Pipe Installation for Metal Roofs

Considerations

• All rooftop pipe installations, including those on metal roofs, begin with a review of manufacturers' information and building codes for the particular situation. Some locations' building codes may require a contractor to complete certain pipe installations. Also, the manufacturer of a chimney pipe may require installers to create a clearance of 2 inches around the pipe where it passes through a metal roof. Non-heating piping such as vent stacks and copper piping are other commonly installed roof pipes. Clearances usually are not required for them; instead, the hole for one of those kinds of pipes in a metal roof fits the pipe's diameter.

Flashing

• One of the most important elements when installing any penetrating roof object is the flashing. It ensures the installation is watertight. Typical sheet metal flashing may not work for metal roofs, especially if they are corrugated. Flexible flashing, however, makes it simple to create a seal on metal roofs. Made of aluminum, silicone or other flexible material, flexible flashing can conform with all kinds of roof textures.

Hole Cutting

• Installing a pipe in a metal roof requires drilling a starter hole in the intended location for the pipe. You can enlarge the starter hole with a jigsaw, cutting the opening through the roof and plywood sheathing based on the pipe's measurements and applicable clearance guidelines. Run the pipe through the roof by following the installation guidelines of the product and building codes. For example, some areas require that a chimney pipe extends 3 feet above a roof and vent stacks reach at least 1 foot above a roof.

Flashing Installation

• The flashing you use should state explicitly that it is compatible with your particular installation and pipe type. Flexible pipe flashing often appears as a cone that is cut to size based on the pipe's diameter. When lubricated with water, it easily slides down a pipe. Verifying that the flashing is watertight and conforms with the metal roof's texture is necessary before applying silicone sealant to secure the flashing in place. An option is to apply more sealant around the flashing's edges to ensure it is completely sealed.