The chimney in my 1929 frame home was originally used for coal/wood stoves, which burn hot and dry.
Now, it vents a gas furnace and gas water heater which produce more of moisture.
The mortar used between the bricks in some cases is very sandy and is crumbling out of the joints. Shoulk I be concerned about the internal moisture, of just tuck-point the crumbling joints?
Which cement is best for this application, portland cement, hydraulic cement, or a sand/cement mix?