We read alot about larch before deciding on the type of treatment. Larch is naturally rot resistant, some people would argue it should not need any treatment. Ours is Japanese larch which is slighly less resistant that other types. They make yatchs out of it and outer boarding for upmarket houses here in the UK. Due to lack of experience we didnt want to damage any of the natural resitance by burning/carring. If they had been pine we would have been tempted to burn. Cheers