Sunday, 31 January 2016 10:52

How Much Does a Roof Weigh?

One important item is the weight of the roofing system. Today’s available roofing materials include a wide range of weights. For comparison, let’s look at the weight of one “square” of various products. A “square” covers 100 square feet of roof area.

  • ALUMINUM: 40 – 70 pounds
  • STEEL: 80 – 125 pounds
  • COPPER: 100 – 125 pounds
  • COMPOSITE / POLYMER PANELS: 150 – 275 pounds
  • FIBERGLASS / ASPHALT SHINGLES: 275 – 425 pounds
  • CONCRETE TILE: 400 – 700 pounds
  • SLATE: 900 – 1300 pounds
  • CLAY TILE: 1100 – 2000 pounds

Why Does Roof Weight Matter?

The weight of a roofing material, when carefully considered, can be a significant portion of your roofing decision.
Weight impacts key areas of overall roof performance

AGING STRUCTURES. As a structure ages, it weakens. Structural lumber may crack and foundations may move. A low weight roof system can prolong the structure’s life and integrity. A case in point is the First United Methodist Church in Sidney, Ohio. This impressive, looming structure had a clay tile roof that was about 80 years old when, at great expense, the decision was made to remove the tiles, clean them, put new underlayment on the roof, and re-install the tiles. Just a couple of years after this work was done, a major beam snapped above the sanctuary. It was unable to handle the weight of the roof.

SEISMIC ACTIVITY. In areas prone to seismic activity, heavy roofing can cause structures to slide off their foundations or even collapse. Lower weight products can be a good choice as much earthquake damage is sustained by structures with heavy roofs.

HIGH WINDS. Regardless of its weight, properly secured roofing materials can meet even the most strict wind uplift requirements. In the case of catastrophic storms, very heavy weight roofing materials pose a huge risk if they become airborne.

FIRE RISK. Many types of roofing materials are designed to resist combustion from exterior fires. However, most home fires start inside the structure. Firefighters are heavily trained in the risks of entering homes with heavy roof systems once the fire reaches the attic. Heavier roofs create a greater risk of collapse that could trap firefighters inside the structure. This means that firefighters have to contain the fire from the outside rather than enter the building and try to stop the fire.

RAW MATERIAL USE. Roofing materials come, in one way or another, from natural resources. The heavier the roofing material is, the more pounds of our natural resources are being consumed in order to create it.

TRANSPORTATION COST. Heavier weight roofing materials require additional fuel for transportation. With a low weight roofing material, as many as 300 squares or even more may fit on a semi-truck but weight limitations can hold that to 20 – 30 squares for very heavy roofing materials.

ENERGY EFFICIENCY. Heavy roofing materials typically have great thermal mass. While this thermal mass can offer some nominal R Value, it also holds heat. This means that summer heat absorbed by the sun can be held by the roof and continue to keep your attic hot even after the sun goes down.