ORN THE ONLY SOURCE FOR PROFESSIONAL ICI ROOFING CONTRACTORS IN ONTARIO   ONTARIO ROOFING NEWS – WINTER 2017  13 Counterflashings serve as rain shields and provide additional protection to the top of the flashing material. There are two primary types of counter- flashing application: surface- mounted and integral. Surface-mounted counter- flashings are fastened to the verti- cal substrate above the top of the flashing material. A bead of sealant is applied over the top of the coun- terflashing and may be the sole line of defence against water entry. Because sealant materials require continual maintenance/repair, this type of attachment is not always recommended. In order for this application to be most effective, al- ways terminate and seal the top of the roofing flashing. This gives two lines of defence against water intru- sion to the roofing flashing. Integral wall counterflashings are set into a reglet joint that is cut into the wall, masonry, stucco or metal, and uses the groove to secure the metal within the wall assembly. These types of attach- ments provide long-term weather- proofing performance because the counterflashing is sealed within the joint. Sealant may be applied at the top of the counterflashing in some cases. However, unlike the surface-mounted application, the sealant is the secondary line of defence and may not be recom- mended. This type of application provides low/no maintenance throughout the life of the system and is highly recommended. Best Design Practice. When possible, the reduction of roof- top equipment is beneficial to the long-term success of a roof system. Fewer penetrations equal lower probability of leaks and help to create no/low maintenance. On re-roof applications it is rec- ommended that all abandoned equipment be removed. The cost of new decking in the abandoned area is usually offset by the elimi- nation of the application of the required curb flashing. Perimeter Flashings. The most common type of wind- uplift damage occurs at raised edges, or perimeter flashings. The IBC Code now requires that all metal applied at the perim- eter of the building be certified by ANSI/SPRI ES-1. Fastening of the perimeter metal must be in compliance with ASCE wind- uplift calculations. The perimeter edge metal shall extend over the base flashing and act as a shield over the flashing joints. There should be a separa- tion layer between the edge metal and the membrane to provide added waterproofing protection and to prevent splits from dif- ferential movement between the metal and the membrane. This condition is most prevalent in colder climates where splits occur at these locations. The edge metal is an important element at this component because it adds to the waterproofing of the system by covering the flashing joints, acts as a termination of the membrane, serves as a rain shield, and provides a surface for anchor- age of the fascia metal. Top of Flashing Material. Ap- ply a termination bar (1/8” x 1”) at the top of the flashing mate- rial to eliminate flashing slump- ing and displacement. Additional waterproofing can be achieved at flashings by sealing the top of the flashing material and termination bar. For modified bitumen systems this can be completed by applying a multi-course layer of fabric and roof cement. For single-ply applica- tions this is achieved by applying a water cut-off sealant. Flashing Seams. The most common maintenance require- ment at flashings is at flashing seams. Openings and splits in seams occur from weathering and building movement. On modified bitumen roofs, apply manufac- turer-approved material over the seams – applied in adhesive, heat- welded or self-adhered. Applying coating at flashing seams and/or entire flashing surface to prevent UV degradation is recommended. On single-ply systems apply man- ufacturer-approved material over the seams especially at changes in direction for extra protection. Sheet Metal. Sheet metal com- ponents are exposed to the ele- ments more often than flashing materials. These are typically the first line of defence in a flashing system. The type of material ap- plied has a significant impact on their performance and mainte- nance requirements. It is recom- mended that the designer specifies a high-grade metal finish, such as Kynar 500/Hylar 5000, or a stain- less steel that prevents corrosion and finish deterioration for no/ low maintenance. Sheet Metal Fastening. Improp- er fastening of perimeter sheet met- al can create continual roof prob- lems. Depending on the fastening frequency and pattern, this may allow for movement of the sheet metal, which can fracture the mem- brane materials under sheet metal, providing potential for leakage and ongoing maintenance. Perimeter sheet metal should be fastened in a pattern and frequency that will restrain this movement. Insufficient fastening could also contribute to wind damage and/ or blow-off. Fastening of the edge metal must be in compliance with ASCE wind-uplift calculations. Fasteners with corrosion-resistant coatings should be specified be- cause they provide longer service life over the commodity-grade zinc-coated fasteners. Metal Joints. The most com- mon seal on metal joints (parapet coping, counterflashings, expan- sion joint covers, etc.) is a bead of sealant. Due to weathering and continual expansion/contraction of the metal, these sealant joints often fail within five to seven years and become the source of moisture infiltration. To eliminate continual maintenance at these locations the designer should specify a sealant tape application. The sealant tape is self-adhered for easy application and most manufacturers provide these materials in widths used for this purpose. On copings always continue the roofing membranes up and over the parapet walls as a primary waterproofing. Accessories Roof accessories are materi- als and products for various pen- etrations such as vents, pitch pans, equipment supports, skylights, roof hatches, etc. They are integral to the waterproofing of the system; how- ever, they are typically not covered by the warranty. In the past these types of products and assemblies were fabricated in the field with metal and/or membrane with roof cement and sealants. These appli- cation methods typically required a fair amount of maintenance, but recent advancements in design and material technology have decreased the level of maintenance needed at these penetrations. Pitch Pans. Pitch pans are typi- cally used to flash a penetration through the roof, and often require continual maintenance. Pitch pans lose their fill material with time; in addition, the material will often harden and shrink away from the penetration, allowing potential for water entry. To provide low/no maintenance design, a sheet metal cone/umbrella (cover) should be fabricated and applied over the pitch pan. This will aid the dissipa- tion of fill material as well as pro- tect from UV exposure and pro- vide added waterproofing. Prefabricated Roof Acces- sories. There is now a plethora of manufacturers that have developed prefabricated roof accessories for 87 Bakersfield St., Toronto, Ontario, M3J 1Z4 Tel: 416-787-0649 Fax: 416-787-0640 Email: service@crawfordroofing.ca Proud Member of: - PMI Programs - Metal Roof Systems - Emergency Services - Roof Top Decks - Modified Bitumen - Waterproofing - Roof Anchors - Sheet Metal Committed to Safety, Quality & Service for over 30 years Services Fully Bonded & Insured - Built Up Systems - Restoration - Single Ply - Inverted Industrial Commercial Institutional Roofing Solutions all types of penetrations that can be used with most roof membrane sys- tems. This eliminates the use of field- fabricated materials and, when used, decreases the need for maintenance in these areas. RoofMaintenanceMaterials In the past decade roof mate- rial manufacturers have made a concentrated effort to provide a full range of maintenance mate- rials that complement their roof systems. The most significant ad- vancement is liquid membrane flashing systems. These materials can be used in the application of the system or as maintenance materials that are used to extend the service life of the existing system. Liquid membrane flash- ing systems are flexible flashing materials that are specifically designed to work with a variety of bituminous roofing systems. These materials can be used as weatherproofing on a wide range of flashing details. They typically consist of a two-part system con- taining a polyester reinforcing scrim and a flashing liquid of various products. These systems are ideal for maintenance appli- cations because they are liquid applied and offer superior bond- ing and durability properties for a long-term service life. These materials can easily be applied in any flashing location. Their main application benefits are that the primer dries rapidly – allowing the application process to move quickly – and the mate- rial can be mixed in the original container or in two-component cartridges that mixes during the dispensing process. The materi- al cures in all temperatures and forms a seamless barrier that provides exceptional strength and flexibility. These materials can be used with all bituminous systems and hybrid systems for use on new and re-roof projects, metal roof- ing, paver systems and historic preservation and restoration. The main attributes of these materials are as follows: •  Low permeability; •  Wide application tempera- ture range; •  Low cost per penetration; •  Minimal odour release; •  Great tensile strength; •  Enhanced workability; and •  Great crack bridging capabilities. The designer should consult with the manufacturer to ensure that the correct materials are used and that they are applied in ac- cordance with the manufacturers’ specific requirements. It is the designer’s desire to design a roof system for long- term performance. Maintenance elements should be considered in unison with the original roof system design. If no/low mainte- nance elements are encompassed in the original design, the building owner can manage the roof sys- tem with relative ease and expect a long-term solution for the protec- tion of their asset. *Source: American Institute of Architects