Sealant: A Critical Step in Metal Roofing

– By Mark Mullins, Fabral, Applications Engineer/Product Training Manager –

The importance of the role of sealant in metal roofing cannot be stressed enough. One common myth when working with exposed fastener panels is that the combination of gravity and a 12” end lap is enough to prevent water from infiltrating the facility. This is a mistake.

The Problem: Leaving the Building Exposed to Moisture Damage
I have examined many open framed structures with multiple end laps. The nesting of the panels actually creates a siphon that will wick water into the end lap and in many cases, enter the building. This causes several issues: water can get into the building and cause damage to nearby items. Water will get trapped in the end lap and possibly causing premature corrosion. Even if water doesn’t get all the way to the top edge of the lower sheet, if it gets to the shank of the end lap fasteners, it can drip around the fastener because there is no sealing washer between the sheets. The biggest issue is that the purlin directly under the end lap rots due to the moisture. This will, in turn, lead to fasteners backing out prematurely and allowing even more water to get to the purlins.

The Solution: Easy, Low-Cost Preventive Measures
An easy and effective way to prevent this is the addition of an end lap sealant tape or gun grade sealant applied between the two sheets at the end lap. I recommend a butyl sealant that will maintain the seal while allowing the panels to expand and contract. This prevents the infiltration of moisture and ensures your buildings stays weather tight.

The sealant must be placed below the location of the fasteners to prevent water entry around the fastener shank. Other places to consider for sealant with metal roofing is between closures and the metal panels and any place where there is metal on metal such as gable trim to panels and sidewall trim to panels. Ridge cap laps are particularly susceptible to water entry because they are almost flat.

 The Results: No Call Backs and Repeat Business
This relatively quick and economical method prevents expensive and time-consuming call backs. As a former installer, I understand the importance of completing a project without having to go back and repair portions of a roof or wall that was not installed properly the first time. It’s hard to maintain a successful business if this is a frequent issue as it affects profitability and maintaining a positive reputation. Repeat business is dependent on word-of-mouth and this only comes from previous customers having a positive experience with your company. Please refer to the installation instructions from your panel manufacturer for a complete and proper installation.

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