Home Room Addition Cost Estimates FAQ

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Building a room addition can be an expensive proposition. However the value to cost ratio is easily justifiable when adding much needed space, functionality and convenience. More information for Home additions that make good financial sense

Uprooting, moving, selling old home has costs that many homeowners may not take into consideration too. Let’s face it, most older homes are solidly well built, to duplicate that today in new home would drastically increase a new home price.

Most home remodeling contractors typically ballpark room addition cost estimates in dollars per square foot. This provides a rough baseline for typical home addition costs. This will help homeowners to get a general idea for a budget and the magnitude of what may occur in a the cost for an addition project. I’ll be frank here, this also helps to screen serious homeowners from the samplers. Some room additions can be more complicated to build due to the fact that not only does it need to be constructed well, but it also has to tie into the existing home in a structurally and aesthetically pleasing way.

Providing a home addition estimate takes effort, time and money, both in the design, planning, coordinating and construction of the room addition. Consequently home construction contractors can and may charge a premium when providing an addition cost estimate.

Home addition cost estimates can vary dramatically due to a number of factors. Primary factor, specifications of in the room addition plans.


  • Home addition cost estimates of $170 to $225 per square foot for a basic family room addition is common.
  • If the home addition includes a bathroom and/or a kitchen, the room addition costs can easily escalate to $475-$1000 per square foot.
  • Quality and materials used are the other cost factors in a home addition.


Your room addition plans specify the construction of 400 square feet of family room living space, without any type of bathroom or kitchen area, you can expect to pay $72,000 – $90,000 for a basic mid-range completed addition. If you are including a bathroom and/or kitchen, you could see room addition cost estimates as high as $125,000 +.

Room addition cost estimates can also vary with market demand for building material availability and home remodeling construction labor costs. Legal professional remodeling contractors are in business to make money, and our time and effort is money, so you need to expect some markup charge for the materials that he orders and has delivered to your room addition project.

Let’s Break it down using an example from several other sources too. ~ *Fixr.com & Remodeling Magazine “Cost vs Value”

New Space Addition Cost

How much does it cost to add 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 400 square foot (16’x25′) 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 in 2017 the average basic addition in which a foundation is added, vinyl siding is applied, adequate roofing is done, interior walls are insulated and finished, pre-finished hardwood floor and windows are installed and all electrical and HVAC works is completed will cost $89,566. The resale value of this update would hold at $62,055, or an 69.3% return on investment.
  • The above figures place the cost of the addition at $223.92 per square foot. This pricing structure assumes that carpenters charge an average of $75 per hour, electricians between $75 to $95 per hour, and painters between $35 and $45 per hour.

Cost breakout

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 and slab if no crawlspace foundation exists – Average price of concrete is $175 per cubic yard, with piers and the full slab it that would require roughly 14 cubic yards and would cost at least $2450;
  • Build roof trusses 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 2×4 wood framing along with OSB structural sheathing;
  • Asphalt shingles with galvanized metal flashing – Average of $100 to $125 per square of 30-year shingles. Total cost of $500, plus installation time of at least 16 hours;
  • Install vinyl siding and trim – Average price of $9.50 per square foot installed, and for the 514 square feet needed, this would total $4883;
  • Finish ceilings and walls – Drywall throughout would require 20 panels of 4’x8′ for walls and ceiling at $12.80 each (plus screws, nails and finishing compound) for an approximate total of $325 plus approximately 24 hours of installation;
  • Fiberglass wall and attic insulation with R-49 and R-28 values respectively value will cost an overall average of $2.75 per square foot (installed) for an approximate total cost of $1100;
  • 1 – six-panel primed steel door – Average of $270 each plus four hours of installation;
  • Three new windows – Average price of $400-$950 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 $25 to $35 per square yard (with padding and installation) totals $533;
  • New moldings – Average of $4.75 per foot of installed molding for a total of roughly $1250;
  • 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 $75 to $95 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 $75 per hour. This project might be priced on a per item basis, or the carpenter might simply base it on the square footage.

Average Home Addition Costs

As a remodeler we are often asked what are some average cost for a given remodeling project. The cost of any remodeling project will vary depending on the type of materials used and the overall complexity of the project. The design of the project can also determine the resale value of the project along with the recouped cost estimates. The following numbers are averages based on remodeling projects completed in the past year.

You can see a few of our room addition, updates and conversions here: Home and Room Additions

Midrange Master Suite Addition

Job Cost $119,533 | Resale Value $77,506 | Cost Recouped 64.8%

Midrange Bathroom Addition

Job Cost $43,232 | Resale Value $23,283 | Cost Recouped 53.9%

Midrange 2 Story Addition

Job Cost $176,108 | Resale Value $125,222 | Cost Recouped 71.1%

Averages based on Remodeling Cost vs Value Report 2017

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