ADU Construction in Gaithersburg, MD — Accessory Dwelling Unit Contractor
Types of ADUs We Build in Gaithersburg, MD
Gaithersburg's housing spans a wider range of construction eras and styles than almost any other Montgomery County community — from 1960s–70s colonials in established neighborhoods to 1990s Kentlands townhomes to 2000s–2010s Crown Farm construction. Here is a realistic assessment of the ADU types that work across Gaithersburg's diverse neighborhoods:
Basement ADU Conversion
Gaithersburg's single-family homes — particularly in established neighborhoods like Lakeland, Diamond Farms, and Flower Hill — have full basements that are strong ADU conversion candidates. Newer construction in Kentlands, Lakelands, and Crown Farm often has higher ceilings and better rough-in infrastructure, making basement ADU conversions particularly practical. Includes egress windows, separate entrance, kitchen or kitchenette, bathroom, fire separation, and COO — from either the City of Gaithersburg or Montgomery County DPS depending on jurisdiction.
Garage Conversion ADU
Where a detached or attached garage exists, conversion is often the fastest ADU path in Gaithersburg — particularly for homeowners in established neighborhoods with older detached garages. HOA consideration: garage conversions that change the exterior appearance of the home (new windows, new door) may require ARC review in Kentlands and Lakelands. DMV-GC Group assesses HOA applicability during the free consultation for every Gaithersburg garage conversion project.
Attached In-Law Suite Addition
A new addition built onto the main home — separate entrance, bedroom, bathroom, and kitchen. Gaithersburg's established single-family neighborhoods (Diamond Farms, Flower Hill, Lakeland) have lots generous enough for additions in many cases. In Kentlands and Lakelands, attached additions require ARC architectural review for compatibility with the community's New Urbanist character. DMV-GC Group designs Gaithersburg additions to ARC standards from the start.
Detached ADU — Backyard Cottage
New construction of a standalone structure in the rear yard. Less common in Gaithersburg's planned communities where lot coverage limits and HOA design guidelines constrain detached structures. More feasible on larger parcels in established neighborhoods outside the planned community boundaries. Where feasible and permitted by the HOA, a detached ADU provides maximum privacy and the strongest rental income potential.
City of Gaithersburg vs Montgomery County — Which Permit Authority Governs Your ADU?
This is the single most important question to answer correctly before any Gaithersburg ADU project begins — and the most commonly mishandled. Gaithersburg's mailing address covers both the incorporated city and surrounding unincorporated county land. The permit authority is determined by your property's parcel location, not your mailing address.
🏛️ City of Gaithersburg Permits
- Issuing authority: City of Gaithersburg Department of Public Works and Planning
- Covers: Properties within the incorporated city limits
- Neighborhoods typically in City: Kentlands, Lakelands, Olde Towne, Lakeland, Diamond Farms, Flower Hill
- City has its own plan review staff and inspection schedule
- City ADU rules must comply with Montgomery County's ADU ordinance for zoning, plus City building code for construction
- HOA ARC approval required for Kentlands and Lakelands before city permits are filed
📋 Montgomery County DPS Permits
- Issuing authority: Montgomery County Department of Permitting Services
- Covers: Properties in unincorporated Montgomery County with Gaithersburg mailing addresses
- Neighborhoods typically in County: Crown Farm, Washingtonian Center area, Rio, parts of Quince Orchard area
- County ADU ordinance and building code apply
- Some county-jurisdiction Gaithersburg properties still have HOA requirements — verified separately from permit jurisdiction
- Montgomery County COO required before ADU occupancy
HOA & ARC Coordination for Gaithersburg's Planned Communities
Several of Gaithersburg's most active ADU markets are governed by HOAs with Architectural Review Committees — adding a design approval step before permits can be filed. DMV-GC Group handles all HOA coordination as a standard part of every applicable Gaithersburg ADU project.
🏘️ Kentlands
Kentlands is a New Urbanist community designed by Andres Duany and Elizabeth Plater-Zyberk — one of the most architecturally cohesive planned communities in the DC area. The Kentlands Community Foundation's ARC maintains strict design standards for all exterior modifications. Any ADU work affecting the exterior — new entrance, new windows, addition — requires ARC review before City of Gaithersburg permits are filed. Basement ADUs with no exterior modification typically proceed with city permits only. DMV-GC Group designs all Kentlands ADU additions to ARC standards from the start, minimizing revision requests.
🏘️ Lakelands
Lakelands is a sister community to Kentlands — same New Urbanist design principles, adjacent location, and similar ARC process. Exterior ADU modifications require Lakelands HOA ARC approval before city permits. Interior basement ADUs with no exterior change typically do not. DMV-GC Group is familiar with Lakelands' ARC review requirements and designs all Lakelands ADU additions for architectural compatibility with the community's character.
🏘️ Crown Farm
Crown Farm is a newer mixed-use development in unincorporated Montgomery County — requiring county permits, not city permits. Crown Farm's HOA has its own design standards for modifications. ADU projects in Crown Farm must comply with both Montgomery County's ADU ordinance and Crown Farm's HOA guidelines. DMV-GC Group handles both layers of the approval process simultaneously.
🏘️ Other Gaithersburg HOA Communities
Many of Gaithersburg's established neighborhoods — Flower Hill, Diamond Farms, Quince Orchard area developments — also have HOAs with varying levels of ARC authority. DMV-GC Group identifies the applicable HOA and its specific ADU-relevant requirements for every Gaithersburg property during the free consultation, before any design or permit work begins.
Gaithersburg's Newer Construction — Why Basement ADUs Are Practical Here
One of Gaithersburg's underappreciated ADU advantages is its proportion of newer construction — Kentlands (1990s–2000s), Lakelands (2000s–2010s), and Crown Farm (2000s–2010s) all have homes built with basement specifications that are more favorable for ADU conversion than older stock. Here is why:
🏗️ Newer Construction Basement ADU Advantages in Gaithersburg
- Higher standard ceiling heights: Homes built since the 1990s in Gaithersburg commonly have 8'0"–9'0" basement ceiling heights — well above the 7-foot habitable space minimum. This eliminates ceiling height as a constraint and creates comfortable, open-feeling ADU spaces.
- Poured concrete foundations: Newer Gaithersburg construction uses poured concrete foundations rather than the concrete block found in older Wheaton and Silver Spring homes — meaning interior moisture management is more straightforward and less costly.
- Rough-in plumbing: Many Kentlands, Lakelands, and Crown Farm homes were built with basement plumbing rough-ins — a drain stub-out in the slab for a future bathroom. Completing an existing rough-in rather than cutting new drain trenches saves $6,000–$12,000 on the bathroom addition. DMV-GC Group checks for rough-ins during every consultation for newer Gaithersburg homes.
- Egress window rough openings: Some newer Gaithersburg homes have basement egress window openings already framed in — or at minimum, window wells already excavated — reducing or eliminating the egress window installation cost.
- Modern electrical panels: 200-amp panels with adequate capacity for ADU circuits are standard in newer Gaithersburg construction — meaning a sub-panel for the ADU can typically be added without upgrading the main panel.
- Wider staircase access: Newer construction basements often have wider stair configurations — improving the sense of entrance to the ADU and simplifying the separate entrance design compared to older narrow basement stairways.
Benefits of Building an ADU in Gaithersburg
Serving All Gaithersburg, MD Neighborhoods for ADU Construction
Kentlands
New Urbanist planned community (1990s–2000s). Basement ADUs are the most practical option here — no exterior modification means no ARC review required for interior-only work. Any exterior addition or garage conversion requires Kentlands Community Foundation ARC approval before city permits. Newer construction with 8'–9' ceilings and often existing rough-ins makes basement conversions particularly practical.
Lakelands
Sister New Urbanist community to Kentlands (2000s–2010s). Same ARC process for exterior modifications. Basement ADUs — interior only — proceed with city permits directly. Higher ceiling heights and newer infrastructure make basement conversions the dominant ADU type here. Strong rental demand from the same Kentlands employer base.
Crown Farm
Mixed-use development in unincorporated Montgomery County — despite Gaithersburg mailing address. Montgomery County DPS permits, not city permits. Crown Farm HOA has its own design guidelines. Newer construction (2000s–2010s) with modern basement specifications. Good rental demand from the Washingtonian corridor employment base.
Diamond Farms / Flower Hill
Established 1970s–80s single-family neighborhoods within the city limits. Full basements with poured concrete foundations — solid ADU conversion candidates. Lot sizes generous enough for additions in many cases. Less restrictive HOA environments than Kentlands/Lakelands for most exterior modifications.
Lakeland / Olde Towne Gaithersburg
Older established neighborhoods near Gaithersburg's historic town center. Mix of construction eras — some older homes with block foundations (assessment recommended) alongside mid-century colonials. Walking distance to the MARC Brunswick Line Gaithersburg station — strong transit-oriented rental demand.
Quince Orchard / Rio Area
Mix of 1980s–2000s single-family homes in unincorporated county area with Gaithersburg mailing addresses. Montgomery County DPS permits. Good lot sizes in many cases — stronger case for detached ADUs on larger parcels than in the denser planned communities. Proximity to Quince Orchard Road and I-270 employment corridor.
Our ADU Construction Process in Gaithersburg
Free In-Home Consultation & Feasibility Assessment
We visit your Gaithersburg home and assess ADU options — basement ceiling height and rough-in presence, garage feasibility, lot size for addition — and identify the most practical and cost-effective ADU type for your specific property. No cost, no obligation.
Jurisdiction Verification — City vs County
We confirm whether your Gaithersburg property falls within the City limits or unincorporated Montgomery County using parcel boundary data. This single verification step eliminates the most common and costly mistake in Gaithersburg ADU construction. Takes less than one business day and is completely free.
HOA / ARC Assessment (If Applicable)
For Kentlands, Lakelands, Crown Farm, and other HOA communities, we determine whether the proposed ADU scope requires ARC review — and if so, prepare all required documentation. Basement ADUs with no exterior modification typically do not require ARC review; additions and garage conversions typically do. This determination happens before any design work begins.
ADU Design Development
Our design team develops a floor plan and, where required, exterior design drawings for ARC submission — all designed to be compatible with your community's architectural character from the first draft. For basement ADUs in newer Gaithersburg homes, we verify rough-in locations and incorporate them into the bathroom design.
ARC Submission + Permit Filing — Concurrent
Where both HOA ARC review and building permits are required, we submit both simultaneously wherever the HOA allows — minimizing the total pre-construction timeline. Our team manages all city or county correspondence and all HOA communications throughout.
Construction — Egress, Mechanicals & Finishes
Egress window installation where needed, then electrical, plumbing, HVAC, framing, drywall, flooring, kitchen, bathroom, and all finish work — coordinated by a dedicated project manager and inspected at each required stage by the correct authority (City or County).
Inspections, COO & 1-Year Warranty
We manage all required inspections with the correct authority and the Certificate of Occupancy process. After COO issuance, we conduct a final walkthrough, address every punch list item, and activate your 1-year workmanship warranty. Your Gaithersburg ADU is legally ready to rent.
ADU Construction Cost in Gaithersburg, MD
| ADU Type | Typical Cost Range | Notes for Gaithersburg |
|---|---|---|
| Basement ADU — Newer Construction (Kentlands / Lakelands / Crown Farm) | $60,000 – $100,000 | High ceilings, poured concrete, often existing rough-ins. Most cost-effective Gaithersburg ADU. No exterior modification = no ARC review required. |
| Basement ADU — Established Neighborhoods (Diamond Farms / Flower Hill) | $62,000 – $115,000 | 1970s–80s construction. Standard ceiling heights, poured concrete in most cases. Full scope including egress, entrance, kitchen, bath, COO. |
| Garage Conversion ADU | $58,000 – $105,000 | ARC review required in Kentlands/Lakelands for exterior changes. Older detached garages in established neighborhoods assessed for structural condition and utility run distance. |
| Attached In-Law Suite Addition | $95,000 – $200,000 | ARC review required in Kentlands/Lakelands. Designed for architectural compatibility. More common in established neighborhoods with larger rear yards. |
| Detached ADU — Backyard Cottage | $140,000 – $260,000 | Feasibility depends on lot size and HOA guidelines. Most practical in established neighborhoods outside planned community boundaries. |
| Rough-In Completion (if present) | Saves $6,000 – $12,000 | Completing an existing basement plumbing rough-in instead of cutting new drain trenches through the slab. Verified during free consultation. |
What Gaithersburg Homeowners Say About DMV-GC Group
"Our Kentlands home had an unfinished basement with a plumbing rough-in already in the slab. DMV-GC Group found it during the consultation, confirmed no ARC review was needed for the interior-only work, and converted it into a legal ADU in 11 weeks. The City of Gaithersburg inspector passed everything first time."
"Two contractors we talked to didn't know Crown Farm uses county permits, not city permits. DMV-GC Group knew immediately, verified our parcel jurisdiction, and filed with Montgomery County DPS. No delays, no permit mistakes. The basement ADU is rented to an NIH researcher at $1,750/month."
"We wanted an in-law suite addition to our Lakelands home. DMV-GC Group designed it to match our home's New Urbanist exterior from the start — before even submitting to the ARC. The ARC approved it without any revision requests. The addition looks like it was always part of the original design."
"Our Diamond Farms colonial had a full basement ready for ADU conversion. DMV-GC Group handled the City of Gaithersburg permits, designed a smart two-room layout within the footprint, and delivered on time and on budget. The rental income has been consistent since month one."
⭐ 4.9-star rated with 97+ verified reviews. Gaithersburg homeowners trust DMV-GC Group for ADU projects that navigate the City vs County permit question correctly, handle HOA ARC coordination in Kentlands and Lakelands, and deliver legal, rentable units efficiently across every Gaithersburg neighborhood.
Serving All Gaithersburg, MD Neighborhoods for ADU Construction
Also serving Rockville, MD — directly south of Gaithersburg
DMV-GC Group builds ADUs throughout Rockville, which borders Gaithersburg to the south. Rockville also has its own city permit jurisdiction separate from Montgomery County — the same dual-jurisdiction expertise that makes DMV-GC Group the right choice for Gaithersburg applies equally in Rockville. View our full ADU construction service page →