How much does it cost to replace roof underlayment?

Reviewed by Larry Pope remodeling expert. Written by Fixr.com.

When most people think about their roof, they may think about the shape, slope, or material. However, there is also the underlayment beneath the visible material covering your roof’s deck. While you cannot see this material when you look at your roof, it is a very important part of your roof’s makeup. Underlayment allows your roofing material to lay smoothly, protects your roof from moisture and ice, and can even improve your roof’s efficiency. It comes in several types, weights, and installation styles and is most commonly replaced when you replace your roof. However, you may need to replace the underlayment periodically to help your roof reach its full lifespan with tile, concrete, and some slate roofs.

The national average cost to replace roof underlayment is $800 to $1,200, with most people paying $900 to replace their roof underlayment on a 2,000 sq.ft. roof when they also replace the roofing material. This project’s low cost is $170 to replace the underlayment on 300 sq.ft. of roof during a roofing repair. The high cost is $9,000 to remove clay tiles from a 3,000 sq.ft. roof, replace the underlayment, and reinstall the tiles.

Roof Underlayment Price

What Is Roof Underlayment?

Roof underlayment is a moisture-resistant material that covers your roof deck. It is installed below your roofing material and is not seen once your roof is fully installed. Underlayment creates a smooth, even surface for your roof material to be installed on. While you can install low-cost materials like asphalt directly on the roof deck without underlayment in some areas, most materials require it, many building codes stipulate its use, and all roofs can benefit from having it installed.

Roof underlayment can prevent leaks by absorbing some moisture. It can prevent ice dams in certain circumstances and can even help keep roofs cooler or more energy efficient. Roof underlayments come in many types and materials, and they may be installed by nailing or tacking the material onto the roof or using an adhesive-backed material that can stick directly to the roof.

Roof Underlayment Cost per Square Foot

Roof underlayment is generally quoted by the square foot or roofing square, which is 100 sq.ft. When replacing your entire roof and installing a new roofing material, the cost to install the underlayment is usually rolled into the total cost. In some cases, the cost of the material may be segmented from the rest, with typical costs for the material and installation running $0.20 to $2 per sq.ft., depending on the material and roof, or roughly $0.05 to $0.65 per sq.ft. for the material.

Because underlayment often wears before long-lasting roofing materials like tile, you frequently need to replace the underlayment without replacing the roofing material. In this case, your total costs are generally $3 to $5 per sq.ft. to remove the material, replace the underlayment, and reinstall the tiles. There is frequently some damage to roughly 10% of the tiles in this process, accounting for the extra costs.

Roof Underlayment Cost by Material

Roof underlayment comes in three basic materials - felt, synthetic, and rubber. Felt is the oldest and one of the most common. It is typically made of an organic material coated in asphalt. It may be called tar paper, asphalt-saturated felt, roofing felt paper, or felt paper. This is the least expensive material, but it lasts the least amount of time, so many people opt for other materials like rubber or synthetics. Rubberized asphalt is a sticky membrane that is completely waterproof and installed with an adhesive back. It is more expensive than others, but if there could be a delay between the underlayment going down and the roof material being installed, it is not affected by rain or adverse weather.

Synthetic materials are newer underlayments. They are much lighter than felt, and you often need fewer rolls, making installation easier. It also lasts longer. It costs more than felt but less than rubberized asphalt, but it is often less costly to install. Below are the average costs for the different underlayment materials.

Roofing Felt Paper

Asphalt-saturated felt underlayment costs between $0.05 and $0.50 per sq.ft. for the material. Felt underlayment is made from recycled corrugated paper, sawdust, and asphalt. Felt has an organic base and can be considered slightly better for the environment in its production. The asphalt strengthens the material and creates a water-resistant surface. This is the most economical material, but it is also more difficult to install. It comes in 15lb and 30lb weights for regular roofing and 40lb weights for tile roofing. The heavier the felt, the longer lasting and more durable it is, but the harder it is to work with and the more costly labor is.

Synthetic Roof Underlayment

The cost of synthetic roof underlayments, or non-bitumen synthetics, is $0.17 to $0.55 per sq.ft. for the material. Synthetic roofing materials are much thinner, lighter, more durable, and water resistant than felt.They are made from laminated polypropylene and polyethylene plastic and come in much thinner sheets and rolls. You only need 2 or 3 rolls of synthetic material to cover a 2,000 sq.ft. roof, while you may need 14 rolls of felt. This makes it faster and easier to install. The more durable and longer lasting the synthetic, the higher its cost.

Synthetics will not degrade the way that organic felt paper will. And another thing is, felt paper has two pounds of tear strength per square inch. Synthetic may have from 34 to 77 pounds per square inch, so it’s not going to rip out from under as you’re walking on the roof. You walk on the product in the cross direction. And that’s where you always want your tear strengths to be. Because if you’re walking on a 6/12 up to a 12/12 pitch, it’s pretty steep, so you want all that strength in that cross direction so that it won’t rip out from under or pull out from the nails as you’ve nailed it down.

Larry Pope, roofing expert

Rubberized Asphalt

The cost of rubberized asphalt roofing underlayment is $0.55 to $0.65 per sq.ft. for the material. Rubberized asphalt roofing underlayment is also called self-adhering underlayment. This material bonds directly with the roof deck below and does not require fasteners. It is easier to install than other types but is more expensive. It is completely waterproof, so if there is a delay in the roofing, it is not impacted and can be left uncovered. This material is sometimes desirable in wet areas because it protects the roof deck from moisture, mold, and mildew.

Roof Underlayment Cost by Weight

Felt paper or asphalt-saturated felt is categorized by weight. The most common weights for this material are 15lbs and 30lbs. Generally, 30lb underlayment is thicker, more absorbent, and more durable than 15lb underlayment. It usually lasts longer and resists tearing better than the lighter-weight material. However, the added weight makes it more difficult to install, lift, and move, so it costs more for the material and labor.

If you have a tile roof and live in a rainy climate, your installer may recommend using 40lb underlayment rather than 30lb since the 40lb underlayment is usually covered in a modified bitumen that makes it long-lasting and weather-resistant. Because you need to replace the underlayment on your tile roof more often than the tiles, the better the underlayment, the longer you can go between replacements. 40lb material is relatively new and may not have been an option for many older roofs undergoing their last underlayment replacement. Below is the average cost per square foot for the various materials.

Roof Underlayment Cost by Brand

Many reputable brands sell roof underlayment. Some companies specialize in specific materials, such as felt or synthetic underlayment, while others produce underlayments that work best under certain materials or in specific climates or conditions. For example, CertainTeed’s RoofRunner is made for asphalt shingles, and Sharkskin and Firestone’s CLAD-GARD are used for metal roofs.

Some materials like Rhino, and ArmorLay are designed for a range of materials, including asphalt, tile, and metal roofs. A few, such as DuPont’s Tyvek and GAF’s Tiger Paw, are among the most commonly used and recognized underlayments available. Most materials are synthetic, but a few are felt, such as Orgill. Many of these are self-adhesive, including MFM, Firestone, and Sharkskin. This makes these materials easier to install and more water-resistant, so some roofers prefer them for their ease of installation. Below are the average costs per square foot for the various brands of underlayment.

Roof Underlayment Replacement Labor Cost

Roof underlayment installation is generally priced by the square foot. If you replace your entire roof, the cost of the underlayment replacement is frequently rolled into the cost of the roof replacement square foot cost. Broken out, you generally pay $0.15 to $0.50 per sq.ft. for the underlayment installation - the tear off of the old roof includes the tear off of the old underlayment.

However, if this is a tile roof, concrete roof, or a reused roofing material, your labor costs are much higher - around $2.75 to $3.50 per sq.ft. These costs include the roofing material removal, underlayment replacement, and roofing material reinstallation. Total costs are also higher for this particular underlayment replacement because some damage is expected to the roofing material in the process, and you may need to replace the damaged pieces.

Underlayment installation is quick and easy. An entire roof can be covered in underlayment in less than an hour, particularly when using a lightweight synthetic or adhesive-backed material. When replacing the underlayment beneath a tile roof, the entire project can take longer - up to 2 days for most roofs, but as long as 4 weeks for old, fragile, or complex roofs. Longer jobs, more complex jobs, and jobs requiring more than one underlayment layer have higher costs per square foot.

Roof Underlayment Replacement Cost by Roof Type

All roofs should ideally have an underlayment under your material. However, several roofs may have special needs for underlayment that impact the cost. For example, cool roofs, which are increasingly popular as a way to help keep energy costs down, may need an insulating or reflecting underlayment to keep your roof and attic from overheating. Green roofs are another good example. These roofs are covered in vegetation and require a waterproof membrane rather than a true underlayment.

Tile roofs have specific underlayment needs because the tile outlasts the membrane. Every 20 years or so, the tiles must be removed to replace the underlayment. While the other roofing types generally get a new underlayment when the rest of the roof is replaced, tile roofs can get a new underlayment without new roofing material, impacting costs. Below are the average costs to replace or install underlayment on different roofs, assuming an average size of 2,000 sq.ft.

Cool Roof Underlayment

Cool roof underlayment replacement or installation costs between $1,600 and $2,400 for a 2,000 sq.ft. roof. Cool roofs are designed to reflect heat from the home, keeping the roof and attic cooler and preventing heat transfer to the home. Several underlayments are designed for specific use with cool roofs to help this process. These underlayments may contain thermal reflective properties, anti-glare coatings, or act as a radiant barrier to prevent heat from getting through the roof to the attic. Depending on the brand, they may be self-adhesive or need mechanical attachment. Most also act as a waterproofing membrane or layer.

Green Roof Underlayment

Installing a green roof underlayment beneath a live or growing roof costs $1,800 to $2,200 for a 2,000 sq.ft roof. Green roofs cannot use many of the same types of underlayment as other roofs because they have a thick, heavy layer of living plant matter installed on the roof. The underlayment must be completely waterproof and durable enough to withstand the weight of the plants. Most green roofs use a waterproof membrane covered in a sheet of plastic rather than a true roof underlayer. Rubber self-adhesive underlayments may be good to use in place of a waterproof membrane, provided the underlayment is waterproof and designed to hold the weight of the material.

Replace Underlayment on a Tile Roof

The cost to replace the underlayment on an existing 2,000 sq.ft. tile roof is $6,000 to $10,000. This includes removing existing shingles, replacing the underlayment, and reinstalling the tiles. These costs assume there is a 10% breakage rate on the tiles. If more tiles break during the process, your total costs can be higher. Your costs may also be higher if this is a complex roof or the roof deck needs repairs once the old underlayment is removed. The underlayment on a tile roof must be replaced every 20 to 30 years to prevent leaks and keep the roof in good condition.

Enhancement and Improvement Costs

Roof Inspection

Roof inspections are good for several reasons, including before you replace your roof or underlayment. Roof inspections can identify issues that may need to be addressed, such as problems with the roof deck, and help determine the right time to address these issues. A roof inspection can also let you know if it is time to replace the underlayment or if the entire roof may need repair or replacement. The average cost of a roof inspection is $100 to $600.

Ice and Water Shield

Ice and water shield or ice and water protector is a specific roof underlayment installed on the roof edge. It is not necessary for all installations but can make a difference in protecting your roof from leaks caused by ice dams. The average cost of this material is $0.75 to $0.90 per sq.ft. It should be installed with another underlayment.

Additional Considerations and Costs

• Warranty. Many roofing material manufacturers cover their materials with a warranty, with common warranties being from 20 to 50 years. However, you may need to follow specific conditions for the installation to meet that warranty. These conditions may include specific fasteners or underlayments. If you are unsure, speak to your installer for more information.
• Code. Roof underlayments are often required by code in many areas. In some areas, two layers of underlayment may be required to protect the roof. Speak to your installer for more information.
• Roof pitch. Your roof’s pitch can impact the cost of your underlayment replacement or installation. Roofs with a steep pitch are more difficult to work on safely, so the installation is slower. Because the material cannot be left on a steep roof, each roll must be brought up individually, increasing time and costs.