The question has been asked before here and got a pretty good answer from u/textandtrowel.

While I was initially going to restrict the question to Norse architecture, looking at this week's theme prompted my curiosity about Polynesia as well.

It wasn't done in New Zealand. The shape issue is even worse, as waka are a much longer and narrower shape than you'd want a building to be. I don't really know about tropical Polynesia, but we can safely assume the same, given that larger waka were double-hulled, with the individual hulls not being much wider than small ones (they were also sewn together from several sections, which would be harder to keep waterproof).

The only post working life use that I'm aware of for Māori waka (often ones rendered tapu by the death of their owners) was cut in half and set upright then carved or painted as a memorial for the dead. For instance, a photo of a late 19th century carved example and drawings of two painted mid-19th century ones. Joel Polack, who was not a terribly gifted artist (or author tbh) has a couple of drawings from the early part of the century here showing some, as well as the observation that some used as coffins as well as simply markers. The webpage for one of these objects in Te Papa Museum (under the unassuming name of a waka whakamaumaharatanga) has a short poem on the practice. Of course the other notable use of ships by the Vikings, the original focus of the question, was funerary as well.