Asphalt roofing shingles used to be specified by their weight as opposed to life expectancy and many “old school” design professionals still refer to them that way. The weight of shingles (represented in pounds) is the sum total weight of a 10’x10’ square of shingles or what roofing contractors will refer to as a “square” when estimating the number of roofing bundles required to complete your roofing project.
Almost forty years ago roofing material manufacturers moved away from weigh-based ratings and elected to go with age-based ratings instead, arguing this was simpler for consumers to understand. Today you will find roofing materials marketed as 15-year, 20-year, 25-year, 30-year and lifetime roofs (which for the uneducated is roofer marketing for 40 years).
It should come as no surprise to find out that heavier roofing materials have a longer life expectancy, so you can do some of your own math.
The vast majority of roof shingle bundles weigh somewhere between 50 and 80 lbs. where 3-tab shingles are on the lower end of the scale weighing 50 to 65 lbs. per bundle and architectural style shingles are at the higher end of the scale weighing 65 to 80 lbs. per bundle.
Generally, three bundles of shingles are required to cover one square (100 square feet of surface area).
This means that one square of shingles typically weighs 150 to 240 lbs. However, the thicker and more dense specialty roofing shingles marketed today may weigh upwards of 320 to 400 lbs. per square.
Because consumers often use the good, better, best methodology of purchase decision, the most popular roofing materials tend to be those rated 25-years – a fact that has not gone unnoticed by the manufacturers and marketers and thus you should expect to experience a greater push towards these materials.
Before you make a purchase decision, make certain you’ve considered the longevity of the structure as well as your personal needs for occupying that structure.