Moisture-ruined plaster should be replaced
Q. Last spring a carpenter removed all the old roof shingles and found that a previous roofer had omitted using a sealer, thus causing a slow leak around a chimney. This eventually caused the paint to peel and stain the plaster over an inside mantel. I had the paint removed and the wall scraped before repainting the plaster. However, the paint is not sticking. It looks as if there still is moisture in the plaster since it is loose and cracked. Should all the old plaster be removed and new plaster applied before repainting? Mrs. Emil Silverness Mondovi, Wis.
A. After making sure that the chimney is not only flashed and counterflashed but also caulked as needed, remove the disintegrated plaster over the mantle where the moisture has ruined it.
Relath and replaster as required, or preferably fill in the area with plaster board. Then repaint or redecorate as desired after making sure the area is completely free of moisture and will remain so.
Chimneys also can leak through the masonry or its cap as well as between the flue joints.