- By: Eric Thomas
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Selecting a roof can be a daunting task. There is such a wide variety of roofing materials to choose from and each one comes with its own set of pros and cons. Weighing these options can often prove confusing and start to feel a little overwhelming. In an effort to avoid this and make the decision process easier, we’re lending some professional insight to the pros and cons of a popular roofing material, metal roofing.
The Pros of Metal Roofing
Metal beats out conventional roofing materials in several ways:
- Expected life. Properly installed, a metal roof should last as long as the structure, sealing out water, surviving high winds, and easily shedding snow. Metal is resistant to fire, mildew, insects, and rot. While warranties vary, most companies guarantee their products for 20 to 50 years. Metal paint finishes generally have a 30-year limited warranty.
- Weight. Compared to the weight of tile at 750 pounds per square (an area equal to 100 square feet), or concrete tile at 900 pounds per square, metal roofing is exceptionally lightweight. Most varieties run from 50 to 150 pounds per square. Because it weighs less, individuals can save money on the supporting structure’s engineering and construction. In fact, for many homes or additions, the number of roof support members can be reduced. Furthermore, thanks to its lightweight properties, some types of metal roofing materials can even be applied over an existing roof without the need for tear-off or additional structural support.
- Speed & ease of installation. Most metal roofing materials come in multiple-shingle sections or in 12- to 36-inch-wide panels. An accomplished contractor can install these quickly. If your roof is stripped off and a storm is on the way, shortening the process by a day or two may offer a critical advantage. Obviously, there is also considerable labor savings if you can ease and shorten the duration of roof installation.
- Fire resistance. Because metal roof materials are noncombustible, they typically have a Class “A” fire rating (the most fire-resistant rating). It’s important to remember, however, that a roof’s overall classification is also determined based on materials beneath the surface—some of which are more prone to ignite when exposed to intense heat. Most metal roofs applied over a combustible material such as wood shingles have a lower, Class “C” rating for this reason.
- Heat conduction. Metal reflects radiant heat from the sun, which in turn minimizes midday heat gain. A material that makes dollars and sense (cents), the result is an energy efficient roof that lowers the need for, and cost of air conditioning during the day. Though the material itself is low in insulation R-value the measure of resistance to heat flow through a given thickness of material), metal roofing can be applied over rigid-foam insulation that has very high R-values. In addition, many systems utilize a dead-air space between the metal and roof deck to increase energy efficiency.
- Minimal roof pitch. Most metal roofing materials can be installed on gently pitched roofs without leaking. That is not always the case with other roofing materials.
- Maximum shedding of rain and snow. Metal roofing is virtually unaffected by rain and snow because of the way its panels interlock and because its surfaces are hard and slippery. Furthermore, dark tones of metal roofing quickly warm in the sunlight, encouraging snow melt—a tremendous advantage in climates where below-freezing temperatures, snow, and ice are common.
The Cons of Metal Roofing
Though metal roofing offers many advantages, it is worth noting its drawbacks. In general, metal roofing manufacturers have improved their products to address or solve many of the following issues:
- Cost. The greatest drawback of metal roofing is its initial cost. Metal roofing is equivalent in cost to other premium materials—from about $150 to $600 per square (100 square feet). It’s important to keep in mind its longevity, however. It ends up saving homeowners money on seasonal maintenance and is a good return on investment for those planning on staying in their residential or commercial construction for a long time.
- Noise. For some, the patter of rain against a metal roof is comforting and homey. For others, it sounds like a snare drum. In a heavy rainstorm or hailstorm, living beneath sheets of metal is going to be noisier than living beneath slate or tile. The noise can be reduced, however, by using materials with structural barriers to minimize the “drumming” effect and by applying them over sound-eliminating insulation and solid plywood sheathing.
- Denting & marring. Like a vehicle, metal roofing is not immune to denting if large hailstones fall on it. Aluminum and copper—much softer than steel—are more prone to denting. It’s worth exploring some of the types of metal roofing guaranteed not to dent. Some painted metal roof finishes can also scratch, peel, fade, chip, or chalk—although almost all of them are guaranteed for 30 years. Walking on some types, especially those with a granulated surface, may cause damage. Installers must be careful not to scratch or dent the roofing during installation, and panels must be treated with care. Unlike conventional roofing, some metal shingle systems are installed from the top down, eliminating the need to walk on them.
- Leaking. To avoid leaking, a metal roof must be installed correctly. Roofs with exposed fasteners are especially vulnerable to improper installation. If screws are incorrectly attached through the flat surfaces (rather than the raised ridges), rainwater can run down the roof and seep into the screw holes. For this reason, special resilient washers must seal around the screw heads. Use knowledgeable professionals to ensure the manufacturer’s instructions are followed precisely.
- Expansion & contraction. Because metal expands and contracts as it warms and cools, most new products have fastening systems that accommodate movement. Older products fasteners that secure the roofing may tend to come loose. Expansion and contraction on hot days can cause a wavy effect.
- Modifications. Metal roofing materials installed in large panels are more difficult to replace if they sustain damage, versus individual shingles. Homeowners should also bear in mind that if they remodel or add on to their home 10 or 20 years after initial installation, it may be difficult to match the original metal roofing used.
- House fire. Though metal roofs are good at guarding against exterior fires (for example, flying sparks and embers from a nearby burn pile), they are not ideal for fires that start inside a home or commercial structure. With a serious house fire, firemen may need to cut through the roof to extinguish the flames—a challenging and time-consuming task.