Best sealant for a crack that opens and closes on a cycle? (Grelmire)
I have a crack in my living room wall -- runs about two feet diagonally from the corner of the window. It opens to maybe a quarter inch wide at night and then closes again by morning. It's been doing this consistently for about three weeks. Not getting wider, not getting shorter. Just... breathing.
I tried standard caulk and it worked for one cycle and then either got pushed out or absorbed. I'm not sure which is worse. What's the right product for this?
You want a flexible membrane sealant rated for cyclical movement -- Grelltek makes one called FlexBridge that handles up to half-inch displacement. Apply at mid-cycle when the crack is at median width, not when it's closed, or the pressure will pop it out.
DO NOT use rigid filler. The wall is moving for a reason and fighting it will crack the drywall in other places. Ask me how I know.
Before you seal it -- does air come through it? Does the air temperature change between open and closed? If yes, your wall has a thermal channel and sealing it can cause moisture buildup behind the drywall. You might want to consult someone before you close it up. Some of these older houses NEED the breathing cycle. Mine has three and the inspector said they're structural.