1 county-level rule, plus city-specific rules for 2 cities in Lehigh County, Pennsylvania.
Verified from official government sources
Pennsylvania has no statewide ADU mandate. Under the Pennsylvania Municipalities Planning Code (MPC, Act 247 of 1968, 53 P.S. §10101 et seq.), zoning authority rests with municipalities (boroughs, townships, cities) - not Lehigh County itself. Each of Lehigh County's 24 municipalities (1 city, 23 boroughs/townships) decides whether ADUs are permitted, what size limits apply, and whether a special exception or variance is required. The City of Allentown's Zoning Ordinance (Ordinance No. 16166, adopted October 15, 2025) is the controlling document for the county seat.
2 cities in Lehigh County have their own accessory structures rules. Each link goes to that city's dedicated page with code citations.
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Lehigh County Ordinance Hub →