The photograph shows a collapsing stone foundation on the privy under the eaves. Damage was cased by uncontrolled roof spillage along the foundation walls. Frequently, the primary cause of damage in freezing climates is the pressure exerted by frozen, moist soil against the foundation walls. Most stone foundations had at some time, a mortar coating on their interior. The purpose of this coating was to help hold the stones in place. This mortar coating will inevitably flake off from water runoff, revealing the surface of the stones. As this coating continues to erode, the soft, sandy mortar in between the stones begins to fall out. Re-pointing is then needed as soon as possible to refill where the old mortar fell out. When repointing the exterior face of an old-house foundation, mortar needs to be softer than the surrounding stones. For this reason, a pre-packaged mortar mix is avoided, since it contains a heavy dose of "hard" Portland cement.  

Before & After Restoration Pictures