What is the biggest problem with metal roofs?

Metal roofs have become increasingly popular in recent years thanks to their durability, longevity, and energy efficiency. However, like any roofing material, metal roofs have some potential downsides that homeowners should consider before installing them. In this article, we’ll examine the biggest potential problems with metal roofs and how to avoid them.

Rust and Corrosion

One of the most common concerns with metal roofs is the potential for rust and corrosion over time. All metal roofing comes with some type of coating or finish to protect the underlying steel or aluminum from corrosion. However, this coating can become compromised over time due to:

• Prolonged exposure to moisture and humidity
• Salt air or environmental pollutants
• Scratches, dents, or other damage that exposes the bare metal
• Degradation of the coating itself over decades of wear

Once the metal’s protective coating is compromised, moisture and oxygen can start to chemically attack the metal, leading to rust and corrosion. This not only damages the roof aesthetically, but can eventually cause leaks, drips, and even structural deterioration if left untreated.

To prevent rust and corrosion on a metal roof, it’s important to:

• Choose a high-quality metal roofing product made with galvanized, galvalume, or other rust-resistant metals.
• Perform regular roof inspections and maintenance to spot any damage or coating deterioration early.
• Keep debris cleaned off the roof to prevent moisture buildup.
• Trim back overhanging tree branches to limit tannic acid exposure.
• Apply fresh protective coatings if the original one starts wearing thin.

With proper care and maintenance, it’s possible to get decades of rust-free performance out of a good metal roof.

Noise and Condensation

Another common complaint about metal roofs is noise, especially during rainstorms. The raindrops hitting the hard metal surface can create a loud, tin-like drumming sound inside the home. Likewise, metal roofs accelerate condensation buildup in certain climates, particularly cold northern areas. The cold roof sheeting causes moisture to condense out of the warm, humid air below the roof deck.

There are a few ways to reduce noise and condensation problems with metal roofs:

• Install insulation boards and/or thermoplastic underlayment beneath the metal roofing to dampen noise.
• Choose metal panels with deeper profile dimensions, which scatter sound better than flat sheets.
• Utilize thicker gauge metal panels, which minimize noise transmission.
• Apply foam strips or other sound dampening materials where the roof framing attaches.
• Ensure proper attic ventilation to control moisture buildup and condensation.
• Add vapor retarders beneath roof sheathing in cold climates to reduce condensation.

With good design and insulation, noise and condensation issues can usually be kept to a minimum with metal roofing.

Dents and Scratches

Although metal roofing is very durable, it’s not completely impervious to dents, scratches, and other physical damage. Lightweight aluminum and steel panels are particularly prone to dents from impacts such as hailstones or falling tree limbs. They can also be scratched by tree branches, storms, walking on the roof, or debris blowing across the surface.

To prevent dents and scratches on a metal roof:

• Consider heavier gauge and thicker metal panels, which resist dents better.
• Install impact-resistant underlayment beneath the metal roofing.
• Use metal panels with peened or textured finishes, which hide minor scratches.
• Avoid walking on the roof whenever possible.
• Inspect and clean the roof regularly to remove debris before it can cause scratches.
• Trim back overhanging trees so branches don’t rub on the roof.
• Repair any dents, scratches, or damage right away to prevent moisture issues.

While no roof can be damage-proof, proactive precautions can minimize the appearance and number of dents and scratches on a metal roof.

Energy Efficiency

Although metal roofs are often praised for reflectivity and solar heat gain reduction in warm climates, they can suffer energy efficiency problems in colder northern areas. The issue arises when metal roofing is installed over a roof with inadequate insulation and attic ventilation. The cold metal sheeting will conduct heat out of the home very efficiently in winter unless there is proper insulation separating it from the living space below.

To ensure good energy efficiency from a metal roof in cold climates:

• Install sufficient insulation with an R-value appropriate for your climate. R-30 to R-49 is recommended for colder regions.
• Ensure proper attic ventilation to remove any moisture before it condenses. 1 sq. ft. of venting per 300 sq. ft. of attic space is recommended.
• Use thermal underlayments and/or insulation boards for enhanced insulation beneath the metal roof panels.
• Install a radiant barrier beneath the roof sheathing to reflect heat back into the attic.

With good insulation and detailing, metal roofs can perform very well energy-wise even in the coldest regions. Proper installation is key though.

Expansion and Contraction

Metal roofing expands and contracts with temperature changes much more than other roofing materials. This thermal movement can cause problems like panel buckling, fastener popping, and stress cracking of paint finishes if not properly accounted for.

Here are some tips to counteract expansion and contraction of metal roofing:

• Allow adequate expansion gaps between roofing panels based on the metal type and roof span.
• Use slidng clips at attachment points rather than fixed hard attachments.
• Install panels in the direction perpendicular to the roof slope rather than parallel.
• Paint metal roofing with elastomeric paints designed to flex and stretch.
• Avoid roof designs with tightly hemmed edging that restricts expansion.
• Attach gutters, skylights, and other roof accessories in a way that allows for movement.

With proper detailing to accommodate expansion and contraction, it doesn’t have to be a major issue for metal roofs. But it’s an important factor to consider during design and installation.

Reflectivity Concerns

The high solar reflectance that makes metal roofing attractive for energy efficiency in hot climates can also have some downsides. The mirrored surface can potentially create glare and reflections that are problematic for neighboring properties or low-flying aircraft in some situations. Reflectivity concerns with metal roofs include:

• Glare reflected into neighboring homes, especially low afternoon or morning sun angles.
• Reflections and glare affecting pilots approaching airports or helipads.
• Increased light pollution at observatories from radiant reflections at night.
• Intense reflective hot spots created on nearby buildings.

There are a few ways to reduce unwanted reflectivity from metal roofs when needed:

• Choose darker, low-reflectance color coatings rather than glossy light colors.
• Install panels with embossed or textured finishes to scatter reflections.
• Orient roof slopes to avoid reflecting sunlight toward problem areas.
• Situate other buildings or plantings to block predominant reflection angles.
• Add rooftop solar panels or coverings to reduce reflectance.

With smart siting and material choices, potential reflectivity issues can usually be avoided with metal roofing.

Higher Upfront Cost

Metal roofing costs significantly more upfront than asphalt shingles and some other common roofing types. The materials are inherently more expensive, and professional installation is recommended, further adding to costs. Here are some of the factors driving the high initial price tag for metal roofs:

• Base material costs for steel and aluminum roof panels run $3-6 per square foot on average.
• Special coatings like zinc, copper, and color finishes add to material costs.
• Standing seam and shingle panel designs cost more than basic corrugated metal.
• Professional installation for a steep, high roof can add $150-$500 per square.
• Flashings, underlayment, insulation, and other extras add to the total installed price.

A typical professionally installed metal roof costs $10-20 per square foot installed depending on factors above. That equates to $20,000 to $60,000 for an average sized home. The good news is that metal roofs offer excellent long term value from their 50+ year service life. But the high initial price tag may be daunting for buyers on a tight budget.

Strategies for Affordable Metal Roofing

There are ways to reduce metal roofing costs for budget-minded homeowners:

• Choose basic corrugated panels rather than expensive standing seam.
• Opt for lightweight coated steel over pricier copper or zinc metals.
• Shop around for competitive contractor pricing.
• Plan do-it-yourself installation for simple roof structures.
• Use roof coating products to upgrade existing materials at a fraction of replacement cost.
• Focus on smaller sections of roof rather than whole replacement.
• Time projects for off-peak seasons when demand is lower.

An investment in metal roofing will pay dividends over decades of service life. But taking advantage of cost savings methods allows more homeowners to enjoy the benefits on a limited budget.

Difficult Repairs and Replacements

While a quality metal roof should last 50 years or more, repairs or partial replacements and additions can be complicated compared to simple asphalt shingles. Metal roof systems often involve complex flashings, precision-fit standing seams, concealed fasteners, and inter-dependent panel systems. Attempting DIY repairs on a metal roof risks causing more harm than good in untrained hands.

To address repair and replacement challenges with metal roofs:

• Have an experienced metal roofing contractor handle any significant repairs.
• Keep detailed records of the original installation and roof layout to assist future work.
• Use compatible materials and joinery techniques matching the original roof.
• Plan ahead by installing attic access ports for future maintenance needs.
• Budget accordingly, as repairs generally cost more with metal than simple asphalt shingles.

With professional work and planning, metal roof repairs and replacements can be made successfully despite more complex detailing. The final lifetime costs of a metal roof are still usually much lower than continuing to replace asphalt every 20 years or less.

Conclusion

Metal roofing provides many benefits but also comes with some drawbacks to consider during selection and installation. Paying attention to factors like rust prevention, noise control, reflectivity, expansion and contraction, and repair accessibility helps ensure good performance from a metal roof. With informed design choices, potential downsides can usually be minimized or avoided. And the overall longevity, durability, and efficiency of properly installed metal roofing make it an attractive choice for homeowners prioritizing lifecycle value over lowest initial cost.