A cricket is a small ridge structure build on the high side of a chimney, designed to divert water around the chimney. The Marine Mansion's plans didn't call for one, the roofers tried to get us to omit it, but at our insistence, a cricket was built. Vancouver's climate includes not only heavy rain, but heavy snow on occasion. It is in a snowfall event, immediately followed by significant rain that a cricket will prove its worth. Without a cricket, snow will pile in the trough, building up the side of the chimney higher than the flashing level. With rain, the snow will saturate; because the water cannot freely drain around the chimney, hydrostatic pressure can force water behind the cladding, up and over the flashing and into the house. With a cricket, saturated snow and meltwater are shed around the chimney, avoiding a snow buildup at the chimney wall. In our experience with chimneys without crickets, there is a high probability of leaking in the long term, so the inclusion of a cricket was a no-brainer for us.