Introduction
GAF Liberty SBS Self-Adhering roofing is a two-ply roofing system designed for low-slope applications, offering a cost-effective and durable solution to water pooling and leakage issues. Unlike traditional flat roofing systems such as TPO or EPDM, this system utilizes a peel-and-stick installation method, eliminating the need for heat-welding or tar applications. The product is particularly suited for areas of a roof where water tends to remain after rainfall, such as overhangs, garages, patios, and dead valleys.
This article explores the key technical aspects of installing GAF Liberty SBS two-ply roofing, including deck preparation, underlayment requirements, installation techniques, and compatibility with other GAF roofing components. It is based exclusively on technical data provided in official documentation and installation guidelines from reputable roofing sources.
Key Technical Specifications and Installation Requirements
Roof Deck Requirements
The roof deck is the foundation of any roofing system and must meet specific dimensional and structural criteria to ensure the longevity and performance of the installed material. According to GAF's installation instructions and general roofing best practices, the deck must be clean, dry, and structurally sound.
Deck Material Options:
- Plywood: Minimum thickness of 3/8" (9.5 mm), though a 1/2" (12.7 mm) thickness is recommended for optimal performance.
- OSB (Oriented Strand Board): Minimum thickness of 7/16" (11.1 mm).
- Solid Wood Boards: Must be dry, seasoned, and no wider than 6 inches.
Deck Spacing and Shimming:
- Plywood or OSB sheets should be spaced 1/8" to 1/4" at butt joints to allow for expansion and prevent buckling.
- Solid wood boards should be butted closely together when nailing in place.
Critical Considerations:
- Any sags or depressions in the deck that could lead to ponding (water remaining on the roof for more than 24 hours after rainfall) must be corrected before installation. Ponding significantly reduces the lifespan of the roof.
- For GAF Liberty SBS, the documentation specifically states that certain systems, such as the GAF Liberty™ one-ply SBS, require a minimum of 4-ply, 15/32" (12 mm) exterior grade plywood. Contractors should contact GAF Technical Services at 1-800-ROOF-411 for confirmation on deck compatibility.
Underlayment Installation
Underlayment plays a critical role in protecting the roof deck and enhancing the performance of the roofing material. For GAF Liberty SBS, the manufacturer recommends installing a secondary water-resistant underlayment beneath the roofing material.
Purpose of Underlayment:
- Acts as a secondary water barrier.
- Prevents interaction between roofing material and natural oils or sap in some wood decks.
Installation Steps:
- Ensure the roof deck is clean and dry.
- Apply the underlayment according to the manufacturer's instructions, ensuring full coverage and secure attachment.
Compatibility:
- The underlayment should be compatible with the specific GAF Liberty SBS product being installed. Refer to the product documentation for recommended underlayment types.
Installation Techniques and Best Practices
Preparing for Installation
Before beginning the installation of GAF Liberty SBS two-ply roofing, several preparatory steps must be taken to ensure a successful and long-lasting result.
Cleaning the Roof Surface:
- The roof surface must be free of debris, loose materials, and any protruding nails or fasteners.
- If re-roofing over an existing membrane, ensure it is clean, dry, and does not exceed the maximum number of allowable layers permitted by local building codes (often three).
Removing Existing Debris or Membranes:
- Some products, such as GAF Liberty™ one-ply self-adhering SBS, require the complete removal of existing roofing materials before installation.
- This ensures that the new material adheres properly and performs as intended.
Handling and Placing Rolls:
- Distribute rolls evenly across the roof to avoid concentrated weight, which can damage the structure or cause sagging.
- Rolls should be placed at right angles to the slope to facilitate even installation and drainage.
- Avoid placing heavy loads in a single location, as this can exceed the roof's design load capacity.
Installation Process
The self-adhering nature of GAF Liberty SBS makes it relatively straightforward to install, but adherence to the manufacturer's guidelines is essential for optimal results.
Peel-and-Stick Application:
- The base layer is applied first by unrolling and pressing it firmly against the underlayment.
- The top layer is then applied over the base, reinforcing the system and improving durability.
Seaming and Overlapping:
- Ensure that seams are properly sealed and overlapped according to the manufacturer's specifications.
- This helps prevent water infiltration and ensures a continuous protective layer.
Nailing and Fastening:
- Use galvanized #11 or #12 roofing nails with 3/8" heads.
- Nails must penetrate at least 3/4" into the wood deck or be "just through" plywood or OSB.
- Avoid using nails that are too short or too thin, as this can lead to nail withdrawal and wind damage.
Adhesive Application:
- If required, apply adhesive evenly and avoid over-application, which can lead to runout and blistering.
- Adhesive should be applied in a thin, even layer to ensure proper adhesion without compromising the integrity of the material.
Compatibility and System Integration
Warranties and Bundling with GAF Products
GAF Liberty SBS is part of the broader GAF roofing system and can be integrated with other GAF components to provide a comprehensive solution for low-slope roofing.
Warranty Benefits:
- When installed alongside other GAF materials, Liberty SBS can be included in GAF's roofing warranty packages.
- These warranties cover both workmanship and material defects, providing added assurance for homeowners and contractors.
System Integration:
- The product is compatible with GAF starter strips, drip edges, and other roofing accessories.
- This allows for a seamless integration during full roof replacements or targeted repairs.
Cost and Project Considerations
Cost Range:
- In areas like Myrtle Beach, South Carolina, where low-slope roofs are common, GAF Liberty SBS is often used for specific areas such as carports or patios.
- The average cost for such projects ranges from $3,000 to $6,000, depending on the size of the area being covered.
Project Factors Affecting Cost:
- Size of the area.
- Number of stories on the home.
- Delivery method for roofing materials.
Installation Timing:
- The ideal time to install GAF Liberty SBS is during a full roof replacement, which allows for better integration with other roofing components.
- However, in cases of active leaks or ceiling staining, immediate installation is recommended to prevent further damage.
Common Installation Scenarios and Use Cases
GAF Liberty SBS is particularly well-suited for specific roofing applications where water pooling and leakage are common concerns.
Low-Slope Roofs:
- Ideal for areas with a roof pitch of less than 2:12.
- Offers superior water shedding compared to traditional flat roofing materials.
Overhangs and Dead Valleys:
- Frequently used in areas where water tends to collect or flow irregularly.
- Provides a reinforced, two-ply protection layer that resists tearing and physical damage.
Garages and Porches:
- Commonly applied to detached structures such as garages or patios.
- Offers a cost-effective solution for areas that do not require full roof replacement.
Repair Scenarios:
- Can be installed in conjunction with partial roof repairs.
- Particularly useful when leaks or water damage are localized to a specific area.
Technical Advantages and Limitations
Advantages
Durability and Resistance:
- The two-ply construction offers enhanced resistance to tearing and physical damage.
- The SBS material is more durable than ice-and-water shield and is not affected by prolonged UV exposure.
Ease of Installation:
- The peel-and-stick method eliminates the need for heat-welding or tar applications.
- Reduces labor costs and installation time.
Cost-Effectiveness:
- Generally less expensive than traditional flat roofing materials such as TPO or EPDM.
- Provides long-term protection at a lower initial investment.
Aesthetic and Maintenance:
- Provides a clean, finished look without the need for extensive maintenance.
- Reduces the likelihood of future repairs and replacements.
Limitations
Roof Deck Requirements:
- Certain installations require a minimum 15/32" (12 mm) exterior grade plywood deck, which may necessitate additional preparation or replacement of existing materials.
Weight and Handling:
- A single pallet of roll roofing can weigh up to 2,100 lbs.
- Proper distribution of weight is essential to avoid structural strain on the roof.
Compatibility Restrictions:
- Some products, such as the one-ply GAF Liberty SBS system, may require a clean, primed surface and the complete removal of existing roofing materials.
Climate and Code Compliance:
- Installation must adhere to local building codes and climate requirements.
- In some regions, such as South Carolina, low-slope roofs must be covered with specific materials to meet code standards.
Best Practices for Longevity and Performance
To maximize the lifespan and performance of a GAF Liberty SBS two-ply roofing system, the following best practices should be followed:
Follow Manufacturer Instructions:
- Adhere to all installation guidelines provided by GAF, including underlayment recommendations, deck preparation, and adhesive application.
Use Approved Fasteners and Adhesives:
- Only use galvanized, zinc-coated steel, or aluminum roofing nails that meet the specified gauge and penetration requirements.
- Apply adhesive in a thin, even layer to avoid blistering and runoff.
Ensure Proper Drainage:
- Address any depressions or sags in the roof deck before installation to prevent water ponding.
- Install the roofing material at right angles to the slope to facilitate even drainage.
Avoid Overloading the Roof:
- Distribute roll weight evenly across the roof to prevent concentrated loads from exceeding the roof's design capacity.
Seal All Seams and Edges:
- Ensure that all seams, overlaps, and edges are properly sealed to prevent water infiltration.
Inspect and Maintain Regularly:
- Conduct periodic inspections to identify and address any signs of wear, damage, or deterioration.
- Clean the roof surface regularly to remove debris that can trap moisture and reduce performance.
Conclusion
GAF Liberty SBS two-ply roofing is a durable, cost-effective solution for low-slope roofing applications. Its peel-and-stick installation method, combined with a two-ply construction, offers enhanced resistance to water pooling, tearing, and physical damage. When installed according to the manufacturer's guidelines, this system provides a long-lasting, low-maintenance roofing solution that integrates well with other GAF products.
Key considerations for successful installation include proper deck preparation, underlayment application, fastener selection, and adherence to weight distribution best practices. By following these technical guidelines, contractors and homeowners can ensure a high-performance roofing system that meets both functional and aesthetic needs.