We have a 1100-square-foot 1950’s ranch. The interior basement walls look good, but we have several hairline cracks visible on the one-foot exterior block that we can see. Is urethane caulking a good idea? Thanks!!
If the cracks are vertical and next to an outside corner, it could indicate some wall movement. When a block wall moves inward, a crack often appears near the corner in the vertical mortar joint. You can check the walls for movement with a plumb bob or a long level. The walls should be within 1/2 inch of plumb when compared to the corners.
Minor cracks on the outside of the block wall could be filled with a urethane or polyurethane caulk but this is not a structural repair – just cosmetic. If you are considering selling your home soon, caulk may not be a good idea because it raises the question of what the caulk is hiding.
Check for movement and other cracks inside. If you do have cracks or movement over 1/2 inch, consider a review by an independent basement consultant.