Home Addition Cost in Philadelphia [2025 Data]

Home addition costs in Philadelphia average $55,368, and most homeowners in the city pay between $26,108 to $86,129. Your total will depend mostly on the type of home addition and the square footage of the new construction. Home additions in Philadelphia tend to be on the small side, but prices are still above average in large part because small property sizes mean building up is more popular, and it’s also more costly.

Home Addition Cost Factors

Many things will affect your home addition costs, but in Philadelphia, Pennsylvania, the type of home addition, the size of the add-on, and the specific materials you choose will all affect pricing. Permit costs, above-average labor costs, and site prep can all play a role, too.

Size

Home additions cost between $80 and $200 per square foot if you’re building out and between $300 and $500 per square foot if you’re building up. The cost to add a 10x10 room to a house costs an average of $12,500 if you build out and $40,000 if you build up.

Whether you build out or up is partially based on personal preference, but in an area like Philadelphia, the below-average property size can make the decision for you, unfortunately. The average plot in Philly is just 0.029 acres, or around 1,260 square feet. 

Most residents simply won’t have room to build a bump-out or another type of accessory dwelling unit (ADU) to expand living space. With building up being the only option for many Philadelphia homeowners, this more expensive option drives up average home addition costs in the area.

The complexity of the room and its finishes also matter and will affect costs regardless of whether you build out or up. For example, adding a bathroom will often cost more than a bedroom since it requires additional plumbing and electrical work.

Materials

As you can imagine, it takes many kinds of building materials to complete a custom home addition. Material prices vary widely, so your price could push closer to $86,129 if you choose luxury or high-end materials at each step of the way.

Interior materials can have just as big an impact on your total home addition costs as exterior materials, but interior materials are based on your preferences, while exterior materials need to withstand local weather conditions and affect local averages more. Philadelphia homeowners experience long, cold winters, so consider upgrading to highly insulative siding materials. 

The city also sees above-average snowfall and rainfall, so pick a leak-resistant roofing material, like metal, that can also shed snow easily and reduce the risk of structural damage. The tables below should provide some insight into how building materials can affect your home addition costs in Philadelphia.

Foundation Materials Cost:

Insulation Materials Cost:

Roofing Materials Cost:

Siding Materials Cost:

Window Frame Materials Cost:

Type

The cost to add on a room varies based on the type of home addition you want and the square footage of the room you’re building. Most plots in Philadelphia are too small to build out, so second-story additions and dormers are the most common types of home additions in the area. Unfortunately, second-story additions cost more than bumpouts, which is one reason why home addition costs are above the national average in Philly.

The type of room you’re adding also affects the total, regardless of how you’re adding onto your home. Rooms like kitchens and bathrooms require plumbing work that a bedroom doesn’t, while an unfinished attic home addition may not require electrical or HVAC work that a bedroom needs. The cost per square foot for your home addition will vary based on utilities and the finishes required for how you plan on using the extra square footage.

Site Prep

On average, site prep for a home addition costs between $1,500 and $5,000. You may not need any site prep in some cases, while other home addition projects may require grading land, demolishing concrete patios, removing trees, and other work that can add to your total.

Site preparation costs will tend to be relatively low in Philadelphia compared to other cities since the small property sizes mean that building up is more accessible.

Permits

All major home renovations and remodels, including home additions, require building permits in Philadelphia. The City of Philadelphia charges a flat rate for permits for home additions, provided the add-on is 500 square feet or fewer, which applies to most additions in the area. The permit fee is just $50, which is well below the national average.

Home Addition Pro Costs

Hiring a homebuilder in Philadelphia will cost you between $22,100 and $33,200 in labor costs alone, which means labor makes up between 40% and 60% of your total. Labor costs are higher in Philly than they are in most other cities since the cost of living is slightly above the national average, and living costs drive labor costs.

While you’re budgeting for your home addition, it’s a good idea to account for sales tax, which your professional will need to charge you. The sales tax rate in Philadelphia is 8%, which means you should add an average of $4,421.04 to your total for the most accurate estimate possible.

Does a Home Addition Increase Property Value?

Yes, a home addition will increase your property value, as it normally offers between a 20% and 50% return on investment (ROI). That puts the average return in Philadelphia between $11,000 and $27,700. The average cost per square foot for real estate in Philly is $213, so you can reasonably expect each square foot of living space you add on to push up your home value by that amount.

You can maximize your ROI by choosing building materials that are more desirable in Philadelphia, like metal or slate roofing that can stand up to above-average rainfall and snowfall, and highly insulative siding materials like brick, stone, or fiber cement that can help reduce home heating costs in the cold Pennsylvania winters.

How Angi Gets Its Cost Data

Home is the most important place on earth, which is why Angi has helped more than 150 million homeowners transform their houses into homes they adore. To help homeowners with their next project, Angi provides readers with the most accurate cost data and upholds strict editorial standards. We survey real Angi customers about their project costs to develop the pricing data you see, so you can make the best decisions for you and your home. We pair this data with research from reputable sources, including the U.S. Bureau of Labor Statistics, academic journals, market studies, and interviews with industry experts—all to ensure our prices reflect real-world projects. 

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