2001Sierra wrote:If the ash is not corrosive why is refractory cement recommended at all chimney tile joints,and a thin layer prior to setting the first tile on the footing, when setting a chimney ?
As I understand the reason behind requirement for refractory mortar is because the very high flue temperatures that can be reached with wood fires. You are unlikely to have such a high flue temperature with coal, hence Type S mortar will be perfectly fine. The typical building code does not make such a distinction however, requiring refractory cement on all solid fuel flues including coal. The refractory cement requirement is interesting because when you look a the manufacture's specs on the refractory cement it must be pre-fired to be cured. At temperatures and durations that would almost be impossible to do in a residential flue.