How To Calculate Roofing Nails

Your roof is one of the most important structural elements of your house, and in order to complete a successful re-roofing project, a significant investment in both time and money is required. It is highly recommended you hire a professional contractor for roofing work, and it can be difficult to cover the costs of pricey mistakes.

If you are undertaking the project yourself, it’s critical to remember roof work can be a risky and potentially dangerous job. Anything you can do take fewer trips up and down the ladder to the roof lessens the chance of injury.

 A simple bit of math when making your supply plan can help you estimate just how many roofing nails are needed for a roofing job. You will need to know the size of your roof, and then you will be able to calculate an estimate of how many points of roofing nails you will need to buy.

When you are planning out a roofing project, it is key to track how much weight they add to the roof, especially if you are working with an older foundation and framing. In order to have an accurate weight estimate, you will need to include the weight of the nails used to hold the roof shingles in place. 

Roofing Nails Per Square 

Most shingle manufactures recommend using four nails per shingle on the main area of your roof and five nails per square in the first row of roofing. This adds up to an average of 320 nails or 100 square feet. If you have high wind areas, you will want to use five nails pers shingle, equating to about 480 per square.

When using a 1.5-inch roofing nail, they usually have a large 11-gauge shank and an oversize, 7/16-inch flathead. These nails are hot galvanized, which helps them withstand sun and rain on your roof. About 140 of these types if nail weighs one pound. You will need approximately 2 ¼ pounds of nails to install a square of shingles in regular conditions, and about 3 ½ pounds if you are dealing with windy conditions. Because nails are purchased by the pound, so can ask your supplier for the correct number of nails for your size roof, in the length you specify.

Estimating Shingles Needed

To gauge how many shingles you’ll need, you will first need to estimate the total square footage of your roof’s surface. This can be done by measuring the length and width of each plane on the roof, including dormers. Next, you will multiply length x width to get the square footage of each plane. Finally, calculate your roof’s total square footage by adding the square footage of each of the planes together.

For example, a shed roof has one roof plane. You can simply measure length (A) x width (B): A x B = 120′ x 100′ = 12,000 sq. ft. for the total square footage of the roof.

Another example is a gable roof that has two planes. Therefore you would multiply length (A) x width (B) to get the square footage for each plane. You can then add the two planes together to derive the total square footage of the roof:

• Plane One: 120′ x 100′ = 12,000 sq. ft.
• Plane Two: 120′ x 100′ = 12,000 sq. ft.
• Plane One + Plane Two = 24,000 sq. ft. gives you the total square footage of the roof.

The surface of your roof is measured in “squares.” A square is an area of roof which equals 100 square feet. To calculate the number of squares on the gable roof above, you can simply divide its total of 24,000 square feet by 100. The result is 240, which means you would need 240 squares of shingles to cover that roof. The most common type of shingle is called a three-tab or strip shingle, and they usually come packaged three bundles per square.

If you are putting in a new roof, you will also need the same amount of underlayment. So, using the gable roof example above, you would need 240 squares of underlayment. Underlayment most often comes in rolls of 4 squares each. So, in order to cover 240 squares, you will need 60 rolls of underlayment.

No underlayment is necessary if you are applying shingles directly over an existing asphalt roof. Don’t forget to add 10% to all your material totals for trim allowance.

You will also need to know the slope of your deck. You can do this by measuring the vertical rise of your deck in inches over a 12″ horizontal distance. If you found the rise is 4″, then your roof slope is 4 in 12. The slope of your roof is always specified with the vertical rise coming first, and the horizontal run (12″) mentioned second.

What if your roof is steep? In order to measure a steep roof, you will have to use an alternate method. To calculate the roof length, first, measure the exterior walls the add the overhang for the length of the house parallel to the ridge. Next, using a rope, you can throw it over the ridge and mark it on each eave. This gives you the width dimension to use in figuring your area. Make sure you do this for each roof section containing a horizontal ridge.

Be sure to measure the lengths of your rakes and eaves to determine the amount of drip edge needed. Always remember if you have any questions about your supply estimate, ask a roofing contractor in your area. Many are happy to give you a free estimate.