Written By Glenn Prescot
A perfectly installed roof is the only barrier between natural disasters and your home. It is what keeps you and your belongings safe.
As an Amazon Associate I earn from qualifying purchases.
We all know about the basic stuff such as what roofing material to choose, its color, and how it will compliment the house.
You call a professional roofer, and in a couple of days, your house has a brand new roof. In fact, most people install a new roof when they are changing houses. This investment increases the value of their house by a huge margin.
What if you live in an area where it rains a lot? Your roof was damaged due to the storm that recently hit the city.
You had just put the house on the market. Here’s your chance to increase the sale price of your house by installing a new roof, but there’s something you need to consider first.
You know your roof protects you.
But have you ever wondered how?
Two words: Roofing Underlayment.
It’s not the roof but this layer of protection that prevents water from entering your house among other things. Without it, your roof will be vulnerable to the harsh elements of the weather.
Table of Contents
- What Is Roofing Underlayment?
- Rubberized Asphalt Underlayment
- Asphalt-Saturated Felt Underlayment
- Non-Bitumen Synthetic Underlayment
- Is roof underlayment necessary?
- Is synthetic roofing underlayment better than asphalt-saturated felt?
- What is the best roofing underlayment for metal roof?
- What is the best roofing underlayment for tile roofs?
- What is the best roofing underlayment for shingles?
What Is Roofing Underlayment?
It is a waterproof or water-resistant barrier material that is installed on the roof deck. The material goes directly underneath the roof and stands as a protective shield against severe weather.
If your roof develops a crack, you can rest easy because this underlayment will prevent further damage.
There are three types of underlayments:
- Rubberized Asphalt Underlayment (waterproof *)
- Asphalt-Saturated Felt Underlayment (water-resistant *)
- Non-Bitumen Synthetic Underlayment (water-resistant *)
The first underlayment is waterproof, while the remaining two are water-resistant.
*Note: Most people are confused regarding the difference between water-resistant and waterproof. The former term (water-resistant) means that the underlayment can withstand water, but only for a certain period of time. On the other, the latter term (waterproof) means that the underlayment is completely protected from water.
Rubberized Asphalt Underlayment
Rubberized asphalt contains rubber polymers and asphalt. Amongst the three underlayments, it is the most expensive one because it is waterproof.
This underlayment is like a sticky paper. Before this underlayment is applied, its back membrane is removed. The sticky material is what acts as a waterproof seal. It also protects the roof edges from causing leaks. This material proves pretty beneficial in areas such as roof protrusions and valleys on the roof.
Pros
- The only Waterproof material for this type of job.
- Low installation cost: It may be expensive, but it is easy to apply
- Longevity: Rubberized asphalt comes in rolls, which means there are few seams. This lowers the chances of water entering the attic. This underlayment can last for 50 years.
- UV resistant: It is resistant to the sun’s ultraviolet rays.
- Durable: Compared to pure asphalt, rubber does not crack, expand, or contract due to weather changes.
- Easy to repair: A special type of tape is used for repairing any tears in the rubber. This usually does the trick.
Cons
- Rubberized underlayment comes in many forms. Some are resistant to fire and some are not.
- You need a professional to install this underlayment, which can add to the cost.
Asphalt-Saturated Felt Underlayment
Known as “tar paper,” this underlayment is made from varying blends of polyester, bitumen, cellulose, or asphalt. It is one of the most common materials used in older houses and usually comes in two different thicknesses: 15-pound and 30-pound. The 30-pound thickness is obviously more resistant to damage and will last longer (see video below):
Asphalt saturated felt is not recommended in areas where it frequently rains. The price of felt varies and mostly depends on the amount of asphalt in it. The more the asphalt content in the underlayment, the more durable and costly it will be.
Pros
- Budget-friendly
- Contains fiberglass, which increases its durability and strength
- Good for low slope roofs as water will slide away easily
Cons
- Weighs more than rubberized asphalt underlayment and non-bitumen synthetic underlayment
- Installation is pretty costly
- Degrades pretty easily if exposed to external environment
- Vulnerable to sun damage
Non-Bitumen Synthetic Underlayment
This synthetic underlayment contains asphalt, along with fiberglass, polyethylene and polypropylene. These three materials give it superior stability and make it resistant to tears. Some manufacturers, add a slip resistance material to it, which protects it from water.
Pros
- Long lasting and durable
- Lightweight
- Prevents water leaks and ice dams
- Fungus resistant
- Is not vulnerable to direct UV radiation
- Easy and safe to install
Cons
- Depending on the materials used in the manufacturing, it can be very expensive, which is its biggest and only drawback
To conclude, if you are installing a new roof, we would suggest that you choose Rubberized Asphalt underlayment. Yes, it is a little more on the expensive side but it will outlast the other material types and will surely protect your house from water leaks, mold and mildew.
Now let us discuss some frequently asked questions that many people have about roofing ubderlayment.
Is roof underlayment necessary?
Roof underlay is more than necessary; it’s the key to having your roof last for years. Roof underlayment is the water-resistant and/or waterproof barrier material that covers the entirety of your roof deck before you add that roof.
Once installed, it offers a much-needed layer of protection from the most severe weather. There are three types of products that fall under the underlayment umbrella: asphalt-saturated felt, non-bitumen synthetic and rubberized asphalt underlayment. Only the rubberized one is waterproof. The other two are water-resistant.
Despite the fact that shingles and other types of roofing material serve as a protective covering for your home or building, underlayment serves myriad purposes.
For example, while shingles overlap, corners aren’t always properly sealed from the elements and if strong winds blow, underlayment to the rescue if roofing materials don’t stand up to weather fluctuations.
Some roofing materials can become brittle with age, and disaster, in the form of an unventilated attic, could further stress out a roof if there’s no underlayment to protect rooms below.
Contractors say that the most vulnerable under-roof areas requiring protection are eaves, valleys, protrusions and low-slope roof surfaces. This is where underlayment comes to the rescue, so homes stay dry and your investment remains protected.
Is synthetic roofing underlayment better than asphalt-saturated felt?
This debate rages among roofers who have preferences, so you might say that both types of underlayments have their own fan clubs.
Synthetics are favored for myriad reasons: they install fast, remain steadfast in high winds and when exposed to bad weather, they offer better traction that asphalt-saturated products. But synthetics come at a cost: They’re more expensive, especially if you choose a synthetic that is categorized as a vapor-permeable product.
Asphalt felt, on the other hand, has an older track record, it’s also easy to install and you won’t go broke if you choose this material. Asphalt-saturated layment was the only option on the market until around 15 years ago when synthetics–known also as non-bitumen synthetic underlayment–became available.
That stated, you may have no choice about the underlayment you choose if local building codes require the installation of asphalt felt.
Some building codes stipulate this material for it’s fire-resistant properties. Sold in grades (#15 or #30), felt underlayment is typically crafted of recycled corrugated paper and sawdust and “impregnated” with asphalt. While it acts as a vapor barrier, this material is best avoided in cases where attics and decks are poorly ventilated.
Your final option, rubberized asphalt, is the only truly waterproof product on the market and it’s extremely expensive, but in areas known for severe winters, rubberized asphalt is often the most highly-recommended and favored by roofers eager to make sure your building has the best protection against cold weather extremes.
What is the best roofing underlayment for metal roof?
Metal roofs offer outstanding waterproofing properties, this roof type is affordable, and it won’t take forever to roof a building if metal is chosen.
Which type of underlayment will get you the most protection and bang for your buck? Just about anything on the market, according to professionals.
Rule of thumb is that if it’s manufactured to be installed under tile roofs, it can be used beneath a metal roof, too.
However, if you had to choose one material type of underlaymet for metal roofs, then synthetic underlayment is the best choice compared to the asphalt types of products.
Metal roof underlayment products usually consist of three layers. The first serves as an ice and water shield that is likely made of rubberized-asphalt or butyl-based adhesive with a polyethylene carrier sheet.
The second layer is commonly a reinforced polypropylene scrim that’s constructed of multiple layers to add a moisture barrier.
The third layer, an essential for homes with metal roofs in areas where the climate is hot, offers reflective or breathing insulation properties that mediate heat build-up, so it’s diffused.
One word of caution if you’re deciding between underlayments for your roof: be sure to choose one that won’t scratch those metal roof panels.
What is the best roofing underlayment for tile roofs?
Since underlayment and flashings create the most critical water barrier protection, you might say that they’re even more important than the roof itself.
Tiles provide the finishing touch adding curb appeal to a home or building so the exterior is beautifully put together. Pair tiles with a proper underlayment and as long as both are installed expertly, you can look forward to 50 years of service.
In terms of tile underlayment materials and construction, you’ll hear a lot about “paper” and “felt,” but most often, these are used interchangeably and referred to as “organic felt paper.”
But felt isn’t the only material you’ll run into: fiberglass mesh may be substituted for this more traditional material. That stated, underlayment materials are regularly categorized by weight.
For example, “90-pound paper” describes a cheap, low-quality gravel-coated material to be used only if there is nothing else around.
A better choice would be a product that consists of 2 layers of 30-pound, asphalt-impregnated felt. This material is likely to last from 20 to 30 years. Upgrade to a double layer of heavy-duty, SBS-modified asphalt underlayment and you’re going to be set for the long haul.
The fiberglass option mentioned earlier remains available to you if you’re convinced it’s the best way to support your tile roof and if you keep up with roofing trends, you know that peel-and-stick self-adhesive membranes that are bonded directly to the roof are currently a favorite of roofers eager to save time, money and energy.
This material is made with synthetic rubber additives and if you choose the 40-pound version, you’ll increase the life of your roof by impressive numbers.
What is the best roofing underlayment for shingles?
Once upon a time, there was only one type of shingle underlayment and you’ll recognize the name if you’ve read this far: Felt-paper.
As the industry welcomed new materials that proved more efficient, sturdy and versatile, myriad moisture-repelling layers were introduced to the market to underpin shingles. The most popular and best-selling alternatives these days for shingle roofs? Synthetics.
Like the synthetic underlayments described in the aforementioned categories, synthetics come with higher price tags, but offer unique advantages that have no comparison. They are lighter weight, offer superior water resistance and when it comes to lying flat so shingles won’t waffle or warp, there is no substitute.
How efficient are synthetic underlayments? So much so, they can serve as a roofing material without shingles for short amounts of time if necessary!
What makes these products so sturdy and adds years of life to a roof? The fact that they usually consist of two different membranes.
The first is installed along the roof perimeter where roof planes form valleys so these areas are sealed. The second layer consists of tear- and water-resistant material that not only seals the deck but offers a high-traction surface so shingle installers can complete the job more efficiently and safely.
Related Posts
- Advantages and Disadvantages of Solar Roof Vents for Homes
- 10 Different Types of Snow Guards for Metal Roofs
- Advantages and Disadvantages of Roof Ridge Vents for Homes
- 5 Unique Roof Upgrades to Consider for Your Home
- Pros and Cons of TPO Roofing – Cost, Advantages, Disadvantages
- What Does EPDM, TPO, and SBS Stand for in House Roofing?
FAQs
What kind of roof underlayment is best? ›
Synthetic Underlayment
This is currently the most popular choice for roof underlayment, and with good reason. Made with an asphalt-saturated basemat and fortified with a mix of fiberglass, this product is not only extremely water-resistant, much stronger and more resistant to tears than other types of underlayment.
With that in mind, synthetic underlayment is more durable than felt underlayment. Felt underlayment is much more prone to rip from high winds and during the installation process. Synthetic underlayment also holds nails better and repels water instead of absorbing it.
What underlayment to use for shingles? ›Roofs built with traditional asphalt shingles tend to pair well with rubberized asphalt and asphalt-saturated roof underlayment. Similarly, rubberized asphalt and asphalt-saturated underlayment is also suitable for slate shingles.
Is Rhino roof underlayment good? ›RhinoRoof's durability is top-notch and can be exposed to wind or sunshine for weeks without sustaining damage. The quoted level of coverage provides roof deck protection from UV exposure for up to 60 days. Not only is RhinoRoof better at protecting against the elements, but it is also better for installers.
What are the different types of roofing underlayment? ›Types of Roofing Underlayment. In general, there are three types of roofing underlayment: felt, self-adhered, and synthetic. Each has its own benefits and advantages, and the type you choose generally depends on what your roofing contractor is comfortable with and your local building codes and regulations.
Will synthetic underlayment leak? ›But on the plus side, synthetic underlayment is much more durable than asphalt. It's less likely to tear, and when properly installed, less prone to leaks, too.
Is peel and stick underlayment better than synthetic? ›Unlike traditional underlayment, synthetic peel and stick roof underlayment is much more durable. When paired with the suitable roofing material for Florida's climate, underlayment can significantly contribute to preserving your roof for many years.
How long does synthetic underlayment last? ›How Long Does Synthetic Metal Roof Underlayment Last? One of synthetic underlayment's advantages is its long lifespan. Synthetic roofing underlayment will have a warranty that ranges from 25-50 years, while felt underlayment only lasts 12-20 years. In addition, synthetic underlayment can be left exposed for months.
Which type of roofing sheet is best? ›PVC Plastisol coated corrugated sheets are very durable. They comprise steel sheets treated with primer paint and PVC rolled on their surface. These roofing sheets don't scratch or fade easily and typically can last for around 25-30 years.
What goes on roof before shingles? ›Underlayment— This is the first layer of waterproofing that goes down in between sheathing and shingles. Underlayment seals the roof from damaging elements like snow, ice and rain. Also referred to as a membrane, underlayment is mandatory for providing the roof with a waterproof barrier.
How many layers of roof underlayment do I need? ›
Two layers of underlayment are required for low-slope roofs. The first course is doubled. Above that, 36-inch wide strips are then applied to the roof in a shingle fashion, starting at the lower roof edge, and overlapping subsequent courses a minimum of 19 inches.
How long can synthetic roof underlayment be exposed? ›Most synthetic underlayments can be left exposed for six months and some for 12 months. The woolly, tan-colored Opus Roof Blanket, though, is approved for 30 months of UV exposure. underlayment for several good reasons. While the price of asphalt felt fluctuates somewhat, it's still the least expensive option.
Is Tiger Paw underlayment better than felt? ›GAF TigerPaw Underlayment
TigerPaw is up to 600% stronger than #30 asphalt felt, and while it isn't completely waterproof, it is highly water-resistant. TigerPaw's main disadvantage lies in its water resistance—other products can be made completely waterproof if need be—and in its weight.
Roofing underlayment or roofing paper comes in three common types: Asphalt-Saturated Felt (Felt Paper) Rubberized Asphalt. Non-Bitumen Synthetics (Synthetic Felt Paper)
Does roof underlayment need to be breathable? ›Why? The shingle creates a vapor barrier, or a nonbreathable layer. Therefore the “breathability” of an underlayment becomes unnecessary. Proper ventilation, not a breathable roof underlayment, is required to prevent moisture from becoming trapped in the roof deck.
Is synthetic roofing underlayment waterproof? ›Because most synthetic roofing underlayment must be installed with cap nails or staples, and because these underlayments do not seal around the fasteners, they are typically considered water resistant, not truly waterproof.
What is synthetic underlayment made of? ›Synthetic underlayment is typically made from woven or spun polyethylene or polypropylene, and it comes in a variety of different thicknesses to suit your needs. These typically weigh a lot less than traditional roofing felt, and many products have layered design.
Can you use Tyvek under shingles? ›Product Description. DuPont Tyvek Protec 120 Roof Underlayment is an engineered synthetic roofing underlayment with industry-leading walkability. It is ideal for slopes 2:12 or higher and can be used under a variety of roofing materials, including asphalt shingles, cedar or metal roof cladding.
Can synthetic underlayment get rained on? ›Underlayment is installed much like the shingles themselves. We overlap the edges to make sure every inch of the roof is covered. But it's not enough to stand up for a whole winter. So, yes – roofing underlayment can get wet.
Can I use synthetic roofing underlayment? ›Roofing underlayment is one of the key components to ensuring a long lifespan for your roof. While there are several different types to choose from, synthetic underlayment is currently the most popular and preferred choice for underlayment in the roofing industry for its superior performance and longevity.
Do roofers still use tar paper? ›
Prospectors during the California gold rush covered the roofs of their temporary shacks with roofing felt, also known as felt paper or tar paper. Fast forward 170 years and roofing felt is still the most popular roofing material (now used as an underlayment) being installed today.
How long does peel and stick last on a roof? ›Peel and stick roofing underlayment is typically rated to last longer. What is this? It comes with at least a 15-year limited warranty up to a 40-year limited warranty for some brands making it more than twice the lifespan of traditional roofing felt.
Is peel and stick better than felt? ›The combination of these materials produces an underlayment that is more tear resistant, elastic, and durable than traditional felt. When it comes to rain or snow, peel and stick underlayment provides a secondary layer of waterproofing protection that helps prevent damage caused by ice dams and windblown rain.
How long does peel and seal last? ›Peel & Seal® carries a 10-Year Warranty.
How often should roof underlayment be replaced? ›In most cases, traditional felt underlayment is rated to last between 12 and 20 years. In other words, in a little over a decade, the underlayment beneath your roof's surface may start to deteriorate. The roof will become more prone to leaks as this added layer of protection breaks down.
How much does roof underlayment cost? ›Porch.com reports that the national average price range for one square of underlayment is between $67 to $82. With labor costs factored in, the price to fully replace the underlayment rises to anywhere from $360 to $510 per square.
How do you fasten synthetic underlayment? ›How To Install ProArmor Synthetic Roof Underlayment - YouTube
What are the 4 most popular types of residential roofing? ›- Asphalt shingles. The first roofing material (and most commonly used in the United States) on our list are asphalt shingles. ...
- Standing seam metal roofing. ...
- Synthetic (composite) shingles. ...
- Cedar shake shingles.
Asphalt Shingle Roofing: Best Overall
Asphalt shingles are the most affordable and cost-effective roofing material.
The most common residential roofing material used in the United States, asphalt shingles are popular because they are economical and easy to install. These shingles can be reinforced with fiberglass or organic materials (cellulose) without changing the appearance of the shingle.
How much does a 30 year shingle roof cost? ›
The cost to install 30 year architectural shingles is usually about $350 to $500 per square. 50 year architectural shingles are even stronger, and are considered premium. The cost of this type of shingle may range from $450 to $700+ per square.
What is the easiest roof to install? ›Rolled roofing is one of the easiest and cheapest roofing materials you can purchase. Plus, it is one of few types of roofs that most homeowners can install on a do-it-yourself basis, although in a limited fashion.
What is the cheapest roof style? ›The cheapest roof design is a roof with just hips, which are the sloping part, while the gable is the triangular bit on the end of the roof. A lot of subdivisions require a roof with hips and gables (rather than just a hip roof) so that is the most common form of roof construction.
Which thickness roofing sheet is best? ›35 to 0.40mm thickness is best for general walling projects and medium roofings like small or medium sized factories. 0.40 to 0.47mm thickness can be used for medium-to large roofing projects such as factories and buildings with high quality constructions.
Which Colour sheet is best for roofing? ›A Light-coloured Aluminium Roofing Sheet will reflect sunlight the best, helping to keep your establishment's temperature cool during the hot weather. Meanwhile, a dark-coloured Aluminium Roofing Sheet will absorb more heat making your home warmer.
Is tar paper necessary under shingles? ›Answer: Roofing felt is a layer of tar paper installed beneath the shingles to provide a backup waterproof membrane in case of leakage. Felt, otherwise known as underpayment, is required when asphalt shingles are installed as a first layer of roofing or when they are applied over wood shingles or a built-up roof.
Do shingles go directly on plywood? ›Metal roofing should not be installed directly over the top of bare plywood. You do not have to install roofing shingles or other roofing material, but a felt sheet over the plywood is the bare minimum.
How far should shingles overhang drip edge? ›Asphalt shingles should overhang the exterior edge of the drip edge by ¼ to ¾-inch. Check local building code for drip edge requirements prior to the start of your roofing project.
What is the most common underlayment for roofing? ›One of the most common types of underlayment used in residential, steep-slope applications is black, ashphalt-saturated felt paper. Felt underlayment may be made from either organic or fiberglass substrate, although the organic is much more common. It's called "organic" underlayment because it has a cellulose base.
Does underlayment go over the ridge? ›For ridges, the underlayment should … be lapped over the ridge at least 4” (102 mm) to 6” (152 mm) as would be done on a new or complete tear-off installation.
How do you attach underlayment to a roof? ›
How To Install Roofing Underlayment - YouTube
Which is better synthetic or felt underlayment? ›With that in mind, synthetic underlayment is more durable than felt underlayment. Felt underlayment is much more prone to rip from high winds and during the installation process. Synthetic underlayment also holds nails better and repels water instead of absorbing it.
Does synthetic roofing felt breathe? ›The short answer is no, they're not! Among Epilay products, perm ratings are quite low. Epilay Superior features a perm rating of 0.154, Ultra has 0.326 and Platinum comes with a perm rating of 0.142, which classifies all of our synthetic underlayments as non-breathable.
Will my roof leak if some shingles blew off? ›all of a shingle doesn't make it more or less likely that your roof will leak. It all comes down to that shingle's location. When a shingle goes missing, the likelihood of a leak depends on whether the lost shingle or tab was covering a seam between two others.
Is peel and stick underlayment better than synthetic? ›Unlike traditional underlayment, synthetic peel and stick roof underlayment is much more durable. When paired with the suitable roofing material for Florida's climate, underlayment can significantly contribute to preserving your roof for many years.
Is synthetic roofing underlayment waterproof? ›Because most synthetic roofing underlayment must be installed with cap nails or staples, and because these underlayments do not seal around the fasteners, they are typically considered water resistant, not truly waterproof.
Which is better Tiger Paw vs deck armor? ›Tiger Paw™ is the best choice (in our opinion) for vented, asphalt shingle roofs (low-perm rating of less than 1 perm); whereas Deck-Armor™ is able to “breathe” (16 perms), which is perhaps good for conditioned, non-vented attic spaces. Low-permeability means an added layer of protection against rain and leaks.
Is synthetic underlayment good for tile roofs? ›The best underlayment for a concrete tile roof is usually a synthetic brand, like Barricade. Barricade underlayment is incredibly durable, as well as possessing anti-slip coating on both sides of it. It has far superior strength compared to felt-based underlayment, as well as superior tear resistance.
Will synthetic underlayment leak? ›But on the plus side, synthetic underlayment is much more durable than asphalt. It's less likely to tear, and when properly installed, less prone to leaks, too.
How long does synthetic underlayment last? ›How Long Does Synthetic Metal Roof Underlayment Last? One of synthetic underlayment's advantages is its long lifespan. Synthetic roofing underlayment will have a warranty that ranges from 25-50 years, while felt underlayment only lasts 12-20 years. In addition, synthetic underlayment can be left exposed for months.
How many layers of roof underlayment do I need? ›
Two layers of underlayment are required for low-slope roofs. The first course is doubled. Above that, 36-inch wide strips are then applied to the roof in a shingle fashion, starting at the lower roof edge, and overlapping subsequent courses a minimum of 19 inches.
Can you shingle over wet synthetic underlayment? ›Do not install shingles over wet underlayments… as the moisture trapped inside the underlayment may cause blistering, buckling or wrinkling of the shingles.
How long can synthetic roof underlayment be exposed? ›Most synthetic underlayments can be left exposed for six months and some for 12 months. The woolly, tan-colored Opus Roof Blanket, though, is approved for 30 months of UV exposure. underlayment for several good reasons. While the price of asphalt felt fluctuates somewhat, it's still the least expensive option.
Should I use 15 or 30 pound felt? ›If your roof does not have a steep pitch, you can use #15. This weight of felt is a good economic choice if you have a standard roof. But if your roof has a steep pitch, #30 is a better option because it is thicker and tears less during installation. With #30 you get a thicker layer of underlayment and protection.
Is Tiger Paw underlayment better than felt? ›GAF TigerPaw Underlayment
TigerPaw is up to 600% stronger than #30 asphalt felt, and while it isn't completely waterproof, it is highly water-resistant. TigerPaw's main disadvantage lies in its water resistance—other products can be made completely waterproof if need be—and in its weight.
A: Hello, Deck-Armor is a premium breathable underlayment, unlike Tiger Paw and FeltBuster which are not breathable. Breathability helps reduce the chance for trapped moisture in the roof system.
What is roof deck protection? ›Roof Deck Protection allows moisture to escape from your attic while providing an exceptionally strong layer of protection against wind-driven rain. Also, Roof Deck Protection lies flatter for a better-looking roof.
How often should roof underlayment be replaced? ›In most cases, traditional felt underlayment is rated to last between 12 and 20 years. In other words, in a little over a decade, the underlayment beneath your roof's surface may start to deteriorate. The roof will become more prone to leaks as this added layer of protection breaks down.
When should you replace underlayment? ›The most common underlayment, felt, has a lifespan of about 12 to 20 years. After this, it begins to deteriorate. However, some factors other than lifespan can lead to deterioration of your underlayment, and these are: Low-grade underlayment.
What is G 40 underlayment? ›VulcaSeal G40 Fiberglass (Modified) is world-class fiberglass based modified asphalt underlayment that provides the best in protection for your home and family under concrete tile, clay tile, or metal roofing.