Steep Slope Roofing

The slope of a roof is often referred to as the pitch. The slope, or pitch, of the roof is deter­mined by the ver­ti­cal rise in inch­es for every hor­i­zon­tal twelve inch (12″) length (called the “run”). A roof with x rise/12 run slope means that for every 12 inch­es hor­i­zon­tal­ly (run), it ris­es x inch­es.

Gen­er­al­ly, roof­ing types and roof­ing prod­ucts are typ­i­cal­ly divid­ed up into two pri­ma­ry cat­e­gories, steep slope roof­ing and low slope roof­ing.  Some­times steep slope roof­ing is also referred to as “res­i­den­tial roof­ing” due to the fact that most sin­gle fam­i­ly homes in the U.S. are con­struct­ed with some sort of pitch or slope to the roof.  Just as steep slope roof­ing is often referred to as res­i­den­tial roof­ing, the term low slope roof­ing is often­times syn­ony­mous with “com­mer­cial roof­ing”.  Again, this is due to the fact that, pre­dom­i­nant­ly, com­mer­cial build­ings have “flat” roof designs.

If we were to clas­si­fy roof­ing slopes more specif­i­cal­ly, the list below con­tains the com­mon roof slopes and the terms which clas­si­fy them.  How­ev­er, in gen­er­al terms, low slope roofs (com­mer­cial roofs) are those below 2/12 or 3/12 while steep slope roof­ing would con­sists of roof pitch­es above either 2/12 or 3/12 and high­er.


      Flat Roof: 2:12

      Low Slope: 2:12–4:12

      Con­ven­tion­al Slope Roof: 4:12–9:12

      High­er Slopes:  9:12 — 20:12

      Steep Slope: 21:12 and high­er

Roof slope is a very impor­tant aspect and it is con­sid­ered the pri­ma­ry fac­tor in roof design. The slope of a roof has an effect on the inte­ri­or vol­ume of a build­ing, the drainage, the style, and the mate­r­i­al used for cov­er­ing. For exam­ple, if you notice water col­lect­ing on the roof the prob­lem is prob­a­bly relat­ed to the slope. The style is affect­ed too because the fram­ing of the roof changes the slope.  Steep slope roof­ing prod­ucts are gen­er­al­ly more visu­al­ly appeal­ing because they are crit­i­cal aes­thet­ic com­po­nents for res­i­den­tial con­struc­tion where the roof can con­sist of 40% of the exte­ri­or visu­al appear­ance of a home.  Steep slope roof­ing also gen­er­al­ly lasts longer than low slope roof­ing because the sys­tems shed water much more effi­cient­ly and gen­er­al­ly are sub­ject to less direct U/V activ­i­ty.