Roofing felts are very necessary for your roof as they protect your roof by sealing water leakage, fire resistance, weather problems, and overall extending the longevity of your roof. 

A low-quality roof felt can be damaged by UV rays of the sun and other weather conditions. They can be easily ripped off.

On the other hand, the weakest grade of polyester reinforced roofing felt is hard to shred. The internal reinforcement prevents it from treating up in every direction.  

Now you may ask, how many rolls of roofing felt do I need? Well, not only that, what quality it should be, what should I choose, how will it protect my roof- all of these questions have been explained in the section below.

So, let’s start our session related to roofing felts.

What is roofing felt?

Roofing felt is a protective covering just under the shingles. It has also some alternative names such as rolling paper, tar paper, or roof felt padding.

It facilitates insulation and fire protection in your home. Good roofing felt should not weigh much. Roofers most commonly use roofing felt that gives the best insulation as well as permits the worker to stand on it without shredding it. 

How Many Rolls Of Roofing Felt Do I Need
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How Many Rolls Of Roofing Felt Do I Need

Roofing felts are usually retailed in rolls. The rolls are wrapped around with paper containing information on how much the product is available in each roll.

When you have calculated the area of your roof that you want roof felt to be installed, the next thing is to perform a division operation.

Roof Area Calculator

The roofing calculator is very important as it helps to know about the roofing square. The first thing while calculating your roof area is to determine the pitch for your roof. If you have a roof with different slanted parts, you have to calculate separately for each subsection.

Now, for determining the pitch you can either go to the attic or to any frame visible location of your house. Along with the pitch of the house, mark a point after each 12 feet distance. 

The next thing is to measure the height of each point. Calculate the difference between the high and low height, and that is your roof pitch. For example, if the height is 4 feet then your pitch is 5/12.

How many rolls are needed

After successfully calculating the pitch, make sure to measure the horizontal and vertical measurements for your roof area.

It is recommended to multiply a certain value with your pitch for the correction factor. Such as multiplying the roof pitch with 1.25 if the pitch is 3/12 or 4/12, for values larger than this a factor of 1.5 to 1.75 is multiplied.

Felt covering for rooftops is offered in one-square-foot rolls. 100 sq ft is equivalent to one roofing square. So, divide the total area of your roof and the felt roll area(that is 100 sq ft in this case). 

It is always a best practice to permit 10% of additional material purchase for waste management.

The necessity of roofing felt

The internal structure of roofing felt consists of both natural and synthetic components that hold back any fluid caused by rain, snow, or other phenomena. 

One of the best parts of using roof felt is it is breathable and also fire resistant. It also helps to extend the lifespan of your roof deck as well as protects it from any further damage if your roof shingles go broken or cracked. Again, roofing felt provides a uniform base for your roof. 

Variations of roofing felt

Roofing felts are available in a lot of thickness options (3k, 3.5k, 4k, etc) for professional and commercial use.  These felts are mainly store-bought or DIY chained roof felt.

It also comes with three different color choices of green, light gray, and dark brown. The most commonly used version is the 3.5k version as it is one of the lightest and thinnest versions.

Installation Process of roofing felt: Step by step guideline

Required Tools

Installation of roofing felt can be done within a very short time and by using simple tools. These tools are:

  • A knife,
  • Hammer,
  • Crowbar,
  • Brush,
  • Rolling paper or roofing felt,
  • Ladder, nails, etc.

Step 1: 

The first thing when you install roofing felt is to take a width measurement and then add 50 to 75 millimeters to the front and back. This creates an overhead in the front and back of the shed behind the barge board.

Step 2:

Next, you have to cut the felt square with the hook blade knife. If you do not have a hook blade knife, standard ones will also do. But it is not just as easy. Carefully cut away any strapping binding the roll and unroll it to a nice flat surface free from anything sharp.

Step 3:

Now, lightly scratch the surface of the felt with the back portion of the knife blade. It will be used as your marking where you should cut your felt. Make sure to check if your line is nice, straight, and parallel. 

Step 4:

After cutting the felt, you have to decide where the felts will overlap. Always take extra care in such areas and also make sure to handle the front and back overlay portions. 

Step 5:

The nailing distance in most cases is 6 to 7 inches in a tough nonripping roof felt. While nailing down on the roofing felts, it should be reminded that it will cover one layer of felt and the timber associated with it. 

Step 6:

Repeat the whole process until you are done. You can hammer a couple of times to check whether it is not saggy in the middle.

Final words 

I really hope after reading this informative article, you have come to meet your thrust with your question of how many rolls of roofing felt do I need in my home.

However, this article will also help you install the roofing felt in your home if you want to do it yourself. 


As a civil engineer and roofer, I love to share the experience that I have gained through the last couple of years. In the roofing industry, practical experience is a very crucial fact that can help you a lot. Hence, I want to help you with my blog.

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