They're pretty shy, I have them indoors but rarely see them (compared to other species). Easier to catch/find them outside & in sheds & out buildings, where they are less spooked by heavy footfall?
"I have them indoors but rarely see them..."
Famous last words, eh?...Just found the 3rd S. grossa in a month, in my flat. :-)
2 males & 1 female. The males are usually easier to see as they are more likely to be wandering about in search of a mate. But, the males are also less distinctive from a distance, unless you notice the black & white, checquer-like pattern on their backs (I had to stick this one under a magnifier to identify it), they have much smaller abdomens and can pass for many other male spiders at a distance/quick glance.