There are quite a few familiarity markers in English - words which take on an ending to make the word sound much more familiar, or everyday, or down to earth.
This might sound off-putting, but it supports Harrison's concept of the building — that the person approaching is intrigued and wonders what will be inside.
And by according to plan, I mean the plan that I just totally made up on my head, that is only vaguely substantiated with real rumours and speculation but it sounds good so.