Do You Speak Roof? Basic Roofing Terms Explained

roofing glossary chicagoLike every other profession, roofers have their own terminology. After all, roofs have a history almost as long as humans. Even cavemen used to have a roof of sorts. They would cover their structures with sod roofs and top them with dirt and plants.

Unless you plan on becoming a roofer, you don’t need to know every single term, but knowing the basics helps. We’ve put together a glossary that includes the most common terms used by roofing professionals in Chicago and its suburbs. Please note that the terms are not in alphabetical order. Instead, we’ve arranged them by how common and important they might be for a typical homeowner (all of the above is, of course, pretty subjective).

SLOPE – Refers to the angle of the roof. A 4/12 slope refers to a roof that drops 4 feet (vertical) in a 12 foot run (horizontal). The 4/12 can be measured in feet or inches. A 12/12 roof is at a 45-degree angle.

ASPHALT, FIBERGLASS, ORGANIC, AND COMPOSITION SHINGLES – These terms are confusing because they are often interchanged. A composition shingle is an asphalt shingle. An asphalt shingle can be organic or fiberglass; asphalt bonds the shingle materials together. The base material for the shingle may be fiberglass (inorganic) or cellulose (organic) felt. About 80 percent of modern shingles have a fiberglass base material. In years past, organic base shingles were more common.

EAVE – The overhanging lower edge of a roof.

RAKE – The pitched edge of a roof that overhangs the wall of a home. This also refers to the board or molding placed along the sloping side of a gable roof end.

RIDGE – The top intersection of two roof planes; the peak.

VALLEY – The internal angle at the intersection of two roof planes. It can be an open metal valley or a valley formed of shingles or asphalt roofing material.

DECK – The wooden board, plywood or oriented strand board (OSB) that supports the roof material and spans the framing joists or trusses.

FELT, TAR PAPER, BUILDING PAPER, UNDERLAYMENT – Asphalt-saturated roll felt material used under roof shingles and siding. It can also be designated 15# or 30# felt. The 30# felt is thicker and heavier than the 15# felt. Also, synthetic underlayment has been gaining popularity lately (for good reasons!). Its function is the same as the one of traditional felt.

FASTENERS – Most shingle manufacturers recommend using nails to fasten shingles to the roof deck. Nails can be driven by hand or with pneumatic nailers.

TEAR-OFF – Removal of existing roofing materials down to the roof deck. 

ICE DAMS – Ice dams occur when snow melts on a warm roof, slides to the cold edge of the roof, and re-freezes as ice in the gutter and overhang. This ice buildup creates a “dam” that blocks water on the roof. The water then leaks through the standard asphalt shingle assembly that is not designed to resist ponding water.

GUTTERS AND DOWNSPOUTS – Gutters and downspouts must be considered when replacing roofing materials. If your home has newer gutters, you can ask the contractor to remove them and re-install them with the new roofing materials.

SQUARE – The amount of roofing material needed to cover 100 square feet. A roof that is 15 square has 1500 square feet of surface area.

FLASHING – Metal or roofing material that is used at starts, stops, penetrations, and changes in direction of the roof. This includes the intersection of the roof to chimneys, vents, valleys, and vertical surfaces. Step flashing is used at intersections to all vertical surfaces such as chimneys. Flashing is also installed around plumbing vents.

ROOF-OVER or RE-ROOF - Applying an additional layer of asphalt shingle roofing over an existing asphalt shingle roof. Normally, the maximum number of roofing layers is two. In most cases, we don’t recommend re-roofing.

MODIFIED BITUMEN – Rolled roofing membrane with polymer modified asphalt and either polyester or fiberglass reinforcement.

CRICKETS –A peaked water diverter installed behind chimneys and other large roof projections. Effectively diverts water around projections. 

SOFFIT VENTILATION – Intake ventilation installed under the eaves, or at the roof edge. 

LAPS – The area where roll roofing or rolled underlayments overlap one another during application

BLOW-OFFS –It’s an occurrence when shingles are subjected to high winds, and are forced off a roof deck. 

ASTM–The American Society for Testing and Materials. Organization that sets standards for a wide variety of materials, including roofing.