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			Home Page Historic Architectural Styles Categorized How-To Historic Homes & Districts Real Estate Resources Historic Building Consultants News and Events Enter your search terms   Web historicbldgs.com Submit search form WHK3 Web Sites	Stone Foundations By Bill Kibbel Stone foundations, the most common type below buildings built before 1915, seem to frequently be a concern for owners of old homes. With their sloping floors and cracked plaster, it's only natural to suspect foundation failure to be the primary cause. A brief visual inspection will quickly disclose bulging, bowing, shifting or settlement that may require an experienced mason to repair. If there is a crumbly mortar coating, some minor gaps in the joints but the stones appear to be generally where the original builder placed them, then most smart do-it-yourselfers can restore and maintain their home's foundation.   Most stone foundations in my area have (or had at some time) a mortar coating on the interior. This mortar coating will inevitably flake off from moisture migration and reveal the interior surface of the stones. As this coating continues to erode, the soft, sandy mortar in between the stones begins to fall out. When this occurs, re-pointing is needed as soon as possible. If enough of the old mortar falls out, stones will start shifting around and the walls start to bulge inward. To avoid perpetual re-pointing, it is best to maintain the foundation by patching the interior mortar coating when needed. There's alot of information about using "soft" mortar, that doesn't contain modern Portland cement, for historic masonry repairs. I see many, many stone foundations repointed and coated with the home centers' pre-mixed hard mortar and honestly, it's never shown any sign of causing problems, when applied on the interior. If doing repointing or repairs on the exterior, lime mortar would be the better choice, particularly if the stones are of the softer, sedimentary type.   Cross section of typical fieldstone or rubble foundation. Moisture penetration through stone foundations not only erodes the mortar, but in excess, can cause pressure against the foundation and frost heaving in cold winter climates. Proper drainage around the perimeter of the building is important to avoid these conditions. The ground and impervious surfaces, like patios adjacent to the foundation, should have a positive slope away from the structure. Roof run-off should be collected in a well maintained gutter system with downspouts discharging well away from the foundation walls. Sump pumps discharge pipes should also be extended well away from the house. Adding sub-grade drainage systems should only be used as a last resort. These systems are not only very costly, but many of them require disturbing the soil against the foundation, which has been well compacted over a very long time. Even worse are "waterproofing" systems, that are installed around the bottom of interior walls and drain into a sump pit. Many of these end up sucking the earth out from under the foundation. Text & Images ©2001 Wm. Kibbel III Bill Kibbel is an experienced historic building consultant and inspector in southeastern PA & central NJ. Bill also writes articles and a column for national and regional publications about historic building restoration & preservation and is a frequent speaker at conferences for preservation groups, building inspectors and restoration professionals.