Different Metal Roof Profiles For The Designer
By Ron Schwartz

Panel selection has always been an issue that architects, contractors and building owners have been concerned with. Each member of this team is in search and desires different results in the selection of the ideal system. In reality they are all after an aesthetic pleasing roof that is functionally durable and priced within a predetermined budget. The three important considerations are the architects design, material limitations and panel system profile.

The architect must design the building in accordance with the building owner’s requirements and budget. The structure’s restrictions are usually the limitations of both the material and panel profile.

Material selection is primarily determined by the building’s environment and the owner’s desire of appearance and end use.

  •  Aluminum – supplied as a pre-painted or coated/finished, or Mill Finished (as it comes from the mill) product, Aluminum offers superior corrosion resistance in coastal areas. One of the draw backs to Aluminum is the amount of movement in extreme temperature variation. This coefficient of expansion limits the lengths that panels can be fabricated or roll formed.
  •  Copper – offering old world charm, 100 year durability and low maintenance. Great workability, easy to repair, currently expensive but offers that great patina colouring as it ages. It is also offered as pre-patented and lead-coated copper. Many manufacturers are producing a lead-free coated product due to the environmental concerns that the construction business is facing.
  •  Carbon Steel – most common and economical material available but will corrode if finish or protective coating is scratched. The protective coating is usually a G-90 coated galvanized/zinc or a Galvalume/zinc aluminum barrier coating that can be painted.
  •  Pre-Painted Aluminum and Steel – The coated material can be painted a Polyester also known as Baked-on Enamel/Series 5000 paint for an economical, no warranty finish with a limited life expectancy of approximately five to 10 years. An improved SMP/Series 8000 (Siliconized Modified Polyester) offering an extended life expectancy over the polyesters. The Fluorpolymers offer excellent resistance and superior film integrity. This is also known as Kynar/Hylar/Series 10,000 painted finish with a minimum paint warranty of 20 years. This can also be coated with custom colours selected by the architect. This will require a minimum of 5000# for a production run. Another option is an Anodized coating. This is a controlled electro corrosion of the exterior surface of the metal and is available in limited selection of colours. This anodic coating provides a hard coat which is highly resistant to abrasion.
  •  Stainless Steel – offering durability, maintenance free and corrosion resistance, Stainless Steel is available as 304-2B for the majority of the roofing application. It is available as a brushed and mirror image material used for more decorative applications. Material can be fabricated but work hardens if roll formed or fractures at the bend point.
  •  Terne Metal and Stainless – used to be called “Tin Roofing Material.” It used to have a tin-lead coating before the manufacture, however the Follansbee Steel Corporation, for environmental reasons, went to a zinc coating. They also offer it with a Kynar painted finish coat. This is usually available in a lighter, 28 gauge product. This is expensive material that offers extensive durability.
  •  Zinc – imported from Germany and France, trade names are Rheinzink and VM-Zinc. The material comes as natural zinc/shiny and weathers down to an attractive flat grey in colour. It is also available as a Pre-weathered and Graphite Grey in colour. This material is expensive, durable and offers a unique appearance. There are some fabrication limitations: material will fracture when fabricated at low temperatures and requires an underlayment during installation unless the material is ordered with a back side coating. Allowance for more expansion and contraction than normally experienced.

Panel selection is traditionally determined by the acquired appearance that the architect designs, building use and the limitation of the chosen material as well as the desired roof pitch. Metal roof systems are broken down into three primary categories: through face fastened, architectural and structural grade panels.

Through Fastened: This panel is also called an agriculture and industrial roof and wall panel. These panels are side-lapped and are sealed with caulk or double faced tape, and then fastened. The economical, light gauge panels offer ease of installation. These panels are also available in thicknesses up to 0.040 aluminum and usually with a painted finish.

The multi-ribbed panel profiles are available in widths of approximately 36-inches wide and can be rolled to lengths up to 20-feet. Exposed fasteners can be a source of leaks due to neoprene washers that degrade over time and panel holes that elongate as the panels repeatedly expand and contract due to temperature extremes. Some panel designs have load bearing capabilities of up to five feet centres. Best suited for straight forward designs, with little or no pitch change, or obstructions – i.e. dormers, gables, mechanical equipment intrusions.

Architectural Panel Systems: These panels are usually installed with concealed sliding clips and a minimum of exposed fasteners. Their recommended installation procedure is over a solid substrate and almost always requires a minimum slope of 3:12 pitch for a positive water shedding. They are also supported by test data for UL-90 or UL-580 wind uplift as well as air and water infiltration, structural performance, Class A fire tested, Class 4 hail tested, and other performance data. Many major manufacturers are offering systems with a 20 year weather tightness warranty. This has become a strong selling point that both owners and architects appreciate. The following are some of the more widely used Architectural Panel Systems.

  •  Double Lock Standing Seam – Metal panels are laid over an acceptable substrate and are held down with a sliding clip. Panels are then mechanically seamed into a double lock configuration. Sealant can be injected into the leg of the panel to make the installation more moisture proof. This profile can also be radiused. Double Lock panels are ideally suited for longer panel runs. The expansion clip allows for longer panel lengths, with few pitch/valley changes, often utilized on larger commercial projects. Very favourable test results and surpasses code requirements

  •  Interlocking (Integral) Seam – These systems have gained popularity due to ease and the economical installation procedures. Some of these are installed with just a fastener in a slotted hole that allows for the expansion and contraction. Other models still require it to be installed with a clip. Center spacing is usually at 12- to 18-inches. The panels are just snapped over the other leg of the next panel. Sealant can also be provided with this style of panel. Widely used on most small to larger projects, with steeper slopes and more intricate in design. Offering excellent weatherproofing when sealant is used in the leg of the panel

  •  Snap-on Standing Seam – These are two piece constructed panel systems that are held down to the deck by a fixed clip and then the batten cover is then snapped in place. Many panels have a built in preventative capillary design to keep water from penetrating the leg of the panel. This also provides added tension to the seam. Seam covers should still be hard fastened to keep them in place. Some shorter legged systems can be radiused. Ideally suited for intricate designed roofs, roof pitches or intrusions of dormers, gables, valleys, mansards, etc.

  •  Flat Lock System – Can be fabricated as square, diamond and rectangular tiles that make up an interlocking profile that can be utilized for wall and roof applications. They have hemmed edges that interlock the tiles to form a simple geometric shape. Many of the tile manufactures offer a textured finish

  •  Flush Panel – These panels can be used on vertical wall applications or as a soffit. Soffit Material can also be vented to provide require air flow

  •  Structural Panel Systems – The seam height are usually higher, at two- to three-inches. Also with ribbed face to add additional strength and is usually installed over open framing of up to five-foot joists. Sealant adds watertight integrity due to installations as low as ½:12 pitch. Panel can be offered at wider dimensions but still require mechanical seaming. These panels are more expensive and well suited for larger commercial/industrial sized projects, with longer single panel runs, that require the best in code compliance and weatherproofing

  •  Trapezoidal – Panel profiles that have a high seamed leg that offers a unique shape and reinforced faced that is able to handle loads. Heavy duty seam clips hold down the panels. This design does have limitations when flashing into some complicated areas like valleys, pitch, changes, dormers, elevation changes. Mostly used in “Large Box” single run panel construction

  •  Vertical Mechanical Seamed – The simple profile is the double lock standing seams just with more vertical height on the leg. Clips are always made from a heavier gauge and are usually rated better in high wind applications

As you can see metal panels are suitable for all of the Canadian regions. They will cover the windy Maritime Province to the snowy and cold central region of Thunder Bay out to the moisture laden West coast of Vancouver. Metal panel systems have been designed to handle the drastic climatic changes that we see in North America. Metal offers the aesthetic look, the functionality, and the ability to last providing that we use the correct material and the appropriate design for the application.