How to Tell If You Can Build on the Rear of Your Lot

Philadelphia Zoning, Rear Setbacks & Rear Additions Explained

Rear additions are one of the most common home improvement projects in Philadelphia. Whether you're trying to enlarge a kitchen, create a family room, or add square footage to an upper floor, the first step isn't designing the space, it's determining whether your property is legally allowed to expand.

Understanding a few key zoning concepts can save months of redesigns and potentially thousands of dollars in engineering and permitting costs.

1. Your Zoning District Controls What Can Be Built

Every property in Philadelphia is assigned a zoning district.

The zoning district determines rules such as:

• Permitted land uses

• Building height

• Maximum building size

• Lot coverage

• Required open space

• Yard and setback requirements

• Parking requirements (where applicable)

Two homes that appear identical may have completely different zoning regulations depending on their zoning designation.

The first step before planning any addition is identifying your property's zoning district.

You can find this information using the City's free Atlas mapping system or the Philadelphia Department of Licenses & Inspections (L&I).

2. What Is a Rear Setback?

A rear setback is the minimum required distance between the back of your building and your rear property line.

Think of it as the portion of your lot that generally must remain open.

Many Philadelphia rowhomes already extend deep into their lots, leaving limited room for additional construction.

If your proposed addition extends into the required rear yard, it may not qualify for zoning approval "by right."

The required rear setback depends on your property's zoning district, not every property has the same requirement.

3. Lot Coverage Can Limit Your Addition

Even if your rear yard appears large enough, another zoning rule may prevent additional construction.

Lot coverage refers to the percentage of your property that is occupied by buildings.

Every zoning district establishes a maximum amount of the lot that may be covered by structures.

For example:

• Existing house footprint

• Existing additions

• Attached garages

• Other qualifying structures

all contribute toward the total lot coverage calculation.

If your property has already reached the maximum allowable coverage, a rear addition may require zoning relief before it can be approved.

4. Existing Additions Don't Automatically Mean New Ones Are Allowed

A common misconception is:

"My neighbor has a rear addition, so I can build the same thing."

Not necessarily.

Your neighbor's addition may have been:

• Built under older zoning regulations

• Approved through a variance

• Approved through a special exception

• Constructed before the current zoning code was adopted

• Built without matching the circumstances of your property

• Built illegally without approval 

Every property is reviewed individually based on its zoning, lot dimensions, existing conditions, and proposed scope of work.

5. "By Right" vs. Variance

If your proposed addition complies with all applicable zoning requirements, it may qualify for approval by right.

That generally means the project satisfies the Philadelphia Zoning Code without requiring relief from the Zoning Board of Adjustment (ZBA).

If the proposal does not comply with the zoning requirements, you may need to seek a variance or other zoning approval before a building permit can be issued. These are not always approved. 

6. A Building Permit Is Not the First Step

Many homeowners think they apply for a building permit first.

In reality, zoning approval typically comes before the building permit process for additions.

For rear additions, Philadelphia generally requires zoning approval before L&I can issue the building permit needed for construction. Smaller residential projects may have zoning and building code reviewed together when the appropriate applications are submitted.

7. You'll Need an Accurate Site Plan

One of the most important documents for evaluating a rear addition is a properly prepared site plan.

Philadelphia generally requires plans showing information such as:

• Property lines

• Existing building footprint

• Proposed addition

• Yard dimensions

• Existing structures

• Building dimensions

• Adjacent streets or alleys (when applicable)

These measurements allow L&I to verify that the proposed work complies with the applicable zoning regulations.

8. Every Property Is Different

Philadelphia is filled with unique lots.

You may encounter:

• Corner lots

• Through lots

• Reverse-frontage lots

• Irregular lot shapes

• Nonconforming lots

• Properties with existing zoning conditions

Because of these differences, two houses on the same block may have different development limitations.

That's why experienced zoning research is one of the most valuable parts of planning a project.

Before Designing a Rear Addition, Answer These Questions

Before investing in architectural drawings, it's worth confirming:

• What is my property's zoning district?

• What rear yard requirements apply to my lot?

• How much of my lot is already occupied?

• Does my proposal meet the zoning requirements by right?

• Will I need zoning relief before applying for permits?

Getting these answers early can help avoid redesigns and delays later in the process.

How Jane Draws Plans Can Help

At Jane Draws Plans, we begin every rear addition project by reviewing the existing property and researching the applicable zoning requirements.

Our team prepares accurate existing-condition drawings, develops permit-ready plans, and helps homeowners understand how their property's zoning may affect the scope of a proposed addition.

If you're considering expanding your Philadelphia home, we're here to help you understand what's possible before construction begins.