How to Patch Stone Foundation
- 1). Prepare the stone foundation by vacuuming up all debris and particles in the crack or space with a vacuum, using a crevice attachment.
- 2). Combine 1 part Portland cement with 3 parts masonry sand in a bucket and wet with a hose to make pasty. Mix thoroughly with a trowel.
- 3). Pour the Portland cement mixture into the crack or hole to fill it. Alternatively, spread the Portland cement mixture over the crack or hole with the trowel. Smooth until flush with the rest of the surface, then scrape away excess cement with the trowel. Let dry for 24 hours.
- 4). Apply a coat of granite and stone sealer over the cement patch on the stone foundation using a paintbrush. Allow the sealer to soak into the patch and dry between five and seven hours, then brush on a second coat of sealer. Let dry for at least 24 hours before walking over the patch.
Source...