Maryland radon requirements for new construction
Maryland county building codes (IRC Appendix F or AF, by county)
What your permit set must show
- Maryland has no single statewide radon appendix adoption; the requirement is mandatory only within named EPA Zone 1 counties, each having adopted its own IRC edition and appendix letter.
- Confirmed mandatory in Baltimore County (2021 IRC Appendix AF), Calvert County (2018 IRC Appendix F), Frederick County (2021 IRC Appendix F), Howard County (2015 IRC Appendix F), Montgomery County (2021 IRC Appendix AF), and Washington County (2021 IRC Appendix AF).
- A project outside these named counties is not automatically covered; confirm the specific county's adopted code edition before drawing a permit set.
Common questions
Is a radon rough-in required everywhere in Maryland?
No. Maryland's requirement is county-level, mandatory only within designated EPA Zone 1 counties (including Baltimore, Calvert, Frederick, Howard, Montgomery, and Washington counties), each on its own adopted IRC edition and appendix letter.
Which appendix letter applies to my Maryland project?
It depends on which IRC edition your specific county has adopted — Appendix F or Appendix AF, depending on the county. Confirm with the local building department before finalizing the permit set.
Get notified when we cover Maryland
Join the waitlist and we will email you the moment Maryland is available.