USA Site Plans
Planning a home addition in Philadelphia? Whether you are adding a rear room, side addition, second floor, kitchen extension, family room, in-law suite, or garage addition, the City needs to understand how the new building area fits on your property.
A Philadelphia addition site plan helps show the proposed addition in relation to the existing house, property lines, setbacks, lot dimensions, driveway, sidewalk, garage, alley, shed, yard space, and nearby structures. It gives the permit reviewer a clear view of the project before construction begins.
This guide explains what a Philadelphia addition site plan should include, why it matters for zoning and building permit review, what homeowners should prepare, and how to avoid common layout mistakes.
What Is a Philadelphia Addition Site Plan?
A Philadelphia addition site plan is a scaled drawing that shows a proposed home addition on a residential lot. It is usually drawn from above and shows the existing property layout with the new addition added clearly.
An addition site plan may show:
- property lines and lot dimensions;
- existing house footprint;
- proposed addition footprint;
- addition length and width;
- front, side, and rear setbacks;
- distance to fences, alleys, streets, and nearby structures;
- existing garage, driveway, shed, patio, deck, or walkway;
- sidewalk and street location;
- rear alley or driveway access if present;
- lot coverage information when needed;
- stairs, landings, or exterior doors if relevant;
- north arrow and scale.
The purpose is to show exactly where the addition will be built. A reviewer should be able to see the existing home, proposed new footprint, property-line distances, and how the project affects the rest of the site.
Does a Home Addition in Philadelphia Need a Permit?
Yes, home additions usually require permit review. The City of Philadelphia says zoning approval is needed for new buildings and additions. The City also says zoning approval is required to get a Building Permit.
Official source: City of Philadelphia – Get a Zoning Permit for New Construction or Additions
Philadelphia also says that, in most cases, you must get a Building Permit before starting a project that constructs a new building, enlarges or adds to an existing structure, changes the interior or exterior of a structure, demolishes a structure, or includes major repairs that are not regular maintenance.
Official source: City of Philadelphia – Get a Building Permit
Because a home addition changes the footprint, size, and sometimes height of a building, the site plan is an important part of showing zoning compliance and project scope.
Why a Site Plan Matters for a Philadelphia Addition
A home addition changes how the structure sits on the lot. It can affect setbacks, lot coverage, open area, drainage, light, access, parking, stairs, and the relationship between the home and neighboring properties.
A clear Philadelphia addition site plan helps show:
- where the addition will be built;
- how large the addition will be;
- how the addition connects to the existing house;
- how far the addition is from property lines;
- whether the addition affects a rear yard, side yard, driveway, or alley;
- whether the addition changes lot coverage or open space;
- whether exterior stairs, landings, or doors affect the layout;
- whether nearby structures limit construction access;
- whether the drawing matches the permit application and construction plans.
A rough sketch can leave too many questions unanswered. A permit-ready site plan helps explain the project clearly and can reduce delays caused by missing layout information.
Philadelphia Site Plan Requirements for Additions
Philadelphia’s general zoning permit guidance says you need to submit a site plan for new construction, additions, lot line adjustments, parking, and signs that do not qualify for an EZ Permit.
Official source: City of Philadelphia – Get a Zoning Permit
The City’s building permit plan requirements also say plans must be professional quality and drawn to scale. Free-hand sketches are not accepted.
Official source: City of Philadelphia – Building Permit Plan Requirements
That is why a clean, scaled site plan is important for addition projects. It gives the City a clear drawing instead of a rough outline.
Common Home Addition Projects in Philadelphia
Addition site plans can be useful for many residential projects, including:
- rear additions;
- side additions;
- two-story additions;
- family room additions;
- kitchen additions;
- garage additions;
- bump-outs;
- in-law suites;
- second-floor additions;
- additions with new stairs or landings;
- additions with basement or foundation work.
Each project type has different site layout concerns. A rear addition may affect backyard depth. A side addition may affect side-yard setbacks. A second-floor addition may affect height and building envelope. A garage addition may affect parking and driveway access.
What Should a Philadelphia Addition Site Plan Include?
A permit-ready addition site plan should be clear, scaled, and specific to the property. It should show the actual existing house and the actual proposed addition.
1. Property Lines
The site plan should show the front, side, and rear property lines. These boundaries help reviewers understand whether the addition fits inside the lot and respects required yard areas.
If the proposed addition is close to a property line, boundary accuracy becomes even more important. A survey can be helpful when lot lines are uncertain.
2. Existing House Footprint
The existing house should be shown and labeled. This helps reviewers understand what is already built and where the new addition will connect.
The drawing should clearly distinguish the existing building from the proposed new addition.
3. Proposed Addition Footprint
The proposed addition should be labeled clearly. The site plan should show the addition length, width, and shape.
For example, the plan may show a 12-foot by 18-foot rear addition, a 10-foot side addition, or a two-story addition over an existing one-story area. The dimensions should match the construction drawings and permit application.
4. Setbacks
Setbacks are one of the most important parts of an addition site plan. The plan should show the distance from the proposed addition to the front, side, and rear property lines when relevant.
For rowhomes, twins, and narrow lots, side and rear distances can be especially important.
5. Lot Dimensions
The site plan should show the lot width and lot depth. These dimensions help explain how much space is available and how the addition changes the property layout.
6. Existing Structures and Site Features
The plan should show important existing site features, such as:
- garage;
- shed;
- deck;
- patio;
- driveway;
- walkway;
- fence;
- retaining wall;
- rear alley;
- sidewalk and street;
- trees or other major obstructions.
These features help show how the addition fits into the real site conditions.
7. Access and Circulation
The site plan should show how people and vehicles move around the property. If the addition affects a driveway, side walkway, alley, gate, stairs, or rear access path, that should be shown.
If the project includes new exterior stairs, landings, doors, ramps, or walkways, include them on the site plan.
8. Driveway, Parking, or Garage Layout
If the addition affects parking or driveway access, the site plan should show the driveway and parking area clearly.
If the project creates, changes, or removes off-street parking, separate zoning considerations may apply.
9. Drainage and Hard Surface Areas
A home addition can change drainage because it adds roof area, foundation work, and sometimes new paving or walkways.
The site plan should show major hard surfaces and drainage direction when relevant. Downspouts, patios, driveways, and low areas may also need to be identified.
10. North Arrow and Scale
A north arrow and scale make the drawing easier to review. They also make the site plan look professional and permit-ready.
Rear Addition Site Plans
Rear additions are common in Philadelphia, especially for rowhomes and properties with small backyards. A rear addition site plan should show how far the new addition extends into the rear yard and how much open space remains.
Important rear addition details include:
- rear wall of the existing house;
- proposed rear addition footprint;
- distance from addition to rear property line;
- side property line distances;
- rear alley or access path if present;
- existing patio, deck, shed, or fence;
- new stairs, landing, or rear door;
- roof drainage and downspouts if relevant.
Rear additions can be straightforward when clearly drawn, but they can cause review questions if setbacks, open area, or property-line distances are missing.
Side Addition Site Plans
Side additions can be more sensitive because they may reduce side-yard space and affect separation from neighboring buildings.
A side addition site plan should show:
- existing house footprint;
- proposed side addition footprint;
- distance to side property line;
- distance to neighboring structures if close;
- side walkway or access path;
- driveway or parking area if nearby;
- fence and gate locations;
- downspouts and drainage direction.
For narrow lots, accurate side-yard dimensions are very important.
Second-Floor and Two-Story Additions
A second-floor or two-story addition may not always increase the ground footprint as much as a one-story addition, but it still needs to be shown clearly.
The site plan should identify the footprint area where the addition occurs. Elevation drawings and building plans can show the height, floors, roofline, and exterior appearance.
For second-floor additions, the plan package may need:
- existing and proposed floor plans;
- elevations;
- building sections;
- structural framing details;
- roof plan;
- site plan showing the footprint and property lines.
Kitchen, Family Room, and Bedroom Additions
Many additions are built to expand living space. A kitchen addition, family room addition, bedroom addition, or in-law suite may involve more than just a site plan.
These projects can include:
- new foundation work;
- new roof framing;
- electrical work;
- plumbing work;
- mechanical work;
- new windows and doors;
- new stairs or landings;
- changes to drainage and downspouts.
The site plan should show the addition location, while the construction drawings should explain the building details.
Garage Additions and Parking Impacts
If the addition includes a garage or changes parking, the site plan should show the vehicle access route. Philadelphia has separate zoning permit guidance for creating or changing off-street parking.
Official source: City of Philadelphia – Get a Zoning Permit for Parking
The plan should show:
- garage footprint;
- garage door location;
- driveway or alley access;
- parking area;
- curb cut if relevant;
- sidewalk relationship;
- distance to property lines.
Parking changes should not be hidden in the project description. They should be shown clearly on the site plan.
Additions Near Property Lines
Additions close to property lines require special care. The closer the addition is to a side or rear boundary, the more important the site plan becomes.
For additions near property lines, show:
- distance from new wall to side property line;
- distance from new wall to rear property line;
- roof overhang or projection if relevant;
- neighboring structure if close;
- fence line if different from property line;
- existing alley, driveway, or easement if known;
- construction access area if limited.
Do not rely only on a fence line to place an addition. If the legal property boundary is unclear, a professional survey may be needed.
Drainage and Roof Runoff
A home addition creates new roof area and can change how water moves on the property. The site plan should help explain drainage when relevant.
Helpful drainage details include:
- new roof area;
- downspout locations;
- existing and proposed hard surfaces;
- yard slope if known;
- low spots or drainage concerns;
- relationship to neighboring property;
- stormwater or drainage features if required.
For larger additions or projects with significant site changes, additional stormwater or drainage documentation may be required.
Other Drawings That May Be Needed
An addition site plan is usually only one part of the permit package. Philadelphia L&I provides plan requirement resources for building permit applications, including new construction, additions, interior and exterior alterations, and other work.
Official source: City of Philadelphia – L&I Plan Requirements
Depending on the project, you may also need:
- existing floor plans;
- proposed floor plans;
- building elevations;
- building sections;
- foundation plan;
- framing plan;
- roof plan;
- structural details;
- energy code information;
- mechanical, electrical, and plumbing information;
- stormwater or drainage details;
- photos of existing conditions.
The site plan explains where the addition goes. The construction drawings explain how it will be built.
Historic Properties and Special Review
If the property is on the Philadelphia Historic Registry or located in a special review area, additional review may be required. Philadelphia’s building permit page notes that some permit exemptions may not apply if the property is on the Philadelphia Historic Registry.
Official source: City of Philadelphia – Get a Building Permit
For additions, historic review can be especially important because the project may change the exterior appearance, massing, roofline, rear facade, side wall, or visible features of the property.
Site Plan vs. Survey
An addition site plan is not the same as a survey.
A survey is prepared by a licensed surveyor and identifies legal property boundaries, existing improvements, and other boundary-related information. A site plan is a project drawing that shows the proposed addition layout on the property.
For a home addition, a survey is often very helpful because the new construction may be close to property lines. If you already have a survey, it can be used as a strong starting point for the site plan.
Common Philadelphia Addition Site Plan Mistakes
Many addition permit delays come from incomplete or unclear site plan information. Avoid these common mistakes:
- property lines not shown;
- existing house footprint missing;
- proposed addition not clearly labeled;
- addition dimensions missing;
- side or rear setbacks not labeled;
- existing garage, shed, driveway, alley, or fence missing;
- stairs, landings, or doors not shown when they affect the layout;
- parking changes not shown;
- hardscape or drainage changes ignored;
- dimensions do not match the construction drawings;
- no north arrow or scale;
- using a free-hand sketch instead of a scaled drawing.
A good addition site plan should clearly show both the existing property and the proposed change.
What to Gather Before Preparing a Philadelphia Addition Site Plan
Before preparing the drawing, gather the basic property and project information.
Helpful items include:
- property address;
- existing survey if available;
- lot width and lot depth;
- existing house footprint;
- proposed addition length and width;
- number of stories;
- addition height if known;
- distance from addition to property lines;
- existing garage, shed, deck, patio, driveway, or fence locations;
- rear alley, sidewalk, or driveway access;
- new stairs, landings, doors, or walkways;
- photos of the project area;
- zoning district if known;
- whether the property is historic or in a floodplain.
The more accurate the starting information, the cleaner the site plan will be.
How to Apply for Philadelphia Permits Online
Philadelphia uses eCLIPSE for online permit and license applications. Applicants can use the City’s online system to apply for permits, upload documents, and manage permit activity.
Official source: City of Philadelphia – eCLIPSE
The City also provides guidance for applying for building permits and zoning permits online.
Official source: City of Philadelphia – Get a Building Permit
Before submitting, make sure the site plan, zoning application, building plans, project description, dimensions, and supporting documents all match. Inconsistent information can lead to corrections.
When an Addition Site Plan Is Especially Helpful
A detailed addition site plan is especially useful when:
- the addition is close to a property line;
- the lot is narrow or irregular;
- the addition extends into the rear yard;
- the project adds a second story;
- the addition affects a driveway or parking space;
- the project includes stairs, landings, or new exterior doors;
- the property has a garage, shed, deck, patio, or alley nearby;
- drainage or roof runoff may change;
- the property is historic or has special review conditions;
- the homeowner wants a cleaner permit package.
In these situations, a simple sketch is usually not enough. A scaled, labeled site plan can make the project easier to understand and easier to review.
Final Thoughts
A Philadelphia addition site plan is an important drawing for home addition projects. It shows the proposed addition footprint, existing house, property lines, setbacks, lot dimensions, driveway, sidewalk, alley, garage, shed, drainage, and nearby site features.
Because Philadelphia requires zoning approval for new buildings and additions, and because most additions also need building permit review, the site plan should be prepared carefully. It should be clear, scaled, and consistent with the rest of the permit drawings.
Before starting a home addition, verify the property layout, check the zoning and building permit path, gather accurate dimensions, and prepare a permit-ready site plan that shows exactly how the addition fits on the lot.
Official Sources
- City of Philadelphia – Get a Zoning Permit for New Construction or Additions
- City of Philadelphia – Get a Zoning Permit
- City of Philadelphia – Get a Building Permit
- City of Philadelphia – Building Permit Plan Requirements
- City of Philadelphia – L&I Plan Requirements
- City of Philadelphia – Get a Zoning Permit for Parking
- City of Philadelphia – eCLIPSE