[samatman]

From the article, he built a house of worship which he intended to offer for consecration. If that had happened, it would have been an oratory, probably, since a church has a resident priest.

The intention is important, I'm not sure what to call it but "chapel" as distinct from oratory is probably closest. To a Catholic these are the same thing, but: any Christian would recognize this as a chapel, just not a Catholic one, and we have the precise term "oratory" to cover that.