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Maryland Building Codes, Permits and Contractor Rules

Here’s every rule from our 50-state guides for Maryland on one page: the residential building code, frost depth, retaining wall permits, the 811 dig law, drainage law, contractor licensing, deposit limits, mechanics lien deadlines, workers’ comp, planting zones and frost dates. Each section links the official source and the full 50-state comparison.

Maryland at a glance

Building code: 2021 IRC (statewide minimum)
Frost depth: Set locally; often 18 in.
811 notice: Start work date must be at least 2 and no more than 12 business days after the ticket is initiated
Contractors: State license required
Deposits: 1/3 of contract price
Liens: 180 days from last furnishing
Workers’ comp: 1+ employees
Drainage rule: Civil law (natural flow)
Planting zones: 5b to 8a

Topic	Maryland	Compare
Residential building code	2021 IRC (statewide minimum)	All states
Frost line depth	Set locally; often 18 in.	All states
Retaining wall permit	Model rule by default: exempt if not over 4 ft from bottom of footing to top of wall, unless supporting a surcharge or impounding Class I, II or IIIA liquids…	All states
811 notice before digging	Start work date must be at least 2 and no more than 12 business days after the ticket is initiated	All states
Contractor license	State license required	All states
Deposit limit	1/3 of contract price	All states
Right to cancel	3 business days, sales made at home	All states
Lien filing deadline	180 days from last furnishing	All states
Workers’ comp required	1+ employees	All states
Drainage between neighbors	Civil law (natural flow)	All states
Planting zones (2023 USDA)	5b to 8a	All states
Frost dates (NOAA)	Last frost early Apr (Hagerstown) to early May (Oakland); first frost early Oct (Oakland) to early Nov (Hagerstown)	All states

Summary for Maryland. Details, exceptions and official sources are in each section below.

Maryland residential building code

Code: 2021 International Residential Code (Maryland Building Performance Standards, COMAR 09.12.51)
How it applies: Statewide minimum, local amendments allowed
In effect since: May 29, 2023
Code agency: Maryland Department of Labor, Building Codes Administration
Who enforces it: Counties and municipalities must implement and enforce the Standards within 12 months of each state update (May 29, 2024 for the 2021 codes) and may amend them for local conditions, with limits on energy, sprinkler and wind provisions.
Good to know: Maryland uses the 2021 IRC, but each county can amend it, so rules in Montgomery County may differ from those in Frederick or Baltimore County.

Compare building codes in all 50 states

Frost line depth in Maryland

Who sets it: Local building department
Local examples: Montgomery County: 30 in.
Wicomico County: 18 in.
Garrett County: 36 in. minimum (finish grade to bottom of footing)
Typical range: 18 in. on the lower Eastern Shore (Wicomico) to 36 in. in western Maryland (Garrett); 30 in. in Montgomery County
Good to know: Queen Anne's County lists 24 in., and Baltimore City's amendment to IBC 1809.5 uses 30 in. below grade. County tables are posted on the Maryland Department of Labor website.

Frost line depth in every state

Retaining wall permits in Maryland

Permit exemption: Model rule by default: exempt if not over 4 ft from bottom of footing to top of wall, unless supporting a surcharge or impounding Class I, II or IIIA liquids (2021 IRC R105.2 as incorporated by COMAR 09.12.51.04, which makes no change to R105). Counties and cities may change it by local amendment, and local amendments prevail (COMAR 09.12.51.05).
Who decides: Your county or municipality adopts and amends the code and decides.
Good to know: Counties and cities can change the 4 ft rule, and their local amendments override the state standard. Check with your county or city before you build.

Retaining wall permit rules in every state

811 dig law in Maryland

One-call center: Miss Utility
Notice before digging: Start work date must be at least 2 and no more than 12 business days after the ticket is initiated
Ticket good for: 12 business days after the selected work date
Hand-dig zone: 18 in. of a facility marking (expose by hand or nondestructive means before using mechanized equipment)
Homeowners: Narrow exemption: the law does not apply to excavation not more than 6 in. deep, done by the owner or lessee of a private residence entirely on that residence's land, without machinery. Deeper or machine digging requires a call.
The law: Md. Code Ann., Pub. Util. § 12-101 et seq.
Good to know: Since HB 994 took effect Oct 1, 2022, the ticket runs 12 business days after the work date you select, and that date can be no more than 12 business days out. The homeowner exemption stops at 6 in. deep, among the shallowest in the U.S.

811 dig laws in every state

Drainage law and stormwater permits in Maryland

Rule: Civil law (natural flow)
The rule: Natural flow with reasonable precautions: landowners are entitled to have surface water flow naturally over lower land, but upper owners may not artificially increase or concentrate the flow and must use reasonable precautions against harm. (Label assigned from the rule.)
Leading case: Mayor and City Council of Baltimore v. Abel (restating Battisto v. Perkins). Supreme Court of Maryland No. 26, Sept. Term 2025 (July 29, 2026); citing Battisto v. Perkins, 210 Md. 542 (1956) and Whitman v. Forney, 181 Md. 652 (1943)
What it means for your yard: Water may keep flowing downhill naturally, but if you regrade, pipe downspouts or add a patio that artificially increases or concentrates runoff onto a neighbor without reasonable precautions, you can be liable.
Construction stormwater permit: Maryland Department of the Environment (MDE); erosion and sediment control plans are approved by local approval authorities: 1 acre or more of planned total earth disturbance (or less if part of a common plan that will ultimately disturb 1 acre or more): General Permit No. 20-CP for Stormwater Associated with Construction Activity (effective April 1, 2023)
State rules below 1 acre: Grading permit and approved erosion and sediment control plan required unless less than 5,000 sq ft and less than 100 cubic yards are disturbed (state law minimum; local jurisdictions may be stricter)
Local rules: Maryland counties and municipalities issue grading permits and may set stricter erosion control and stormwater thresholds than the state.
Good to know: Maryland lets water flow naturally downhill but bars artificially increasing or concentrating it onto a neighbor. Disturbing 5,000 sq ft or 100 cubic yards of soil generally needs a grading permit and erosion control plan.

Drainage laws in every state

Contractor licensing in Maryland

Statewide rule: License
Agency: Maryland Home Improvement Commission (MHIC), Maryland Department of Labor
Who needs it: Only MHIC-licensed contractors may contract with homeowners for home improvement work; subcontractors working for a licensed contractor need no license.
Check a contractor: Official lookup
Good to know: The MHIC lists no dollar threshold for the license. A 2023 law (Ch. 429) raised the Guaranty Fund cap per contractor from $100,000 to $250,000.

Contractor license requirements in every state

Contractor deposits and your right to cancel in Maryland

Deposit limit: A contractor may not receive a deposit of more than one-third of the home improvement contract price before or when the contract is signed, and may not demand or receive any payment before the contract is signed (Md. Code, Bus. Reg. § 8-617).
Who it covers: Home improvement contracts under the Maryland Home Improvement Law (Bus. Reg. Title 8), i.e., work on existing residential property by MHIC-licensed contractors.
Right to cancel: Door-to-door sales of $25 or more (including when the buyer invited the seller): 3 business days to cancel; business days exclude Sundays and listed holidays, so Saturdays count (Md. Code, Com. Law §§ 14-301, 14-302). If the contract is secured by a mortgage or lien on your home, the contract must state on page one that you may rescind within 3 business days (Bus. Reg. § 8-501(c)(2)).
Written contract: Required. Must include the contractor's name, address, phone and MHIC license number, each salesperson's name and license number, approximate start and substantial completion dates, description of work and materials, agreed price, payment terms and any finance charge, and Commission notices on licensing, consumer protections and the right to buy a performance bond; the owner gets a signed copy before work begins (Bus. Reg. § 8-501).
Other protections: Maryland Home Improvement Guaranty Fund covers losses from licensed contractors; there is no Guaranty Fund protection when an unlicensed contractor is used (per MHIC).
The law: Md. Code, Bus. Reg. §§ 8-501, 8-617; Com. Law §§ 14-301 to 14-306 (Door-to-Door Sales Act)
Good to know: Maryland contractors can't take any money before you sign, and can't take more than one-third of the price as a deposit. Hiring an unlicensed contractor means no Guaranty Fund protection if the job goes bad.

Contractor deposit limits in every state

Mechanics lien deadlines in Maryland

Lien deadline (prime): File a petition to establish the lien in circuit court within 180 days after the work is finished or materials furnished (Real Prop. § 9-105).
Lien deadline (sub/supplier): Same 180 days, after the 120-day notice (Real Prop. §§ 9-104, 9-105).
Preliminary notice (sub/supplier): No pre-work notice; see the 120-day notice of intention under notice of intent (Md. Code, Real Prop. § 9-104).
Notice of intent: Subcontractors: sworn 'Notice to Owner or Owner's Agent of Intention to Claim a Lien' sent by certified or registered mail or personally delivered (or posted on the building before a witness if delivery fails) within 120 days after doing the work or furnishing materials (Real Prop. § 9-104).
Enforce within: Petition to enforce within 1 year after the petition to establish the lien was first filed (Real Prop. § 9-109).
Homeowner rules: For a single-family dwelling built for the owner's own residence, a sub has no lien if the owner paid the contractor in full before receiving the sub's notice, and the lien can't exceed what the owner still owed when notified (Real Prop. § 9-104(a)(2), (f)(3)). Repairs or improvements are lienable only if they reach 15% of the building's value (§ 9-102(a)).
The law: Md. Code, Real Property Title 9, Subtitle 1 (Mechanics' Liens), §§ 9-101 to 9-114
Good to know: In Maryland, a remodel must add at least 15% to a building's value to be lienable, and on a new home built for the owner, a sub has no lien if the owner paid the contractor in full before getting the sub's notice.

Mechanics lien deadlines in every state

Workers' comp requirements in Maryland

Who must carry it: Every employer with 1 or more employees in Maryland must provide coverage, with few exceptions (Md. Code, Lab. & Empl. Title 9; Maryland WCC). No separate construction threshold.
Owners and officers: Corporate officers and LLC members paid for services are covered employees but may elect exemption by written notice to the Commission and insurer: officers of close corporations; up to five officers of other corporations; 20%+ owners of farm or professional corporations; LLC members owning at least 20% (Lab. & Empl. § 9-206). Sole proprietors are not covered unless they elect coverage (§ 9-227); partners are covered only if the partnership elects (§ 9-219).
Subcontractors: A principal contractor that subcontracts part of work in its own business is considered the employer of the sub's covered employees and liable for compensation, with indemnity rights against the sub; it is not liable for exempt officers/members, non-electing partners, or sole proprietors who haven't elected coverage (Lab. & Empl. § 9-508).
Homeowners: The principal-contractor rule applies only to a contractor doing work that is part of its own business, so a homeowner hiring a contractor isn't made the employer of the contractor's crew by § 9-508.
Penalties: Fine of up to $10,000 for failing to secure coverage; corporate officers with general management responsibility in Maryland are personally liable for the fine (Maryland WCC employer FAQ, Form C-98).
The law: Md. Code, Lab. & Empl. Title 9; §§ 9-206, 9-219, 9-227, 9-508
State agency: Maryland Workers' Compensation Commission
Good to know: Maryland requires coverage with one employee. A general contractor is treated as the employer of a sub's workers, so collect proof of coverage from every sub.

Workers' comp requirements in every state

Planting zones in Maryland

2023 USDA zones: 5b to 8a
Coldest-night range: −15°F to 15°F
Coldest area: The Backbone Mountain area of Garrett County
Warmest area: Downtown Baltimore and the Atlantic coast around Ocean City
Example cities: Baltimore: 8a, Annapolis: 7b, Frederick: 7a, Ocean City: 8a
Good to know: Maryland spans more zones than its size suggests, from the cold Garrett County mountains in the far west to the mild Atlantic coast and downtown Baltimore.

Planting zones in every state

Frost dates in Maryland

Station	Last spring frost	First fall frost	Frost-free days
Baltimore Central Maryland (BWI airport station)	April 10	October 31	204
Salisbury Eastern Shore	April 10	October 30	201
Hagerstown Western Maryland valley	April 7	November 4	209
Oakland Garrett County mountains	May 6	October 9	156

Typical range: Last frost early Apr (Hagerstown) to early May (Oakland); first frost early Oct (Oakland) to early Nov (Hagerstown)
Good to know: These are typical (50%) dates from NOAA's 1991–2020 climate normals, so about half of years still bring a 32°F night after the listed spring date. In Maryland, the last spring frost at the stations listed ranges from early April around Hagerstown to early May around Oakland.
Local frost or planting guide: University of Maryland Extension

Frost dates in every state

Frequently Asked Questions

What building code does Maryland use?

2021 International Residential Code (Maryland Building Performance Standards, COMAR 09.12.51). It applies as follows: statewide minimum, local amendments allowed. Your local building department can confirm the edition and amendments for your address.

How deep is the frost line in Maryland?

Frost depth is set by local building departments. Typical local values: 18 in. on the lower Eastern Shore (Wicomico) to 36 in. in western Maryland (Garrett); 30 in. in Montgomery County. Footings for houses, additions and attached decks go below it.

How much can a contractor ask for up front in Maryland?

A contractor may not receive a deposit of more than one-third of the home improvement contract price before or when the contract is signed, and may not demand or receive any payment before the contract is signed (Md. Code, Bus. Reg. § 8-617). Cancel rights: Door-to-door sales of $25 or more (including when the buyer invited the seller): 3 business days to cancel; business days exclude Sundays and listed holidays, so Saturdays count (Md. Code, Com. Law §§ 14-301, 14-302). If the contract is secured by a mortgage or lien on your home, the contract must state on page one that you may rescind within 3 business days (Bus. Reg. § 8-501(c)(2)).

How long does a contractor have to file a mechanics lien in Maryland?

File a petition to establish the lien in circuit court within 180 days after the work is finished or materials furnished (Real Prop. § 9-105). Subcontractors and suppliers may have different notice rules; see the section above.

What planting zone is Maryland?

On the 2023 USDA map, Maryland runs from zone 5b to 8a. Examples: Baltimore 8a, Annapolis 7b, Frederick 7a. Enter your ZIP on the USDA map for your exact zone.

Do contractors need workers' comp in Maryland?

Every employer with 1 or more employees in Maryland must provide coverage, with few exceptions (Md. Code, Lab. & Empl. Title 9; Maryland WCC). No separate construction threshold. Owner exemptions and subcontractor rules are in the workers’ comp section above.

When is the last frost in Maryland?

At the NOAA stations we list: Last frost early Apr (Hagerstown) to early May (Oakland); first frost early Oct (Oakland) to early Nov (Hagerstown). These are typical (50%) dates from the 1991–2020 climate normals, so about half of years still bring a 32°F night after the spring date.

This page is general information, not legal or tax advice. Rules change; the agencies and statutes linked above have the final word.

Maryland in each 50-state guide: Frost line depth · 811 dig laws · Retaining wall permits · Contractor licensing · Contractor deposit limits · Building codes · Planting zones · Mechanics lien deadlines · Workers' comp · Frost dates · Drainage laws · Noxious weed laws · Rainfall and snowfall · Landscaper pay · Pesticide applicator licensing · Landscaping sales tax · All state guides

Soil: Maryland’s most common soils, state soil, and how much ground is wet, clayey or shallow to bedrock by county. Maryland soil types

Last checked October 31 and November 1, 2026 against official state and local sources for this state. Rules change; your state agency or local building department has the final word. Spot something out of date? Email info@muthlerlandscaping.com and we’ll fix it.

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