Roofing Glossary

Butt - the exposed end of a roofing slate.

Clear - in regions where slate contains bands of rock compositionally different from the main body of slate, "clear" denotes slates which have been trimmed of all such ribbons.

Commercial Standard Slate - most common and available roofing slate. Exact definition varies by region, but generally this slate is 3/16" thick with varying widths (8" to 14") and a length between 18" and 24". Each slate has a bevelled edge and pre-punched nail holes. Quality is fairly consistent.

Comb Ridge - ridge finishing treatment in which the combing slates on the north or east side are laid
extending 1\16" to 1" over the other side. The grain of the combing slates may be either vertical or horizontal.

Cox Comb Ridge - the combing slates (those projecting at the top) alternately projecting on either side of the ridge.

Curb - the line formed by the junction of two different slopes on one side of a roof--especially on Mansard and Gambrel roofs.

Exposure - the length of each slate exposed to the weather, i.e., not covered by the next above course. Exposure is expressed in inches. A simple formula is used to compute the exposure: Deduct 3" (standard lap) from length of slate and divide by two. For a 24" slate, usual exposure is 24-3= 21, 21 divided by 2=10-1/2".

Freaks - slates having an unusual combination or variation of color, bought for special effects on special order. They are thicker than usual--never split under 1/4" and up to 2" or more.

Graduated roof - variation on the Standard slate roof described below. Slates are arranged so that the thickest and longest are at the eaves, diminishing in size and thickness to the ridges. Usually this is combined with other generally more labor-intensive treatments such as closed valleys.

Lap (headlap) - that part of a slate overlaying the slate two courses below. The standard lap is 3". Roofs with less slope (flatter) often take a 4" lap; those very steep need only a 2" lap.

Ribbon Stock - slate which contains bands of rock differing in composition and color from the main body of stone. It is always labelled as such. Usually from Pennsylvania quarries.

Saddle Ridge - finish in which the regular roofing slates are extended to the ridge line so that slates on both sides of roof are butted flush. Then another course of slates is laid with its grain horizontal (combing slates) and lapped horizontally to cover the previous combing slate's nail holes. They are butted flush on either side of the ridge.

Standard Roof - one composed of Commercial Standard Slate (approx. 3/16 in. thick) of more-or-less uniform standard width and length, with butts laid to a line, in standard slate colors. (No color patterns, no freaks.) Encompasses those slates with butts (exposed ends) trimmed to have an hexagonal, diamond, or Gothic pattern.

Square - number of slates needed to cover 100 square feet of plain roof surface, when laid with the customary lap of 3". (Roofs with a flatter slope require only a 4" lap, so more slates are need to cover 100 sq. ft.; very steep roofs take a 2" lap, so fewer slates are needed per square.) Commercial Standard Slate weighs 650-750 lbs. per normal square.

Textural Roof - in between a Standard roof and a Graduated roof. Generally, such a roof has more visual interest than the Standard, with use of rough slates instead of smooth, or with unevenly laid butts, or variations in the thickness, size, and color of slates. (Not usually over 3/8" thick.)

Unfading - a color designation given to those slates that do not "weather" appreciably or change color over the years. (As Unfading Red.)

Weathering - the exposed surface of a shingle, or a modifying word describing the color characteristic of a slate. Weathering slates react chemically with the atmosphere to gradually change hue over the years; does not affect longevity or hardness of the slate. See Unfading.