How To Measure a Roof (Step By Step)

Knowing how to measure a roof can help homeowners estimate costs when they need to reinstall roofing materials. Unfortunately, measuring a roof is more complex than calculating the square footage of a house. Other elements will come into play, including the pitch and multiple peaks or valleys. 

This step-by-step guide will help you accurately determine your roof’s measurements without requiring a professional to complete this task. 

What Is a Roofing Square?

If you are exploring roofing solutions, you may come across the term, “roofing square.” A roofing square is equal to 10 feet by 10 feet totaling 100 square feet of roofing surface. 

When shopping for materials, many manufacturers will bundle products to cover one roofing square as an easy way for customers to select the proper amount they need. Therefore, if you know how many roofing squares will cover your home, you are sure to estimate roofing costs accurately and purchase the right supplies. 

Many homeowners will use an online calculator to determine their roofing surface area once they take the necessary measurements. 

A Step-by-Step Guide to Measuring Your Roof 

Measuring your roof is easier than you think. You can quickly calculate your roof surface with proper planning, even with different dormers and multiple sections. So, all you need to do is follow these steps for a precise number. 

Step 1: Gather Your Supplies 

You can take accurate measurements if you are comfortable enough to get on your roof. Before heading up there, you should gather the supplies you need for this task. These items include: 

• Pencil
• Notepad
• Tape measure 
• A level 
• Non-slip shoes 
• A stable ladder

Some homes will include a roof access door, while others require you to climb a ladder to reach the roof surface. It’s important to wear non-slip shoes while walking around on the roof so that you minimize any chance of losing your balance.

Step 2: Determine the Number of Roof Planes On Your Home

A roof plane is a section of the roof where two angled sides come together in a peak. Some homes have a straightforward roofing design that only uses two planes. In contrast, other houses contain several planes that extend from the roof surface, such as gable sections or dormers. 

Draw out a rough sketch of the roof before ascending so you have the design laid out to input the measurements. Include every part of the roofing system, including vents, chimneys, skylights, or other elements present on the surface. 

Step 3: Measure the Length and Width of Each Roof Plane 

The next step in calculating your roof’s surface area is to get the basic measurements for each plane. You can use a standard tape measure or a measuring wheel to get these numbers. 

For example, if you have a flat roof, you will only need to measure one plane’s length and width. However, each plane requires measurements if you have a roof with multiple planes. With these numbers, multiply the length and width together for each plane to determine the square footage.

Step 4: Combine the Plane Measurements 

Next, take the square footage amounts from each plane and add them together. The result will give you the total surface area of your roofing system without considering external elements like skylights, vents, pipes, or other fixtures. 

Step 5: Determine the Roof’s Pitch or Slope

Having a steep roof can make it challenging to measure manually. Therefore, knowing how to calculate a roof’s pitch can save you the trouble of climbing on a severe incline to take measurements. This way, you can get roof measurements without climbing ladders and walking on the roof. 

The roof’s pitch is how much the slope increases with every 12 inches. To figure out your pitch, you will consider the rise of the roof and the run. The rise is the total vertical height of the entire roof structure, right from the peak to the top of the stud wall support. The run is the horizontal length of one side of the roof structure. 

You will need to use a level longer than 12 inches to determine the slope of your roof. This slope is easy to calculate by heading to the attic with your level, a tape measure, and a pencil. 

Position the level against the bottom of a rafter in your attic where the roof meets the supporting wall. First, ensure it is level, then mark your level at 12 inches. From this point, measure the from the mark up to where it directly meets the roof slope. This measurement will be your roof pitch. 

For example, if you measure straight up from where your mark meets the rafter above, giving you an 8-inch measurement, you have an 8:12 roof pitch. You can also use online roof pitch calculators to help you determine this number.

Step 6: Consider the Waste Factor

It’s essential to consider the small amount of materials you will waste when calculating how much product you need to cover your roofing area. 

A standard rule is adding 10-15% more to your final measurements to account for any waste. This way, you will have enough roofing materials to finish the job correctly, even if you accidentally damage some material during installation. So, if you have a total roofing area of 1,500 square feet, adding 10% will mean you should purchase 1,650 square feet of material. Alternatively, 15% of having extra material works out to 1,725 square feet.

In Conclusion 

Knowing how to measure a roof is a helpful and simple tool for estimating material costs when you need to reinstall a new roofing system. Even if you decide to use a professional contractor to complete the job, having this estimate ahead of time can provide the information you need to budget for this renovation. 

For example, re-shingling a roof of 1,500 square feet will cost $10,500 on average, but for the same surface, using metal roofing tiles will be approximately $17,000. Therefore, measuring your roofing area is an excellent way to explore which roofing material suits your budget and lifestyle.