1. What’s the difference between the use of an exposed fastener as well as standing seam roofs made of metal?
There are some fundamental differences between the installation method of hidden and exposed roof panels. One of the most obvious differences is the method used to attach panels. Exposed fastened systems are based on an attachment device (most usually screws) cutting through the metal, and then connecting to the structure below.
However, standing seam (or concealed fastened roofs) generally rely on attaching clips to the substructure, and later connecting roof panels using that clip either by pressing or mechanically securing the panels. The width of the cover is another major distinction between two types of panels. Standing seam systems typically provide the 16-18″ per panel, whereas exposed fastener panels most often cover 36″. Thus, exposed fastener panels systems can be installed more quickly than concealed fastener panels.
2. What is the importance of selecting the right fastener and the installation?
The function of the fastener in an open roofing system that uses fasteners is to connect the panels of metal to the roof deck, or the substructure.
A proper selection and fitting of the fastener is essential for the installation of metal roofing in Manchester with exposed fasteners. Screws should be positioned at a perpendicular angle to the roofing plane (not in an angle) and the washer must be correctly installed. The following image illustrates an appropriate fastener installation but is too loose and tight.
As you might imagine, screws that are installed too loose, frequently called underdriven, create an easy entrance for water into the envelope of the building. Conversely, screws that are installed too tight, often referred to as overdriven, can perform better than those that are underdriven initially. However, the washers that are on the screws aren’t designed to be compressed, and they often break and become brittle when they are driven too much during installation.
The washer that is attached to the screw is an crucial component that can vary in a wide range. It is not surprising that the standard screws have washers that are separate and distinct from the screw head. However there are many companies that offer screws that include a washer that is bonded to the head of the screw. The one-piece design of a cap/washer that is bonded will prevent water to pass through the gap between the head of screw and washer.
3. What distance should fasteners that are exposed be on a roof made of metal? And where should they go?
There isn’t a definitive and dependable guideline to install fasteners across every type of panel and manufacturer. It is important to recognize that the manufacturers have developed and tested every panel for attachment to a specific way and it’s essential to follow the instructions. we even provide the order of when a fastener should be used first, next, etc. across the length that the panel. For more information, go to the Downloads section on our site and browse the Installation and Product Information Books.
4. What is the best method to ensure that you hit the support structure under the panels by fasteners?
The chalk line continues to be the most popular tool however some contractors prefer to measure and drill panels prior to putting them on top of the roof. When drilling panels is important to clean the shavings off the panel promptly, as the shavings could stick to the panel, and eventually rust.
5. How can metal roofs that have exposed fasteners account for the expansion and contraction triggered from thermal cycle?
Because of the panel attachment method exposed fastener panels will not permit expansion or contraction triggered by temperature changes. Therefore, over time, a slot may be created due to the pressure of contraction and expansion around the fastener, creating what is referred to by the term “slotting,” shown in the picture below. If this happens and it becomes bigger than the washer that is on the fastener, water integrity of the structure is affected. In this case the issue is easily solved simply by replacing it with a screw bigger than that of the fastener originally.
In light of this that is a common occurrence, it’s recommended to utilize standing seam panel systems in projects with panels that run 40′ or more. Standing seam systems utilize clips to connect on the roofing structure, which allows an expansion or contraction that is required in long panel runs.
However, projects with panels with runs of 40′ and smaller employ exposed fastener systems to huge success because the shorter length of the panels experience minimal growth and shrinkage.
6. What kind of paint system is best to paint an exposed fastener roof?
It’s essential to select an Kynar(r) paint product over one based on a Silicone Modified Polyester (SMP) system since Kynar paint systems maintain their fresh appearance and exhibit little chalk and fade in time. The panels shown below were identical in color when they were first installed. 8 years on, and the stark chalk and fade in the SMP system in contrast to Kynar 500 Kynar 500 illustrates the stark distinction in performance between both systems.
7. What is the ideal material for an exposed fastened steel roof?
The most well-known steel substrates that are used in the siding and roofing business include Galvanized as well as Galvalume. Galvanized substrates have been coated using zinc alloy. Galvalume substrates have an alloy made of zinc with aluminum. This combination enables Galvalume substrates to be superior to Galvanized alternatives for all types of projects with the exception of animal confinement.
The pictures below illustrate the differences in performance. It is evident that the Galvanized G90 panel displays total red rust, even after 18 years of living in an agricultural setting The Galvalume sheet shows almost no changes in the same period.
The superior quality of Galvalume is confirmed by over forty years of field data. Actually, the performance of Galvalume for construction is superior that steel mills offer a warranty to that the material will not be damaged due corrosion. Similar warranties do not exist for Galvanized.
