November 16, 2016
Standing seam metal roofs have proven record of longevity and value in providing a very weathertight roofing solution. But the performance of any roof can be compromised by needed penetrations to accommodate other building systems. Done poorly, those penetrations can cause leaks, building damage, and unnecessary expenses. When properly designed and installed however, roof penetrations can be integrated into metal roofing successfully without compromising performance.
Pipe penetrations, whether for plumbing vents, flues, or other miscellaneous pipes, are probably the most common type of roof penetration in commercial metal roofs. Here are five proven and practical guidelines to help avoid problems.
A qualified roofing installer is the best person to cut and install an appropriately flashed and booted pipe penetration. If that isn’t possible or practical, then any penetration installed by another contractor should be fully coordinated with the architect/owner’s representative and the roofing contractor. This is the only way to be sure that the integrity of the roofing system is maintained.
To properly seal around the pipe penetration, use only a rubber roof jack made specifically for use with metal roofs. Do not use residential-type roof jacks or those designed for other roof types – they will not last over time. Further, do not use materials that are dissimilar to the standing seam metal roof, such as copper, lead, or galvanized metal roof jacks, which can corrode the metal roof system, or are an inferior quality with a short service life (less than 20 years). Proper commercial roofing products combine an EPDM rubber boot (or silicone for high heat applications) with a bonded aluminum band to allow a compression seal to be formed at the roof panel.
All planned penetrations should be assessed first to be sure they are not inadvertently creating a potential leak or other problem. Rather, they should be located so they can be properly sealed with no immediate obstructions that would make the seal to the roof unnecessarily difficult or compromise long-term performance.
The penetration must allow for thermal movement of the roof. Pipes or other penetrations that are rigidly attached to the structure below may not be able to move as the roof expands and contracts. In these cases, the hole in the standing seam roof should be large enough to allow for this movement without the roof panels impinging on the penetration.
If the penetrations are to be included in a manufacturer’s weathertightness warranty, the manufacturer must approve in writing beforehand the materials and methods to be used to install the penetrations. Failure to follow this guideline may result in the penetrations being excluded from the weathertightness warranty.
If everyone involved with the roofing penetrations is aware of, and follows these five guidelines, then in the end everyone should be quite happy with the long-term performance of the roof. If not, the potential for roof leaks and other related problems only increases.