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Montgomery County, PA Accessory Structures: ADU Rules (2026)

Some Restrictions

Compiled from the official code textEditor Martyn O'NeillLast verified July 2026

ADU rules in Montgomery County, PA, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.

Key Facts

County ADU rule: None: municipal only
Governing law: PA MPC, Act 247
Enabling section: 53 P.S. §10603(b)
Who decides: Your borough/township
Municipalities in county: 62 boroughs/townships

ADU Eligibility Quick-Check

An Accessory Dwelling Unit (ADU) is a smaller, independent living unit on the same lot as a single-family home: converted garages, detached cottages, basement or attic conversions, and attached additions all qualify. Most states have streamlined ADU permitting since 2020, but local rules still control size, height, and setback.

Is your lot zoned single-family or multi-family residential?
Does your lot have at least 1,200 sq ft of buildable space?
Is your existing home owner-occupied (in most states this is not required, but some require it for ADU permits)?
Will the ADU stay under your state's size cap (commonly 850-1,200 sq ft for detached)?
Can you provide one off-street parking space (waived in many states within 0.5 mi of transit)?

If you answered 'yes' to most of these, you likely qualify in Pennsylvania under recent ADU streamlining laws. The Montgomery County, PA rules below cover local size, height, and setback requirements.

Summary

Montgomery County does no land-use zoning. Whether an accessory dwelling unit is allowed, and its size and setbacks, is decided by your borough or township under the PA Municipalities Planning Code. Check your municipality's zoning ordinance.

These county ordinances apply to unincorporated areas of Montgomery County. Incorporated cities within the county may have their own rules that take precedence over county-level regulations.

Zoning ordinances... may permit, prohibit, regulate, restrict and determine:... Size, height, bulk, location, erection, construction, repair, maintenance, alteration, razing, removal and use of structures.

Source: PA Municipalities Planning Code (Act 247) - 53 P.S. §10603View official code

Full Breakdown

Under the Pennsylvania Municipalities Planning Code (MPC, Act 247), counties do not zone residential land; each of Montgomery County's 62 boroughs and townships adopts its own zoning ordinance. MPC Section 603(b) authorizes those local ordinances to regulate the 'size, height, bulk, location, erection, construction... and use of structures,' which is where ADU, in-law-suite and accessory-dwelling standards live. Some municipalities permit ADUs by right, some by special exception, and some prohibit them. Contact your township or borough zoning officer, or read your local zoning code, for the exact rule that applies to your parcel.

Violations & Fines

Building or occupying an unpermitted ADU is a municipal zoning violation; the borough or township can issue enforcement notices and daily fines and require removal. Penalties are set by local ordinance, not the county.

Frequently Asked Questions

Does Montgomery County have an ADU ordinance?

No. The county does not zone residential property. ADU rules are set by your individual borough or township under the state MPC.

How do I find my ADU rules?

Read your municipality's zoning ordinance or call its zoning officer. Rules vary widely between the county's boroughs and townships.

Sources & Official References

[1]PA Municipalities Planning Code (Act 247), DCED

Other rules in Montgomery County

Parking Rules: Overnight ParkingSome Restrictions Parking Rules: Street Parking LimitsSome Restrictions Noise Ordinances: Quiet HoursSome Restrictions Shed & Carport RulesSome Restrictions Parking Rules: RV & Boat ParkingSome Restrictions Garage ConversionsSome Restrictions Tiny HomesSome Restrictions Noise Ordinances: Vehicle NoiseSome Restrictions Parking Rules: Abandoned VehiclesSome Restrictions

All Montgomery County rules

How Montgomery County compares: Easiest Cities to Build an ADU·Compare Montgomery County to another location·View the Pennsylvania accessory structures overview

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ADU Rules in Cities Across Montgomery County

Pottstown, PA