Are you looking to add roofing felt on your roof but still wondering if it’s waterproof?
Roofing felt is a fiberglass mat made of a synthetic, inorganic material known as asphalt. The combination of materials makes it waterproof, so it’s used as an added layer of protection to commercial and residential roofs. It goes between the roof deck and the shingles.
First Things First: What is Roofing Felt?
Roofing felt is a type of material that is commonly used in the construction of roofs. It is made from various materials, including paper, fiberglass, and asphalt.
Roofing felt is typically used as an underlayment for shingles or tiles, and it’s installed on top of the roof sheathing and below the roof covering to help protect it from weather damage and leaks. It also provides a smooth, flat surface to enable easier installation and an even, beautiful appearance.
You can choose a few different types of roofing felt depending on your needs. Paper-based roofing felt is the most common type of felt, and it is made from recycled paper products.
Fiberglass-based roofing felt is also popular, and it is made from glass fibers bonded together with resin. Finally, asphalt-based roofing felt is the heaviest and most durable type of felt and is often used on commercial roofs.
Roofing felt can also be categorized according to their weights. 15-pound felt and 30-pound felt are the most common weights used. 15-pound felt is the lighter of the two options and is typically used on residential roofs. 30-pound felt is much heavier and often used on commercial roofs.
30-pound felt is used for steeper roof slopes, as it is less likely to buckle under the weight of the shingles. It is also a good choice for areas that receive a lot of snowfall, as it is less likely to be damaged by the heavy snow.
15-pound felt is typically used on shallower roof slopes and is often used in areas that do not receive a lot of snowfall. It is also a good choice for roofs prone to leaks, as it can help seal any gaps or cracks in the roof.
Is Roofing Felt Waterproof?
Roofing felt can shed water, but it’s not 100% waterproof. It can absorb water and slowly evaporate the moisture to the exterior, but only to a certain extent. If it’s directly exposed to water for too long, its fibers will start to break down and fray, impairing its ability to keep your roof’s integrity.
Roofing felt is a water-resistant, protective layer that contains wood cellulose or synthetic materials like polyester, and is coated with asphalt.
The combination of these products produces water-resistant material that repels water allowing the roof to breathe. However, while it has water-repellent properties, it’s not waterproof and can be damaged if exposed to moisture for too long.
If it rains after laying the roofing felt, you can continue to install your roofing cover. You aren’t going to ruin the roof with just a few hours of rain.
The issue is when something that is roofing felt is rained on for long hours and left on the roof for long periods of time without a roof cover. The immediate response is not to wait for too long but give it a few hours to dry before installing your shingles.
Note: If roofing felt is wet for an extended period of time, it will create holes and leaks in your roof layers that will be more trouble than you want. And even if you give it time to dry, you may notice permanent bumps and bulges that might prevent the new shingles from properly adhering.
Can Roofing Felt Get Wet?
This is one of the common questions that roofers and homeowners alike ask. And it’s understandable because while installing a new roof or repairing a damaged roof, you may not finish the job in time, or it might rain during the process.
Roofing felt can get wet and still keep your roof dry because of its water resistant properties. It repels water instead of absorbing it. However, exposing it to moisture for too long can damage its fibers, affecting its ability to protect your roof.
So what happens when roofing felt gets wet? Because roofing felt acts more as a shield than a sponge, you shouldn’t leave it wet for a long period of time. Otherwise, its water repellent fibers will break down and fray, unable to keep your roof’s integrity.
So, that brings us to the next question: Is tar paper still good if it gets wet? While roofing felt can get wet, you must limit the amount of time it is exposed so that it doesn’t remain wet for too long. Upon initial exposure, the fibers will repel the water. But, with time, the water will go through your roof.
In a nutshell, tar paper is not good if wet because the trapped moisture will not evaporate when the sun heats the shingles. Therefore, you must give it several hours to dry before installing the shingles.
Can you Roof Over Wet Felt Paper?
Now that it’s clear that roofing felt shouldn’t get wet, or if it does, it shouldn’t be for a long time, can you roof over wet felt paper?
The simple answer is NO. Typically you should wait until the roofing felt is completely dry before putting the shingles. Installing shingles over wet roofing felt causes premature aging of the roof because the trapped moisture will not evaporate when exposed to direct sunlight or heat. Most shingle roofs can last up to 20 years when properly installed and maintained.
Additionally, the moisture trapped inside the felt paper may cause the shingles to blister, buckle, or wrinkle. Under normal circumstances, when installing shingles over a dry felt paper, the shingles lay down flat, producing an aesthetically pleasing appearance.
However, when wet tar paper is not given enough time to dry, the wrinkling and bubbling that forms once the shingles are installed can be detrimental in the long term.
The most important reason you must avoid roofing over wet felt paper is the risk of mold and mildew. When water gets trapped under the shingles, it creates a dark, moist environment ideal for mold growth. Sooner or later, the mold multiplies and moves upwards from the sheathing to the shingles at the top. At this point, without a doubt, you’ll need a new roofing installation.
How Long can you Leave Roofing Felt Exposed?
Placing shingles on the roof can take a few days, so roofing felt will always be exposed until the cover is installed. Many things can compromise your felt’s integrity during this time, and the most obvious is rain.
Roofing felt can be exposed to the elements for one or two weeks. However, just because exposed felt paper can still protect your roof from moisture doesn’t mean you should leave it completely open. Eventually, the elements will damage the roofing felt underlay if it’s left exposed for a long period of time.
In the United States, most residential homes have roofs between 1,600 and 1,700 square feet. Therefore, you’ll need 2-3 days to install shingles in such a house. This is where you have to check the weather before laying your roofing felt because it’s not appropriate to continue with the roofing project in either extremely wet or dry climates.
If it rains before you can finish installing the shingles, the best way to prevent further damage is to let the exposed part dry or tear down only what can be fixed within a day.
How Long does it Take for Roofing Felt to Dry?
We’ve established that you shouldn’t leave your roofing felt exposed for more than two weeks or install shingles on wet roofing felt. So, if it rains, how long should you wait for it to dry before installing the shingles?
Typically, roofing felt requires at least 24 hours to dry before installing shingles. If the felt paper isn’t fully dry, the trapped moisture will be a breeding ground for mold, causing the roof to age prematurely.
We’ve already talked about why shingling over wet roofing felt is a bad idea, but I wanted to elaborate on other reasons.
Roofing shingles have a lifespan, and manufacturers provide warranties for their products. However, they also have conditions you must follow for the warranty to be valid.
For example, you can’t make a warranty claim after being negligent and compromising the quality of the shingles. Installing shingles on wet roofing felt or under harsh weather conditions like rain is negligent on your part, and the company will unlikely honor the warranty.
This problem is worsened if you’re reroofing. When installing a new roof, you have all the time to inspect the shingles for bulges or wrinkles and point them out to the contractor for repair before they part with your money.
A reroofing job is different because it only takes a few days, and you don’t usually have enough time to inspect the roof. Therefore, if a bad reroofing job is caused by wet roofing felt, it’s tricky to make a warranty claim or ask for repairs.
How to Care for Roofing Felt During a Roofing Installation Project
Here are a few things to help you care for your roofing felt during a roofing installation project.
- Prepare for the project in advance. Ensure you understand what needs to be done. Collect all the tools and roofing materials you need for the project. If you are unsure about any step of the process, get advice from roofing experts.
- Prepare for any eventualities. Something may go wrong while you are in the middle of the process. Think about how you will handle such a situation if it occurs.
- Purchase some tarps. They may help you keep your working surface dry. This may help if it starts raining suddenly.
- Avoid working with wet roofing felt. Keep your synthetic underlayment as dry as possible. If there is moisture on your roof, let it dry before you try to lay the synthetic underlayment.
How to Install Roofing Felt the Right Way
Building codes require that you install roofing underlayment beneath the shingles. This is extremely important if you live in cold climates.
The non-bitumen synthetic underlayment protects damming. Damming can easily damage the other components of your roof.
The wooden deck, for example, needs to stay completely dry. The roofing underlayment provides a protective layer for the roof deck.
Installing roofing felt need not be a complex process. But if you miss a few important things, you may end up with a shoddy job.
Here are a few tips to follow to install your roofing felt properly. But if you are unsure about how to proceed, you can get roofing experts. They will complete the proper installation of the roofing felt with the roof shingles.
- Put your roofing felt underlayment in overlapping layers. This will ensure there is no space in between the roofing felt. Therefore, ensure the shingles overlap perfectly.
- Ensure the sheathing is completely dry before you mount the synthetic underlayment. Placing the felt on a wet sheathing will be counterproductive. In addition, the felt will easily lose its functionality if it gets wet for a long time. Therefore, avoid wet roofing felt.
- Ensure the strips lie completely flat. Avoid having wrinkles along the strips. They may easily cause moisture and dust leakages.
Conclusion
Properly installed roofing felt can protect your roof from excess moisture and even increase its lifespan. However, don’t install shingles over wet roofing felt because it can damage your roof beyond repair.