Roofing Felt 101: A Guide | Everything You Need to Know

October 29, 2020

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What is roofing felt? When homeowners think of needed roof inspections and repairs, they’re typically considering the condition of asphalt shingles or tiles; however, the felt or paper under those materials is a vital roof component! This paper should always be in good condition and replaced as needed.

Roof felt or tar paper starts with a base from natural or synthetic materials such as wood cellulose, fiberglass, or polyester; this base is then saturated with a protective coating, typically liquid asphalt. This protective coating repels water, keeping it out of the home’s interior and away from its framing.


roof felt installation

Since roofing felt is such an important roof component, homeowners should know the basics of how it’s maintained and when it needs replacing. This information will protect your home from water damage and ensure the roof is in good repair!

Before you go another month or, worse yet, a full year without needed roof repairs, check out this handy guide to roof felt including why it’s needed, when it needs replacing, and how to replace it properly, as well as some mistakes to avoid when it comes to roof felt installation and repairs. You can then discuss your home’s roof with a contractor near you as needed, and ensure it’s always in good condition and looking its best.

What is Roof Felt?

Roofing felt is an added layer of protection between the roof’s lower layers, including your home’s interior trusses, and outside elements. As roof felt repels water, it also reduces the risk of standing water on the roof, protecting shingles and tiles from water damage.

To better understand the purpose of the roof felt, first note the basics of roof construction. A home’s roof is built in layers:

  • Trusses are large beams set at a slope or angle, as part of the home’s framework.
  • Plywood panels or roof decking boards are attached to the top of those trusses, to provide a solid base or foundation for the rest of the roof’s layers.
  • Rigid foam insulation is placed over that roof decking.
  • Roof felt is attached to that rigid foam.
  • Nailing planks are placed over the roof felt. Shingles, tiles, or metal panels are nailed or otherwise connected to these planks.
  • The roof’s shingles, tiles, and flashing are then attached as the last layer.
  • Along with these layers, a roof will also typically have an ice dam, to encourage snow and ice to fall away from the roof, and drip edges, which prevent standing water on a roof’s surface.  

Will Roofing Felt Stop the Rain?

Roofing felt’s waterproof coating helps direct rainwater off the roof and away from shingles and tiles. That coating also stops roof decking and other materials from absorbing rain, snow, melting ice, and excess humidity. This waterproof coating protects roof layers, as said, and keeps that moisture from seeping into the home’s interior.

Is Roof Felt Optional?

Since a roof’s rigid foam insulation helps stop moisture from damaging a roof’s lower layers, some roofers might consider roofing felt as unnecessary. In turn, homeowners might wonder if they can forego roof felt and avoid that added expense during roof installation.

While roof felt might add to the cost of a new roof or roof repairs, this paper is far cheaper than fixing a water-damaged roof or cracked interior ceilings! Roof leaks also increase the risk of dangerous, costly mold growth inside the home.

Roof felt’s added barrier also helps protect your home in case of missing shingles. After a strong storm, or if shingles have broken away due to age and everyday wear and tear, it might be some time before a roofer can arrive to perform repairs. Tar paper or roof felt helps protect roof layers and your home’s interior in the meantime.

Roof decking, trusses, and other materials also absorb humidity, not just rain! Consider the benefits of adding roof felt in tropical or coastal areas or any location with high humidity levels. Melting snow and ice also increases the risk of roof water damage; if you live in the Midwest or anywhere with heavy winter snows, ensure your home is protected with a layer of high-quality roof felt.

How Long Will Roofing Felt Last?

In most cases, the roof felt will last between 12 and 20 years. Roofing felt’s lifespan depends on its initial quality, as reputable name-brand manufacturers often use more durable materials than cheap, off-brand suppliers. Heavy clay or slate tiles also put more pressure on tar paper, risking tears and premature damage.

old roof continues to be durable

When Should you Replace Roof Felt?

No matter tar paper’s expected lifespan, remember that decaying roof felt increases the risk of roof leaks and water damage. Rather than waiting until your home’s roof felt is degraded completely, invest in new tar paper at the first sign of decay. New roof felt will keep the roof and home’s interior protected from water damage and in good repair.

If you’re not sure about the condition of your home’s roof felt, have a roofing contractor perform a complete inspection every year or two, and especially after strong storms or inclement winters. He or she will typically pull up a few shingles and inspect that roof paper before replacing those tiles, so they know if the tar paper itself needs replacing.

How Often Should a Felt Roof be Replaced?

Note that a felt roof is different than roofing felt. A felt roof consists of three roofing layers; a vapor control barrier, a felt layer, and a cap sheet. These layers are then welded or torched together, creating a strong roofing system.

Felt roofs are often preferred for flat roofs, as the waterproof barrier built into a felt roof helps repel water away from those surfaces. A felt roof itself might last some 10 to 20 years, depending on the quality of materials and installation and overall weather conditions.

Removing Old Roof Felt

In most cases, the old roof felt doesn’t need to be removed before you apply new tar paper. If the roof decking under it is damaged and needs repairs or replacing, however, a roofer typically removes those layers and applies new decking, and then new roof insulation and felt over it.

roofing material removal

Can you Put New Felt on Old Felt?

If the roof decking is in good repair and the existing roof felt flat, you can often add new felt onto that old felt. Roofers will often apply a bitumen primer to fill in any gaps and crevices, much like applying primer to a wall before painting! Bitumen primer also ensures the surface is as level and flat as possible, and ready for new felt.

In some cases, existing roof felt might have large gaps, tears, or other such damage so that it provides a poor base for new felt. Old, outdated felt might also be thin and poor-quality, and peeling away from the roof decking or insulation. Removing that felt, even if it’s flat, is then a better option than putting new felt over it.

Note, too, that a roofer might quote your repair job as “removal down to decking” or similar wording. As roof felt goes over the roof decking, a roofer should then remove the felt and insulation if this work is included on your quote! It’s extra work for him or her to scrape away that felt but if it’s included in your quote, it should be included in their repairs.

What is the Best Adhesive for Roof Felt?

Bitumen adhesives designed for roof felt are the best choice for roof felt; these adhesives ensure a secure fit. However, bitumen adhesives usually require the use of a blowtorch, something a homeowner should not try on their own!

Self-adhesive roof felt is a much better choice for homeowners tackling DIY roof repairs. Ensure you invest in a high-quality tar paper brand, so the adhesive is firm and lasts as long as possible. Avoid using glues and other adhesives not designed for roof felt, as these might lose adhesion or get brittle and then crack and fall away during hot summer months.

Can Roof Felt Be Repaired?

While roof felt cannot be repaired, you can patch the felt surface if there are only a few missing sections or small areas of damage. To remove damaged pieces of roof felt, score the area with a specialty roof knife or cutter meant for roofing materials.

Once scored, you can then cut through the felt and pull away from the damaged section. Use a scraper to pull up the stuck adhesive and other such pieces.

Ensure you don’t cut into the roof decking or chip and splinter any roofing layers while you work. Also, don’t just toss away damaged pieces of felt but use them as a template for cutting new sections; cut out a piece just larger than what you need, as you’ll want your patches to overlap the existing felt.

As you attach the new patch to the roof, work from the middle outward, and press its adhesive into place. Once you reach the edges, take an extra minute to push them onto the roof decking or adjoining felt, to ensure a secure fit. You can then cover the patched area with a liquid roof sealant product, to ensure the patch stays in place and keep it protected from leaks and water damage.

roofing service for felt on roof

What Can You Use Instead of Roof Felt?

Roof felt, coated in or saturated with a bitumen coating, provides an excellent waterproof barrier against outside water and humidity. If you need an effective alternative, however, such as for a shed, consider a synthetic roof underlayment.

The term underlayment refers to the layer underneath shingles or tiles; a synthetic underlayment made of a polymer or material other than felt also provides an effective moisture barrier and is easy to cut and fabricate. Many also have a self-stick backing, so you don’t need to worry about bitumen or other such adhesives.

The downside to synthetic materials is that they do not self-seal around nails and other fasteners, so you invest in some liquid roof sealant to apply in these areas. Also, note that using certain synthetic materials might void the warranty on your roof’s shingles or tiles! Be sure to check any paperwork you have from your roofer or shingle manufacturer before deciding on a synthetic underlayment for your home’s roof.

Can You Replace Roof Felt From Inside?

It’s never recommended that a homeowner get on their home’s roof, as even experienced roofers and other contractors can fall and suffer serious injuries; how much more dangerous is a sloped or slick roof for a homeowner not accustomed to walking on its surface! Dropping tools and other equipment is also dangerous to anyone on the ground below.

In turn, it’s best to manage as many DIY repairs from the safety of your home’s interior as possible. If your home has an attic loft or crawlspace with exposed felt, you might notice holes or rotted and damaged material in certain sections, and these can typically be repaired from the underside area inside your home.

  • To repair a hole in the roof felt from the inside, you’ll need what’s called flash banding or roof deck seam tape. You’ll note that the sticky side of this tape is covered with a backing paper, as its adhesion is very strong and shouldn’t be exposed until you’re ready to apply the tape.
  • Start your repairs by cutting a piece of that flash banding tape, large enough to overlap the damaged area by several inches. Once cut, remove the backing paper from the adhesive side, using caution as you work and avoiding getting the tape stuck to your skin or hair, or any nearby surfaces.
  • Facing the adhesive side of the tape over the damaged roof felt, work from the top downward, pressing the tape into place while pushing out any air bubbles or gaps. Run a finger over the edges to ensure they’re in place and there are no gaps.
  • If you do notice gaps or air bubbles over the flash banding, use a small, firm roller along with the heat gun or hairdryer; the heat will melt the adhesive slightly so you can roll out those bubbles. Avoid using a blowtorch or open flame in your home’s attic or crawlspace, to avoid the risk of fire. Once cool, the tape forms a watertight, airtight seal over damaged roof felt.

homeowner confused by roofing felt

Shingling Over Wet Roof Felt

Ideally, roof repairs and new roof installation would be scheduled for a mild, sunny day. However, even with the best weather reports available, you can’t always foresee showers and storms the day of your scheduled roof work!

While you might not want to put off those repairs, it’s never okay to shingle over wet roofing felt. If you do, that trapped moisture will have nowhere to go once it begins to evaporate. In turn, your shingles or tiles might suffer from water damage, or the paper itself might crumble and fall away.

Can Your Roof Felt Rot or Mold?

Since you want to avoid installing shingles or tiles over wet felt so moisture doesn’t get trapped between those layers, does this mean that roof felt can rot over time? First understand that there are different types of roof felt, and higher-quality brands offer more protection against water damage and the potential for rot.

Low-cost bitumen roof underlayment is probably the most common roof felt type, and the one most likely to suffer wear including rot when exposed to sunlight around gutters and seams. Lightweight alternatives such as high and low water vapor resistance underlayment allow vapor to pass through, protecting them from rotting.

Can You Roof in the Rain?

Whether or not a roofer will work in the rain depends on how hard it’s raining and the work at hand. A roofer might replace shingles during a light drizzle, as he or she will typically work fast enough to protect roof felt and decking from absorbing water.

However, along with protecting decking and other roofing layers and materials from water damage, a roofer also needs to be concerned with their own safety! A wet roof is typically slick and dangerous even for the most experienced roofer, and certainly, a homeowner should never attempt DIY repairs in the rain.

A roofer might also need to cover exposed roof areas with a tarp or other material during rainy weather, as he or she can only work so fast! Whatever the case, remember that having your roof repairs or replacement delayed a few days is often worth the inconvenience if it means protecting roof decking and felt from water damage and resultant rot and decay.

commercial roofing contractor installing roof

Roof Felt Maintenance 

To keep the roof felt in good condition, it’s vital that you remove leaves and other materials regularly. Leaves, twigs, branches, and other such debris hold moisture against a roof, which can seep under tiles and shingles and damage those roofing layers.

Since added weight might tear roof felt, avoid walking on a roof as much as possible, as your footsteps tug and pull at roof tiles and shingles and increase the risk of roof felt tearing. Trim back any branches hanging over the structure so they don’t scrape the roof in high winds and inclement weather.

One last but very vital tip is to schedule a professional roof inspection every year or two years at the most, and especially after a particularly stormy season or if a strong storm has moved through your area. Regular inspections find roof damage quickly, allowing a roofer to repair roofing felt as needed and ensure your structure’s roof is always in good condition.

A Word From Our Team at Overland Park Roofing Contractors

No matter what aspect of roofing our customers want to hear about, our roofing company is there for you with high-quality resources. Our roofing contractors put together this article at Overland Park Roofing in order to spread the word about roofing felt and answer common questions our clients have about it. If you ever require roof repair or roof installation services in the Kansas area, we’re the roofing team for you! 

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