What is the best way to repair a large crumbling block on a corner of the house wall?
My house was built in the 1880s and has a stone foundation, mostly sand stone. The best fix for situations like this I have found is building a form and packing in stiff cement and as large of pieces of the original rock as I can get. If you do the form in a couple layers (say using a 2x4 or 2x6, the long way). Let the cement s set around 24 hours and brush off any excess with a wire brush.