How To Calculate Area Of Roof ?

Are you wondering to reroof the house on your own and want the estimate of material you will require for roofing? Thus, math’s formulas can rescue you when you need to evaluate the area of the roof including some complex structures over it. the general formula to evaluate the area of the roof is

Roof Area = (length of roof * slope height) * 2

However, there are different steps discussed in brief below that you need to follow.

General Concept To Calculate Roof Area

The area of any of the surfaces is calculated by multiplying length and width. Measurements of base length and base width are needed to evaluate the square footage of the roof.

Base length is the distance from one roof corner to another following the long side of the house, whereas base width is the distance from one roof corner to another following the short side of the house.

The calculation is done at the point for a flat roof. However, many roofs have angles that mean one last measurement is needed to calculate the roof area, i.e., roof pitch.

Roof Area Calculation Guide

All you need to do is to follow some steps

  • Divide your roof pitch by 12. It means roof pitch is the inches in a change of height over the distance of one foot. Dividing by 12 will give you the ratio of inches rising every distance. For instance, the standard roof pitch is about 4. Hence for the pitch angle of 4, divide it by 12
  • Square your result of step 1, and so keeping with the roof pitch angle of 4, it gives 1/9.
  • Add one and then square root it. Adding one to the 1/9 will give you 10/9, and the square root of 10/9 will give 1.0541.
  • Multiply by the square footage of the single house floor. Let us continue the example if you have a two-floor house having a total square foot of 2700 square feet. It means each floor has 1350 square feet, so multiply 1350 by 1.0541 for getting the result of 1423 square feet. Thus, you will need 1423 square feet of roofing.

However, this is a simple concept that you have to keep in mind. Let us start briefing steps to calculate the area of the roof from scratch.

Roof Area Calculation Steps

how to calculate roof area

Things You Require

  • Calculator
  • Tape for measurements
  • Paper
  • Pen and pencil
  • Strong extension ladder

Measurements You Need

  • Roof pitch
  • Square footage of the house

Step 1 – Pitch Measuring

It is the first thing to do whenever you set to evaluate the roof area. Utilize the measuring tape for measuring 12 inches on the significant level and put a mark at a 12-inch line.

Then place a ladder beside the building at the gable corner. Ascend to the rooftop and place the level against gable trim and flat against the house side.

Utilize the measuring device for measuring from the 12-inch mark on your level to the bottom of the gable trim’s edge.

Step 2 – Estimation Of Area Of Roof Calculation

You can use your calculation for pitch easily for getting the area estimation of your roof. What you have to do is to follow the simple concept discussed above.

It means taking the pitch number and dividing it by 12; squaring the result; add 1 to it. Then find the square root of the new consequence; check out the square footage of one floor.

Step 3 – Exact Calculation Of Roof Area

For figuring out the exact area calculation of the roof, follow the below steps –

  • Take the pitch number; divide it with 12. Then square your result and add 1 to it. Evaluate the square root of your new number.
  • Measure the length and width of the house, including the overhangs. Now multiply the size of the house with the width for getting the area result.
  • Then multiply the area with the pitch to get the exact area of the roof.
  • For allowing hips, waste, and ridges, it is recommended to add about 10% of your final area of roof for the gable roof or around 17% in the case of the cottage roof. Thus, as a result, you must be working with 1386 square feet or about 1474 square feet for the cottage roof or gable roof, respectively (if the pitch is 4).

So, follow these above steps for calculating the roof area. Before you start work on any of the roofing projects, it is essential to have accurate measurements of the roof area. It allows you to work according to the size and type of the roof.

Gable Roof Area Calculation

You will first need to evaluate the roof length as it is the length of the roof’s ridge from end to end. Then you will need to assess the slope height of the roof.

It is the length from eaves to the ridge, not the distance between your roof deck and apex. If you do not know about these measurements, you can find them on the building plans when you purchase the property.

To calculate the roof area, multiply the length of the roof by the slope height of the roof and multiply it by 2. It will give you the total roof area, excluding chimneys or other sections not covered by tiles.

Area of roof = roof length * slope height of the roof

For instance, the slope height of the roof is 7 meters, with 9 meters roof length having a pitch angle of 45 degrees. Using the above calculation – (7 * 9) * 2 = 126 square meters. Add about 10% extra for the damages if any occurs.

Complex Roof Area

If you do not have a gable-shaped roof or many sections like valleys and hips, it is advisable to split the roof in each section and to work out the areas mainly. Follow the same steps as above for each team and find out the area of the roof.

Summing Up

Evaluating the roof area is a challenging task, so take a glance at the above guide that shows you the calculation and estimation of the roof area.