More frequently we we are receiving inquiries on the subject of metal roofing.
One of the top questions asked pertains to how metal roofing should be properly installed.
As there are a variety of metal roofing options available, there can be some variation in methodology which relates to the specific product being selected.
The most common metal roofing involves the use of metal panel sheets. Such products are typically manufactured for residential and commercial applications; to extend from the peak of the roof to the eaves of the roof.Having a continuous metal roof panel is most ideal as it eliminates seams in the roof assembly.
Metal roof panels can be manufactured with different surface profiles. They can also be produced with various configurations in terms of how they are joined to one another.
If for example one had a barn or a shed; a panel system which is installed by overlapping one sheet over an adjacent panel by one foot, and securing the panels using coated screws and washers at a prescribed rate; would be very typical and relatively easy to install.
On buildings which are not heated, such as garages and storage sheds; one could install (2×4)” cross strapping (running in opposing directions). This would eliminate the need for roof sheeting, and as a result ,is likely the most economical method for installation of a metal roof system.
On a heated structure, the installation procedure would bea more involved procedure.
To note is that metal roof panels are also available in configurations which provide for locking one panel to another by way of using cleats and standing locking seams.
When such a metal panel is being installed (starting from the rake edge);the outer edge of the roof panel hooks onto a rake edge flashing. On the opposing side of the panel, a series of metal cleats hook onto the standing seam of the panel and are screwed onto the roof deck. The cleats are typically spaced about four feet apart, and running the length of the panel. This is designed to help the metal roof panels to resist wind uplift from the roof deck.
Once the panel cleats have been secured; the next step involves closing the standing seam between two adjoining metal roof panels. Seaming is often completed by hand using long folding pliers most typically on small roofs. On larger panel roofs, an electric seamer clamps onto the two adjacent panel seams and folds or double folds as the case may be; the two panels to create a water-tight seam.
Variations of seams include T-battens, boxed battens, and soldered standing seams. Such work requires the experience ,equipment and expertise of a metal roof technician and or a metal smith.
The metal panels themselves are manufactured in various gauges (thicknesses of sheet metal), and are extruded through a machine which creates the various panel styles ( referred to as ribs), which lend additional strength to the extruded steel panel. Such panels are fabricated using galvanized steel sheeting and also receive a paint treatment on bothe sides of the panel to resist corrosion.
As a result; many steel sheet manufacturers will warrant their panels for over twenty years.Major brands such as Stelco, Vic-West and Ideal represent leadership in the production of such goods in Canada. Some roofing contractors own portable milling machines which can form and extrude such panels from flat stock materials.
A minimum 26 gauge metal panel is suggested for residential application along with s heavier 24 gauge being popular for commercial applications.
When installing a metal roof on a structure which is heated; certain preparatory steps should be completed and certain system design elements should be incorporated prior to undertaking such work.
As a first step, one should survey the existing roof structure and determine if it is relatively plumb and square. Structural repairs may be necessary if for instance the roof deck exhibits undulation. Removal of existing roofing materials is the best approach due to removing excess weight from the roof, insuring that there is no underlying rot and or hidden conditions may be revealed. It also helps insure that fastening through the roof deck is properly secured.
Once the roof substrate is in good order, underlay materials should be applied.
Breathable 15lb. felt paper is a good choice, or synthetic underlayment which is vapour permeable if one is applying over a plywood or tightly laid boarded roof deck.
Covering the entire roof surface with ice and water membranes beneath metal roof panels may result in condensation forming beneath the roof deck in colder weather. Ice and water resistant membranes should be used at roof eaves area, roof appliance areas such as chimneys and pipes, valleys, etc.
It is important to insure that a balanced intake and exhaust ventilation system is incorporated in such a roof design, especially when considering climates which experience a dramatic change in temperature from summer to winter. In concert with such design considerations are the need to insure air leaks through the attic/ceiling are addressed. Such items include breaches in ceiling vapour barriers, pipe holes through the roof which should be foam sealed, and the top plates of exterior walls where warm interior air and cold external air may collide.
In fact the ideal metal roof system would incorporate an air space below the metal roof panels by way of cross strapping over the roof deck to create a continuous two-inch air space. Such a technique refers to a cold roof assembly. Such work will also require modification of fascias at perimeters of the roof.
The metal roof panels may then be installed on the strapped portion of the roof.
It is highly advised to enlist the services of a qualified building envelope engineer to study the existing conditions of a building and in relationship to how the existing structure may have an impact on that particular roof installation.
When retrofitting an older home or building with a metal roof system It is money well spent to achieve a set of specifications that protects both the property owner and the installation contractor from unforeseen perils which can develop due to issues such as condensation. After all, metal roofs can sweat under the right circumstances.
Other forms of metal roofing involve the use of fabricated copper leaded copper. or zinc panels.
Such metal roofing represents the pinnacle of metal roofing systems; many of which can last up to one hundred years.
When installing a metal roof system, it is also important to consider lightning strikes. If one’s property is rural, set among tall trees, situated in a large open space, or is constructed at a higher elevation; there may be the need to install lightning rods with copper grounded wires. One will most typically observe this on structures like churches, farm houses, barns, etc.
In the past twenty years or so, there have been metal shingle panel roofs that have been manufactured by various suppliers. Some have come and gone although offering fifty-year and lifetime warranties. As a result, it is important for the consumer to research the history of such suppliers to insure they do not end up with a product that can no longer be serviced due to lack of product availability.
When considering the investment in a metal roofing system, which can be substantial; it is important to insure that the finished appearance will work well with the architecture of the particular structure. Many modern designs favour the appearance of metal roofing, and in some instances, it may not fit the character of a particular neighbourhood. Having said this; metal roofing has been a proven system for hundreds of years and certainly a go-to in the commercial and industrial roofing area.
To learn more about roofing. masonry, and building envelope work, visit www.avenueroadroofing.com.