How Much Does It Cost to Add a New Space?

Adding on to any home, whether it is an expansion of the existing "footprint" or an entirely new level is a very complex project. For this discussion we will examine the requirements and general costs associated with adding a single-story 192 square foot (12'x16') room. This type of project will not be considered a "DIY" project in the least, and several contractors will be necessary for the job (carpentry, installation, electrical, etc.).

For the new addition such as described above, the typical costs include:

• According to Hanley Wood and their "Remodeling" magazine the average basic addition in which a foundation is added, vinyl ¹ siding is applied, adequate roofing is done, interior walls are insulated and finished, new carpet and windows are installed and all electrical and HVAC works is completed will cost $23,804. The resale value of this update would hold at $19,757, or an 83% return on investment.

• The above figures place the cost of the addition at $124 per square foot. This pricing structure assumes that carpenters charge an average of $70 per hour, electricians between $65 to $85 per hour, and painters between $20 and $35 per hour.

Cost Breakdown

What needs to be included:

• Architectural design services to ensure that new addition is housed in a structure in a style appropriate to the existing house, and up to code for the neighborhood or area in which the home is located. This should require no more than 10 - 17% of the total building budget;
• Arrange any required demolition, excavation, or site preparation - Average costs are going to vary according to the level of work necessary;
• Pour concrete footings ² and slab if no crawlspace foundation exists - Average price of concrete is $75 per cubic yard, with piers and the full slab it that would require roughly 14 cubic yards and would cost at least $1050;
• Build roof trusses ³ and support beam system and tie into existing structure - lumber prices will vary as will the design used by the carpenters constructing the new space. The project should require 2x4 wood framing along with OSB structural sheathing;
• Asphalt ⁴ shingles ⁵ with galvanized metal flashing ⁶ - Average of $80 to $100 per square of 50-year shingles ⁵. Total cost of $450, plus installation time of at least 16 hours;
• Install vinyl ¹ siding and trim - Average price of $7 per square foot installed, and for the 514 square feet needed, this would total $3600;
• Finish ceilings and walls - Drywall ⁷ throughout would require 20 panels of 4'x8' for walls and ceiling at $9.80 each (plus screws, nails and finishing compound) for an approximate total of $250 plus approximately 24 hours of installation;
• Fiberglass ⁸ wall and attic insulation with R-49 and R-28 values respectively value will cost an overall average of $2.00 per square foot (installed) for an approximate total cost of $825;
• 1 - six-panel primed hardboard door ⁹ - Average of $178 each plus four hours of installation;
• Three new windows - Average price of $300-$700 per window, plus installation time of two to five hours per window. Be sure that the windows purchased will qualify for tax deductions;
• Carpeting - Averages at $15 to $25 per square yard (with padding ¹⁰ and installation) totals $533;
• New moldings - Average of $3.00 per foot of installed molding for a total of roughly $850;
• Tie into existing HVAC - Average cost will vary according to pre-existing system;
• Provide electrical wiring and lighting to code - This is going to depend upon the amount of work required, but electricians average from $65 to $85 per hour. This project might be priced on a per item basis, or the electrician might simply base it on the square footage; and
• Provide carpentry to code - This is going to depend upon the amount of work required, but carpenters average $70 per hour. This project might be priced on a per item basis, or the carpenter might simply base it on the square footage.

Enhancement and Improvement Costs

• 6 recessed ceiling lights; and
• Painting of trim and walls.

Remodeling Terms Cheat Sheet

¹ Vinyl: A synthetic plastic made from ethylene and chlorine. Vinyl has many applications in the construction industry and it is widely used in sidings, window frames, roofing and gutters, among others

² Footings: A support for the foundation of a house that also helps prevent settling. It is typically made of concrete reinforced with rebar, but can also be made of masonry or brick. It is usually built under a heavier part of the house like a wall or column, to distribute the weight of the house over a larger area.

³ Trusses: Structural framework used to support a roof

⁴ Asphalt: A viscous, black mixture of hydrocarbons often used for roofing and waterproofing. It is also used in asphalt for paving roads

⁵ Shingles: A smooth, uniform, flat piece of construction material, available in a wide variety of materials and laid in a series of overlapping rows, used to cover the outside of roofs or walls to protect against weather damage and leaks.

⁶ Metal flashing: A thin sheet of metal used around the edges and junctions of the roofing material,such as around a chimney or vent, to prevent water from entering the structure through those joints

⁷ Drywall: Type of plasterboard, commonly used to build walls and ceilings, composed of gypsum that is layered between sheets of heavy paper

⁸ Fiberglass: Plastic that is reinforced with glass fibers. The fibers may be mixed randomly throughout the plastic, or come in the form of a flat sheet, or be woven into a fabric

⁹ Hardboard door: A door finished with a surface made of high-density fiberboard, an engineered wood product also called hardboard, and factory painted to look like wood. This term can also refer to a door with a solid hardboard core and wood veneer panels

¹⁰ Padding: A cushion placed under a carpet to absorb impact, thus extending the life of the carpet