It’s been said many times – A roof is most likely going to leak at either a protrusion or a change in direction. That is why the selection of hardware to use, when waterproofing protrusions, is critical.
Firstly, the correct hardware must be chosen for each protrusion. Protrusions can be varied but the majority of protrusions are drains, plumbing vent stacks, fan and furnace/hot water tank vents or attic space static and non-static air vents. Material choices are plentiful so it’s easy for an inexperienced contractor to make a wrong decision. The choices include lead, copper, steel, plastic, rubber or aluminum. Let’s analyze each.
Lead This is most commonly used in steep slope roofing applications for plumbing vent stacks. Many years ago it was also used in lower slope applications such as tar and gravel and torch on. Drains also used to use lead sheets for a waterproofing detail. Today, lead is still acceptable for tar and gravel roofs however not much tar and gravel roofing is being installed any more. Lead should definitely not be used in torch on applications as it melts too easy when it gets close to the open flame required for a quality torch on roof system application.
Copper This is primarily used in drains on flat and low slope roofs. It is also used for drains in hidden gutter or built in gutter applications on steep slope roof systems. Most all roofing materials are compatible with copper when appropriate primers are chosen.
Steel Commonly used for vents of either static or forced air. Galvanized steel is primarily chosen as the regular texture and style. Steel is most commonly used in flat and low slope roofing but it is also used on steep slope roofing for fan vents such as bathrooms, kitchen hood fans or furnace and hot water tanks. “Gooseneck” vents are the most common shape of steel vents.
Plastic Only used on steep slope roofing. Not necessarily a quality piece of hardware as it is prone to either warp or dry and crack. The only plastic I use in my roof systems is as a static
air roof vent along the ridge of my shingle roof systems.
Rubber Used on steep slope roof systems in conjunction with plumbing vent stacks. Commonly called “5-in-1s”. These are prone to drying, shrinkage, deterioration or anything else that effects long term performance. I do not use them. The only time rubber is acceptable for a hardware piece is when it is used on an EPDM rubber roof system and is supplied by the system manufacturer.
Aluminum The selection of choice for plumbing vent stacks on torch on roofs. Do not accept anything else.
The second most important factor is sizing. You don’t want to put a 3” lead plumbing vent stack on a 1.5” ABS plastic pipe. It just doesn’t work for long term performance. Ensure the sizing is appropriate.
And thirdly is the preparation of the hardware. Does it need priming, cleaning, scratching, cutting, burning or stretching? Most every piece of hardware needs to be modified somewhat from the original condition it was delivered in.
In the attached photo I have burned and scratched these copper drains. They are now ready for the appropriate primer to be applied. Ensure your roofer knows the critical details of hardware selection. It could make or break your roof.