Storms and high winds can drive rain beneath shingles. Without underlayment, this rain will soak into the roof deck and cause problems ranging from mold and rot to leaks within the home's interior. Snow sitting on roofs and the ice dams that form along a roof's edge can also allow water to seep beneath shingles.
The underlayment is the actual waterproofing, to answer your question you absolutely have to put the underlayment. The shingles is what protects the underlayment from drying out or being damaged from everything in the environment.
Remember, roof underlayment protects your decking if water ever gets underneath your roofing material. Without underlayment, this water eventually rots your roof decking leading to leaks, mold/mildew forming, and even structural damage.
You need to put down a synthetic felt (which is like tar paper; they come in 4-foot rolls and are made out of paper, tar, oil, and other things) or underlayment, and you want to put that down before you put the tiles down.
Underlayment. Directly beneath the shingles is something called “underlayment,” also known as “roofing felt.” As you may have guessed, underlayment is usually either made of fiberglass paper or felt. It covers the entire roof deck.
Another big reason why roofing contractors recommend synthetic underlayment is for safety reasons. Synthetic underlayment is a non-skid material, so you don't have to worry about it tearing or crew members slipping. This makes it safer for your roofer to work as they install your asphalt shingles.
The purpose of the shingle underlayment is to provide an additional moisture-resistant layer to back up your roof shingles.
Neither shakes nor shingles should have a waterproof underlayment installed unless the shakes or shingles are installed on a batten system, which allows for good air flow between the underlayment and the underside of the shakes or shingles. You may occasionally see shakes installed without interlayment.
While tar paper might not be mandatory for every shed, we strongly advocate for its use. Here's why: Climate Considerations: After putting it to the test, we've found that in areas prone to heavy rain, snow, or high humidity, tar paper can significantly bolster your roof's defense against moisture.
Underlayment is necessary to provide a moisture protection, sound insulation, and a smoother surface for the laminate. Installing laminate directly on the subfloor can lead to noise issues, discomfort, and potential damage from moisture.
It smooths out the subfloor
If you have areas in your subfloor that are bumpy, uneven or rough, laying carpet directly on it will lead to uneven wear and significantly shorten its lifespan. By installing underlay first you negate a lot of these imperfections, keeping your carpet looking its best for longer.
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.
Felt roofing underlayment is a traditional material that has been used for decades and is still a popular choice for many roofing projects. Felt is made from either organic or synthetic materials, and is designed to provide a durable, waterproof barrier between the roof deck and the shingles.
House Wrap Cons
Not designed for use on roofs, where it may not provide adequate protection.
All roofs have underlayment. At a minimum, a roof with asphalt shingles should be completely covered with one layer of underlayment. Roofers may consider adding layers of underlayment for superior protection, which is especially useful on low-pitch roofs.
In neutral climates, you can reasonably expect the following lifespans out of custom wood shingles: Cedar: 30 to 50 years or more. Wallaba: 35 to 60 years or more. Teak: 50 to 80 years or more.
The best underlayment for roofing is typically synthetic underlayment. It offers better protection against water and has superior tear resistance compared to traditional felt underlayment. Additionally, synthetic underlayment is lighter and easier to work with during the installation process.
Lifespan: Metal roofs are one of the longest-lasting roofing materials and last as much as three times longer than traditional roofing materials such as asphalt shingles, which need to be replaced as often as every 12 years.
It's typically made from thin layers of wood veneer, known as plies, that are glued together in a cross-grain pattern to improve strength and durability. Roof plywood provides a stable base for roofing materials such as shingles, tiles, or metal panels.
It's often required for fire ratings and to keep buildings up to code. It acts as secondary weather protection. It separates the roof deck from the shingle which prevents any interaction between resins in green lumber often uses in roof decks and the shingles.
Felt Underlayment/Tar Paper
Felt underlayment is usually made from synthetic materials like fiberglass or natural materials like wood cellulose. They're then layered with a protective asphalt coating to defend against debris and moisture. This is a traditional underlayment option for cedar shingles.
Underlayment is basically a must-have for areas that tend to be wetter and more prone to humidity because this also increases the amount of moisture in your subfloors.
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.
#1 Synthetic Underlayment
Synthetic underlayment is made of tough materials that effectively resist water and UV rays. Its textured surface provides improved traction for roofers, making it safer to work on sloped roofs, especially in wet or icy conditions. Estimated lifespan: 20 to 35 years.