Green’s Dictionary of Slang

(N.Z.) a general negative: unpleasant, disgusting etc.

1968		J. O’Grady Gone Troppo (1969) 64: Bill reckoned he wasn’t cut out to be a shouse mechanic. [...] Ned said later he was good at it.
1988		McGill Dict. of Kiwi Sl. 102/1: shouse something very bad, contraction of ‘shithouse’.