fireplace has double pipe exhaust going straight up. Present construction has NOTHING near that pipe and the only place the pipe structure is touched [mounted] is a couple of places. one is the transition from room into attic. That transition is done with a square sheet flashing made for such. The wood surrounding only touches the outer edges of that flashing, about 1-2inches at the smallest. Round pipe through a square metal flashing section. and the flahsing has vertical metal pieces extending up/down approx 1.5 inches.
The question relates to the fact that I need to make a robust structure in that area and a 2x4 may be touching the double pipe's outside surface. Is that a good idea? [Poorly worded question garranteed to get the answer, no.] Does code allow it in most cases? Does safety dictate the 2x4's should be kept at least the distance from the outside of the pipe the same distance that the flashing provides, at the minimum separation?