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Montgomery County Addition Permit Cost (2026)

Building a home addition in Montgomery County, Maryland, needs a building permit, and the fee is pulled directly from the official Montgomery County Department of Permitting Services (DPS) residential construction fee schedule. Montgomery County prices a residential addition at $0.767865 per square foot of construction plus a filing fee equal to 50% of the permit fee or $286.60, whichever is greater. A typical 400 sq ft addition works out to about $593.75. Maryland has no statewide percentage levy. The published schedule carries a FY2022 printed effective period, so confirm current rates with DPS before budgeting.

Addition Rate
$0.767865 per sq ft
Filing Fee
50% of permit fee or $286.60 (greater)
400 sq ft Addition (typical)
~$593.75 building permit
State / Local Percentage Levy
None (Maryland has no statewide levy)
Electrical / Plumbing / HVAC
Separate trade permits (not priced here)
Fee Status
Official schedule - FY2022 printed date, verify current rates
What This Guide Covers - and What It Does Not

This guide covers: Montgomery County, Maryland residential addition building permit fees as published in the DPS residential construction fee schedule. An addition is $0.767865 per square foot of construction plus a filing fee equal to 50% of the permit fee or $286.60, whichever is greater. This building permit covers the structural side of the addition.

This guide does NOT cover: Trade permits - the electrical, plumbing, and mechanical (HVAC) permits for the new space are each filed separately on Montgomery County's own trade fee schedules and are not priced here. Whether DPS counts gross or net square footage for a specific addition - confirm chargeable area with DPS. Zoning, setback, and stormwater approvals. HOA approvals. Contractor labor and material costs.

Important note on fee schedule age: The DPS AllFees.pdf currently published carries a printed effective period of July 1, 2021 - June 30, 2022 (FY2022) - more than 24 months old. Confirm the current per-square-foot rate and filing-fee minimum with DPS at 240-777-0311 before relying on any figure for a load-bearing budget.

How the worked totals are labeled: The dollar totals below are computed estimates, derived by direct arithmetic from the two verified inputs (the $0.767865/sq ft rate and the 50%/$286.60 filing fee). The square footage you enter and whether DPS uses gross or net area will change the result, so treat each total as an estimate, not a quotation.

Key Takeaways
  • Montgomery County prices a home addition at $0.767865 per square foot plus a filing fee - the same per-square-foot rate it uses for new detached construction.
  • The filing fee is the larger of 50% of the permit fee or $286.60. For smaller additions the $286.60 floor governs; the 50% figure only takes over above roughly 746 sq ft.
  • A typical 400 sq ft addition is about $593.75 ($307.15 permit + $286.60 filing). A 1,000 sq ft addition is about $1,151.80 ($767.87 permit + $383.93 filing).
  • Maryland has no statewide percentage building-permit levy, so there is no 2% add-on like Virginia's USBC levy. The per-square-foot fee plus filing fee is the building permit charge for the structure.
  • Trade work is separate. The electrical, plumbing, and mechanical permits for the new space are filed on Montgomery County's own trade schedules and are not included in these figures.
  • The DPS schedule carries a FY2022 printed effective period. Montgomery County may have adjusted rates since then. Always confirm the current per-square-foot rate and chargeable area with DPS at 240-777-0311 before filing.
Open the Permit Fee Calculator All Montgomery County Permit Fees

Montgomery County Addition Permit Fee Structure

Montgomery County prices a residential addition on a per-square-foot basis with a filing fee on top. There is no percentage levy. The permit fee is the area times $0.767865, and the filing fee is the larger of 50% of that permit fee or $286.60. Trade permits for electrical, plumbing, and HVAC are billed separately.

Component Amount How It Is Calculated
Permit fee (per square foot) $0.767865 / sq ft Construction area × $0.767865.
Filing fee 50% of permit fee or $286.60 Whichever is greater. The $286.60 floor governs up to ~746 sq ft.
Electrical / plumbing / HVAC Separate Filed on Montgomery County's trade fee schedules - not priced here.
State / local percentage levy None Maryland has no statewide USBC-style percentage levy. No 2% add-on.

Source: Montgomery County DPS residential construction fee schedule (AllFees.pdf), Additions line - $0.767865 per square foot, filing fee 50% of the permit fee or $286.60 (whichever is greater). Printed effective period FY2022 (July 1, 2021 - June 30, 2022). Trade permits (electrical, plumbing, mechanical) are billed separately. Confirm current rates and chargeable area with DPS before filing.

Worked Examples - Real Addition Projects in Montgomery County

Each total below is a computed estimate from the two verified inputs: $0.767865/sq ft for the permit fee and a filing fee equal to 50% of the permit fee or $286.60, whichever is greater. Trade permits are separate and not priced here. Confirm chargeable area with DPS.

Example 1: 400 sq ft single-story addition

A homeowner adds a 400 sq ft family-room extension on a single-family home in Rockville.

  • Permit fee: 400 × $0.767865 = $307.15
  • Filing fee: greater of 50% ($153.57) or $286.60 = $286.60 (floor governs)
  • Maryland percentage levy: $0.00 (none)
  • Building permit total (estimate): $593.75
  • Electrical / plumbing / HVAC: separate - not priced here

For additions up to about 746 sq ft, the $286.60 filing-fee floor governs, so the total rises only with the per-square-foot permit fee.

Example 2: 800 sq ft two-room addition

A homeowner adds an 800 sq ft addition with a new bedroom and bathroom. Above ~746 sq ft, the 50% filing fee now governs.

  • Permit fee: 800 × $0.767865 = $614.29
  • Filing fee: greater of 50% ($307.15) or $286.60 = $307.15 (50% governs)
  • Maryland percentage levy: $0.00 (none)
  • Building permit total (estimate): $921.44

The plumbing permit for the new bathroom and the electrical permit for the new circuits are separate Montgomery County trade permits, not included in the $921.44.

Example 3: 1,000 sq ft addition

A homeowner builds a large 1,000 sq ft addition.

  • Permit fee: 1,000 × $0.767865 = $767.87
  • Filing fee: greater of 50% ($383.93) or $286.60 = $383.93 (50% governs)
  • Maryland percentage levy: $0.00 (none)
  • Building permit total (estimate): $1,151.80

Each total is direct arithmetic from the verified $0.767865/sq ft rate and the 50%/$286.60 filing fee. The square footage and whether DPS uses gross or net area will change the result - confirm with DPS.

Montgomery County Addition Cost vs Other Verified Jurisdictions

Montgomery's per-square-foot-plus-filing addition fee is on the higher end of the verified Maryland cluster. The comparison below uses a 400 sq ft addition and mixes fee bases, so read the basis column. Trade permits are excluded everywhere because they vary by scope.

Jurisdiction Addition Fee Basis 400 sq ft Addition
Montgomery County, MD $0.767865/sq ft + filing ~$593.75
Howard County, MD $0.25/sq ft + 10% tech fee ~$160.00
Baltimore County, MD $85 (≤600 sq ft) / $130 (over) $85.00

Montgomery charges $0.767865/sq ft plus a filing fee (about $593.75 for a 400 sq ft addition); Howard County charges $0.25/sq ft plus a 10% technology fee (about $160 for the same addition); Baltimore County uses a flat $85 up to 600 sq ft and $130 over. None of the three adds a state levy, and trade permits are excluded everywhere. Montgomery figures carry a FY2022 printed effective period; Baltimore County figures a November 2018 effective date.

Side-by-Side Math

See how Montgomery compares head-to-head against its Maryland neighbors.

Frequently Asked Questions

A Montgomery County residential addition building permit costs $0.767865 per square foot plus a filing fee equal to 50% of the permit fee or $286.60, whichever is greater. A 400 sq ft addition works out to about $593.75 ($307.15 permit + $286.60 filing). Maryland adds no statewide percentage levy. Electrical, plumbing, and HVAC are separate trade permits. These figures come from the DPS schedule carrying a FY2022 printed effective period; confirm current rates with DPS at 240-777-0311.
The filing fee is the greater of 50% of the permit fee or $286.60. The 50% figure exceeds $286.60 once the permit fee passes $573.20, which happens at roughly 746 sq ft ($573.20 / $0.767865). Below that area, the $286.60 floor governs; above it, the 50% filing fee takes over.
No. The per-square-foot fee plus filing fee covers the building permit for the structural side of the addition. New circuits, plumbing fixtures, and heating or cooling extensions need separate electrical, plumbing, and mechanical permits filed on Montgomery County's own trade schedules and not included here. Contact DPS at 240-777-0311 for current trade-permit fees.
No. Maryland has no statewide percentage building-permit levy. In Virginia, every permit carries a mandatory 2% USBC state levy on top of the local fee. In Montgomery County, the per-square-foot permit fee plus the filing fee is the building permit charge for the addition - there is no percentage add-on.
Generally yes. For a 400 sq ft addition, Montgomery's ~$593.75 is well above Howard County's ~$160 ($0.25/sq ft + 10% tech fee) and Baltimore County's flat $85 (up to 600 sq ft). See the Howard vs Montgomery comparison for the per-square-foot head-to-head.
The figures come from the Montgomery County DPS residential construction fee schedule (AllFees.pdf) that carries a printed effective period of FY2022 (July 1, 2021 - June 30, 2022). Because that printed date is more than 24 months old, we flag a source-age caveat and recommend confirming the current per-square-foot rate and filing-fee minimum with DPS at 240-777-0311 before relying on the figure for a budget.
No. The Montgomery addition permit fee is the county building permit cost only. It does not include any contractor work. A home addition in the Montgomery County market typically runs $200-$500+ per square foot for the contractor scope depending on finishes and whether it includes a bathroom or kitchen. The permit fee is a small line item in your overall addition budget.

Sources

Official Sources - Recorded June 2026
Next Step

Confirm your specific Montgomery addition permit cost or compare against neighbors.

Always verify with the Montgomery County Department of Permitting Services (DPS) before budgeting or filing. The DPS residential construction fee schedule on file carries a printed effective period of FY2022 (July 1, 2021 - June 30, 2022). Montgomery County may have adjusted rates since then. Call 240-777-0311 or check the DPS department page to confirm the current per-square-foot rate, filing-fee minimum, chargeable area, and trade-permit rates before submitting an addition application.
Disclaimer: All fee information on PermitPrice is for informational purposes only and is not an official permit quotation. Actual permit fees are determined by Montgomery County DPS at the time of application. The dollar totals on this page are computed estimates derived by direct arithmetic from the verified $0.767865/sq ft rate and the 50%/$286.60 filing fee; the square footage and chargeable-area method will change the result. Fee schedules and permit requirements can change without notice. The published fee schedule carries a FY2022 printed effective period; confirm current rates before relying on any figure. Electrical, plumbing, and HVAC trade permits are billed separately and are excluded from the figures on this page.

Written by: Munib Ur Rehman

Data verified against official fee schedule documents.