Dear GBA folks,

This fieldstone carriage house, built in 1910, has 22″ thick stone walls (see picture). Inside on the second floor, 2×4 stud walls built about 2″ away from the stone are covered with 1″ plaster.

In the kitchen, also on the 2nd floor, there’s a 6ft wide dormer whose back wall is the back of the fieldstone chimney, so there is no stud wall, but the masonry has been parged, skimmed with spackle and painted. There is a copper cricket roof above. It and all the flashing around the chimney has been checked and re-mudded where necessary and the 3′ x 4′ chimney crown, which had a big crack, was repaired. Most of the voids and cracks in the chimney have been pointed. Some more work left to be done there.

So apparently, there’s enough moisture coming through the 6ft wide wall that the finish material and paint keep crumbling and peeling off. It happens on certain areas, others are dry. There’s no dripping water, it’s just enough to mess up the finish on the wall.

Now I know that most likely there is some quantity of water getting into the two flues by condensation of the heating system’s exhaust gases and/or just rain getting in—one of the flue pots has an open top. A camera snake also revealed some voids between the flue tiles. A chimney man suggested putting stainless steel liners in both flues, which would help with the boilers exhaust gases and also keep any water in the flues. This and more pointing might keep water out of the chimney structure.

Meanwhile, my wife is very much wanting to have a nicely finished wall there sooner than later! Our stone mason, James, suggested taking off any joint compound and finish and just leaving the chimney masonry exposed and lightly sealed so that it can dry out. I kind of like this idea depending on the aesthetic appearance but it might look a little too rough!

So the next thought was about creating a 2×4 stud wall backed off the stone an inch or two with concrete board and attaching tile to that. But the wall would have a space under it and above it or long vents top and bottom. Maybe even a little computer fan or two blowing into the lower vent to create just enough airflow to keep the masonry behind dry.

The last (for now) is to clean up the existing wall which means pull off any finish material like joint compound, paint—loose or otherwise. Then level it with thinset and attach veneer brick or terra cotta tile or some other very porous stone that would look nice but also take the water migration and allow it dry. Will the thinset just break down? So this is my question: does this last option seem viable to you or have you created or seen anything similar?

Thank you so much in advance and I eagerly look forward to your reading your thoughts.

Rob Cramer
[email protected]

By the way, we live in New York State (Rockland County) about 1hour north of Manhattan, zip code 10901.