No wooden beams or joists shall be placed within two inches of the outside face of a chimney or flue, whether it be for smoke, air or any other purpose. No woodwork shall be within four inches of the back wall of any fireplace. All spaces between the chimney and the wooden beams shall be solidly filled with mortar, mineral wool or other incombustible material. The header beam, carrying the tail beams of a floor and supporting the timber arch in front of a fireplace, shall be not less than twenty inches from the chimney breast. No wooden furring or studding shall be placed against any chimney but the plastering shall be directly on the masonry or on metal lathing. Woodwork fastened to plaster which is against the masonry of a chimney shall have a layer of asbestos board at least one-eighth inch thick placed between the woodwork and the plaster.