What is the maximum variation of mullions out-of-plumb in a 12' run of a storefront?

The maximum variation of mullions out-of-plumb in a 12-foot run of a storefront is indeed 1/8 inch. This standard is set to ensure structural integrity and the proper fit of the storefront system. Maintaining such a precise tolerance is crucial for several reasons: it ensures that the system remains aesthetically pleasing, prevents water intrusion, and allows for proper operation of doors and other movable parts.

When mullions are not plumb, it can lead to misalignment issues, causing problems such as difficulty in opening doors, gaps that may allow air or water leaks, and overall structural imbalances. Adhering to the 1/8 inch maximum variation helps ensure that the installation is both functional and visually acceptable. Properly following these tolerances is a vital part of glazing contractor practices as it directly influences the performance and longevity of the storefront installation.

Variations exceeding this standard, such as those suggested in other choices, may lead to the aforementioned problems, which is why they are not appropriate in this context. The 1/8 inch tolerance is recognized and accepted within industry standards for storefront systems.