ADU Pass
Lehigh County
ADU Pass helps homeowners in Lehigh County, Pennsylvania navigate the permit paperwork for building an accessory dwelling unit. We cover 22 cities and 34 ZIP codes in this county.
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County ADU details
County ADU ordinance
Lehigh County sits in Pennsylvania, which has not enacted a statewide ADU preemption or by-right ADU statute. Authority over ADU zoning, setbacks, parking, size limits, owner-occupancy, and permitting therefore rests with the local jurisdiction. The county adopts its own zoning ordinance for unincorporated territory, and each incorporated municipality inside the county adopts its own.
State-floor overlay: No Pennsylvania statewide ADU preemption is in force as of 2026-04-27. The county and its incorporated municipalities retain full authority over ADU zoning and permitting.
Adopting body: Lehigh County Board of County Commissioners / County Council
County permitting (unincorporated parcels)
Lehigh County issues building permits for parcels in unincorporated territory through its development services / planning department, with separate review tracks for zoning conformance, building-code compliance, on-site sewage where applicable, floodplain compliance, and addressing. Inside incorporated municipalities, city departments handle their own permits; the county's authority is geographically limited to unincorporated territory. An ADU permit application is typically processed as a residential building permit with a zoning verification step against the county's ordinance for the parcel's zoning district.
Process overview: Typical workflow: (1) jurisdictional verification (parcel confirmed in unincorporated Lehigh County, not inside city limits or extra-territorial jurisdiction); (2) zoning verification against the county ordinance; (3) building-code plan review against the adopted state building code; (4) site-plan, septic (where applicable), and floodplain review; (5) issuance, construction with inspections, and certificate of occupancy.
Impact fees: Lehigh County permit fees are itemized at intake. Counties in Pennsylvania commonly do not levy municipal-style impact fees on residential additions in unincorporated areas; verify current fee schedule at the development-services counter.
County assessor
The Lehigh County property assessor / equalization office maintains parcel-level assessment records for all real property in Lehigh County. ADU additions are typically captured as improvements to the host parcel via shared permit data with the building department. Pennsylvania property-assessment rules govern annual revaluation cycles, homestead or principal-residence caps where applicable, and the procedures for protesting an appraisal.
Assessment policy: Improvement value for an ADU is added to the parcel record on the next regular revaluation cycle. Homestead / principal-residence caps where applicable shield the existing structure from rapid valuation increases but do not exempt new improvement value.
County overlays (2)
Lehigh County administers flood-hazard, and (where mapped) coastal, wildland-fire, historic, and airport overlays that shape ADU project feasibility. The most consistent overlay across the county is FEMA NFIP floodplain regulation; other overlays apply to specific geographies inside the county.
- FEMA NFIP Special Flood Hazard Areas in Lehigh County — A new ADU in a mapped SFHA must be elevated to or above the Base Flood Elevation; cost impact on the project is often material.
- Historic districts and individually-listed historic resources
Pennsylvania state — ADU law and programs
State ADU law
Pennsylvania has NOT enacted a statewide ADU preemption law. Under the Pennsylvania Municipalities Planning Code (Act 247 of 1968, 53 P.S. §§10101 et seq.), local governments retain broad authority over zoning, including ADU permission, setbacks, parking, size limits, and owner-occupancy. ADU rules vary widely by township, borough, city, and county. One active bill in the 2025-2026 session, HB 2186 (chief sponsor Rep. John Inglis), would amend Title 53 of the Consolidated Statutes to provide for ADUs, but was laid on the table on 2026-04-13 after a Housing and Community Development Committee vote (reported as 19 yes, 7 no during committee action) and has not advanced to third consideration.
State financing programs
Pennsylvania does not operate an ADU-specific statewide loan, grant, or forgivable-loan program. The Pennsylvania Housing Finance Agency (PHFA) administers general first-time-homebuyer, down-payment-assistance, and purchase-plus-improvement programs that can apply to properties with ADUs when eligibility criteria are met, but none target ADU construction as a distinct product. Notably, PHFA's HFA Preferred conventional product explicitly excludes two-unit properties, which can complicate financing an owner-occupied primary home that has (or plans to add) an attached ADU depending on how the appraiser and investor classify the unit.
State housing programs
Pennsylvania does not run a state-level pre-approved-ADU-plan catalog, statewide impact-fee-waiver statute for ADUs, or streamlined-review mandate. State-level programs that touch ADU-adjacent policy are primarily coordinated through the Department of Community and Economic Development (DCED) and PHFA, and act by funding or assisting local jurisdictions rather than by preemption. Local ADU momentum — Pittsburgh's by-right ADU ordinance in designated zones and Philadelphia's 2020 zoning-code ADU provisions — is authorized under municipal authority granted by the Municipalities Planning Code (Act 247 of 1968), not by state mandate.
- Keystone Communities Program — DCED program that provides planning, design, and construction funding to municipalities for downtown revitalization, elm-street neighborhood improvement, facade grants, and blight remediation. Not ADU-specific. Participating municipalities can direct Keystone Communities funds toward housing-rehab and missing-middle projects where local policy supports ADUs.
- Pennsylvania Land Use Planning Assistance (PALUPA) / DCED Land Use Planning Technical Assistance — DCED and associated local-government-services staff provide model-ordinance drafting, zoning-code review, and planning technical assistance to municipalities interested in modernizing zoning (including ADU permission). Acts through local adoption rather than state preemption.
- Pennsylvania Municipalities Planning Code (Act 247 of 1968) Model-Ordinance Guidance — The DCED-published Pennsylvania Municipalities Planning Code PDF and companion Planning Series documents include model language municipalities can adopt, including for accessory uses, home occupations, and mixed-use areas. Not a statewide ADU mandate; a guidance and boilerplate library that municipalities may or may not adopt.
Federal (United States) — ADU-relevant rules and programs
Federal ADU law
The United States has no federal statute that directly regulates accessory dwelling unit entitlement or design. Land-use authority over ADUs resides with states and local governments under the traditional police power. Federal engagement is limited to financing (Fannie/Freddie/FHA/VA/USDA), flood insurance (FEMA/NFIP), and discretionary housing programs (HUD), which are recorded in sibling sections of this file.
Federal financing programs
Federal housing-finance agencies and GSEs set nationwide underwriting rules that govern whether an ADU can be financed, appraised, and counted toward mortgage qualifying income. The relevant actors are Fannie Mae, Freddie Mac, FHA (HUD), VA, and USDA Rural Development.
Federal tax credits
There is no ADU-specific federal tax credit. ADUs may incidentally qualify for existing federal energy-efficiency and clean-energy tax credits when the ADU construction includes qualifying measures.
Federal housing programs
HUD administers several discretionary programs that can fund ADU-related activity at the grantee's election, but none is an ADU-specific program.