What is the Advantage and Disadvantage of Self Adhesive Felt Strips

Roofing underlayment is a critical component of a healthy roof system. The roofing underlayment acts as a second layer of defense for the roof, prevents water intrusion from wind-driven rain, protects the structure prior to roofing installation, and helps to reduce air infiltration.

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There are a range of roofing underlayment options available, offering varying levels of performance. It’s important to evaluate which underlayment is most suited to your project, considering factors like roofing materials, climate, budget, and more.

What to Know About Popular Roofing Underlayments

Here are factors to consider when deciding on a roofing underlayment:

Pros & Cons of Roofing Felt Paper

The most common roofing underlayment, and one of the oldest, felt paper is created by saturating paper or fiberglass mat with asphalt. Felt paper is one of the least expensive options and is readily available. It also is vapor permeable, so it will allow moisture from the attic to escape.

Felt paper can be challenging during installation for a number of reasons: It damages easily, it can only be left exposed to UV rays for a short period of time, and moisture can cause it to wrinkle, preventing the shingles above from lying flat. Felt paper also is challenging to use as an air control layer.

Pros & Cons of Synthetic Roofing Underlayment

Synthetic roofing underlayments are mechanically attached, laminated polypropylene or polyethylene plastic materials. They provide better performance than traditional felt paper.

Synthetic roofing underlayment offers an easier installation option versus felt paper because it’s stronger, allows for increased UV exposure, is thinner and lighter weight, comes in wider rolls, and has better walkability. Synthetic options also typically have high heat tolerances.

In exchange, synthetic roofing underlayments carry a high price tag versus felt paper. They also are not vapor permeable, which can lead to trapped moisture from the attic, and they do not self-seal around fasteners to provide an air control layer.

Also, keep in mind that not all synthetic underlayment products are compatible with every type of roofing material. Before starting your project, check the manufacturer’s recommendations to ensure the underlayment is suitable for the roofing material you plan to use.

Pros & Cons of Pre-Weatherized Sheathing

Pre-weatherized sheathing combines two products in one—a sheathing with an integrated weather barrier—allowing for faster roof construction and a quicker dry-in time. It’s a versatile option and can also be specified in insulated panel options.

Though installation combines two steps, pre-weatherized sheathing does still require precise taping at seams. Installers also must treat the coated layer with care to prevent damage. Over-driven fasteners can create an entry point for water.

Pros & Cons of Self-Adhered Asphalt Roofing Underlayment

An ice and water protector sometimes referred to as “peel and stick,” self-adhered asphalt roof underlayment is a waterproof membrane developed to protect vulnerable areas on a roof from ice and water damage. Because it is vapor impermeable, this type of underlayment may not be appropriate for covering an entire roof.

Self-adhered asphalt underlayment installs fast and is resistant to wind uplift. And because of its adhesive backing, it self-seals around fastener penetrations.

Some drawbacks to self-adhered asphalt roofing underlayment include a heavier weight for carrying, a short UV exposure time, and temperature sensitivity.

Pros & Cons Self-Adhered Acrylic Roofing Underlayment

Synthetic underlayment and an acrylic adhesive combine for a powerful roofing underlayment option. Self-adhered acrylic underlayment is resistant to wind uplift, it is vapor permeable with drying potential for the full roof application, and the acrylic adhesive bonds well to all common materials. Plus, it self-seals around fasteners to provide an air control layer.

The higher performance of a self-adhered acrylic roofing underlayment does come with a higher cost. Installers may need assistance to handle wider rolls, and they’ll need to apply pressure to the underlayment to activate the adhesive.

It’s important to note that self-adhered underlayment is equal to ice and water shield; not all peel-and-stick underlayments are the same. Also, some self-adhered products, like VaporDry SA, have total adhesive coverage on the underlayment, while others only provide adhesive in strips of bands; having one with complete adhesion coverage is critical to meet performance expectations.

Pros & Cons of Ventilated Roof Mats

Roof ventilation mats are designed to create an airspace/cavity to promote air flow in all directions between the roofing material and the sheathing below. They are lightweight and easy to handle, conform to various roof shapes and contours, and are suitable for roofs with steep slopes, multiple angles, or unique architectural features. By facilitating air movement within the roof assembly, ventilation mats contribute to improved energy efficiency. They also effectively manage moisture by allowing air to circulate freely between the roof sheathing and the roofing material.

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Roofing mats come at a higher cost than traditional underlayments, and they cannot be used for all shingle types. Installers should avoid over-tightening fasteners to avoid compressing the mats.

How to Choose the Right Roofing Underlayment for your Project

When weighing the pros and cons of each type of roofing underlayment, you’ll want to consider a number of factors:

• Roofing type: What underlayment does the manufacturer of the roofing material recommend? Ensure you’re following manufacturer requirements or you could risk voiding the warranty. (Learn about ideal roofing systems for cedar, metal, and asphalt roofs here.)
• Cost: Cost is always going to be one of the biggest considerations. But it’s important to not let budget completely dictate your decision. Ensure homeowners understand the importance of building a quality, high-performance roof system. The roof is the first line of defense for the house, so it’s worth making a larger investment even if it means sacrificing an interior design feature.
• Climate: Not all roof systems require all the bells and whistles if you don’t need them. In much of Arizona, for example, moisture isn’t as big of a concern, and felt paper might be a suitable choice. But in Florida, which is plagued by wind and rain, you have to assume rain will get in under the shingles and therefore a more robust underlayment, such as VaporDry SA self-adhered acrylic roofing membrane, will be worth the investment.
• Attic: If the home’s attic is conditioned, moisture from the rising heat within will need a way to escape. A vapor-permeable underlayment such as VaporDry SA will help the moisture exit the roofing system, thereby helping the system to dry out and protecting the wood from rot.
• Installation trade-offs: Felt paper is a go-to choice because it meets code and is less expensive. But it’s also a hassle on the jobsite, prone to tearing and wrinkling. The extra steps to fix these issues may not be worth the lower price.

Choose an Underlayment to Protect the Roof Investment

The roof is a home’s first line of defense. No single roofing material is designed to be waterproof—they’re water-shedding—so water will get through and underneath. That’s why you need a robust underlayment underneath to protect the sheathing and the structure from moisture intrusion and the resulting rot and decay.

Remember—the roof is only as strong as what’s under it!

Trent Cotney, FRSA General Counsel, Cotney Construction Law

Over the past 15-20 years, the roofing industry has made a significant shift away from traditional asphalt felts to other types of underlayments, including self-adhering direct to deck membranes. In Florida, under the guidelines of the Florida Office of Insurance Regulation, to qualify for a Secondary Water Resistant (“SWR”) discount on your homeowner’s insurance, the underlayment you must use is a peel-and-stick membrane bonded directly to the roof sheathing. While the
peel-and-stick products that qualify as SWR can also be installed on top of a layer of felt, only installations that are attached directly to the wood sheathing can qualify for an SWR insurance discount. Thus, it’s possible to use the correct product but install it on top of a layer of felt in a way that still does not obtain an insurance discount because it’s not directly attached to the sheathing. There is nothing wrong with this installation; it just does not qualify for an insurance discount.

Use of these peel-and-stick membranes can also present significant challenges when roof removal is required. The Asphalt Roofing Manufacturers Association issued a technical bulletin recommending that if one layer of self-adhering underlayment is in place and cannot be removed without damaging the roof deck, installing a second layer over the existing self-adhering underlayment is permissible. In Florida, this recommendation to leave existing self-adhering underlayment in place may conflict with the Florida Building Code. Specifically, the Florida Building Code Existing Building Section 706.7 requires that when a roof covering on an existing site-built single-family residential structure is removed and replaced, the roof decking must be verified and attached per section 706.7.1. Regarding SWR, Florida Building Code Existing Building Section 706.7.2 states in relevant part as follows:

706.7.2 Roof secondary water barrier for site-built single family residential structures

A secondary water barrier shall be installed using one of the following methods when roof covering is removed and replaced:
1. In High-Velocity Hurricane Zone regions:
    a. All joints in structural panel roof sheathing or decking shall be covered with a minimum 4 inch (102 mm) wide strip of self-           adhering polymer modified bitumen tape applied directly to the sheathing or decking. The deck and self-adhering polymer             modified bitumen tape shall be covered with one of the underlayment systems approved for the particular roof covering to be         applied to the roof.
    b. The entire roof deck shall be covered with an approved asphalt impregnated 30# felt underlayment or approved synthetic              underlayment installed with nails and tin-tabs in accordance with Section .2, .3 or .4 of the Florida Building              Code, Building. (No additional underlayment shall be required over the top of this sheet.) The synthetic underlayment shall            be fastened in accordance with the manufacturer’s recommendations.

Although they have many benefits, self-adhering membranes present a significant challenge in complying with these and other provisions of the Florida Building Code if removal cannot be accomplished without damaging the deck. In many, if not most cases, the peel-and-stick membrane has adhered so solidly to the substrate it can not be removed, and replacement of the entire deck may be necessary.

In light of this possibility, roofing contractors should take steps to protect themselves from this condition when contracting with owners, in particular through the scope of work provisions in their contract. Most litigated disputes arise out of, or relate to, problems with the scope of work. Often, contractors are seeking payment for extras that were not originally contemplated in the contract. However, the owner may believe that the contract included all roofing work to be performed on the project.

In this instance, a roofing contractor who is providing a roof replacement for an owner may encounter self-adhering underlayment that cannot be removed without replacing the whole deck. The roofing contractor incurs additional costs for the deck replacement and seeks to charge the owner for the additional charge. However, the contract does not specifically detail the cost or price for replacing the deck and the owner objects stating that the contract did not mention that the decking would be an extra charge.

This example demonstrates the need to specifically define the scope of work for a roofing project to factor in the possibility of having to remove a previously applied peel-and-stick membrane. If replacement of decking, fascia, soffits or other work are extras, the contract should not only state that those items will be extra charges, but indicate the method of pricing for the additional work (e.g., time, materials).

It is also important to note the nature and limits of any workmanship warranties provided by the roofing contractor to the owner, as the owner may misconstrue the scope of warranty work if it is not specifically spelled out in the contract documents. Other contract provisions that may need to be revised to take into account potential extra work caused by removing a self-adhering membrane include delay and damage provisions, change order provisions, and disclaimers for pre-existing and unexpected conditions.

While self-adhering underlayment has many demonstrable benefits over its traditional asphalt felt predecessors, roofing contractors can run into trouble when a roof replacement requires removing the old peel-and-stick membrane and most likely the entire roof deck. As more and more roofs that had self-adhering underlayment installed 15 to 20 years ago are starting to be replaced, contractors are cautioned to take steps now to contractually protect themselves in case such a situation arises to hopefully avoid a potentially costly dispute with an owner down the road.

FRM

Disclaimer: The information contained in this article is for general educational information only. This information does not constitute legal advice, is not intended to constitute legal advice, nor should it be relied upon as legal advice for your specific factual pattern or situation.

Trent Cotney is an advocate for the roofing industry, General Counsel of FRSA and a Florida Bar Board Certified Construction Lawyer. For more information, contact the author at 866-303- or go to www.cotneycl.com.

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