Reading the walls

by John-Manuel Andriote
Tuesday, May 13, 2014

What distinguishes a New England stone wall from a pile of stones? Noted stone wall expert Robert M. Thorson, a geologist at the University of Connecticut, considers a stone wall to be “any continuous row of large stones or stack of smaller ones that is more than four times as long as it is wide.” Anything shorter, he says, “is a cluster or pile of stones, not a wall.”

Most of the walls we find today in New England — on active farms or trailing off into overgrown forests — were built to divide fields, separating animals and crops, but each wall is unique, Thorson says, and classifying them requires distinguishing their function and structure.

Stone Type

Regional differences in the type and color of stone used in walls usually don’t reflect cultural differences, but are simply indicative of the type of stone available in the area and the purpose of the wall. As the most common rock in New England, granite was also the most popular stone for wall building, but gneiss and limestone were also used. Most of the estimated 380,000 kilometers of stone walls that had been built in New England by the end of the 19th century were made of fieldstone — the generic term for rocks found lying in a field.


Most New England stone walls are only as tall as the average man’s thigh, which, Thorson explains, “was governed more by the ergonomics of lifting and tossing stone than by the mandate of fencing.” Laws in Colonial America required a farm fence to be 1.2 to 1.5 meters high. Because most stone walls did not reach this height, farmers added wooden rails on top to help pen in animals. Owners of shorter fences forfeited the right to recover compensation from another farmer whose animal crossed the fence and caused damage.


Stone walls typically are either the “single” type, built to surround pastures, or sturdier “double” walls, parallel rows of stone that lean toward each other or have a center trough filled with small stones.

Other types of walls can be classified according to the degree of care and detail with which they were built. Unlike “dumped walls,” which are simply rows of piled stones, “tossed walls,” in which the stones were stacked loosely like firewood, reflect the attention that went into building them. Most old New England walls are tossed. Those requiring the most effort include orderly “laid walls,” in which stones fit into a “weave”; “mosaic walls” featuring different sizes and shades of stone arranged in a geometric pattern; and “copestone walls,” distinguished by a top tier of stone laid on edge rather than flat.

Walls could be mortared, known as “wet walls,” or unmortared, known as “drystone walls.” The latter proved more durable because chemical reactions between the mortar lime and the fieldstone can weaken wet walls, making them less resistant to tree roots and more prone to crumble.

For more information, visit the Stone Wall Initiative at

© 2008-2021. All rights reserved. Any copying, redistribution or retransmission of any of the contents of this service without the expressed written permission of the American Geosciences Institute is expressly prohibited. Click here for all copyright requests.