Calculating the Cost of a Roof

So how much does a shingle roof cost?

One of the most widely searched roofing topics on the internet is how much does a shingle roof cost.  Roofing your home is a big expense and most people want to have an idea of what they are getting into before they start requesting estimates from local roofing companies.  Most homeowners want to know how much they should expect to budget for.  In this article, we are going to help you determine the cost of installing an architectural shingle roof on your home based on the square footage of your home, at least at a high level anyway. 

There are several factors that need to be considered when calculating the cost of a roof replacement.  The primary factors are square footage, roof pitch, and roof complexity.  For the sake of this exercise, let’s assume that you are using a standard quality architectural shingle (CertainTeed Landmark, GAF Timberline HDZ, or Owens Corning Duration) and a double layer of synthetic underlayment.  This is standard practice in North Florida.  We will not be factoring in any, permitting, venting, skylights, drip edge, gutters, nails etc. For simplicity’s sake this is just for the largest components: shingles and labor.

For the sake of this example, we will use a 2000 square foot home.

Factor #1:  Square Footage:

The first thing you will need to calculate the approximate cost of installing a new architectural shingle roof on your home is your square footage.  Make sure to obtain the total square footage under roof, not just air-conditioned square footage.  This will include the square footage of your garage, front and back porches, etc.   You can obtain this number from the property appraiser website for your county.  In this example, we will use 2000 square feet under roof.  Square footage under roof typically doesn’t take the additional square footage of your overhangs into account.    To calculate the square footage of your over hangs, multiply the width of your soffits by the perimeter of your roof.  For example, if you have 24 inch soffits, and your roof has a perimeter of 300 feet, you would multiple 2 feet by 300 feet to get a total additional square footage of  600 square feet.  Add this to your total square footage under roof for a total roof area prior to factoring in a pitch.   In our example, our total square footage including over hangs would be 2600 square feet.

Factor #2:  Roof Pitch:

If your roof was completely flat, then the square footage you calculated in the previous example would be the square footage of your roof, but most roofs have a pitch.  A pitch adds additional square footage to your roof.  The higher the pitch, the greater the square footage that needs to be factored in.

Roof pitch is determined by how many inches of rise your roof has per each horizontal foot of distance.  For example a 4:12 pitch roof has 4 inches of rise for every 12 inches of horizontal distance.  Roofs fall into three categories for shingle roof systems: 

• Low pitch 2:12 and 3:12 pitch 
• Standard Pitch 4:12 pitch to 6:12 pitch
• High pitch:  7:12 pitch and above. 

Below is a table that provides a pitch factor for each roof pitch.  To determine the total square footage of your roof, you will need to multiple the pitch factor that corresponds with your roof to the square footage you determined in the previous example.