Your roof is one of the most important features when it comes to your home. It helps with your home’s curb appeal, as well as keeping you warm and dry. It also protects your home from getting damaged by hail and other rough weather conditions. But underneath your home’s asphalt or architectural shingles is something that’s even more important to keeping your home safe and secure: your roof’s underlayment!
Is underlayment necessary for roofs?
When your local roofing company installs architectural or asphalt shingles on your roof, during the installation they do not simply nail the shingles onto the wooden roof deck. If your local roofing company were to nail the shingles directly onto these sheets of wood, if there were any kind of damage to the shingles, water would be given the opportunity to seep into the substrate and cause damage to your roof structure. This would potentially lead to rot, mold and interior leaks.
Shingle underlayments provide a barrier between the roof frame material and your home’s shingles. Making the right decision for your home can extend the life of your roof and minimize the need for maintenance and repairs.
Felt roofing underlayment
If you’re deciding to go on the cheaper route, go with the underlayment that is made up of felt that’s saturated with asphalt in order to make it water resistant. Roof felt underlayment can vary in price depending on its degree of saturation; since asphalt is its more expensive component, the more asphalt it contains, the more durable and expensive it will be. Often, felt roof underlayment also contains fiberglass reinforcement, which increases its strength and durability. Over time however, even the highest quality asphalt will eventually wear down and become penetrable by water.
Roof felt underlayment is usually a good option for steeply sloped roofs, which allows water to quickly run off. However standing water is able to seep into it and infiltrate your roof’s structure. Felt underlayment is also vulnerable to sun damage, which accelerates deterioration of the asphalt, so it’s not the best choice for roofs that get a lot of direct sunlight. Felt as well lacks the overall quality, durability and total water resistance. Therefore, if you’re installing a long lasting roofing material like high quality architectural shingles or extremely durable options like stone coated steel roofing, a felt underlayment would not be recommended.
Hot applied rubberized asphalt membrane
With good reason, most professional local roofing contractors would not recommend a hot applied roofing membrane. However, many property owners still go choose them for their property. Asphalt can be polymer modified with bitumen, a viscous mixture of hydrocarbons, which gives it rubber or plastic-like properties. The hot applied rubberized asphalt membrane is applied in large panels which are bonded together or heat fused into one seamless membrane. Due to its flexible and elastic nature, it is able to fill in space around nails or staples, bridge cracks in the substrate surface, and conform to surface irregularities.
This type of underlayment is better suited for high temperature climates than felt. Another benefit is that it is able to resist moisture penetration, because there are no seams for water infiltration. Because of this, it is also better for use on flat roofs or other roofs where there is a danger of water pooling. Rubberized asphalt membrane underlayment contains materials that can resist expansion and contraction as well as reflecting harmful UV rays. This makes it more durable and longer lasting than felt. However, installation is problematic and overheating can compromise the integrity and longevity of the membrane. Not heating the product enough will also cause serious problems as the layers will not be able to form a proper bond. This makes proper installation a careful balancing act and something you definitely a task you would not want to entrust to your average local roofing contractors.
Synthetic Roof Membrane
Synthetic roof underlayment is similar to a hot applied rubberized asphalt membrane underlayment in design, but its composition is a synthetic rubber or thermoplastic rather than bituminized asphalt. Also, being fully waterproof there is also an added highly protective layer of insulation between your roof frame and shingles. Incongruously, it is also more breathable, allowing humidity to escape while resisting water penetration.
Synthetic underlayment effectively protects against wind, rain, and ice, helping to prevent ice dams and water leaks no matter the roof slope. A synthetic membrane is durable, long- lasting, lightweight, fungus resistant, and also highly reflective of direct UV radiation. Overall, this type of roof underlayment receives better safety ratings than the alternatives.
Synthetic roof underlayments are made from engineered materials such as polypropylene or polyester. Felt is sometimes referred to as organic when it contains some organic materials, as well as being saturated with asphalt.
Fire Resistance Ratings
On the topic of safety, another important factor to consider when choosing an underlayment is its fire resistance rating. Most underlayments have similar protection from smoke, however flame protection can differ when it comes to the roofing material. Underlayment products are rated A, B, or C, with A being the most and C being the least fire resistant. Depending on your area’s level of risk, a more highly rated underlayment could significantly decrease your home’s vulnerability to fire caused by lightning striking your home.
The price differences between underlayment options usually add up to a few hundred dollars in your overall roof replacement project. If you are investing in a high quality roof that will improve your home’s value for years to come, choosing a better quality, more durable, water-resistant underlayment may well be worth the extra cost.
Roof underlayment can act as a temporary protection of the building’s interior and the roof deck before the final roof covering material is installed. Usually, the roof covering material would be installed right away, however in some circumstances a roof might be protected by just the roof underlayment for days, weeks, or sometimes months. Protecting the building interior is especially important when an old roof covering material is being replaced and the home interior is finished. During that time, the underlayment may be under attack from weather elements such high winds, UV radiation, and precipitation. It also needs to resist the wear and tear that occurs when the roof covering material is being installed.
Preventing chemical degradation
Underlayment provides a layer that separates the roof sheathing and the roof covering material. Newer homes use plywood or an engineered panel called oriented strand board for sheathing. For many years, pine and fir boards were used as sheathing, and many older homes still have these kinds of boards in place. Resin pockets in these boards can react chemically with some roof covering materials, such as asphalt shingles. In these situations, missing underlayment can cause accelerated deterioration and premature failure of the roof covering material.
Is synthetic roof underlayment better than felt?
Asphalt-saturated felt is a blend of cellulose, polyester, bitumen, and asphalt, soaked in a waterproofing agent. It comes in two thicknesses. Thirty pound felt is more thick and stiff than fifteen pound, so thirty pound is more resistant to damage during installation and can protect the roof longer if exposed to outside elements like rain, wind, hail, and snow. Asphalt-saturated felt underlayments are semi-permeable and typically have a perm rating of five to seven.
Most synthetics on the other hand are spun or woven from either polypropylene or polyethylene. The specific manufacturing process produces synthetic underlayments with different properties such as the thickness, exposure time, and resistance to damage during the installation process. Like asphalt saturated felt, comparisons between synthetic underlayments are by weight . However, synthetic underlayments utilize grams per square as their measurement.
What is the best underlayment for your roof?
Synthetic underlayment is much lighter than felt underlayment. Therefore, using synthetic will add less weight to the roof than any asphalt felt underlay. Synthetic underlay is also far more tear-resistant when exposed to high winds and foot traffic than asphalt felt underlayment. Many synthetics also have a higher UV protection rating and can be left exposed on a roof for a far longer period than felt underlay. However, you will find that synthetic roof underlay is the more expensive option. When it comes down to it, sometimes you might be limited by your budget. However, if you have the extra money for a synthetic roof underlayment installation, you will likely see the extra you spend returned through the extra long-term lifespan of your roof and lower long-term repair and maintenance costs.
Can Synthetic underlayment get wet?
There are several components to a shingle roofing system, each playing an important role in keeping your house protected. The shingles are the first line of defense and add to the overall look of the home. The underlayment provides another layer of protection. The decking or sheathing provides stability to those top two layers, while the rafters and trusses hold everything up. Of those components, only the shingles are designed to get wet for long periods of time. That is one of their primary jobs, after all. But what about the other parts of the roof? Especially during a roof installation when the weather isn’t so cooperative? Will wet conditions ruin the whole job? The answer is, it depends on how much the rain and for what duration. However, once the underlayment is installed, the roof is protected.
Underlayment is an added layer of protection for your roof. The shingles do the heavy lifting, but if water managed to get under the shingles, the waterproof underlayment is there to protect the decking underneath. Now the question remains, can roof underlayment itself protect the roof when it’s raining? The answer would be for a couple of days at the most. Underlayment is installed much like the shingles themselves. Your local roofing company would overlap the edges to make sure every inch of the roof is covered, however that is not enough to stand up for a whole winter and water would start to penetrate between the layers all too quickly.