Wiktionary
adv. Being built or under construction, as a structure or a vessel.
Usage examples of "a-building".
He would not be able to construct a Gothic cathedral, which had come at the end of centuries of experimentation and accumulated wisdom in Europe, nor a great Catholic church like those now a-building in Italy, where the same kind of knowledge was available, but he would be quite competent to build a smallish house of worship which seemed to be a part of the forest and a logical outgrowth of the river, and such a building, if it were perfect in each detail and inwardly harmonized, would acquire its own cathedral-like beauty.
But a dozen others took a minute or three minutes and said things about Chicago in 1920 or Culver City in the mid-Twenties when there were meadows and fields and the false civilization of MGM was a-building and ten or twelve nights a year the big red car pulled up on a siding behind the studio and Louis B.
Then a hook for reaching up through that opening and pulling the stone down and out between the testicles, and an assortment of variously sized and shaped rakes for scraping the inside of the bladder and probing up into the ureters to find and withdraw any smaller stones that might be a-building in the crannies.