Ballasted Roofs – A New Look at an Old System
November 6, 2019
While ballasted roof systems aren't as popular today as they used to be, they are still being installed successfully across the country.
  
Stone-ballasted roof systems began appearing sometime in the early 1970s. While they appear superficially similar to built-up roofing (BUR), there are major differences between the two systems. Both are topped with rocks, but BUR uses a thin layer of pea gravel or crushed stone no larger than a quarter-inch diameter partially embedded into the asphalt topcoat to protect it from the sun's UV rays. In a ballasted roof, the stones are much larger - at least an inch in diameter - and applied much more heavily. In fact, the weight of the stone ballast is what holds the roof components in place. The weight can vary from 10 pounds per square foot (the minimum allowed by code) to 25 pounds or more. The most common ballasted assembly was a loose-laid EPDM membrane over a rigid insulation board.

By the 1980s, designers were integrating concrete pavers into ballasted roof designs, creating access paths, pedestrian walkways, and even rooftop plazas. When the green building movement came along in the late 1990s, it was natural to transition the ballast from stone to soil, creating vegetated or "green" roofs.

Ballasted roofs are loose-laid; this means the contractor can assemble all the components, including the roofing membrane and insulation, without fastening them to each other or the roof deck. Membrane seams are sealed, of course, and the waterproofing layer is secured to the parapet and at roof penetrations, but it isn't adhered to the roof deck or the layers beneath it.

By eliminating nearly all the adhesives and fasteners other assemblies require, ballasted roofs typically cost less and are quicker to install than other systems. EPDM is popular because it can be ordered in large sheet sizes, which minimizes seaming. TPO and PVC are also popular as single-ply roofing membranes under ballast.

For designers, ballasted roofs provide a natural-looking surface that blends well with a range of architectural styles. With paver-ballasted designs, the roof can become a plaza, patio, or other usable outdoor space suitable for recreation, walking, or relaxation.

 For the building owner, ballasted roofs are durable and long lasting. Stones or concrete pavers protect the waterproofing layer from UV rays, hail, and foot traffic. If repairs are needed, the loose-laid layers are easily taken up. And at the end of the roof's designed lifespan, the lack of adhesives ensures the membrane will be fully recyclable.

Advantages

Economy: Ballasted roofs use economical materials and are among the fastest to install. In fact, they have one of the lowest lifecycle costs of any roofing system on the market today.

Scheduling:
These roofs can be installed in a wide range of weather and temperature conditions, and close in the building envelope faster than most other systems. For occupied buildings, there are no offensive smells associated with the install.

Aesthetics:
Ballast can vary from large round cobblestones to pavers. This natural look is appealing to many building owners and architects. Rock can be combined with pavers to provide a variety of textures and utilitarian purposes.

Amenity Space:
With proper planning, ballasted roofs are suitable for plaza decks, walking paths, recreation areas, and other uses.

Energy Efficiency:
Ballasted roofs reduce heating and cooling loads. A system with a weight of 17 pounds per square foot saves as much energy as an ENERGY STAR-rated reflective roof.

Fireproof:
Stone and concrete are virtually fireproof, so ballasted roofs provide the highest fire rating available. Class-A fire resistance can be achieved without gypsum board underlayments or expensive fire-retardant chemicals.

Durable:
The stone or concrete pavers also provide protection from UV rays, hail, foot traffic, and extreme temperature fluctuations.

Ease of Repair:
Removal and re-installation of the ballast and insulation is easy, and both can be reused. No adhesives or fasteners are used, so it's easy to separate the components. Even in a complete replacement of the waterproofing membrane, the ballast stone or concrete pavers can be reinstalled.

Recyclable:
Most of the components are reusable and/or recyclable. Rocks, pavers, and rigid insulation board can be reused. The unadhered membrane is easy to remove and recycle.

Stormwater Management:
Green roofs and other options like Carlisle's Stormwater Retention Option can retain as much as 65% of the rainwater that falls during a storm. This can help owners and developers reduce fees.

 Consult the EPDM Specification on the Carlisle SynTec Website here or consult the Ballasted Stormwater Retention Brochure here or contact Craig Tyler at [email protected] for further questions.
January 8, 2020
Air and Vapor Barriers for Roofs

In 2012, the International Energy Conservation Code (IECC) introduced the continuous air barrier requirement for new commercial construction. This meant that air and vapor barriers were now required for walls, and they must be tied to both the roofing assembly and the foundation. For years, many architects and designers only utilized an air and vapor barrier on the roof deck for high-humidity occupancies, such as swimming pools or food processing facilities. But the new requirement meant taking a hard look at the needs of all buildings and what a roof assembly could do for the building envelope. A single-ply membrane, as stated in the IECC and as tested utilizing the ASTM E2178 standard, qualifies as an air barrier and can satisfy the requirement for an air barrier on any given project. So why would you consider adding an additional air and vapor barrier to the roofing assembly? There are a couple of very simple reasons: Reason 1: Air Intrusion. While a properly installed roofing system will not allow air leakage (e.g., conditioned indoor air from exiting the building thermal envelope), it does allow air movement within the roof assembly. As the single-ply roof membrane is on the top of the assembly, indoor conditioned air can infiltrate into the roofing system and travel into the layers of insulation or cover boards. Why is this an issue? See Reason 2… Reason 2: Moisture Migration. Adding a deck-level air and vapor barrier is a great solution to prevent air intrusion and moisture migration. This also allows the wall air and vapor barrier to be tied together at the deck level, which allows the roof to be replaced more easily in the future. The contractor will not be modifying the continuous air barrier when re-roofing, as the roof is no longer that barrier. Carlisle SynTec provides many options for deck level air and vapor barriers: VapAir Seal MD for steel deck construction, direct to deck; VapAir Seal 725TR for Concrete Decks; VapAir Seal Flashing Foam for sealing around penetrations such as pipes; Go to the Air and Vapor Barriers Product Page on the Carlisle SynTec website for more information, specifications, and details. Contact Craig Tyler at [email protected] with further questions.

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December 18, 2019
Cold Weather Installation Tips Part 2 - Membranes and Insulation

As discussed in the previous SpecTopic, "Cold Weather Installation Tips Part 1 - Low-VOC Bonding Adhesives and Primers", specifying and handling of building envelope products is challenging during the colder winter months. Single-ply membranes and rigid insulation boards need some extra consideration, as they can be adversely affected by outside temperatures. For starters, all membranes will need time to "relax" after being unrolled from the original packaging; this applies to EPDM, TPO, PVC and KEE HP. It is also suggested that membrane widths be limited to a maximum of 10 feet for adhered roofing systems. Treat flashing products and accessories as you would adhesives and primers, by utilizing heated storage enclosures or "hot boxes". This practice is strongly recommended when ambient temperatures are expected to fall below 40°F for an extended period of time. In all applications, but especially in cold conditions, insulation and underlayments must be stored so that they are kept dry and protected from the elements. Insulations should be stored on a skid, covered with a breathable tarp, and weighted to prevent wind damage. In winter months, ice and frost can form on the membrane. This can be difficult to see and can remain on the roof well into the day, especially on white membranes. This can be especially hazardous when working near the edge of the roof. Additionally, frost on metal edges and copings can create a very slick surface and cause ladders to slide and shift. Never step onto a metal coping when it is frost- or snow-covered. So for your next cold weather specification for single-ply membranes and rigid board insulation, include some installation precautions as mentioned. Contact Craig Tyler at [email protected] with further questions.

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December 4, 2019
Cold Weather Installation Tips Part 1 – Low-VOC Bonding Adhesives and Primers

As temperatures fall and winter approaches, specifying and handling building envelope products – especially adhesives and primers – becomes a concern. Low-VOC adhesives and primers contain more water than standard adhesives and primers and can be adversely affected by outside temperatures. When specifying a low-VOC bonding adhesive or primer for a winter installation time frame, make sure to include information in the specification regarding cold weather application. This should include heated storage enclosures, or "hot boxes", for jobsite adhesive storage. This practice is strongly recommended when ambient temperatures are expected to fall below 40°F for an extended period of time. Adhesives and primers should be stored in locations where temperatures are between 60°F and 80°F. While working with adhesives, they should be rotated in hot boxes to ensure the temperature of the product stays above 40°F. Adhesives may appear gelled or lumpy when left for extended periods of time at temperatures below 40°F. If this occurs, return the material to room temperature for a minimum of 24 hours prior to use. In all applications, but especially in colder conditions, make sure you achieve the proper coverage rates for the adhesive or primer being used. Following coverage rates for Low-VOC adhesives and primers allows proper flash-off and reduces the trapped solvents which could lead to membrane blistering. For applications in very cold temperatures, Flexible FAST™ Adhesive may be necessary. Flexible FAST is a two-part polyurethane foam adhesive which is spray-applied and used with a fleece-backed single-ply membrane. The advantage of this system is that it can be sprayed using 15- or 50-gallon drums of Part A and Part B, which can be heated using drum or band heaters. This allows the material to stay warmer during application and lowers the minimum application temperature to 25°F. So for your next cold weather specification of Low-VOC adhesives and primers, include some installation precautions as mentioned. Contact Craig Tyler at [email protected] with further questions.

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