Q: My limestone house was built in the 1920s. Streaks have developed over time on the limestone in the area where a porch is attached. What caused them, and how can I remove them?
— Robert Sturtz
A: After reviewing photos of your house and talking with you further, Mariangela Pfister of the Ohio Historic Preservation Office determined the streaks are probably either efflorescence — salts that have migrated out from the stone — or leachate from the mortar or limestone. They were probably caused by a roof leak, which you addressed long ago.
She recommended gently brushing the streaks with a natural bristle brush and hot water. If staining remains, try cleaning it with the same kind of brush and some water mixed with a very gentle dish washing liquid, such as a natural product. If suds are left behind, rinse them gently with a garden hose.
Pfister said she wouldn’t recommend cleaning stone on a house where water damage is recent. Wait till the house dries out, she said. She also cautioned against using commercial cleaners. While they can be used successfully, they need to be tested properly on your particular stone, she said. Otherwise they can react and cause a worse stain.
Pfister said every state and Puerto Rico has a historic preservation office that can answer questions from its residents on maintenance issues with older buildings. She also noted that the National Park Service has free preservation briefs and other information at www.nps.gov/history/preservation.
Have a question about home maintenance, decorating or gardening? Akron Beacon Journal home writer Mary Beth Breckenridge will find answers for the queries that are chosen to appear in the paper. To submit a question, call her at 330-996-3756, or send email to firstname.lastname@example.org. Be sure to include your full name, your town and your phone number or email address.