A roofing square is a unit of area measurement equal to 100 square feet. Roofing materials like shingles are often sold by the square.

Roof pitch is expressed as a ratio of vertical rise to horizontal run, typically “X in 12”. For example, a 6/12 pitch means the roof rises 6 inches for every 12 inches of horizontal distance.

A waste factor accounts for material lost during cutting, trimming (especially around hips, valleys, and edges), and potential mistakes. Simple gable roofs might need 10-15%, while more complex hip roofs or those with dormers may need 15-20% or more.

Typically, there are 3 bundles of standard asphalt shingles per square. However, this can vary by manufacturer and shingle type, so always check the product specifications.

Underlayment is a water-resistant barrier material installed directly onto the roof deck before shingles. It provides an extra layer of protection against water intrusion and is required by most building codes and shingle manufacturers’ warranties.

Drip edge is metal flashing installed along the eaves and rakes of a roof to direct water away from the fascia and prevent it from seeping underneath the roofing components.

Ridge cap shingles are specifically designed to cover the peak (ridge) of a roof where two sloping sections meet. For hip roofs, they also cover the hip lines.

Eave overhangs extend the roof surface beyond the building’s walls, increasing the total roof area. This calculator adds the overhang to the building width for a more accurate pitched surface calculation.

Standard 3-tab asphalt shingles might last 15-20 years, while architectural or dimensional shingles can last 25-30 years or more, depending on climate, installation quality, and maintenance.

Signs include widespread granule loss, curled or cracked shingles, missing shingles, leaks, or if the roof is nearing the end of its expected lifespan. Get a professional inspection if unsure.