St. Mary's County, MD Building Permits & Zoning

St. Mary's County, Maryland requires a building permit for a single-family home, whether stick-built, modular or mobile, processed through the county's Drop Off application procedure¹. The county also runs its own zoning program, with the Development Services Division reviewing site plans, subdivisions and zoning determinations, unlike neighboring states where only towns or townships zone². Septic systems go through the St. Mary's County Health Department's Environmental Health Division, which requires a perc test, a Maryland-registered surveyor's site plan, and an inspection before the system is covered³. Selecting "Myself" as the builder on the county's own permit application does not exempt a project from the building permit, inspections, or the certificate-of-occupancy requirement⁴.

At a glance

Building permit: Required for a new single-family home; $20 application fee plus other agency fees and excise tax¹⁵
Zoning: Yes, administered by the county's own Development Services Division²
Septic: Permitted by the county Health Department's Environmental Health Division; permit valid 2 years³⁶
Owner-builder: You can name yourself as builder, but that doesn't remove any permit, inspection or certificate-of-occupancy requirement⁴
RV on your land: One camping trailer allowed on a 1+ acre lot for intermittent recreational use only, up to 7 consecutive nights, never as a permanent residence⁷
Wells: A well construction permit is required statewide, issued only to licensed well drillers⁸
Septic soils: Only 1% of the county's soils are free of severe limits for a conventional septic drain field⁹
Property tax: Effective rate about 0.9%, typical bill near $3,392/year¹⁰¹¹

Who to call

Building permits

St. Mary's County Department of Land Use & Growth Management, Permit Services Division

Building permits and other permits including environmental (Critical Area and Floodplain), residential entrances, home occupations and sign permits for St. Mary's County

(301) 475-4200

41770 Baldridge Street, Leonardtown, MD 20650

Zoning

St. Mary's County Development Services Division (Land Use & Growth Management)

Zoning determinations, and multi-agency review of site plans, subdivision plans, boundary line adjustments and confirmatory plats for St. Mary's County

(301) 475-4200

41770 Baldridge Street, Leonardtown, MD 20650

Floodplain permits

St. Mary's County Floodplain Management (Land Use & Growth Management)

Floodplain development permits for construction wholly or partially within, or in contact with, a flood hazard area in St. Mary's County

(301) 475-4200

41770 Baldridge Street, Leonardtown, MD 20650

Septic permits

St. Mary's County Health Department, Environmental Health Division

Individual septic system construction, expansion and repair applications, perc tests and pre-covering inspections for St. Mary's County

(301) 475-4321

[email protected]

21580 Peabody St., Leonardtown, MD 20650

Contact details are copied from each office’s official page and were checked against it on September 24, 2026.

Do you need a building permit in St. Mary's County, Maryland?

Yes: St. Mary's County requires a building permit for construction of a single-family dwelling, whether stick-built, modular or a mobile home, along with additional living space, accessory apartments, townhouses and other specified residential development¹. The county uses a Drop Off process for most residential applications, and additional reviews kick in for septic or private wells, public water or sewer connections, soil disturbance over 5,000 square feet, floodplain, or Chesapeake Bay Critical Area land¹. Expect a $20 base application fee, with the new-dwelling fee itself running $0.16 per square foot and a single-family excise tax of $6,697 added on top, plus other agency fees such as the Health Department review ($21 to $90) and Soil Conservation District review ($75 to $500)⁵. The county updated its local Building Code effective July 15, 2024, adopting the 2021 IBC, IECC, IEBC and ISPSC alongside the 2018 IFGC, IMC and IPC¹².

Who is the St. Mary's County building department, and how do you reach them?

The Permit Services Division of the county's Department of Land Use & Growth Management processes building permits along with environmental, residential entrance, home occupation and sign permits¹³. Reach them at (301) 475-4200, 41770 Baldridge Street, Leonardtown, MD 20650; permit applications are only accepted Monday and Thursday from 8:30 a.m. to 2:00 p.m., and Tuesday, Wednesday and Friday from 8:30 a.m. to 4:30 p.m.¹³. The same department's Development Services Division handles zoning determinations and site-plan or subdivision review at the same address and phone number¹⁴. Floodplain development permits, required for any work wholly or partially within a flood hazard area, are also processed there¹⁵. Before your final inspection, contact the Health Department's Environmental Health Division about septic sign-off, since a Certificate of Use and Occupancy requires every required agency's sign-off on the final inspection card¹⁶¹⁷.

Does St. Mary's County have zoning?

Yes: unlike many rural counties, St. Mary's County administers its own countywide zoning, and the Development Services Division reviews concept, major and minor site plans, subdivision plans, boundary line adjustments and confirmatory plats, and issues zoning determinations on request²¹⁸. Maryland state law confirms counties hold this authority directly: the state's policy is that planning and zoning controls are implemented by local government¹⁹. That said, several specific numbers a buyer wants are not confirmed in any official county page reviewed for this guide: minimum lot size, building setbacks, lot coverage, minimum dwelling size and an agricultural exemption from zoning were all searched for and not found published, so call Development Services to get the number that applies to your specific parcel and zoning district rather than assuming one².

How do septic permits work in St. Mary's County?

The Health Department's Environmental Health Division receives applications for the construction or expansion of individual septic systems, and also reviews repair applications when a system fails³¹⁶. A perc test is required for new construction or repair, and for all new construction a Maryland-registered land surveyor's site plan must be submitted for review; construction may begin once the application is approved, and the approved permit is valid for 2 years from issuance⁶. Before the system is covered, you must contact the Health Department to have it inspected¹⁶²⁰. Any property not served by public water and sewer must complete this perc test before beginning construction of any structure with plumbing at all, not just a house²¹. Soils are a real constraint here: only 1% of St. Mary's County's soils are rated free of severe limits for a conventional septic drain field by the USDA soil survey, so budget for engineering and site work on most parcels⁹.

Can you live in an RV or tiny home on your land in St. Mary's County?

Not as a full-time residence: the county's Zoning Ordinance is explicit that recreational vehicles may not be occupied as permanent residences⁷. The ordinance does allow one camping or recreational trailer on a lot of at least 1 acre in an allowable zoning district, but only for intermittent, private recreational use such as camping or hunting, for no more than 7 consecutive nights, screened from neighboring dwellings by a fence or evergreen buffer, and equipped with an authorized self-contained sewage holding tank⁷. St. Mary's County's own published pages and ordinance provisions were searched specifically for tiny-home occupancy rules and none were found, so a tiny home's legal status here is genuinely unconfirmed rather than a clear yes or no; call Development Services before you buy or place one². Whatever the zoning answer, an occupied dwelling still needs its own building permit, septic approval and certificate of occupancy¹³.

Building a home in St. Mary's County: the steps, in order

Contact Development Services for a zoning determination on your specific parcel, since minimum lot size, setbacks and lot coverage are not published countywide and depend on your zoning district¹⁴².
Complete a perc test through the Health Department's Environmental Health Division if the property is not served by public water and sewer, and apply for your septic construction permit before any plumbed structure goes up¹⁶²¹.
Apply for your building permit through the Drop Off process at the Permit Services Division, budgeting the $20 application fee plus the new-dwelling square-footage fee and excise tax¹³⁵.
If your site touches a flood hazard area, apply for a floodplain development permit and arrange an Elevation Certificate from a licensed engineer or surveyor¹⁵²².
If soil disturbance will exceed 5,000 square feet, have a licensed surveyor or engineer prepare a Sediment & Erosion Control Plan for Soil Conservation District review²³.
Keep permitted work visible and accessible for every required inspection; work may not proceed past an inspection point without approval²⁴.
Before you move in, have each required agency sign the final inspection card and bring it to the Department of Land Use & Growth Management to get your Certificate of Use and Occupancy¹⁷.

What to check before you buy land in St. Mary's County

Zoning: get a written zoning determination for the specific parcel from Development Services, since setbacks, lot coverage and minimum lot size are not published countywide¹⁴². Septic and soils: only 1% of the county's soils are free of severe septic limits, and any unserved property needs a perc test before construction of anything with plumbing, so budget for engineering⁹²¹. Water and sewer: some parcels near the MetCom service area may need a waiver to use private water or septic in the interim, with a requirement to connect to public service later once it becomes feasible²⁵. Wells: a well construction permit, issued only to licensed drillers, is required for any well built in the county⁸. Flood: confirm whether the parcel touches a mapped flood hazard area, since new flood-prone building sites are prohibited in any subdivision regardless of size or number of lots²². Access: direct residential driveway access to a major collector or arterial road is allowed only when no feasible alternative exists, with a minimum 150-foot separation between entrances measured from centerline²⁶. Taxes: St. Mary's County's effective property tax rate runs about 0.9%, with a typical annual bill near $3,392¹⁰¹¹.

Watch-outs

A new single-family home in St. Mary's County carries a $6,697 excise tax on top of the $20 application fee and per-square-foot dwelling fee, a cost many buyers don't budget for⁵.
Maryland law requires every county to adopt a local law authorizing accessory dwelling units by October 1, 2026; confirm with Development Services whether St. Mary's County has adopted or updated its ADU rules before assuming a guest house or in-law suite is allowed as described here²⁷.
Minimum lot size, setbacks, lot coverage, building height and any agricultural exemption from zoning were searched for on St. Mary's County's official pages and could not be confirmed; get a written zoning determination for your specific parcel rather than assuming a number².

Sources

Written September 24, 2026 from the rules quoted below, each taken from an official source and re-checked by an independent reviewer. This is research, not legal advice: rules change, so confirm with the office before you buy or build.

How St. Mary's County scores

Seclusion25100% ev.

Self-Sufficiency75100% ev.

Admin Boringness42100% ev.

Durability80100% ev.

Property Autonomy43100% ev.

Carry Cost55100% ev.

Evidence strength: 100%. This reports direct-source completeness and fallback use; it is separate from the score and is not a confidence interval. How it works →

$440kTypical home

0.9%Property tax

$8,652Land / acre

45.3"Annual rain

1.6% of yrsSevere drought

4.4 / yr (+4.2)Mid-century 100°F days

13 daysMid-century dry spell

2.16" (+5.6%)Mid-century 1-day rain

1.45×Wildfire change factor

100%Forward climate coverage

$1,748Home insurance / yr

3.2% / yrInsurance growth

0.3%Nonrenewal rate

county median (2+ published ZIPs)Insurance basis

58,850People within 30 min

6,612,918People within 2 hr

119,176Radius comparison (15 mi)

321.5People / sq mi

3.9%Federal land

89.8%Land at 15% slope or less

1%Septic soil without severe limits

2,058 acWorkable land screen

57.5%Wooded land

78.8 tonsBiomass / forest ac

57.4°FAvg temp

Answers from the rulebook for St. Mary's County

What the ordinances and state agencies actually say — one answer per question, each quoted from the official source and independently re-checked.

St. Mary's County rules

Building permitRequired
Residential land in St. Mary's County, including construction of a single-family dwelling such as a stick-built, modular, or mobile home.
- The county uses a Drop Off process for construction of a single-family dwelling, additional living space, accessory apartments, townhouses, and specified other residential development.
- Additional reviews may be required for septic or private wells, public water or sewer, soil disturbance exceeding 5,000 square feet, floodplain, Chesapeake Bay Critical Area, or other environmental features.
- A building permit application requires the applicable application materials and a $20 application fee; other agency fees, bonds, and excise tax may also apply.
application fee: 20 USD (Other agency fees, bonds, and excise tax may also apply.) · soil disturbance threshold for Soil Conservation District review: > 5000 square feet (A Sediment & Erosion Control Plan prepared by a licensed surveyor or engineer is required.)
“Use this procedure to obtain a Building Permit on Residential land if the following kind of development is proposed: • Construction of a single-family dwelling (stick built, modular, mobile home)”
How to Apply for a Residential Building Permit ↗Re-checked Sep 24, 2026
Owner-builder exemptionConditional
An owner-builder applicant for a residential construction project in St. Mary's County.
- The county permit application allows the applicant to identify the builder as either a contractor or 'Myself'.
- Selecting 'Myself' does not exempt the project from the building-permit requirement, inspections, certificate-of-occupancy requirements, or other applicable approvals.
- The official sources reviewed do not establish a broader exemption from Maryland home-builder registration, trade licensing, or other licensing requirements.
“Who will be the Builder? Contractor_____________________________________ Myself____”
St. Mary's County Permit Application ↗Re-checked Sep 24, 2026
Building code adoptedAdopted (with conditions)
Building-code adoption and enforcement in St. Mary's County, Maryland.
- The ordinance updates took effect July 15, 2024.
- The adopted codes include the 2021 IBC, IECC, IEBC, and ISPSC, and the 2018 IFGC, IMC, and IPC.
- The 2018 IFGC, IMC, and IPC are to be updated to 2021 versions once adopted by Maryland; those changes become effective six months after the state's effective date or publication date, whichever is later.
- Future editions of referenced codes become effective six months after the state's effective date or publication date, whichever is later.
- The new requirements do not apply to work under a valid building permit issued after the ordinance effective date when the permit application was filed before the effective date and some commencement of work is evident within 12 months of the ordinance effective date.
- LUGM implements and enforces the Maryland Building Performance Standards, including plan reviews, building permits, inspections, and use and occupancy certificates.
ordinance effective date: 2024-07-15 · future state-code update delay: 6 months (after the state's effective date or publication date, whichever is later) · permit-work commencement threshold: 12 months (some commencement of work must be evident)
“During their business meeting on June 25, 2024, the Commissioners of St. Mary’s County (CSMC) approved proposed updates to the local Building Code Ordinance to repeal and reenact Chapter 203 entitled, "Building Construction" and repeal Chapter 223 Article IV entitled, "Inspection Fees.” These changes will take effect on July 15, 2024.”
St. Mary's County Building Code, Ordinance No. 2024-11 ↗Re-checked Sep 24, 2026
InspectionsRequired
Construction or work for which a St. Mary's County building permit is required.
- The work must remain visible and accessible for inspection until approved.
- Work may not proceed beyond each successive inspection point without approval.
- The permit applicant must bear expenses associated with removing or replacing material needed to allow inspection.
“Construction or work for which a permit is required shall be subject to inspection by the code official and/or the building inspector and such construction or work shall remain visible and able to be accessed for inspection purposes until approved.”
St. Mary's Building Code ↗Re-checked Sep 24, 2026
Certificate of occupancyRequired
Occupancy of a newly constructed dwelling in St. Mary's County.
- The certificate is issued after construction is completed and the building has been inspected and found compliant with applicable regulations tied to the building permit.
- The applicant must obtain required agency final-inspection sign-offs; if an agency sign-off is not required, permits staff mark the card N/A.
- The final inspection card must be brought to the Department of Land Use and Growth Management after all required agencies have signed it.
“For an applicant to occupy a newly constructed dwelling, regulations administered by the Department of Land Use and Growth Management require issuance of a Certificate of Use and Occupancy pursuant to Section R110 of the Building Code and Section 22.7 of the St. Mary’s County Zoning Ordinance.”
Certificate of Occupancy - Residential ↗Re-checked Sep 24, 2026
County-wide zoningPresent (with conditions)
County-administered zoning and zoning determinations in St. Mary's County, Maryland.
- Development Services coordinates reviews for concept, major and minor site plans, subdivision plans, boundary line adjustments, and confirmatory plats.
- Zoning determinations are provided upon request.
“The Development Services Division coordinates multi-agency reviews for Concept, Major and Minor Site Plans, Subdivisions Plans, Boundary Line Adjustment and Confirmatory Plats, and provides zoning determinations upon request.”
Development Services - St. Mary's County ↗Re-checked Sep 24, 2026
Living in an RVLimited
Occupancy of one camping or recreational trailer on an owner's lot in an allowable St. Mary's County zoning district.
- Recreational vehicles may not be occupied as permanent residences.
- The parcel must be at least 1 acre.
- Use must be intermittent and for private recreational use and enjoyment of the owner's property, such as camping or hunting.
- Occupancy may not exceed seven consecutive nights.
- The trailer must be completely screened from dwellings on adjacent lots by a fence or evergreen buffer.
- The trailer must have an authorized self-contained sewerage holding tank.
- Recreational vehicles must comply with the Ordinance's floodplain provisions.
minimum parcel size: >= 1 acre · maximum consecutive occupancy: <= 7 nights
“Recreational vehicles may not be occupied as permanent residences.”
St. Mary’s County Comprehensive Zoning Ordinance, Article 5: Regulation of Uses ↗Re-checked Sep 24, 2026
Who permits septicCounty
Individual septic-system construction, expansion, and repair applications in St. Mary's County.
- The St. Mary's County Health Department Environmental Health Division administers the application process.
- State requirements under COMAR 26.04.02 apply.
“The Environmental Health Division receives applications for the construction or expansion of individual septic systems. When a septic system fails, the staff also reviews applications for repairs.”
On-Site Septic Systems ↗Re-checked Sep 24, 2026
Septic permitRequired
Construction or expansion of individual on-site sewage disposal systems in St. Mary's County.
- A perc test is required for new construction or repair.
- For all new construction, a Maryland-registered land surveyor site plan must be submitted for review.
- Construction may begin upon approval of the septic construction application.
- The approved permit is valid for 2 years from issuance.
permit validity: 2 years from issue date
“Pursuant to COMAR 26.04.02, I hereby apply for a permit to construct an On-Site Sewage Disposal to serve the below property. This application serves as the permit for installation and must be present while onsite. This permit expires 2 years from issue date.”
On-Site Septic Systems ↗Re-checked Sep 24, 2026
Septic inspectionRequired
Individual septic systems installed or repaired in St. Mary's County.
- The Health Department must be contacted to conduct the inspection before the septic system is covered.
- Inspection occurs after construction approval and during installation; additional requirements may apply to particular system types.
“Contact the health department to conduct an inspection of the septic system before covering”
On-Site Septic Systems ↗Re-checked Sep 24, 2026
Off-grid sanitationLimited
Private on-site sewage disposal for properties in St. Mary's County that are not served by public water and sewer.
- Properties not served by public water and sewer must complete a perc test before construction of any structure with plumbing.
- An approved septic construction application is required before construction begins.
- A Health Department inspection must occur before covering the system.
- The private system remains subject to site-plan, septic-permit, and applicable state requirements.
“A perc test is a soils test to determine if the soils and groundwater conditions on a property are suitable for use as an on-site sewage disposal system. All properties not served by public water and sewer must have this test before beginning construction of any structure with plumbing.”
Building Permit Process ↗Re-checked Sep 24, 2026
Mandatory utility hookupConditional
Properties subject to public water or sewer connection requirements in the St. Mary's County Metropolitan Commission service area.
- A waiver or deferral may permit interim private water or sewer service.
- The private service must be approved by the Office of Environmental Health.
- The private service must be designed for future connection to a public system.
- When MetCom determines connection is feasible, the private service must be discontinued and the property connected to the public system.
- The cited project document identifies the requirement as applying when a waiver from water and sewer connection is required.
“The applicant has obtained a waiver or deferral to connect to the public _I__, and subsequently the resulting private _2_ service shall be: a. approved by the Office of Environmental Health; and b. designed for future connection to a public system when the Metropolitan Commission determines that a connection is feasible and the private _3_ service shall be discontinued and the property shall be connected to the public system.”
The Greenery Technical Evaluation Committee Package ↗Re-checked Sep 24, 2026
Subdividing landRegulated (with conditions)
Subdivision plans and subdivision-related development review in St. Mary's County
- The county's Development Services Division coordinates multi-agency reviews for subdivision plans.
- Permit information is routed to other required agencies for review and approval.
- Applicable requirements may include the county Building Code, Zoning Ordinance, and Subdivision Regulations.
“The Development Services Division coordinates multi-agency reviews for Concept, Major and Minor Site Plans, Subdivisions Plans, Boundary Line Adjustment and Confirmatory Plats, and provides zoning determinations upon request.”
Permits - St. Mary's County, MD ↗Re-checked Sep 24, 2026
Driveway accessLimited
Residential driveway access governed by the St. Mary's County Subdivision Ordinance, particularly subdivision entrances and access to public roads.
- Residential driveway access is limited to cul-de-sacs, local roads, and minor collector roads.
- Multi-family and cluster subdivisions must have direct access to a public road.
- Direct residential access to major collectors and arterials is permitted only when no feasible alternative exists.
- Where direct access to a major collector or arterial is allowed, minimum separation between driveways or entrances is 150 feet measured from centerline.
- Entrances onto public roads must comply with the Department of Public Works and Transportation Manual of Design and Construction Standards and the ordinance.
minimum separation for permitted direct residential access to major collectors or arterials: 150 feet (Only when no feasible alternative exists; measured from centerline)
“Residential driveway access shall be limited to cul-de-sacs, local roads and minor collector roads. Multi-family and cluster subdivisions shall have direct access to a public road.”
St. Mary's County Subdivision Ordinance ↗Re-checked Sep 24, 2026
Building in a floodplainRequired
Development or construction wholly within, partially within, or in contact with a flood hazard area in St. Mary's County.
- A permit must be obtained before starting covered development or construction.
- Covered activities include filling, grading, new structures, substantial improvement or repair of substantially damaged structures, placement or replacement of manufactured homes, erecting or installing temporary structures, and alteration of a watercourse.
- Creation of any new flood-prone building site is prohibited in any subdivision governed by the County's Zoning Ordinance regardless of size, number of lots, or location.
- For a permit to build in the floodplain, the applicant must agree to have an Elevation Certificate prepared by a licensed engineer or surveyor.
- Structures in Special Flood Hazard Areas that are substantially improved or substantially damaged must comply with current floodplain regulations.
- Substantial damage includes repair costs equal to or exceeding 50 percent of original market value.
substantial damage threshold: >= 50 percent of original market value (Repair cost threshold described by the county)
“A permit must be obtained prior to starting any development or construction which is wholly within, partially within, or in contact with any flood hazard area including filling; grading; construction of new structures; the substantial improvement of any building or structure including the repair of a substantially damaged building or structure; placement or replacement of manufactured homes including the substantial improvement or repair of a substantially damaged manufactured home; erecting or installing a temporary structure; or alteration of a watercourse.”
Floodplain Management - St. Mary's County, MD ↗Re-checked Sep 24, 2026
Permit feesPublished (with conditions)
Published residential permit fees administered by St. Mary's County Department of Land Use and Growth Management.
- The source is marked Revised 8/24/2023; this is treated as a revision stamp rather than an effective date.
- Fees vary by permit type and may include application, square-footage, excise-tax, review, inspection, entrance-bond, and utility-connection charges.
- Health Department Review Fee is $21.00 to $90.00; Soil Conservation District Review Fee is $75.00 to $500.00; MetCom connection fees require calling 301-737-7400; Building Inspection Fees require calling MDIA at 301-884-4547; Entrance Permit bond is $5,000.00 or $10,000.00.
application fee: 20 USD · new dwelling fee: 0.16 USD/sq. ft. ($20.00 minimum) · new dwelling excise tax - single family: 6697 USD · new dwelling excise tax - multi family: 3218 USD · residential addition fee: 0.16 USD/sq. ft. ($20.00 minimum) · detached residential accessory structure fee: 0.03 USD/sq. ft. ($20.00 minimum) · health department review fee: 21-90 USD · soil conservation district review fee: 75-500 USD · entrance permit bond: 5000 or 10000 USD
“FAQ #12: What fees can I expect to pay for my residential permit? Application Fee $ 20.00”
FAQ #12: Residential Permit Fees ↗Re-checked Sep 24, 2026
Permit processPublished (with conditions)
County permit processing by the Permit Services Division for building, environmental, residential entrance, home occupation, family daycare, business occupancy, and sign permits.
- Applications are processed under applicable Building Code, Zoning Ordinance, and Subdivision Regulations.
- Permit information is routed to other required agencies for review and approval.
- The page does not establish that every permit type follows identical steps or timelines.
“The Permit Services Division’s principal function is to process building and other permits including environmental (Critical Area and Floodplain), residential entrances, home occupations, family daycare, change of business occupants, and sign permits in accordance with the applicable regulations, such as the Building Code, Zoning Ordinance and Subdivision Regulations. The Permits staff must also coordinate the routing of permit information to other required agencies for their review and approval.”
Permits - St. Mary's County, MD ↗Re-checked Sep 24, 2026

Maryland rules that apply here

Zoning districtsPartial
Statewide generalized zoning information published by the Maryland Department of Planning for planning and regional analysis; it is not a substitute for the applicable county or municipal zoning ordinance.
- Each local jurisdiction is responsible for its own zoning, except certain municipalities that do not exercise planning and zoning authority.
- Maryland has hundreds of unique local zoning categories.
- MDP groups generalized zoning into Rural, Residential, and Other, further divided into 11 generalized zoning categories.
- The generalized categories do not establish the complete regulatory zoning districts or permitted uses for a specific parcel.
“To aid regional and state-level planning purposes, MDP classified zoning districts under three main groups—Rural, Residential, and Other—which are further broken down into 11 distinct Generalized Zoning Categories.”
Geospatial Applications and Modeling (GAM) ↗Re-checked Sep 11, 2026
Accessory dwellingsLimited
Accessory dwelling unit development statewide under Maryland Land Use Article Title 4, Subtitle 5.
- The subtitle applies only to land with a single-family detached dwelling unit as the primary dwelling unit.
- Each legislative body must adopt a local law authorizing accessory dwelling unit development on or before October 1, 2026.
- A local law may establish accessory dwelling unit safety standards.
- A local law may prohibit full or partial conversion of an accessory structure when the only vehicular access is from an alley.
- Construction must meet public health, safety, and welfare standards, including relevant building codes and adequate public facilities provisions.
- A local law must exclude the accessory dwelling unit from density calculations and residential-growth limits applicable to the lot, parcel, or tract.
- A local law may not establish side- or rear-yard setback requirements exceeding existing accessory-structure setback requirements.
- Additional off-street parking requirements may be established only under the statutory considerations, with a waiver process and a completed parking study.
local authorization deadline: 2026-10-01 · primary dwelling type: single-family detached dwelling unit · side and rear setback ceiling: <= existing accessory structure setback requirements
“each legislative body shall adopt a local law authorizing the development of accessory dwelling units in accordance with this section.”
Maryland Land Use Article §4-502 ↗Re-checked Sep 11, 2026
Well permitRequired
Construction of any well in Maryland, including wells serving private or non-community water supplies.
- A hard copy of the permit application must be provided for the County, Survey, Driller, Well Owner, and Department to the Approving Authority at submission.
- If a new well replaces an unused well, the unused abandoned well must be sealed.
- For residential and other establishments not served by a community water supply, the well must satisfy COMAR 26.04.04; alternatively, a permitted surface-water system meeting COMAR 26.04.01 may be used.
- A well may not be constructed to provide potable water to property already connected to a community water supply unless authorized by the Department.
“A well construction permit is required for any well that is constructed in the State of Maryland.”
Well Construction Permit Applications and Forms ↗Re-checked Sep 11, 2026
One more reviewed finding on this topic
- Required — Any well constructed in St. Mary's County, under Maryland's statewide well-construction permitting requirement.
  “A well construction permit is required for any well that is constructed in the State of Maryland.”
  Well Construction Permit Applications and Forms ↗Re-checked Sep 24, 2026
county zoning authorityGeneral
Maryland counties adopting and enforcing zoning and planning laws, including for unincorporated county territory within the county's jurisdiction.
- The authority is exercised through local laws and remains subject to other public general law, public local law, and any applicable State-government regulatory authority.
- The statute states that the State policy is that planning and zoning controls are implemented by local government.
“A county may enact local laws relating to zoning and planning to protect and promote public safety, health, morals, and welfare, including: [...] It is the policy of the State that planning and zoning controls shall be implemented by local government.”
Maryland Code, Local Government Article ↗Re-checked Sep 21, 2026
county building authorityLimited
Maryland counties requiring building permits and adopting or enforcing building codes for residential construction in unincorporated areas.
- Local Government Article § 13-901 applies to all counties except Anne Arundel County, Baltimore City, Baltimore County, Cecil County, Charles County, Howard County, Prince George’s County, Queen Anne’s County, and Worcester County.
- Under § 13-901(c), covered county governing bodies may regulate building construction, adopt and enforce building codes, require building permits, impose permit and inspection fees, and inspect buildings and structures.
- Section 13-902 applies only to Calvert, Caroline, Dorchester, Frederick, Harford, Kent, and Worcester Counties.
- Under § 13-902(c), a building or housing code generally does not apply to a building on a farm or premises devoted solely to agricultural uses, except that it applies in Calvert County to dwellings on which construction began after July 1, 1979 and in Frederick County to residential buildings or buildings constructed for human habitation regardless of location or auxiliary use.
- Kent County must adopt a building code and housing code; Calvert, Caroline, Dorchester, Frederick, Harford, and Worcester Counties may adopt them.
- A building code adopted under § 13-902 must require a building permit before a building is built or improved and include standards for structural safety, fire prevention, lighting, ventilation, and proper access.
- Later amendments to codes incorporated by reference are not effective in Caroline, Frederick, Harford, Kent, and Worcester Counties until incorporated into the county code.
- Separate county-specific provisions apply to Cecil, Charles, Queen Anne’s, and St. Mary’s Counties, including the Charles County exemption for farm buildings and other outbuildings costing less than $2,500.
- The Maryland Building Performance Standards apply statewide to each building or structure for which a building permit application is received by a local jurisdiction on or after August 1, 1995.
building permit before building is built or improved: true (Required in a building code adopted under Local Government Article § 13-902.) · Charles County farm-building or outbuilding cost exemption: < 2500 USD (The Charles County building code does not apply to farm buildings or other outbuildings costing less than $2,500.) · Maryland Building Performance Standards application date: >= 1995-08-01 (Applies to building permit applications received on or after this date.)
“This section applies to all counties except: [...] The governing body of a county may: (1) regulate the construction of buildings and signs; (2) adopt a building code; (3) provide for enforcement of the code; (4) require permits for the construction of buildings and signs; (5) impose permit and inspection fees; (6) provide for inspection of buildings and structures;”
Maryland Code, Local Government Article, §§ 13-901 through 13-906 ↗Re-checked Sep 21, 2026

Still unanswered

We looked and could not find an official answer yet. Silence is not permission — ask the county directly.

Minimum dwelling size — Minimum dwelling-size requirements in St. Mary's County
Minimum lot size — Minimum lot-size requirements in St. Mary's County
Setbacks — Setback requirements in St. Mary's County
Lot coverage — Lot-coverage limits in St. Mary's County
Building height — Building-height limits in St. Mary's County

3 more unanswered

Tiny homes
Agricultural exemption
Short-term rentals

Each answer was extracted from an official source and independently re-checked against that source by a second reviewer. That is an evidence check, not legal advice. Rules change; confirm with the authority before you buy or build.

Living off-grid in St. Mary's County, Maryland

Is St. Mary's County a good place to live off-grid or homestead?

St. Mary's County scores 55/100 on the Bolthole Index, a solid county profile. Its strengths: mixed durability signals and strong self-sufficiency basics: 45.3″/yr rainfall plus 57.5% wooded land. Watch-outs: about 58,850 people within a 30-minute drive.

Do you need a building permit in St. Mary's County, Maryland?

St. Mary's County generally requires a residential building permit, and it enforces county zoning. Onsite septic is permitted by St. Mary's County Health Department - Environmental Health Division. Owner-builders may act as their own contractor to build their home. These answers are quoted from official sources and independently re-checked. Rules change and cities within the county differ — always confirm with the county before you buy or build.

Can you live in an RV or tiny home on your land in St. Mary's County?

Living in an RV on your own land in St. Mary's County is limited to specific cases: Occupancy of one camping or recreational trailer on an owner's lot in an allowable St. Mary's County zoning district. Recreational vehicles may not be occupied as permanent residences. The parcel must be at least 1 acre. Confirm with the county before relying on it.

How much does land cost in St. Mary's County, Maryland?

Land in St. Mary's County runs about $8,652 per acre, based on the latest county data.

What is the water situation in St. Mary's County?

St. Mary's County gets about 45.3" of rain a year, with severe drought in roughly 1.6% of years.

How remote is St. Mary's County?

A representative private-land location has about 58,850 people within a 30-minute drive and 6,612,918 within two hours. The road-network catchments count population across county lines and clusters of smaller cities; straight-line radius values remain available as a comparison.

Building permits, zoning and land rules in St. Mary's County, Maryland

At a glance

Who to call

Do you need a building permit in St. Mary's County, Maryland?

Who is the St. Mary's County building department, and how do you reach them?

Does St. Mary's County have zoning?

How do septic permits work in St. Mary's County?

Can you live in an RV or tiny home on your land in St. Mary's County?

Building a home in St. Mary's County: the steps, in order

What to check before you buy land in St. Mary's County

Watch-outs

Sources

St. Mary's County in Maryland

How St. Mary's County scores

Find land. Bring the promising ones back.

Parcel due diligence

Answers from the rulebook for St. Mary's County

St. Mary's County rules

Maryland rules that apply here

Still unanswered

Living off-grid in St. Mary's County, Maryland

Is St. Mary's County a good place to live off-grid or homestead?

Do you need a building permit in St. Mary's County, Maryland?

Can you live in an RV or tiny home on your land in St. Mary's County?

How much does land cost in St. Mary's County, Maryland?

What is the water situation in St. Mary's County?

How remote is St. Mary's County?

How St. Mary's compares in Maryland