There’s no denying that shingles are one of the most important elements of a residential roof. After all, shingles form the primary line of defense against rain, snow, ice, and whatever else Mother Nature throws at it. If your shingles break down due to old age or physical stress, your home may become subject to dangerous water leaks.
Yet for all the importance paid to shingles, a roof contains numerous other components as well. While they may not be as high-profile as shingles, such components still play a vital role when it comes to your roof’s structural integrity — or lack thereof. Keep reading to learn more about three other components crucial for a well-built roof.
Underlayment can be found directly beneath the shingles on a roof, sandwiched between them and the wooden deck that gives the roof its strength and rigidity. Underlayment attaches directly to the deck, providing an extra degree of protection against water. Even if your shingles become damaged — or go missing entirely — underlayment protects your vulnerable wooden roof deck.
With that said, it is important to understand that most underlayment is not fully waterproof. Rather it is usually billed as a water-resistant product, meaning that it will slow the passage of water — but not prevent it forever. For that reason, homeowners should always address damaged or missing shingles as quickly as possible.
In addition to protecting against water coming from outside of your home, underlayment serves another key purpose: protecting against water vapor migrating upward through your roof. No matter how well insulated your attic may be, some degree of warm air will always escape in this fashion.
All such warm air contains a certain proportion of water vapor. As that air passes through the roof deck and reaches the relatively cold shingles, it often condenses, causing wet spots on your roof deck. Over time, such condensation can lead to wood rot, mold growth, and other serious structural problems.
Many types of underlayment are vapor-permeable, meaning they still allow that heat and water vapor to leave your home. But by providing an extra layer of insulation, the underlayment insures that by the time that vapor cools off and condenses into water, it will not collect on your roof deck but on the top side of the underlayment.
Types of Underlayment
There are several different types of roofing underlayment available on the market. If you are building a new home, or replacing your entire roof, it is important that you consult with a professional roofer about the best underlayment to meet your needs. Here are the three main varieties of underlayment used today.
Asphalt saturated felt — often known as roofing felt or even tar paper — is the oldest type of underlayment. As its name suggests, it consists of a sheet of felted fabric made from natural plant fibers and/or polyester. This felt has been soaked through with a special blend of asphalt emulsion. The felt gives the underlayment body and strength, while the asphalt provides the water-resistance.
Asphalt-saturated felt comes in different thicknesses, with 15 pound and 30 pound being the most common. The heavier the felt, the greater its lifespan, and the more protection it provides against water. That said, 30 pound felt tis commonly reserved for heavy-duty commercial uses, with 15 pound being the preferred choice for residential homes.
Synthetic underlayment first hit the market in the early 2000’s, and since then it has rapidly gained ground as an alternative to asphalt-saturated felt. Made from polyester or fiberglass matting that has been soaked in a waterproof chemical, synthetic underlayment offers numerous benefits, including:
- Weights less
- Captures less radiant heat
- Retains flexibility in cold weather
- Provides a safer surface for roofers to work on
In addition, most synthetic underlayment boasts lower permeability than asphalt-saturated felt. In other words, water and water vapor will have a harder time moving through the underlayment. This is a benefit when it comes to blocking outside water. However, it means your roof must have adequate attic ventilation to prevent condensation becoming a problem.
Homeowners should be aware that, while prices often fluctuate, synthetic underlayment generally costs more than asphalt-saturated felt.
Rubberized Asphalt Underlayment
Rubberized asphalt underlayment uses a blend of asphalt and rubber polymers. This combination usually grants the underlayment a greater degree of water-resistance. Unlike other forms of underlayment, which are manually fastened to the roof deck, rubberized asphalt attaches by means of heavy-duty adhesives on the back of the underlayment. While effective, rubberized asphalt may not be a good choice for all roofing systems. Homeowners should also be aware that rubberized asphalt underlayment tends to be more expensive than the two other varieties.
The shingles and underlayment on your roof have to be held in place by means of physical fasteners — i.e. roofing nails. Those who have never worked in the roofing industry commonly assume that all roofing nails are the same thing. Yet a surprising range of variation actually exists in the world of roofing nails. Here are three of the most important features a contractor must consider.
In the early days of roofing nails, all nails had a smooth shank. These are still the most common — and the least expensive — type of roofing nail. Yet a smooth shank also provides the least amount of long-term durability. That smooth shank makes the nail more liable to work its way free as the months and years go on. Loose or missing nails are among the most common causes of roof leaks.
For stronger and longer lasting results, roofers often recommend either screw-shank or ring-shank nails. As their name implies, screw-shank have a twisted ridge along their shank, which helps the nail grip the deck more tightly. Ring-shank nails have a similar benefit, but usually come with larger heads, which makes them easier to install.
Another important factor is the type of metal from which the nails are made. Three main choices exist:
- Galvanized steel
- Stainless steel
Aluminum nails are the most cost-effective option, as well as the best suited to withstand corrosion caused by water. However, aluminum will corrode if exposed to copper ions, which may present problems if any of the flashings on your roof are made from copper.
Galvanized steel nails have a core made out of steel, but with a protective layer of zinc applied to the outside. The zinc ensures that the steel does not corrode. But if the zinc coating gets scratched or damaged, the nail may soon begin to rust. Stainless steel nails avoid the threat of corrosion entirely, but will cost significantly more than the other two types.
In order to provide as strong a hold as possible, a roofing nail should either pass all the way through the underlying roof deck, or penetrate it to a minimum depths of 19mm. To accomplish this, you must utilize roofing nails of an appropriate length, taking into consideration the thickness of the depth, the thickness of the shingles, the number of shingle layers, and other factors.
If a nail isn’t long enough for a particular roof, then it stands a far greater chance of popping out as time goes on. For this reason, an experienced roofing contractor will always assess the particular structural attributes of a roof before selecting nails for a roof replacement project.
Ice and Water Shields
The cold winters of Michigan put even the most well-built roofs at risk of leaks caused by ice dams. Ice dams form at the edges of a roof, which tend to be colder than the main portion of the roof since they aren’t warmed by heat rising up from your home. Snow that melts on your roof soon runs down to the edges and freezes back up again.
Ice dams can persist long into the spring season, causing water to back up along the bottom portions of a roof. Even a roof with good shingles and well-attached underlayment may experience leaks as this standing water forces its way down your roof deck. To prevent this issue, roof contractors often install a type of component known as an ice and water shield.
Remember the rubberized asphalt underlayment discussed above? An ice and water shield is a lot like that, except that it is fully waterproof. It adheres to the surface of a roof deck thanks to heavy-duty adhesive, thus providing a base layer that water cannot get through. Obviously, ice and water shields don’t need to be applied to an entire roof, just to the edges where water pools up as ice dams form.
A well-designed roofing system utilizes a diverse array of components, from humble roofing nails and underlayment, to specialized forms of protection like ice and water shields. If you have plans to replace the roof on your home, it is important that you invest in the best possible components for the job.
For more information about how to make your next roof replacement in Farmington Hills, MI a success, please contact the roofing industry experts at Twelve Oaks Roofing.