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May 8, 2019 - 10 min

Cover Boards: Ease Of Installation and Stellar Performance Make High-Density Polyiso an Attractive Product Choice

Published by Justin Koscher

When planning for a roof on a new building or reroofing an existing structure, finding the right products that balance cost and performance is a tall order. Whether it’s replacement on an older building or new construction, the right roof system can save money and dramatically improve building performance.

Many architects, specifiers and contractors include cover boards in their roof designs to enhance overall system durability and lower long-term maintenance costs, particularly for low-slope commercial roof applications. There are many cover board products currently available, ranging from traditional sheets of gypsum to cement boards to highly engineered polyisocyanurate (or “polyiso”) technologies. These products are an important component in roof systems, providing a rigid substrate for the rest of the roof.

High-density polyiso cover boards are increasingly being used because they offer the following:

  • Compressive strength that protects the roof system from traffic, puncture, hail damage, and other weather impacts.
  • 2.5 R-value insulation that helps meet updated energy code requirements.
  • Rigid boards with a coated glass facer that lies flat, improving building aesthetics.
  • Lightweight boards that are easy for installers to handle and cut to size.
  • Improved roof system durability and longevity.

In addition, high-density polyiso cover boards are manufactured with coated glass facers that provide well-recognized versatility during installation, as well as service-life durability. Adding a cover board can enhance the long-term performance of a commercial roof system in addition to providing many advantages.

Benefits of High-Density Polyiso Cover Boards


High-density polyiso cover boards, on average, weigh 66 to 80 percent less when compared with same-thickness gypsum products. Individual boards are light enough to be carried by a single worker, reducing manpower requirements.

Water Resistance

The water absorption by volume of high-density polyiso cover boards is about four percent—much lower than traditional boards. The boards will not rot or dissolve; they maintain their integrity under adverse weather conditions.

Fewer Truckloads

High-density polyiso cover boards can be shipped with about three times more square feet per truckload, thus requiring fewer trucks, which leads to fuel and transportation savings as well as reduced traffic congestion on job sites.

Reduced Product Staging Time

High-density polyiso cover boards require less crane time with lower hoisting, loading, and staging costs. The cover boards are easier to carry and maneuver around the roof. Pallets need not be broken or redistributed should they need to be placed with other products.

Ease Of Cutting

Unlike traditional gypsum boards which require heavy-duty saws or cutters to resize, high-density polyiso cover boards can be easily scored and cut using a utility knife. A single worker can measure and cut boards to size, increasing the productivity of the roofing team.


When considering a building’s structural design, high-density polyiso cover boards will contribute less dead load to a roof than other alternatives. These lighter dead loads can add up to savings in structural costs for new construction and fewer headaches when reroofing an existing building.

Greater R-Value

In addition to providing suitable protection to a roof system, high-density polyiso cover boards contribute extra thermal resistance to the roof, and can provide two to five times more R-value than gypsum-based products.

Virtually Dust-Free

High-density polyiso cover boards are made of the same polyisocyanurate found in many insulation products and do not generate the dust produced by gypsum products during cutting. This decreases potential seam contamination during the installation of the waterproofing layer. Less mess equals better productivity for installers, while the absence of silica particles in the air enhances worker safety.


High-density polyiso cover boards resist mould growth when tested under ASTM D3273. This makes high-density polyiso cover boards highly suitable for applications prone to elevated moisture conditions.


Higher compressive strength and flexibility in high-density polyiso cover boards improve a roof’s resistance to damage from foot traffic, heavily loaded carts, dropped hammers, and other tools.


High-density polyiso cover boards can be used in new construction, reroofing, and recover applications. They are suitable for mechanically attached, adhered, and ballasted roof assemblies.

Agropur – Dairy Cooperative

Agropur Cooperative is a North American dairy industry leader founded in 1938. In 2016, the dairy cooperative Agropur opened a new, two-story office building in Longueuil, Québec that went on to earn a Leadership in Energy and Environmental Design (LEED) certification from the Canada Green Building Council in 2017. The ambitious project allowed Agropur to consolidate four existing offices into a single, unified 23,226-m2 (250,000 square foot) campus in a tranquil wooded environment adjacent to its existing distribution center and quality assurance labs.

The new campus offers a state-of-the-art office environment, underground parking for 700 cars, with carefully designed amenity areas, including a cafeteria, gymnasiums, and relaxation and conference rooms. Conceived as a series of narrow wings, the building layout takes advantage of plentiful windows to bring in natural light and continuous views of the surrounding forest.

The building was designed by Le Groupe Architex and the roof was installed by Truchon Roofing. Since the exterior of Agropur’s building is glass, care was taken in the plans to facilitate efficient regular window washing. The roof needed solid bases to protect it from the heavy equipment and accompanying workers who would launch from the roof.

The architect chose SOPREMA high-density polyiso cover boards to ensure that roof materials installed below the cover board would not be damaged by the additional loads and traffic. Unlike other types of cover board, the high-density polyiso cover boards also added thermal resistance, contributing to improved energy efficiency.

“The architect was looking for something solid and durable under the SBS-modified bitumen that would keep the lower roof materials from being damaged by the extra loads.” said Sylvain Dion, Architectural Sales representative at SOPREMA. “They had been considering the cement board, but when they learned more about the durability and added thermal value of the high-density polyiso cover board, they selected it for the roof.”

During installation, Truchon Toiture et Imperméabilisation noted that the high-density polyiso cover boards were light and rigid, and much easier to work with than other cover board options.