Steel Door Inc.

Technical Education Series - SDI 108

SDI 108 (Recommended Selection and Usage Guide for Standard Steel Doors) is one of the Steel Door Institute’s most referenced standards. This document assists architects and specifiers with the proper selection of steel doors and frames for various applications. It is intended to guide design professionals in choosing the correct door level and design for their projects.

Table 2 in SDI 108 suggests a door level and design for various building types such as offices, industrial, schools, and hotels, among others. Door levels are from 1 (Standard Duty) through 4 (Maximum Duty). The lower the Manufacturers’ Standard Gauge (MSG), the thicker the steel. A very general rule of thumb is that the gauge number is how many sheets it would take to be an inch thick. Therefore twenty MSG #20 steel sheets stacked together would be about an inch thick.

In addition to showing which level door to select, the table also shows which of the six most common door designs are ideal for a project. For example, if a design professional is seeking an entrance door to a hotel, SDI 108 suggests a Level 1 or 2 flush door (see image below). Please note this document is solely a guide and the ultimate decision is up to the specifier.

The last page of the standard has 27 popular door designs along with their nomenclature. SDI documents are reviewed every five years to determine if revisions need to be made. This standard was last revised in 2010, when more door designs and nomenclature were added. There are more designs available beyond the 27 shown, which vary by manufacturer.