Few roofing materials can compete with metal roofing in terms of strength, performance, and longevity. Despite this, leaks in metal roofs continue to occur. Understanding what causes metal roofs to leak is critical to extending their lifespan. In this blog, we’ll go over the five most common reasons for metal roof leaks.
1. Metal Roofing Screws
The roofing screws used to attach the panels to the building’s frame are the most common cause of metal roof leaks. Screw design, installation method, and angle can all have an impact on how the roof performs over time. Metal roofing screws create a hole in the roof, but generally do not seal the opening. Even when a sealant is used, screws that are under-driven, over-driven, or installed at an angle can allow moisture to leak under the metal panelling and present opportunities for moisture to leak.
Over-driven screws: Many roofing companies will overdrive the screw to ensure a tight seal between the metal panels and the screw head. The excessive torque breaks the rubber washer and causes it to spin to the side.
Under-driven screws: These issues are caused by insufficient screw torque, which fails to properly seat the rubber washer to the metal roofing panel. As a result, a gasket cannot be formed because the rubber washer is not compressed.
Screws are driven at the wrong angle: These prevent the rubber washer from sitting flat on the metal roofing. A portion of the screw is sealed, but another portion is not.
Screws that have missed the metal strut or wood framing: When the screw misses the underlay, it has nothing to seal against. These can be difficult to find because the screw is still present. Without physically checking, it is impossible to know whether the screw hit anything and created a seal or missed its target altogether.
Wear and tear: Even properly driven screws will eventually back out. Over time, the gaskets dry out and weaken. This, too, has the potential to cause the metal roof to leak around the screws.
Since the instalment of metal roof screws is so vital to the longevity of the roof, it’s crucial to hire a reputable team like Hamilton Metal Roofing. Hot summers followed by harsh winters are rough on rubber washers, especially in Hamilton, Ontario, Canada. They deteriorate and lose their seal, making it difficult to tell which screw is leaking and which is not. Get in touch with our team today for professional metal roof leak repair.
2. Curb Flashings
HVAC systems are commonly installed on metal roofs. Most HVAC units are mounted on top of a roof curb, a metal structure designed to support the unit’s weight and provide a way to connect the ducting.
The region around a roof curb is one of the most common locations for leaks to develop on metal roofs. Even if the curb is properly flashed, water can eventually seep through, particularly on the curb’s upward-facing side. Without removing metal roofing panels and starting over, this Catch-22 is hard to resolve.
3. Missing Sealants
Metal roof sealants never last as long as the metal panels they’re installed on. Therefore sealants need to be replaced regularly to keep up with the longevity of the roof. Sealants beneath trims like metal ridge caps and Z flashings, around roof transitions, counter flashings, reglets, and pitch pans need to be “topped off” as they wear.
Always use a metal roof sealant that is specifically designed for metal roofing. This is significant for several reasons. Other silicone caulking products may not adhere to the paint on the roofing panels and trims. Furthermore, metal roofing undergoes a daily expansion and contraction cycle, and any sealants that are to last must be flexible and stretch with metal without breaking their seal.
4. Stack Flashings
When pipes or vents protrude from a metal roof, “boots” or flashings are installed. They are commonly made of rubberized material and are used to seal around pipes and air vents.
Because stack flashing is only built to last for half as long as the actual roofing material, this is a common place for metal roof leaks. Heat-induced expansion and contraction of metal roofs put a lot of strain on stack flashings over time. When they break, it is best to have a certified roofing professional replace the stack flashings.
The sun also deteriorates the rubber flashings, which only last about half as long as the metal roof. The more caulking, sealant, or tar used behind and around the stack, the more they appear to hold water and cause leaks. Plan on replacing worn or rotten stack flashings to keep your building dry.
5. Seams and Overlaps
Gaps and areas where panels overlap are unavoidable on a metal roof. These areas must be adequately sealed when your roof is first installed because Poor installation will eventually cause metal roof leaks due to capillary draw.
Capillary draw, also known as capillary action, occurs when water moves through the tiny gaps (capillaries) between the steel roof sheets where they meet. When the roof is initially built, rubber or mastic seals are on either side of the fasteners between the roof sheets.
Over time, these seals will deteriorate because of the metal roof’s daily expansion and contraction. Water can flow in any direction and even defy gravity in these small spaces. This is due to surface tension, cohesion, and adhesion forces.