ADU Types / Detached
Detached ADU Builder in Maryland
A standalone second home in your backyard — its own foundation, its own utilities, its own front door. The most private option, the strongest rental, and the biggest build of the five.
A detached accessory dwelling unit is a purpose-built small house set behind or beside the main one. Unlike a conversion, nothing about it is a compromise with an existing structure — the layout, the ceiling height, the window placement, and the insulation are all designed from scratch for the way the unit will actually be lived in.
That freedom is why detached units rent for the most and appeal most to aging parents who want genuine independence rather than a finished basement. It is also why they cost the most: you are paying for foundation, utility runs, roof, siding, and windows that a conversion already has.
Is Your Property a Candidate?
- Backyard depth. You need room for the unit plus the setbacks the county requires on every side. A deep lot is worth more here than a wide one.
- Equipment access. There has to be a way to get an excavator and a concrete truck to the build site. A narrow side yard between two houses can quietly rule a project out, or add real cost.
- Utility routing. Water, sewer, and electric have to reach the new structure. The distance from the main house and whether you are on public sewer or septic drives a meaningful share of the budget.
- Septic capacity. On a septic system, adding bedrooms may require the system to be evaluated or expanded. This is common on parts of the Pasadena peninsula and worth checking early.
- HOA covenants. County approval is only half the question in planned communities like Crofton, where covenants may restrict detached structures outright.
What the Build Involves
Site work comes first — clearing, grading, and the foundation, whether that is a slab, a crawlspace, or a full foundation depending on the site and what you want underneath. Utility trenching runs from the main house or the street. From there it is conventional construction: framing, roof, windows, exterior envelope, then mechanical, electrical, plumbing, insulation, and interior finishes.
The detail that separates a good detached ADU from an obvious add-on is how it relates to the main house. Matching roof pitch, siding, and window proportions makes the property read as one considered whole rather than a house with a shed behind it — and that difference shows up in appraisals.
Cost and Permitting
Detached ADUs in Maryland typically run $150,000 to $300,000 and up. Size, foundation type, utility distance, and finish level move that range more than anything else. Our ADU cost guide breaks down how hard and soft costs divide.
A detached unit needs a permit through Anne Arundel County under Bill 6-23, with Maryland’s statewide ADU Act setting the by-right baseline — see our guide to Maryland ADU law. We handle the permitting.
Detached ADU Questions
How big can a detached ADU be?
Local standards cap ADU size, and the cap is often expressed as a percentage of the main house or a fixed square footage, whichever is smaller. Setbacks and lot coverage limits frequently bind before the size cap does. We check both against your specific parcel at the consultation.
Does it need separate utility meters?
Not necessarily. Many detached ADUs run off the main house’s service, which is simpler and cheaper. Separate metering makes sense when you intend to rent long-term and want utilities billed to the tenant, and it is a decision worth making before the trench is dug rather than after.
Is a detached ADU worth more than a conversion?
It usually commands higher rent and appeals to a wider set of tenants, because it is a genuinely separate dwelling rather than part of someone else’s house. Whether that premium justifies the extra cost depends on your lot and how long you plan to hold the property. We will tell you honestly when a conversion is the better economic answer.
Find Out What Your Backyard Supports
We build detached ADUs across Anne Arundel County — Annapolis, Glen Burnie, Pasadena, Severna Park, Crofton, and Odenton. Call (410) 755-7663 and we will walk the lot before anyone pays for drawings. Comparing options? See all five ADU types.