The construction industry is constantly evolving. Today’s construction professionals utilize new materials and techniques to create increasingly durable structures. Some examples of this include exterior metal wall panel systems and metal-capped parapet wall details that support structures while offering helpful properties such as corrosion resistance.
However, in order to take advantage of these types of systems, the contractor must understand how metal wall panels generate excess heat within a structure. Heat buildup can cancel out the beneficial properties of these systems. Therefore, it’s imperative that contractors understand the proper application procedures for vertical underlayment installations. In this two-part article, a Tallahassee construction lawyer will provide practical application tips for vertical underlayment installations.
Minimizing Heat-Related Damage
Before you install self-adhered underlayments, you must be absolutely certain that they have the appropriate high-temperature rating to perform sufficiently. Installing vertical underlayments for roof and sidewall systems helps combat the immense amount of heat typically generated underneath metal panels. If your underlayments are not rated for high temperatures, they could be broken down by excessive heat limiting their ability to safeguard the structure against water, moisture, and air.
Tips for Successful Vertical Installations
Any self-adhered underlayments must meet the requirements established in ASTM D1970, such as adhering to the thickness requirement (40 mils or thicker). These requirements essentially establish that successful installations require a heavier membrane that must be fastened in place whether being installed horizontally or vertically.
Horizontal Installation: When installing an underlayment horizontally, the installer must begin at the bottom and back nail and apply button caps in 12-inch intervals along the center of the top edge. Then, they will install a 3-inch side lap to protect the button caps from exposure. The end laps must be installed with a 6-inch overlap to ensure full protection.
Vertical Installation: Similar to a horizontal installation, the installer must work from the bottom to the top. If the membrane falls short of the top, back nail button caps in 12-inch intervals along the center. A 6-inch end lap can be used to protect the button caps.
Another important piece of information regarding underlayment installation dictated by ASTM D1970 is that the underlayment is required to be self-sealing around fasteners. More information about self-sealing underlayments can be found in ASTM D7349, but the premise is that an adhesive system should form a waterproof seal around the button caps to prevent any water from reaching the substrate underside, fastener shank, or between the membrane and substrate.
Lastly, under ASTM E96, the underlayment membrane must have a moisture vapor permeance of ≤0.1 perms and the contractor is required to account for proper ventilation by ensuring that a 1-inch wide air gap is included.
To learn about other important factors regarding the installation of vertical underlayments, read part two.
Disclaimer: The information contained in this article is for general educational information only. This information does not constitute legal advice, is not intended to constitute legal advice, nor should it be relied upon as legal advice for your specific factual pattern or situation.