Crofton
- Pasadena
- Glen Burnie
- Odenton
- Arnold
We also take on ADU projects across the county line in Howard County (Columbia, Ellicott City), Prince George’s County (Bowie, Laurel), Baltimore County (Towson, Catonsville, Dundalk), and Baltimore City — contact us to confirm we cover your address.
FAQ
Maryland ADU Questions
The ADU Builder is a licensed Maryland ADU builder serving Severna Park, Annapolis, Crofton, Pasadena, Glen Burnie, Odenton, Arnold, and surrounding communities across Anne Arundel, Howard, Prince George’s, and Baltimore counties. As the accessory dwelling unit division of Madrid’s Contracting, we bring 35+ years of local construction experience to every detached ADU, attached ADU, and garage, attic, or basement conversion we build. See our ADU cost guide and Maryland ADU law guide for more.
