Asphalt roofing shingles are available in grades with an expected life of 20-50 years depending on the price. The main drawback to asphalt shingles is related to the service life. They weigh at least 250 pounds per 100 square feet, on the light end for roofing materials. Asphalt shingles are likely the most affordable roofing option for moderate and steep sloped roofs, running between 50 cents to $1.50 per square foot. They’re easy to install, relatively long-lasting, and available in virtually any color and style an architect could desire. They’re economical, versatile, and work well on most residential roof pitches. All three products, clay, concrete, and slate, weigh between 900 to 1,200 pounds per 100 square feet, so the roof deck and supporting structure must be able to support this additional weight.Īsphalt shingles are the most commonly used roofing material in North America. They’re typically warranted for at least 30 years. Concrete roof tiles are available at prices similar to clay, and can imitate both slate and clay tiles. Clay tile runs $6 to $10 a square foot in most areas of the country. The primary drawback to tiles is their cost and weight. They have been used for roofing for hundreds of years, and are still a great choice for conventional roof pitches.Ĭlay tiles and natural slate have a proven track record stretching back centuries, and modern products will last a lifetime if properly applied. For conventional and steep-slope roofing, shingles and tiles are the best way to go. Synthetic wood and slate are durable, long-lasting, and appear identical to the natural materials they imitate. Tile provides a long-lasting roof with little maintenance. The Army Corps of Engineers estimates that 75% of the roofing industry consists of re-roofing existing structures, so issues such as construction noise, fire hazards, fumes, and building access can also come into play.įor steep and conventional pitched roofs (4/12 and above) shingles and tiles are an attractive option that perform well. Hot-applied or torch-down roofing is not compatible with rigid foam insulation. Similarly, roof underlayment and insulation can eliminate some roofing materials from consideration. Vegetated and ballasted roofs, for instance, can put a significant load on structural elements. Often, the weight of the roof plays a deciding factor. Of course, roof pitch is not the only factor in system selection. On the other hand, visually appealing roofing products such as shingles or tiles do not work well on low-slope roofs. For instance, single-ply or torch-down roofs are not appropriate for high-slope applications. Roof material selection is highly dependent on roof slope. However, they also cost more because of the additional materials required to build them, and are impractically tall for larger buildings. Steeper sloped roofs are generally more visually pleasing and tend to last longer, as the water runs off immediately and ice damming is avoided. The minimum allowable slope for drainage is ¼” per foot. Roofs with a pitch of less than 2/12 are considered flat, even though they technically have some slope. In commercial work, low-slope roofs (with a pitch between 2/12 and 4/12) are most common. Roofs with a pitch exceeding 9/12 (37 degrees) are termed steep slope roofs. Conventional slope roofs, with a pitch between 4/12 and 9/12, are the most common in residential work. A roof with a rise of six inches per foot would be called a 6/12 roof. The slope, or pitch, of a roof is typically expressed as the amount of vertical rise (in inches) for every foot of horizontal length along the gable. An understanding of the major commercial roofing systems-and how their performance is affected by roof slope-is critical to maximizing the effectiveness of the covering. It also has a major impact on the finished style of the building, whether it’s a steep-pitch sloped roof visible from street level, or a low-slope roof design with less visual impact. It is considered the primary factor in roof design. The roof pitch selected affects drainage, maintenance requirements, and materials used more than any other single factor. Finding the right system involves weighing a multitude of variables including cost, weight, lifespan, maintenance requirements, and most importantly, aesthetics. Of all these variables, roof slope (a.k.a. However, not every roofing system works in every application. It’s also no overstatement to say that we now enjoy a wider range of roofing materials and roofing system than at any other time in history. It’s no exaggeration to say that the roof is the most vital part of the building envelope, and therefore, the most critical investment.
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