Cost per square foot to build an addition

Home Additions Cost Breakdown

Home addition costs can vary greatly based on the size and scope of your project, who you hire, and the permits and materials you need to complete the job. While it can seem daunting at first, hiring a home improvement contractor can take some of the burden off your shoulders and ensure you’re getting the job done right.

Photo: Sidekix Media / Unsplash

Size

While you may have your heart set on a large home addition, the bigger it is, the more expensive it will be, so you’ll want to factor that into your budget. Be sure to include other costs as well, such as the laying of a new foundation (which costs $75 per yard), along with insulation, site preparation (if extending the perimeter of a house; excavation costs $2,559 on average), and electrical wiring.

Home Addition Contractor 

Building a home addition is a difficult task, so you want to ensure it’s done correctly. Avoid wasting time and money (and potential need for a rebuild if something goes awry) and ask a home addition contractor near you for an estimate. General contractors oversee and manage the full scope of a project and charge about 10% to 20% of your total project cost. Ideally, ask multiple contractors for bids to understand the full scope of your options.

Some contractors offer free estimates, but if your project requires substantial consulting or design work, you may need to factor in an extra $150 to $1,000 to cover the expense of the consultation. 

Architect 

An architect helps ensure your addition blends in with the rest of your house and is structurally sound. They can also help optimize the design and use of your new space. While an architect is not required, hiring one can improve the end result of your addition. A local architect charges between 5% and 20% of the total project cost.

Permits

Before starting a new home addition project, you’ll have to apply for various building permits from your city or township. The permits you need for a home addition may include structural, electrical, plumbing, gas, and other local permits outlined by your municipality.

The average cost of a building permit is $1,300, but it can cost as little as $150 in rural areas or as much as $7,500 in some cities.

Materials

As you can imagine, it takes many kinds of building materials to complete a custom home addition. Common building materials you’ll need to complete a room addition include:

• Foundation material costs: $8,000

• Lumber for framing costs: $5 per standard 4x4

• Insulation costs: $0.20–$2 per square foot

• Window costs: $250–$1,000 each

• Exterior door costs: $500–$2,000 each

• Interior door costs: $250–$1,150 each

• Drywall installation costs: $1.50 per square foot

• Electrical costs: $50–$100 per hour 

• Plumbing project costs: $600–$1,600 

• Roofing materials costs: $120–$400 per 10-foot-by-10-foot square

• Siding and trim costs: $1–$30 per square foot

• Flooring costs: $1,485–$4,485 

• Painting costs: $100–$525 

Site Prep

Some demolition and land excavation may be necessary to prepare your site for the new addition. On average, site prep for a home addition costs between $1,500 and $5,000, but if you’re adding a second floor or installing a basement, costs could go up to $10,000. 

Labor

Skilled laborers and tradespeople ensure your home addition is beautiful and well-built. Depending on the type of addition, you may need to hire the following pros:

• Carpenter: $75–$100 per hour

• Electrician: $40–$100 per hour

• Structural engineer: $100–$200 per hour

• HVAC technician: $50–$100 per hour

• Plumber: $50–$200 per hour

• Roofer: $40–$80 per hour

• Interior painter: $20–$50 per hour

Location

If you live in an area with a high cost of living, construction costs can top other areas, such as rural locations. If you live in a dense neighborhood, there may be additional costs due to limited space and access to your lot.

How Much Does a Room Addition Cost by Type?

The cost to add on a room varies based on the type and size of the room you’re building. When you’re looking to add a room, you can choose to build out or up. If you build out, the cost averages $80 to $200 per square foot, while second-story rooms typically run $100 to $300 per square foot.

Bedroom

It is common to add rooms such as an extra bedroom so you can host guests from out of town or a family room perfect for movie nights. A 9-by-12-foot bedroom, for example, would cost $8,600 to $21,600. However, a full primary bedroom suite could cost over $100,000 with the inclusion of a bathroom.

Bathroom

A standard bathroom addition might cost between $6,200 to $15,500 to build. The square footage and extent of new plumbing and electrical wiring needed will majorly influence your overall bathroom addition price.

Sunroom

The cost of adding a sunroom typically costs $20,800 to $72,600, but building a large, luxury sunroom can cost as much as $140,000. Sunroom addition costs vary depending on the amount of space it will cover, location, and extra necessities such as electric wiring and heating. When making sunroom addition plans, consider saving money by opting for a three-season sunroom, which typically costs $10,000 to $40,000 to build. This option is a less-insulated version of a four-season sunroom, which costs between $25,000 and $80,000.  

Living Room or Family Room

A comfortably sized 18-by-12-foot living room add-on costs in the range of $17,300 to $43,200. The cost of this addition project depends on the room’s square footage and necessary HVAC and electrical additions.

Kitchen

The cost of a new kitchen addition typically costs $100 to $300 per square foot. However, since kitchens feature many different appliances and electrical outlets to power all your gadgets, you’ll need to budget for any new electrical wiring needed for the room, averaging $1,175.

Detached Garage, Shed, or Outbuilding

Detached additions vary in style and price. The cost of a shed averages $2,500 without electricity or heat, and full guesthouses average about $24,700. Enlisting the help of professionals like a local general contractor, electrician, and painter is often needed to finish a detached addition.

In-Law Suite

Rates vary widely for in-law suite home additions. A simple bedroom unit costs around $8,600 to $21,600, while it can be as much as $100,000 for a full unattached suite. Research your city ordinances before starting an in-law suite project, as they may not be allowed in your area.

Front Porch

The cost of adding a new front porch can also vary greatly, ranging from $4,600 to $22,200. Before starting a home addition construction project, it’s best to get at least three quotes from the general contractors you’re looking to hire in order to get the most accurate price estimate.

Adding a Second Story 

The average cost of a second-story addition falls between $80,000 and $250,000. But a full second-story addition can cost anywhere from $100,000 to $600,000 or more. A local structural engineer can help assess if your home and foundation can support a new second story.

How Much Does It Cost to Build a Home Addition Yourself?

Building a home addition is a complicated job you shouldn’t tackle entirely on your own. Most homeowners consult an architect to ensure the design matches the rest of the house and a structural engineer to ensure safe construction. Often, you’ll also need to hire an electrician, plumbing expert, or other construction contractors to make sure you build your home addition is up to code.

However, there are certain parts of a room addition project that you can do yourself, such as hanging drywall, laying flooring, installing cabinetry, or painting. Taking a DIY approach to these tasks can save you money on the cost of labor to have a contractor perform them. Contractor labor costs typically make up about 30 to 50% of your total budget.

DIY Home Addition Cost Vs. Hiring a Contractor 

We don’t recommend constructing a home addition without building experience and expertise in demolition, zoning, and building codes. Not only could you make costly mistakes, but your home addition might not be safe and structurally sound. A local general contractor with home addition experience will ensure your addition is safe, stays on budget, and meets local building codes. They also handle hiring and managing other pros, such as plumbers and electricians.

How to Save on Home Addition Costs 

Many home improvement projects can go over estimate, usually anywhere from 5% to 20% of the project quote. But you can still save on the cost of your home addition without sacrificing quality by following these tips:

• Choose standard finishes, such as vinyl plank flooring.

• Opt for a simple home addition floor plan with standard height ceilings.

• Complete some tasks yourself, such as painting the family room or installing light fixtures.

• Compare bids from at least three general contractors to ensure the best value. 

• Research whether you qualify for tax credits or refunds. Sometimes home additions are considered capital improvements with energy-efficient designs.

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