The Cost Of Adding An Addition Onto My Home

living room

Adding an addition to your home can be an exciting yet intimidating prospect. Many homeowners have decided that building an addition to their existing home is preferable over moving to another home. Perhaps they love the neighborhood, want to stay in the same school district, or like the proximity to work, shopping or medical needs. Whatever the reason, they have decided to stay put, but need more space.

How Much Does it Cost to Add an Addition to a House?

The national average cost of building an addition is $41,726, with most homeowners spending between $21,000 and $64,000. An addition to your home is a huge investment in time and money so it will pay to become as knowledgeable and organized as possible about all aspects of the project.

The average cost of adding an addition to a house, according to, takes into account the following:

  1. Architectural services make sure that the design of the new addition looks good with the style of the home. This typically accounts for 10% to 17% of the total project budget.
  2. Excavation, demolition and site-preparation costs vary depending on the amount of work that needs to go into the prepping. For example, removing a wall costs $300–$500, while excavation costs around $2,559 on average.
  3. Pouring concrete footings and a slab foundation costs an average of $75 per cubic yard.
  4. The support beams and roof trusses have to be integrated with the rest of the home's structure. The average cost runs from $15–$30 per square foot, depending on the lumber charges and labor costs.
  5. Roofing for the new addition averages $80–$100 per square foot for asphalt shingles and galvanized metal flashing. Metal roofing and slate are two pricier options.
  6. Installing vinyl siding and trim finishes the exterior of your addition for an average cost of $7 per square foot.
  7. Finishing the interior by drywalling the ceiling and walls costs an average of $9.80 for each 4-foot by 8-foot sheet of drywall.
  8. Insulation costs $2 per square foot.
  9. A door costs anywhere from $175 or more, depending on the material and the style of the door.
  10. Adding windows for light and ventilation costs an average of $300–$700 per window.
  11. Molding for ceilings costs around $3 per foot.
  12. Electrical wiring and making sure the electrical system is up to code is important and it requires a licensed electrician, which typically costs $50–$100 per hour.
  13. Flooring options include ceramic tile ($1,640), carpeting ($1,490), laminate ($2,748), vinyl/linoleum ($1,185), natural stone tile ($1,826) or wood flooring ($4,396).
  14. Tying into the existing HVAC system varies in cost, but the average cost for installing ducts and vents is $1,050.

Home Addition Considerations

Having a clear vision of what you want and need will be the first step in your planning. Deciding whether you are building out or up will come with its own positives and negatives and will impact many of the decisions you need to make. No matter if you build out or build up, this is a major construction project with average costs running approximately $80 to $200 per square foot. Don't forget to check zoning restrictions.

Building Out

Building out involves increasing the footprint of your home by extending your house's perimeter outward. The advantages are less disturbance to the rest of the home, while having to pour a new foundation. A disadvantage would be the decrease of yard square footage. Consider also that a zoning variance may be required depending upon local regulations.

Building Up

Building up involves adding space to the existing footprint of the house. While a new foundation is not needed, strengthening of the existing foundation may be required to support the extra weight. Here again, local regulations may limit the height of your home, and a staircase may need to be added.

Types Of Additions

Sunrooms can be a budget-friendly way to add space to a home with average costs running $16,315 for the average sunroom. The amount of space, location of the sunroom and the addition of electrical wiring and heating can add to the costs.

Detached additions such as guesthouses, detached garages or other types of additions run around $15,000 to $24,000 on average. Factors such as whether or not you are buying a prefabricated addition or building it from the ground up, possible excavation, and exterior design will all have an impact on the cost.

In general:

  • Electricians charge an average of $50–$100 per hour
  • Carpenters charge an average of $70 per hour
  • Painters usually charge $20–$35 per hour

Return on Investment for Home Additions

Most homeowners will want the addition to add value to their home in terms of resale value so doing the job correctly and within budget is important.

According to, the Return On Investment (ROI) for a home addition is as follows: 

  • 49% for sunrooms
  • 53% for bathrooms
  • 63% for master suite additions
  • 65% for two story addition with upstairs master suite and a downstairs living area

Additions may return less on your investment than remodels. However, adding significant square footage to your home or adding rooms such as bedrooms and bathrooms may show a higher return on your investment.

How to Get Started with a Room Addition Project 

  • One of the first steps in adding an addition onto your home is to get everything in writing from your contractor. Agreeing on the total cost before going forward is vital. Make sure they are licensed and insured and check references. Contractors will usually expect some advance money and then again after specific goals in the project are reached. Advancing too much money could put the homeowner at risk, but advancing too little could put your contractor at risk. These terms need to agreed upon in writing before any work is started.
  • Find out what your contractor's policy is on changes. During construction, the homeowner may change their mind about the layout, the fixtures to be used or even colors. Another consideration is that the contractor may run into unforeseen problems which may have a big impact on the budget. These contingencies need to be addressed in writing before the construction is started.
  • Hiring an architect for your project is another consideration. The size and complexity of your addition will determine whether an architect is needed. Using an architect will certainly add to the cost, however, the finished project may be worth the cost. Hiring an architect will insure that your budget estimates will be more exact and construction is done in a way that blends in with the style of your home and adds to the resale value.
  • Remember that an addition will most likely involve exterior work. The cost of siding and roofing materials plus landscaping costs all add to your budget. Adding an addition onto your home can be a daunting prospect. However, with the correct planning and the right professionals, your project can add to the beauty and functionality of your home.

Need a Contractor in the Charleston Area?

Harper Construction specializes in high-end custom construction and remodel projects. Our reputation for quality construction and attention to detail have made us a five-time " Best of Houzz" award. Browse our entire portfolio of homes at