According to Fairchild's Dictionary of Textiles, Broadcloth was "a fabric made on a wide loom, specifically one wider than 27 inches." Since the narrowest weave found commercially is typically 45 inches wide, it seems odd that 27 was once considered broad! But, width was not the only consideration. Specific to weaving on the broader loom, the fill or weft threads are heavier and have less twist, creating a heavier hand than the lighter habotai or china silks.
In addition to the dictionary definition of broadcloth, Julie Parker provides that silk broadcloth is typically woven of spun silk, versus filament silk. So what is the difference between spun silk and filament silk? From Fairchild, filament is "a fiber of indefinite or extreme length, for example, silk filament, which runs from 300 to 1400 yards and more." This unadulterated length allows for the filaments to be woven as is, with no additional twist. This is not to say they are NEVER twisted, because that would be grossly inaccurate. But in the case of broadcloth, twisting would be unnecessary. And this is because of the spun silk threads used in the weft.
Again from Fairchild's, spun silk is made of the short lengths of silk waste. When silk cocoons are harvested, they are typically unraveled to obtain the unbroken filament. But they can also be harvested after the silk moths have broken out of the cocoon. This will create many slubs. One way to work with the slubs to card the silk, like wool is carded, then spin it in to threads for weaving. And in this way is broadcloth made...a plain weave silk, but with a very different hand and texture than habotai.
Because broadcloth has a bit more texture, it is very easy to work with, and holds a crease. While we don't sell Silk Broadcloth (yet) it is relatively easy to come by commercially and is sometimes known as shirting silk.