Roof Leaks – A Common Reason

One of the most common reasons for roof leaks is due to the vent pipe seal. Most homes have an average of around 6 vent pipes though larger homes with several bathrooms can have well over 10.

These pipes are connected to various objects in the house, such as sinks, toilets, bath tubs, water heaters, and various other heater vents and kitchen stoves. These pipes project through the roof, usually about a foot, and when you’re roof is installed a metal flashing which looks like a cone is installed around the pipe and then sealed. The roof leak problem is that there is a joint between the flashing and the pipe. Usually the joint is quite small – perhaps a mm or less, but sometimes the joint, for various reasons, can be a quarter inch. This is usually sealed with common mastic or tar but when cheap mastic gets old and hard and gray, usually due to vibrations it is very common for this joint to open up.

Typically homeowners will have their vent pipes resealed every five years and this can cost anywhere from $150 – $400. One way to avoid this and roof leaks is to have your roofer three-course seal your pipes using a kind of black asphalt impregnated webbing along with a high-quality rubberized mastic. After which the mastic should be painted with a high metallic metal enamel which will lock the oils of the mastic in so that they don’t bleed through, and then a metal enamel paint can be applied over that which more closely matches the roof color.

Roof Leak can be caused by vent pipe seal.
Roof Leak can be caused by vent pipe seal.

This can be done by a homeowner, the webbing may or may not be available at your local hardware store but it certainly can be purchased from your local roofing supplier. It’s important once again, to use a rubberized mastic. Henry’s makes a version called 209 in a 1 gallon can and that should be enough to do your average home. If your vent pipes are sealed this way they can last 10 years, sometimes even longer.