Montgomery County, MD · Montgomery County Zoning Ordinance (Chapter 59)
Higher-density residential detached zone. Minimum lot area 4,000 sq ft. Allows duplex and townhouse under standard method. Workforce Housing optional method available.
Development standards in R-40
Front setback
25 ft
Chapter 59 Div 4.4
Rear setback
20 ft
Chapter 59 Div 4.4
Maximum height
Set by the building type you propose -- the R-40 Standard Method Development Standards table sets this per building type (detached house, duplex, townhouse, apartment), so no single figure is true for the whole zone — see Chapter 59 Div 4.4
Maximum lot coverage
Set by the building type you propose -- the R-40 Standard Method Development Standards table sets this per building type (detached house, duplex, townhouse, apartment), so no single figure is true for the whole zone — see Chapter 59 Div 4.4
Minimum lot size
Set by the building type you propose -- the R-40 Standard Method Development Standards table sets this per building type (detached house, duplex, townhouse, apartment), so no single figure is true for the whole zone — see Chapter 59 Div 4.4
Side setback
For a detached house (or a building for a cultural institution, religious assembly, public use or conditional use), 8 ft each side and 18 ft combined; for a side-by-side or over-under duplex, 10 ft each side — see Chapter 59 Div 4.4
Maximum height, Maximum lot coverage, Minimum lot size and Side setback are banded in the ordinance — it depends on what you build or on the lot itself, so no single figure is true for the whole zone. The cited table is the authority; read the tier that matches your intended structure.
Read from Montgomery County Zoning Ordinance (Chapter 59), effective through 2026-02-03. Amendments adopted after that date (most recent 2026-04-13) are not yet reflected.
How complete is this market? Across 304,119 parcels we answer 60.0% of the 6 questions this site is built to answer, each with a source you can check. The rest are shown as “not recorded” rather than filled in — we would rather be short than wrong.
Permitted uses in R-40
AllowedSingle-Unit Living Permitted by right. Use Table, Sec. 3.1.6 (Chapter 59, Div 3.1), row 20, column R-40. Use-specific standards: Sec. 3.3.1.B.
AllowedTwo-Unit Living Permitted by right. Use Table, Sec. 3.1.6 (Chapter 59, Div 3.1), row 21, column R-40. Use-specific standards: Sec. 3.3.1.C.
ConditionalTownhouse Living Varies -- Limited under some conditions and Conditional under others. This pairing is not in the Section 3.1.1 key; the use's own standards decide which applies, so it is served as the stricter of the two. Use Table, Sec. 3.1.6 (Chapter 59, Div 3.1), row 22, column R-40. Use-specific standards: Sec. 3.3.1.D.
ConditionalMulti-Unit Living Varies -- Limited under some conditions and Conditional under others. This pairing is not in the Section 3.1.1 key; the use's own standards decide which applies, so it is served as the stricter of the two. Use Table, Sec. 3.1.6 (Chapter 59, Div 3.1), row 23, column R-40. Use-specific standards: Sec. 3.3.1.E.
Not AllowedAttached Accessory Dwelling Unit This use is not listed for this zone in the Use Table. Section 3.1.1.D: "A blank cell indicates that a use is prohibited in that zone". Use Table, Sec. 3.1.6 (Chapter 59, Div 3.1), row 34, column R-40. Use-specific standards: Sec. 3.3.3.B.
ConditionalHome Occupation (No Impact) Varies -- Limited under some conditions and Conditional under others. This pairing is not in the Section 3.1.1 key; the use's own standards decide which applies, so it is served as the stricter of the two. Use Table, Sec. 3.1.6 (Chapter 59, Div 3.1), row 40, column R-40. Use-specific standards: Sec. 3.3.3.H.
AllowedShort-Term Residential Rental Permitted by right, subject to the limited use standards in Div 3.2-3.7. Section 3.1.1.B: an "L" indicates that the use is permitted if it meets the limited use standards -- there is no hearing. Use Table, Sec. 3.1.6 (Chapter 59, Div 3.1), row 44, column R-40. Use-specific standards: Sec. 3.3.3.I.
AllowedFamily Day Care (Up to 12 Persons) Permitted by right. Use Table, Sec. 3.1.6 (Chapter 59, Div 3.1), row 49, column R-40. Use-specific standards: Sec. 3.4.4.C.
ConditionalPrivate Club, Service Organization Allowed only as a conditional use: it must meet the conditional use standards in Div 3.2-3.7 and requires approval by the Hearing Examiner (Sec. 3.1.1.C). Use Table, Sec. 3.1.6 (Chapter 59, Div 3.1), row 55, column R-40. Use-specific standards: Sec. 3.4.8.
AllowedPublic Use (Except Utilities) Permitted by right. Use Table, Sec. 3.1.6 (Chapter 59, Div 3.1), row 56, column R-40. Use-specific standards: Sec. 3.4.9.
AllowedReligious Assembly Permitted by right. Use Table, Sec. 3.1.6 (Chapter 59, Div 3.1), row 57, column R-40. Use-specific standards: Sec. 3.4.10.
AllowedCultural Institution Permitted by right. Use Table, Sec. 3.1.6 (Chapter 59, Div 3.1), row 47, column R-40. Use-specific standards: Sec. 3.4.3.
Not AllowedCharitable, Philanthropic Institution This use is not listed for this zone in the Use Table. Section 3.1.1.D: "A blank cell indicates that a use is prohibited in that zone". Use Table, Sec. 3.1.6 (Chapter 59, Div 3.1), row 46, column R-40. Use-specific standards: Sec. 3.4.2.
Not AllowedBed and Breakfast This use is not listed for this zone in the Use Table. Section 3.1.1.D: "A blank cell indicates that a use is prohibited in that zone". Use Table, Sec. 3.1.6 (Chapter 59, Div 3.1), row 75, column R-40. Use-specific standards: Sec. 3.5.6.B.
Not AllowedHotel, Motel This use is not listed for this zone in the Use Table. Section 3.1.1.D: "A blank cell indicates that a use is prohibited in that zone". Use Table, Sec. 3.1.6 (Chapter 59, Div 3.1), row 76, column R-40. Use-specific standards: Sec. 3.5.6.
Not AllowedRestaurant This use is not listed for this zone in the Use Table. Section 3.1.1.D: "A blank cell indicates that a use is prohibited in that zone". Use Table, Sec. 3.1.6 (Chapter 59, Div 3.1), row 68, column R-40. Use-specific standards: Sec. 3.5.3.B.
Not AllowedConference Center This use is not listed for this zone in the Use Table. Section 3.1.1.D: "A blank cell indicates that a use is prohibited in that zone". Use Table, Sec. 3.1.6 (Chapter 59, Div 3.1), row 94, column R-40. Use-specific standards: Sec. 3.5.10.C.
Not AllowedRecreation and Entertainment Facility, Indoor (Capacity up to 1,000 Persons) This use is not listed for this zone in the Use Table. Section 3.1.1.D: "A blank cell indicates that a use is prohibited in that zone". Use Table, Sec. 3.1.6 (Chapter 59, Div 3.1), row 97, column R-40. Use-specific standards: Sec. 3.5.10.F.
Not AllowedOffice This use is not listed for this zone in the Use Table. Section 3.1.1.D: "A blank cell indicates that a use is prohibited in that zone". Use Table, Sec. 3.1.6 (Chapter 59, Div 3.1), row 84, column R-40. Use-specific standards: Sec. 3.5.8.B.
Not AllowedLife Sciences This use is not listed for this zone in the Use Table. Section 3.1.1.D: "A blank cell indicates that a use is prohibited in that zone". Use Table, Sec. 3.1.6 (Chapter 59, Div 3.1), row 83, column R-40. Use-specific standards: Sec. 3.5.8.A.
Not AllowedResearch and Development This use is not listed for this zone in the Use Table. Section 3.1.1.D: "A blank cell indicates that a use is prohibited in that zone". Use Table, Sec. 3.1.6 (Chapter 59, Div 3.1), row 85, column R-40. Use-specific standards: Sec. 3.5.8.C.
Not AllowedRetail/Service Establishment (Up to 5,000 SF) This use is not listed for this zone in the Use Table. Section 3.1.1.D: "A blank cell indicates that a use is prohibited in that zone". Use Table, Sec. 3.1.6 (Chapter 59, Div 3.1), row 104, column R-40. Use-specific standards: Sec. 3.5.11.B.
Not AllowedRetail/Service Establishment (15,001 - 50,000 SF) This use is not listed for this zone in the Use Table. Section 3.1.1.D: "A blank cell indicates that a use is prohibited in that zone". Use Table, Sec. 3.1.6 (Chapter 59, Div 3.1), row 106, column R-40. Use-specific standards: Sec. 3.5.11.B.
Not AllowedFilling Station This use is not listed for this zone in the Use Table. Section 3.1.1.D: "A blank cell indicates that a use is prohibited in that zone". Use Table, Sec. 3.1.6 (Chapter 59, Div 3.1), row 119, column R-40. Use-specific standards: Sec. 3.5.13.C.
AllowedFarming Permitted by right. Use Table, Sec. 3.1.6 (Chapter 59, Div 3.1), row 6, column R-40. Use-specific standards: Sec. 3.2.6.
Not AllowedEquestrian Facility This use is not listed for this zone in the Use Table. Section 3.1.1.D: "A blank cell indicates that a use is prohibited in that zone". Use Table, Sec. 3.1.6 (Chapter 59, Div 3.1), row 4, column R-40. Use-specific standards: Sec. 3.2.4.
AllowedFarm Market, On-site Permitted by right, subject to the limited use standards in Div 3.2-3.7. Section 3.1.1.B: an "L" indicates that the use is permitted if it meets the limited use standards -- there is no hearing. Use Table, Sec. 3.1.6 (Chapter 59, Div 3.1), row 15, column R-40. Use-specific standards: Sec. 3.2.10.C.
Not AllowedLight Manufacturing and Production This use is not listed for this zone in the Use Table. Section 3.1.1.D: "A blank cell indicates that a use is prohibited in that zone". Use Table, Sec. 3.1.6 (Chapter 59, Div 3.1), row 144, column R-40. Use-specific standards: Sec. 3.6.4.C.
Not AllowedHeavy Manufacturing and Production This use is not listed for this zone in the Use Table. Section 3.1.1.D: "A blank cell indicates that a use is prohibited in that zone". Use Table, Sec. 3.1.6 (Chapter 59, Div 3.1), row 143, column R-40. Use-specific standards: Sec. 3.6.4.B.
Not AllowedStorage Facility This use is not listed for this zone in the Use Table. Section 3.1.1.D: "A blank cell indicates that a use is prohibited in that zone". Use Table, Sec. 3.1.6 (Chapter 59, Div 3.1), row 163, column R-40. Use-specific standards: Sec. 3.6.8.E.
Not AllowedFreight Movement This use is not listed for this zone in the Use Table. Section 3.1.1.D: "A blank cell indicates that a use is prohibited in that zone". Use Table, Sec. 3.1.6 (Chapter 59, Div 3.1), row 159, column R-40. Use-specific standards: Sec. 3.6.8.A.
ConditionalPublic Utility Structure Allowed only as a conditional use: it must meet the conditional use standards in Div 3.2-3.7 and requires approval by the Hearing Examiner (Sec. 3.1.1.C). Use Table, Sec. 3.1.6 (Chapter 59, Div 3.1), row 157, column R-40. Use-specific standards: Sec. 3.6.7.E.
"Conditional" means the use generally requires a public hearing or special-exception approval — a very different timeline and risk profile from a by-right permit.
This is the zone. What about the parcel?
Zone rules are the starting point — the answer for a specific property also depends on lot
size, overlays, existing improvements and site conditions. Run a free address lookup to see
what applies to one property.
Standards as recorded by Zonescore: Chapter 59 Div 4.4, PDF (Feb 3 2026)
Coverage note: our ordinance review for this jurisdiction is still in progress. Treat the values above as a starting point and confirm against the ordinance before relying on them.