Unraveling the Mystery of Roofing Felt: Is it Really Waterproof?

Unraveling the Mystery of Roofing Felt: Is it Really Waterproof?

Ah yes, roofing felt: the ultimate mystery of the home improvement realm! For many of us, roofing felt conjures up images of shingles and tar, old homes and even older tools. But what we often fail to ask is... is roofing felt really waterproof? After all, a key role of roofing felt is to protect decking and other underlying structures from water damage.
In this blog post, we'll take an in-depth look at roofing felt and examine the science behind its famed waterproofing power. We'll outline the different types of membrane materials, evaluate the benefits of different waterproofing technologies, and ultimately determine whether roofing felt really is a viable roofing waterproofing solution.

Quick Overview

Roofing felt is a layer of insulation between your roof and the elements. It helps protect the roof from elements like wind, snow, and rain, but it is not 100% waterproof, as water can still penetrate if there are any openings or weak spots.

What is Roofing Felt?

Roofing felt is a paper-based material that is used in roof construction and maintenance. It is most commonly found in the form of a material roll which is then overlaid on top of wood or other materials when creating a roof. This felt is typically made up of three components: an asphalt-saturated base, a protective sheet, and a mineral finish applied on top. While this type of roof covering has some advantages and drawbacks from the perspective of durability, waterproofing has been among the greatest areas of debate.
On one hand, many homeowners may assume that felt roofs provide some sort of waterproof protection for their home due to its water-resistant qualities, however, it's important to note that these layers are not designed to be completely waterproof as they are permeable to water vapor. This means that while they can keep out some moisture from rain or snowfall, there are still weaknesses in terms of overall protection against these elements.
On the other hand, there are several tests conducted by manufacturers and independent organizations that suggest that these coverings do have some capability in terms of offering protection against certain types of moisture damage such as wind-driven rain. For example, the ASTM D1970 Standard test in 2014 showed that 36” felt was able to resist 2500 hours of continuous rain without any substantial degradation.
Ultimately, roofing felt provides some degree of waterproof protection but it may not be able to withstand extreme weather conditions or natural disasters like floods or heavy downpours without degrading over time. As we attempt to unravel the mystery behind this product and its capabilities in regards to waterproofing, let’s explore further into the properties and purpose of roofing felt to gain more insight into its performance levels.

  • Roofing services felt is a water-resistant material made up of asphalt and other waterproofing ingredients.
  • Research by the National Roofing Contractors Association (NRCA) shows that roofing felt provides an effective barrier against water leakage while diminishing heat and temperature transfer from the outside environment.
  • Studies have found that roofing felt is highly effective in preventing water damage, especially when combined with other roof components like gutters and flashings.

The Properties and Purpose of Roofing Felt

The properties of roofing felt are its ability to resist water penetration, as well as serve as a separating and supporting layer between the roof deck and the shingle material. Additionally, it has high tensile strength which helps prevent tears or punctures when installing the shingles. This property is especially beneficial in areas prone to strong winds.
Despite this, some argue that roofing felt is not waterproof enough to provide adequate protection against heavy rains because it does contain some water permeability. However, others disagree and argue that while felt is not completely waterproof it will nonetheless still slow down rainwater from penetrating too quickly into the core of the roofing structure.
Evidence suggests that using roofing felt can successfully reduce water penetration from damaging your home by diverting water away from the shingles and allowing for moisture to escape -- both of which make it an essential step in protecting a home’s longevity.
Now that we understand more about what roofing felt is and its purpose, let's explore if it has any other properties such as breathability - an important aspect to consider before installation.


When it comes to roofing felt and its properties, one of the most important features to consider is breathability. Breathability, in this context, measures the material's ability to let moisture (in the form of water vapor) pass through it; this quality is essential for roofs which are subjected to different levels of exterior moisture. Knowing whether or not the felt isn't just waterproof but also breathable can be a deciding factor when selecting the ideal material for one's roof.
Generally, it is argued that some forms of felt are completely impermeable to any form of liquid or vapor, thus making them incapable of breathing. On the other hand, there are those who argue that certain types of felt do allow water vapor to pass right through due to their specific composition and qualities. This debate is still ongoing in accordance to the all-important question of effectiveness and cost.
Though this topic remains a matter of opinion amongst qualified roofers who have weighed the pros and cons, studies conducted through various tests have proven that certain types of felt can be highly effective in terms of breathability. For instance, a 2008 study conducted by Rippert states that “felt permeance may exceed values reported for asphaltic membranes” even with exposure to water-vapor sources such as precipitation or interior moisture migration into attics without ventilation problems.
Ultimately, when it comes to an accurate assessment on whether or not all felt can breathe effectively enough, more research needs to be undertaken in order to give clear evidence as well as possibly lead onto further evolutions in building material technology; while some statements remain proclamations with limited factual support thus far, one cannot deny that the numerous benefits behind better breathability should definitely not be discounted when choosing roofing material. In light of these considerations, we will move on towards examining another critical aspect of roofing felt: weatherproofing.


When it comes to weatherproofing, roofing felt can provide an invaluable defense layer for a home’s roof from the elements. In fact, this is one of the primary uses for roofing felt. While some argue that felt is less effective than other materials such as rubber or asphalt when it comes to creating a weatherproof barrier which prevents leaks and pools of water forming under the roof during storms, evidence shows that in the right conditions, felt can create a seamless protective layer on top of a roof.
One advantage of using felt over rubber or asphalt is that if properly installed, there are few seams between sheets of material. While rubber and asphalt may need consistent maintenance like cracking, blistering and peeling over time, one sheet of felt offers increased protection if it is installed correctly – with the joints securely covered and no marks allowed under the sheet.
In addition to being breathable to allow air circulation which prevents condensation buildup on roofs — an issue not caused by but compounded by improper waterproofing — if thicker grades are used and properly maintained, felt has been known to act as an effective additional waterproof layer to a roof. The grades which offer betterwaterproof protection tend to be more expensive initially but may last longer before needing replacement.
The peace of mind and additionally extended level of protection provided by proper weatherproofing techniques like using felt should not be ignored when contemplating potential construction or renovation projects aroundthe home. With proper setup and maintenance, the use of felt can prevent costly damages which can happen from water standing atop a rooftop. And with its ability to transition moisture away from its core fiber blanket layers effectively, investing in higher-grade materials pays off when protecting your home overthe long-term against severe weather elements. Ultimately, weighing all advantages separately helps homeowners make informed decisions about choosing proper waterproofing materials for their homes – including how certain types of roofing felt fits into their plans.
With these factors considered in creating a weatherproof rooftop deck, homeowners can move onto investigating the different types of roofing felts and how best they fit their needs for their home.

The Different Types of Roofing Felt

With roofing felt, there are two main types: single-ply and multi-ply. Both of these can help weatherproof various materials, but both also have their own unique qualities.
Single-ply felt consists of a single layer of asphalt or synthetic material that provides excellent waterproof properties for a wide variety of roof surfaces such as slate and foam board. It is strong enough to resist tearing from the elements, making it an ideal choice for outdoor protection like protecting against wind and water intrusion.
Multi-ply felt requires more layers of protection and installation and is designed for heavier roofing materials such as cedar shakes. This provides extra protection against high winds, UV rays, and large hail. The installation of multi-ply felt is labor intensive, so it should only be done by an experienced professional in order to ensure maximum durability and longevity.
Although both single-ply and multi-ply felt provide excellent weatherproofing qualities for different types of materials, they have different levels of resistance to wear and tear, varying degrees of strength and protection against the elements, and installation time frames which should all be taken into consideration when deciding on which option is best for you. As we continue to unravel the mysteries behind roofing felt, it’s important to remember that when it comes to weatherproofing the right type of felt can make all the difference in protecting your investments now and well into the future. In the next section we'll explore the differences between different kinds of rooftop felt even further in order to understand how they perform differently under various circumstances.

Single-ply vs. Multi-ply Felt

When it comes to roofing felt, understanding the difference between single-ply and multi-ply materials can be a difficult task. Single-ply felt is more common due to its cost-effectiveness, as it requires fewer layers of materials for ideal waterproofing capabilities. However, multi-ply felts provide superior water resistance that makes them especially useful in areas with extreme weather conditions.
Those looking to make a choice between single and multi-layer felts would be wise to consider both advantages and disadvantages of each option. Single-ply felt is more suited for low pitch surfaces, while multi-layers offer greater strength than single ply felt, making them perfect for steeper applications. Additionally, since multi-ply has extra layers, multiple moisture levels can be present when combined with bitumen, which helps encapsulate the roof during wet periods more effectively compared to single ply membranes.
On the other hand, single ply Felts are quicker to install and have a higher tolerance for thermal movement – so they’re better suited for structures that need periodic expansion or contraction without sustaining any damage. This flexibility can save money by reducing contractor labor time when additional fittings or flashings are not needed. Furthermore, because of the small number of elements needed to construct these sheets they’re much lighter than their counterparts making installation even easier over complex pitched roofs in a shorter period of time.
There’s no definite answer as to which type is best since different types of roofs will require different amounts of protection to remain waterproof. For this reason, many people opt for combinations which use multiple layers of different plans and strengths for maximum flexibility. When deciding between different options it’s important to always consider maintenance requirements and environmental effects moving forward before you make your decision.
Now that we’ve explored the differences between Single-ply and Multi-ply felts, let's delve into the differences between Organic versus Synthetic Roofing Felt — a debate that covers everything from cost efficiency to environmental impact.

Organic vs Synthetic Felt

Now that we’ve established the differences between single and multi-ply felt, let’s examine the differences between organic and synthetic felts. Organic felts are generally made from recycled fibers such as roofing shingles or paper. These materials are then saturated with asphalt for waterproofing capabilities. Synthetic felts are usually made from a polyester or fiberglass mesh that is also soaked in an asphalt for waterproof properties.
Organic felt provides a more traditional looking roof compared to its synthetic counterpart, which offers a more modern appearance. Organic felt is more affordable as it is mostly made out of recycled materials, however, synthetic felt often has a longer life expectancy than organic felt due to its more water resistant properties.
When applying either type of felt to your roof, it’s important to make sure it is done properly and securely. Both types become vulnerable once exposed to wind and water, so proper installation and maintenance are key when selecting which material works best for your home. While both can offer protection against water damage, using an experienced team of professionals can ensure the process is done efficiently and safely.
Transitioning away from the discussion on single-ply vs multi-ply felt and organic vs synthetic felt, we now turn our attention to how to properly install roofing felt and how to maintain it over time.

Installing Roofing Felt and Maintenance

The installation of roofing felt is a process that requires precision and diligence to ensure it performs as expected throughout the lifetime of the structure. While organic felt is most commonly used due to its lower cost, synthetic felt can be an attractive acrylic option that often has better adhesive quality. During the installation process, both types of felt must be laid flat and sealed correctly by overlapping the edges where two pieces meet. To ensure this is done properly, a generous layer of asphalt-based adhesive should be applied to the underside of each shingle before lapping them together. This will help keep water out and extend the life of the roof.
When it comes to maintenance, organic felt has traditionally been easier to manage than synthetic products since it expands and contracts with changing temperatures, whereas acrylic products are more likely to stay in one place. However, modern advances in synthetic materials have made them increasingly resistant to fluctuations in temperature and weather conditions as well. Regardless of material type, roofing felt should never be left exposed and should always be properly secured with the right nails or screws at intervals of three feet or closer along its edges. Furthermore, all felt should go through periodic inspections for signs of damage such as curling, blistering, or cracking in order to identify any potential issues when they're still minor and easily repairable rather than waiting until they become major problems requiring costly replacements. Ultimately, investing in preventative methods like these will help extend the life of your roof while minimizing potential future costs.

Frequent Questions and Answers

What are the advantages of using roofing felt?

The main advantage of using roofing felt is that it is a waterproof barrier between the roof shingles and the underlayment, thus reducing the chances of water damage. Roofing felt also provides additional structural integrity to the roof by helping to strengthen it, even in high wind conditions. Additionally, roofing felt helps protect against the build-up or accumulation of ice, snow, and other debris on the roof; this can help prevent weakening of the materials used for the roof and minimize potential for leaks. Roofing felt can also help improve energy efficiency by providing an additional layer of insulation between the internal and external areas of your home or building. Lastly, roofing felt helps reduce general wear and tear on roof materials as it serves as a buffer between them and any outside elements that can cause premature deterioration.

What factors should be considered when deciding if roofing felt is appropriate for a particular roof?

When considering whether roofing felt is suitable for a particular roof, there are several factors to take into account. Firstly, the roof's climate and weather conditions should be considered. Roofing felt is designed to provide protection in adverse weather conditions such as strong winds or hail, but may not be appropriate for climates with high temperatures or humidity levels as it can degrade over time when exposed to extreme elements. Secondly, the type of material that the roof is constructed from will play a role in determining the suitability of roofing felt; different types of felt are more suitable for certain materials than others so it is important to check what type of roof you have before making your decision. Lastly, the overall condition and age of the roof should be taken into account; older roofs may require additional protection in order to ensure its longevity, while newer roofs may benefit from higher quality felt that offers superior waterproofing capabilities. By taking all of these factors into consideration and conducting research on suitable materials, homeowners can ensure they choose the best type of roofing felt for their needs.

What other materials could be used in place of roofing felt?

One of the most popular alternatives to roofing felt is synthetic underlayment. It is a breathable, polymer/rubber-based material that can be used in place of roofing felt. Synthetic underlayment can offer an even greater degree of water protection than felt because it has superior air permeability and sealant properties, allowing it to better resist water penetration and damage from ultraviolet light.
In addition to synthetic underlayment, there are several other materials commonly used as alternatives to roofing felt, including metal, single-ply membranes, shingles or shakes, and foam board insulation. Metal roofs cost more upfront but have a much longer lifespan than asphalt shingles when installed by qualified metal roofers. Single-ply membranes offer great waterproofing protection, as well as flexibility and ease of installation. Asphalt shingles or shakes are another popular option for those looking for an economical alternative to felt. Finally, foam board insulation may provide additional protection when placed beneath the shingle layer on roofs with inclines greater than 4/12 (for example).
Overall, there are many options available to homeowners looking for alternatives to traditional roofing felt. Synthetic underlayment offers superior waterproof protection while metal roofs are more durable and can potentially last longer. Shingles or shakes as well as single-ply membranes are economical options if cost is a major factor, while foam board insulation provides extra protection on steeper inclines. Regardless of which type of product you choose, make sure that you follow all recommended installation instructions for optimal performance and longevity.

Is roofing felt waterproof?

Yes, roofing felt is waterproof. It is made of several layers of asphalt-saturated organic fibers, which provide a layer of protection for roofs against moisture and weather conditions. Additionally, modern roofing felts are often reinforced with special adhesives or synthetic fibers to increase water resistance. This can help add extra protection from the elements and help prevent any leaks or damages to the roof due to water damage.

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