
Roofing Seattle provides significant benefits to homeowners, but timely repair is essential to maintain its performance over time. Identifying common issues and applying the proper techniques can help prevent costly repairs and prolong the lifespan of your roof.
Patch holes with a metal-specific sealant, such as high-solids polyether or silicone. Pre-drill holes in the new patch, then apply butyl tape to both sides.
Water Infiltration
Metal roofs are known for their durability and low maintenance requirements, but even the toughest of materials can develop leaks. If caught early, these minor problems can be easily repaired to prevent further damage and costly repair bills.
The first signs of a leak in a metal roof are often found around fasteners or other roof penetrations. This is because these areas are not as sealed as the rest of the roof, allowing moisture to seep in and cause damage. Likewise, leaks can also occur along seams or in the flashing that wraps around chimneys, vent pipes, skylights, and roof curbs.
Other common signs include water stains on the ceiling or walls. These can signal that the sealants or fasteners in these areas have become weakened by exposure to UV radiation and rain. It’s essential to regularly inspect these parts of the roof to ensure they’re protected.
It’s also important to understand what type of metal roof you have so that the appropriate repair methods and materials can be used. For example, architectural metal roofs sit on top of the existing roof deck, while structural steel roofs rely on the support of the deck for their strength and durability. Therefore, a structural metal roof may require more extensive repairs than an architectural metal roof.
Lastly, if you’re noticing higher than usual heating and cooling costs, it could be a sign that a leak is developing. This is because moisture can saturate attic insulation, forcing your HVAC system to work harder to maintain a comfortable temperature.
Leaks in metal roofs are caused by a variety of factors, including UV radiation, rain, and fluctuations in temperature that cause the metal to expand and contract. This can weaken the seals and washers around fasteners, causing them to loosen over time. Also, a lack of proper ventilation in an attic can trap warm air near the cooler surface of the metal panels, causing condensation to form. This can then drip down the surface of the roof and cause water damage. It’s important to ensure there is adequate attic ventilation and that any condensation is quickly removed to prevent this from happening.
Loose Fasteners
The longevity of a metal roof is highly dependent on the quality of the fasteners. Modern exposed fastener metal roofing systems utilize corrosion-resistant screws with neoprene washers to ensure a watertight seal. However, these screws can become loose due to thermal expansion and contraction or movement of the substrate under the panels. This can result in a loss of seal and moisture intrusion.
The most common reason for loose fasteners is improper installation. Screws should always be installed at perpendicular to the panel ribs. Any angle other than this results in stress concentration points that work against the design holding strength of the fasteners. Additionally, low-quality screws or those with inferior threading deteriorate quickly under weather exposure and lose their ability to maintain a tight connection to metal panels.
Another cause of loose fasteners is over-tightening. It is important to use a screw gun that has a depth-setting nose or torque-limiting clutch, and only crank down metal roof screws until the rubber washer begins to bulge slightly. Over-tightening can crush the washer and force it out of its seat, leaving a gap where water can penetrate the roof.
When replacing a screw, it is important to use a fastener that is one size larger than the previous screw in order to create new threads. It is also a good idea to install a metal-to-metal washer, which will prevent the screw from loosening or damaging the panel.
Exposed fastener metal roofs are an economical choice for residential, commercial, and industrial structures. They are available in a wide variety of profiles and finishes, and can be installed over existing roofing. These systems can be coated with silicone-modified polyester (SMP) or polyvinylidene fluoride (PVDF) paints for added weather protection and UV degradation resistance.
Standing seam and exposed fastener metal roofs offer premium longevity and durability, and come with a variety of weathertight warranty options. Each type has its own advantages and disadvantages, but both can provide a long lifespan and beautiful aesthetic. Both types of metal roofing require regular maintenance to inspect for signs of aging and damage.
Seams and Joints
Metal roofs offer a clean, modern look and strong resistance to corrosion and rot, but they require careful planning and installation to perform well. The upfront cost is often higher than shingle systems, but over a lifetime of use, a metal roof can outlast asphalt shingles and provide substantial savings on energy costs with proper insulation and ventilation.
Leaks and damage are common in areas of the roof where panels meet or connect, and the seams are one of the most vulnerable points. There are many options for joining or connecting the panels, each with its own advantages and drawbacks. These include mechanically seamed, snap-lock, nail hemmed, and systems with exposed fasteners.
Snap-lock panels with clips are a good choice for most homeowners, as they hit the sweet spot between performance, cost, and installation ease. They snap together like giant puzzle pieces, and the raised seams interlock tightly while hidden clips underneath handle the attachment to the roof deck. This eliminates the need for unsightly screw washers and hides them from UV rays, moisture, and wind damage.
All standing seam systems can suffer from oil canning, which causes visual ripples or waves on the roof surface. This is caused by the fact that the panels are fastened at several points along their seams, and if these fasteners loosen or degrade over time, they can flex or bend in small areas. In contrast, seamless metal roofs have fewer fastening points and are less susceptible to this problem.
Another common issue is dents. These can occur if a metal roof is walked on improperly, or if there are structural issues with the building, such as a low pitch. It’s important to avoid walking on a metal roof, or if access is necessary, to wear rubber-soled shoes and walk pads. Additionally, some types of metals (such as galvalume and aluminum) are more prone to denting than others.
A standing seam metal roof can also be prone to clogged gutters, as the vertical panels act as a slide for snow, water, and debris. This can lead to ponding and rust in the gutters, and it’s important to regularly inspect and clean your metal roof. Consider installing gutter guards to reduce the risk of clogging and make sure you have good drainage solutions in place.
Corrosion
Corrosion is a common problem that can affect metal roofs. The corrosion process occurs when water or air contacts a metal surface, and the metal oxidizes to form rust. If not addressed, this deterioration can weaken the roof structure and cause leaks in the house. There are three types of corrosion: galvanic, crevice and filiform.
The type of corrosion depends on the environment and the metal used. For example, a zinc roof is inherently resistant to rusting because it forms a protective patina when exposed to the elements. Copper roofs, on the other hand, corrode in a different way. They develop a green patina when they oxidize, similar to the Statue of Liberty. While the patina acts as a barrier to further corrosion, it can be damaged by hail and other environmental factors.
If you live near the coast, you may be more likely to experience problems with salt corrosion. This type of corrosion accelerates the oxidation of metal and can damage coatings. Salty air and mist can penetrate tiny cracks in the surface, causing the corrosion to spread under the coatings or to bare metal. Regular cleaning to remove salt deposits and periodic re-coating can help protect the lifespan of your metal roof.
Steel roofs are susceptible to corrosion, but they can be protected by a layer of zinc (galvanized), a mixture of aluminum and silicon (galvalume) or a pure chromium alloy (stainless steel). These coatings can significantly extend the life of a metal roof. If a steel roof is not properly maintained, however, the corrosion may accelerate. Poor installation also contributes to hidden corrosion risks. If the flashing around chimneys, vents, skylights and other roof penetrations isn’t installed or sealed correctly, it can allow water to enter at these vulnerable points and corrode the seams and edges of the metal panels.
To learn more about identifying and repairing potential problems with metal roofs, read the InterNACHI series Mastering Roof Inspections. This series teaches home inspectors, insurance and roofing professionals to recognize proper and improper conditions when inspecting steep-sloped residential roofs.



