A sound, well-drained foundation is essential for maintaining any building. Foundation failure can lead to structural collapse. Many buildings are at risk today because during cold weather they no longer house animals, whose body warmth prevented the heaving of foundation walls.

Fieldstone forms the foundations for most historic agricultural buildings built before about 1915. The earliest barns and many smaller buildings simply had large stones under main posts for support. Shallow stone walls or piers "dry laid" (without mortar between stones) supported most barns before about 1840. After that, bank barns began a trend of usable basements that required more extensive masonry, often dry laid but sometimes mortared. In the twentieth century, concrete replaced fieldstone in foundations, a trend accelerated by sanitary regulations requiring washable concrete floors in dairy barns.

Poor drainage and frost heaving are the primary foundation problems. Drainage problems occur when rain and snow runoff from roofs or nearby roads, yards, and fields drains into the foundation rather than away from the building or when migrating groundwater flows into the foundation. Poor drainage contributes to the problems of frost heaving, which is caused by the natural freeze-thaw cycle of the soil. Frost heaving will most greatly affect a foundation that is not heated or is not secure in the ground below the frost level. Dry laid and even mortared stone walls may bulge and collapse, and concrete floors may buckle. Heaving will also put stress on the structural frame of the building, and may put parts of it in contact with the soil, encouraging rot and other problems. Water pressure in the soil can crack even the strongest reinforced concrete if the drainage around a building is not good.

Improving drainage is one way to help avoid costly foundation problems. The soil around a foundation should be sloped so that surface water flows away from the building. Do not allow vegetation, debris and other materials that retain water to accumulate around the foundation. Closing up openings and sheathing foundations or banking them with hay may help reduce cold penetration and frost action (but remember to remove any banking material in the spring to prevent water damage). Underground drains within the foundation may sometimes be necessary; they should flow to the surface well beyond the foundation. If you are rebuilding a foundation wall or constructing a new foundation, dig a trench around the perimeter and install drainage materials, including drain tile, crushed stone, and water barrier cloth.

Repairing a foundation often involves jacking up the building, rebuilding its underpinning, and grading the surface so that water drains away from the building. Some contractors have developed innovative methods of pushing heaved stone foundations back into place with jacks and heavy equipment. Sometimes a cracked or heaved foundation can be stabilized with a reinforced concrete buttress, but if the area is unheated a concrete buttress on a stone wall will eventually separate from the stone. If a stone wall is severely heaved or has collapsed, however, the best repair will be to rebuild the wall using the original stones. Consider a new reinforced concrete wall if the existing foundation is not historically important. When rebuilding or installing a new wall or piers, place the footings below the frost level (as much as five or six feet below grade in Vermont), and install good drainage (see above).

Potential archeological remains should always be considered when working on foundations. Disturbing as small an area around the foundation as possible will help to preserve any remains. If while digging you discover any unusual and notable artifacts, consider contacting the State Archeologist at the Vermont Division for Historic Preservation.

© 1995 Vermont Division for Historic Preservation and Vermont Housing and Conservation Board. All rights reserved.

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