I had to replace a furnace pipe recently and the exhaust goes out a basement wall made of lime mortar that's extremely crumbly. A lot of the crumbling mess ended up in the pipe and blocking the flow so that the carbon monoxide and other gases end up in the house. I need this fixed before the next cold patch. How can I strengthen and shore up the wall in this particular area so that it won't crumble into and around the furnace exhaust pipe? Please do not lecture me on vapor barriers and wall rot. I'm only after a fix for this small area versus the many cubic feet of crumbling lime mortar that I have. I'd just rather not have my family gassed to death. I would consider space heaters but I'm not sure where all the water pipes are and if I could reach them to install electric heating and insulation.