The difference between a residential and a commercial roof may seem obvious: although there are exceptions to the rule, one is typically for houses while the other is for businesses, schools, medical facilities and other non-residential buildings. The differences go well beyond those simple definitions, of course. Both have the basic purpose of covering and protecting the top of a building, but that is where the similarity ends.
Most commercial roofs are flat or low-sloped (usually defined as having a maximum slope or “pitch” of three inches of vertical rise for every twelve inches of horizontal distance), where a residential roof typically has a slope that’s steeper than that. Because of a building’s size and the amount of (e.g., HVAC) equipment on the roof, a commercial building will structurally require a flat roof.
Flat roofs can be varied and complex, with multiple layers of decking, insulation and surface material that vary from building to building, and tend to need more maintenance. Plus, because they have little pitch, there can be problems with drainage and ponding water.
Because a commercial roof is flat or low-sloped, the materials used on the building are different than for steep-sloped applications, which are usually shingles, tiles or architectural standing seam metal. Shingles aren’t practical for low-sloped applications because they don’t promote good rooftop drainage. Common flat commercial roofing materials are single-ply membranes (there are several very different product types), structural metal panels, or built-up roofing systems. In recent years, single-ply membranes have become the most popular choice for commercial roofs because of their proven durability and watertight effectiveness in virtually any climate.
It’s not uncommon for a home owner to repair or replace their own shingle roof, although there are plenty of contractors who specialize in residential roofing. However, commercial roofing demands professional attention because of the multitude of technical factors involved. It is important to hire specialists who understand how to properly manage a commercial roof installation.