Metal roofs are a good investment for homeowners, as they have a lifespan of 50 years or more. In addition, with the right tools, a little help and some degree of patience, metal roofs can even be installed by homeowners. However, before beginning the process, it is helpful to know how to avoid certain critical mistakes when installing a metal roof. Below are several things to keep in mind that will prevent a failed installation:
Align the roof panels correctly
If you take a close look at metal roof panels, you will notice the long edges are not identical. One side contains a lip with a flange extending another half-inch, while the other side has a lip with no flange. The flanged edge of the roof panel should be laid on the roof decking with the lip of the non-flanged edge overlapping the bottom lip. This is essential, as the flange prevents moisture penetration under the seam and into the decking. Since most metal roofs are installed from left-to-right, this means the flanged edge of the panels will be positioned to the right.
Drive screws to the proper depth
Another mistake made by some amateur installers is driving the screws to an improper depth. Metal roof screws consist not only of a short sheet metal screw, they also contain a rubber washer that lies beneath the screw's wide head. This washer is designed to seal off the screw opening and make a watertight seal against the metal.
If an installer drives a screw too deeply into the panel and into the decking beneath, the washer will be stretched and pushed outward beyond the edge of the screw head. This will permit water to enter around the inside edge of the washer where it meets the screw. On the other hand, a screw that isn't driven deep enough will leave a gap between the washer and roof, thus allowing water to seep beneath the washer.
Therefore, be sure to drive metal roofing screws until the bottom of the screw head touches the washer beneath and holds it in place against the roof. You have screwed too deep, if the washer bulges outward. You can test the fit of the washer and screw by attempting to turn the washer by hand; if it can't be budged, the seal should be adequate to prevent leaking.
Extend roof panels past the edge an adequate distance
Metal roofs must be installed so the edges of the panels are appropriately placed in relation to the roof eaves. If the panels are cut too short, there is a risk of water penetration beneath the edge of the roof, especially during storm conditions and high winds. On the other hand, panels that are too long can permit rain run-off to overshoot the gutters. As a result, cut panels to a length where they extend two inches over the edge of the roof.
Securely fasten flashing to the roof's surface
Flashing on an asphalt shingled roof is typically installed using a few nails, but it's a mistake to use only a couple of roofing screws to attach flashing around a chimney, vent or other penetrations. Attempting to compensate for lack of flashing with caulk is also a poor idea, since caulk can weaken with exposure to sunlight or the elements.
That's why it is ideal to use adjacent metal roofing screws to attach the flashing. Using several screws will cause the flashing to conform to the metal roof surface, and this will keep the seal against the roof strong and prevent leaking. Using a minimal amount of caulk is acceptable, but try to keep caulk in areas away from direct sunlight to lengthen its lifespan.rockymountainroofers.com