We tear off down to the deck, every layer, not just the top course of shakes. Once the old roof is off, we check the sheathing underneath. If it's original skip sheathing — the gapped board pattern most older Burnaby cedar roofs were built on — we replace any rotted sections and keep that same skip pattern rather than switching to solid plywood. Skip sheathing lets air move under the shakes; solid ply traps moisture against the wood, and that's where a lot of cheaper re-roofs start failing early, sometimes within a few years instead of a few decades.
From there, we install pressure-treated cedar with interlay felt spaced properly between courses for drainage, so water sheds the way the roof was designed to shed it in the first place. It's the same process whether the crew is working a straightforward gable roof or the steeper, more cut-up rooflines common on Capitol Hill's older character homes.