Dry stone foundations

[duckchow at ix.netcom.com]

At 10:47 AM 1/1/97 -0600, Eric wrote:

>        Can anybody describe to me how a dry stone foundation works?  I was
>looking at the Earthsweet Home WWW page (a non-profit in Vermont I believe)
>and they were saying that this method has been used in New England for a
>long time and is much more common in Europe.  Its kind of hard for me to
>visualize how a foundation can take lateral loads when its not connected by
>mortar.  Must be something else holding it together.

Points from Building With Stone by Charles McRaven -

re: drystone foundations

use a heavy sill to distribute the weight of the structure [I think this
assumes a wood-frame structure, rather than earthen]

not essential to go below frost; just somewhere below topsoil - but it *is*
essential to dig WIDE... the author's rule of thumb being that the base
should be twice as wide as the foundation wall, which in turn should be
twice as wide as the building wall ... "a six-inch building wall should go
on to a 12-inch stone foundation set on a dry footing base 24 inches wide"
[again appearing to assume a wooden structure]

downward friction is relied upon for lateral strength [clever and
considered stone placement creates an interlocking puzzle of sorts]

drystone foundations should be one stone wide [as much as possible, anyway,
judging from the illos] - the weight of a house can push a double-wall
foundation apart - [so we're talkin' pretty big stones here, the bottom
ones being two feet wide...]

"There's really no point in setting bolts to anchor the sills - or any
practical way to do so - since each stone in the foundation is loose.
You're counting on gravity to hold it all in place anyway."

bind corners with alternate long stones

[So it seems that weight is the thing; the house isn't 'plugged into' the
ground at all, but rather floats on the stones. Sorta like the old Swedish
barns up north built on drystone piers. (Sorry folks, that's a Minnesota
reference.)]