Don't Blow It

By Mark J. Donovan

March 13, 2017 5 min read

When your home is undersized, outdated or lacking vital amenities, it may cost less to improve than to move. A room addition is great way to transform your home into the ideal fit for your lifestyle and personal taste. That said, it is a costly endeavor that almost always far exceeds the do-it-yourself realm of home improvement projects. With careful planning and knowledge of what an add-on project entails, you can develop a firm budget and a clear vision.

HomeAdvisor is a leading nationwide online home improvement marketplace. It reports that the average national cost of adding a room or building an addition is $40,942. Understanding the costs associated with such a grand total will help you navigate the project.

Most homeowners hire a general contractor for a room addition, who provides a project cost estimate and handles the hiring and managing of subcontractors. Some act as their own general contractor to save anywhere from 15 to 30 percent of the overall project cost. However, this job involves a lot of work, including developing build plans, calculating material and labor costs, finding and hiring subcontractors, and scheduling and managing the team all the way through.

There are two main ways to add onto your house: horizontally or vertically. The direction is often dictated by the purpose of the addition and the existing floor plan. One article on the HGTV website titled "Building Up Vs. Building Out" cites pros and cons for each. Building out, which generally involves installing a new foundation or slab, typically involves the least disruption of your existing space and lifestyle. But Roy L. Fyffe, a spokesman for the American Association of Code Enforcement, says you might have to acquire a zoning variance from the town, and "You could also face limitations from the town's Floor-Area-Ratio rating, which dictates what proportion of a lot can be built on (including the house, garage and driveway)." Conversely, building up will not restrict your yard or add to the existing footprint of the house. However, many towns limit the maximum housing height, and, Fyffe adds: "If you're adding a whole additional story, you'll also need to account for a stairwell, which can easily eat up around 80 to 120 square feet or more of living space. And your contractor will likely have to tear apart the walls and ceilings in the space below to beef up the structural supports and feed in the electrical, plumbing and heating lines." These factors are important to consider given how contractors calculate the cost estimate.

Room addition costs are quantified in dollars per square foot. And contractors charge a premium when providing a room addition cost estimate. A U.S. News & World Report article online notes that according to, a bathroom or bedroom addition could cost $25,000 to $50,000, and a large room, such as a family room, could run as high as $100,000. Bill Millholland, executive vice president at Case Design/Remodeling Inc., says: "'I would guess somewhere between $200 to $600 per square foot. ... The more you build the less it costs per square foot."

Certain cost variables are independent from your specific project, such as market demand for building materials and home-construction labor. Price gouging is not uncommon when the housing market is hot, so study contractor proposals carefully. Do not hesitate to visit your local home improvement store and compare material costs against those listed in your estimate; they will differ slightly but shouldn't differ drastically.

Visit my website, at, for practical, comprehensive room addition construction bid sheets, contractor bid sheets and home building guides for any room. Included are questionnaire forms (like checklists and requests for quotes) that you can give to potential contractors for them to fill out when bidding the job. These forms will not only help you learn the right questions to ask potential construction partners but also reduce risk, and save you time and money. You can price out every single building item, down to the curtain rod.

The key to obtaining an accurate cost estimate is to have a complete set of building plans and specifications and vet those plans through the proper authorities. The U.S. News & World Report article mentions a cautionary tale of a resident in Myrtle Beach, South Carolina, who ran into trouble when his homeowners association said the his add-on wasn't up to code. Check with your HOA, county and insurance company before beginning the build. The more thorough your plan the less likely it will be that you meet unwanted surprises.

Though a room addition can be a costly, tedious process, the benefits of walking in the door to a home that you love and that is of your creation is priceless.

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