The usual route heads up the second stream that drains into the Hapuku W branch above the hut. Since the earthquake it's become a bit more chossy in places but still OK - at some point gain the spur on your left (some routefinding required) - once you arrive at the level viewpoint at 1400m the route from there to the summit is obvious - just follow up the winding spur (there's a section of soft scree and some easy rock clambering). Other more adventurous/sporty options include the long winding (and at time exposed) ridge that starts just north of the Kowhai hut (`middle spur') or via Mt Manakau - but both are much longer and harder.