Figure 13.—A, Elevation of protection around a stovepipe passing through a frame partition; B, sectional view.
Figure 14.—Method of insulating wood floor joists and baseboard at a chimney with 4-inch walls. A single header is used as it is less than 4 feet long.
Insulation
No wood should be in contact with a chimney. Leave a space of 2 inches between the outside face of a chimney and all wooden beams or joists except when 8 inches of masonry is used outside flue lining, in which case the framing may be within one-half inch of the chimney masonry. The space between the floor framing and the chimney may be filled with porous, nonmetallic, incombustible material, such as loose cinders. Brickwork, mortar, and concrete are not suitable. Place the filling before the floor is laid, as it not only forms a fire stop but prevents accumulation of shavings or other combustible material. Subflooring may be laid within one-half inch of the masonry. Baseboards, when fastened to plaster that is directly in contact with the wall of a chimney, can be protected by a layer of fireproof material, such as asbestos, at least one-eighth of an inch thick between the woodwork and the plaster ([fig. 14]).
Wooden studding, furring, or lathing should not be placed against a chimney but set back, as indicated in [figure 9]; or the plaster may be applied directly to the masonry or to metal lath laid over the masonry. The former is the better method, as settlement will not crack the plaster. It is recommended that a coat of cement plaster be applied directly upon the outside surfaces of masonry chimneys that are to be incased by a wooden partition or other combustible construction. Metal lath, lapped 6 inches on the masonry, at the intersection of chimneys with partitions prevents corner cracks. (See plan in [fig. 34].)