Alright thanks , I appreciate the detail . So far I ' ve only found some code not my area though that specifies a minimum of 4 inches height for a hearth . Now I run into an issue , because if I put that down , it will block the air intake at the bottom of the fireplace . It will probably be completely covered up if I put down either tile or brick , as the hearth needs to be 4 inches thick at the minimum , which will even block the windows to be opened . I ' m trying to get my hands on the building code for Ontario , but man , is that hard to find . So far I ' ve found something for the city of Ottawa where we are , but that only specifies noncombustible material . Nothing about how thick and what type of boards I would need to use . I ' ll keep digging in the mean time .