Published on February 16th, 2014 | by Henri


Water seeps through mortar and stonework of fireplace

Q.    My problem, which has been on-going for several years with many failed attempts to correct, is water that finds its way through the mortar (or the stone) of my fireplace chimney and then into the house.

The chimney is located in the center of the house and is constructed of the limestone which came from the blasting and excavating work for our house. The fireplace is in the living room, which has a cathedral ceiling supported by a large structural/decorative truss located directly above the fireplace mantle. Water somehow gets to the truss and from there drips onto the mantle.

The most recent (and so far successful) thing that was done was to tightly wrap the chimney with a tarp. That was several weeks ago and with all the rain we’ve had since then, not a drop in the house. The roofer showed me what he thought to be the problem: the mortar in the chimney seemed to be deteriorating and had moss growing out of it in places. He also thought the stone itself might be porous.

My question: is there a remedy? Something I can brush or spray on, or some other solution short of tearing down and rebuilding the chimney. Would it be wise to have the outermost part of the mortar removed and replaced?

A.    The deteriorating mortar should be removed, but you don’t have to remove it entirely. A competent mason will know how to tuck-point the mortar joints. Then the entire chimney — stones and all — should be coated with a clear water-repellent with a siloxane base, as it may also be that the stones are porous. The chimney cap should also be checked and repaired if it has cracked — a common problem.

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