5 county-level rules, plus city-specific rules for 2 cities in Lehigh County, Pennsylvania.
Verified from official government sources
Pennsylvania counties do not zone, so ADU rules come from your municipality. Allentown has no ADU category. Adding a unit is a 'residential conversion,' allowed only in detached buildings of 3,000+ square feet, and a garage may not be used as a dwelling.
Allentown Zoning Ordinance §1315.05.GG.1
Residential conversions are limited to the conversion of detached structures containing 3,000 sq. ft. or more of floor area.
Sheds are 'accessory structures' governed by your municipality, not the county. In Allentown residential districts a shed needs a 3-foot setback from side and rear lines, may not sit in the required front yard, and is capped at 15 feet tall.
Allentown Zoning Ordinance §1315.04.C.2, §1315.04.H
A minimum setback of 3 feet is required from side and rear property lines for all accessory structures located in the required rear yard... A maximum height of 15 feet shall apply for any accessory structure.
Allentown zoning flatly prohibits using a private garage for dwelling purposes. Converting a garage into living space is not allowed; adding living area instead requires a 'residential conversion' of a detached building of at least 3,000 square feet.
Allentown Zoning Ordinance §1315.04.J
A private garage, whether attached or detached, or any portion thereof, shall not be used for either of the following: 1. dwelling purposes, 2. any repairs to motor vehicles within the garage, other than vehicles registered to or leased to an owner or lessee of any dwelling unit located on the property.
Allentown zoning has no separate carport code; a carport is an 'accessory structure' under §1315.04. It may not stand in the required front yard, must meet the 3-foot residential side/rear setback, and is limited to 15 feet in height.
Allentown Zoning Ordinance §1315.04.B, §1315.04.H
In any district, an accessory structure shall not be permitted within a required minimum front yard... A maximum height of 15 feet shall apply for any accessory structure.
Allentown zoning has no tiny-home category. A permanent tiny house must meet minimum habitable floor areas (no new efficiency units) and PA building code. A tiny home on wheels is treated as a manufactured/mobile home, allowed only in a licensed manufactured-home park.
Allentown Zoning Ordinance §1315.05.GG.2, §1315.05.GG.3
One dwelling unit shall have a minimum of 700 square feet of habitable floor area... No new efficiency dwelling units shall be permitted.
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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