The Proper Installation of Roofing Shingles Around Soil Stacks

Roof Decks and Roofing Paper

• Roofing paper, or felt paper, covers a shingle roof's plywood or OSB decking. Roof vent pipes penetrate through both roof decking and roofing paper. Before roofers usually complete roof installation, plumbers bore through roof decking with a power drill, slide the vent pipe through the hole and join the vent pipe to the plumbing system. Roofers may sometimes install roofing paper before plumbers install vent pipes. In either case, roofers cut an access hole through roofing paper with a utility knife. Many roofers fold excess paper up the sides of the pipe and apply sealant around the pipe's base.

Roof Vent Jacks

• Although manufacturers continually improve roof jack designs, the most common roof jack design consists of a metal tube attached to a flat, square base. The tube protrudes from the base at an angle. When placed over a vent pipe on a pitched roof, the base slopes downward and the tube aligns with the vertically oriented vent pipe. Roof vent jacks are available in sizes that correspond to the diameter of the vent pipe, such as 1 1/2 inch or 3 inches.

Preparing to Install the Roof Vent Jack

• Also called "flashing" the vent pipe, installation of roof vent jacks occurs during shingle installation. Roofers begin shingle installation at the roof's eaves and install successive courses of shingles up the roof until they encounter the vent pipe. When roofers reach the shingles that require cuts to fit around the pipe, they cut notches from the shingles with a utility knife, lay the shingles around the vent pipe and complete the course.

Installing the Jack

• With the course of shingles that intersects the vent pipe complete, roofers lay the course above the pipe until a shingle or two shy of the pipe. Because the course of shingles above the pipe must lap over the jack's top edge, roofers set aside the shingles and install the jack. Although installation techniques vary, roofers typically slide the jack over the pipe and fasten the jack's upper edge to the roof decking with nails or screws. Additionally, many roofers apply roof sealant beneath a jack and around its upper edge's perimeter.

Overlapping Shingles

• After installing the jack, roofers resume shingling by laying and fastening shingles as normal, cutting the overlapping course of shingles to fit around the roof jack's tube. Thus the overlapping, upper course of shingles sheds water onto the jack's base while the jack's base overlaps and sheds water onto the underlying, lower course of shingles.