permaculture

["Lawrence F. London, Jr." <london@sunsite.unc.edu>]

---------- Forwarded message ----------
Date: Mon, 10 Mar 1997 08:45:36 -0500 (EST)
From: Heidi Wrighton <heidi@heronbay.demon.co.uk>
To: greenbuilding-digest@crest.org
Subject: GBlist: ADV: Foundations for ecological housing.

FOUNDATIONS - from the book Simply Build Green, a Technical Guide to the
Ecological Houses at the Findhorn Foundation. Access this page by visiting
http://www.gaia.org/evis/sbgbook/pg32.html
Will be displaying approximately 3 articles from this book per week during
March. General access to these pages at the following URL
http://www.gaia.org/evis/whatsnew.html



Foundations
Strip, wide strip, deep strip, pad, mass pier, raft and pile are all
different kinds of house foundation. The particular one you choose will
depend on the wall construction and how it needs to be supported, how the
building itself is being supported, the ground conditions and, of course,
the soil type and its bearing capacity. With the exception of pile
foundations, concrete (a mixture of cement, sand and rock, or aggregate) is
the universal material used for foundations. It is very strong in
compression and ideal for transferring loads from walls or columns to the
soil. However, it is weak in tension. Foundations that are subject to any
bending movement, which involves a tensile stress, may need to be
reinforced to give them extra strength. Steel is the normal reinforcing
material and is very strong in tension. So steel-reinforced concrete
foundations offer the best strength qualities of each material. Both
concrete and steel come in different stress grades for different
conditions. Pile foundations can be made from timber or steel as well as
concrete. Foundation design and soils engineering are complex skills and
should always be carried out by a qualified person.


Our Experience
We have tried several different types of foundations. In the first two
houses we used mass pier foundations located to support timber ground
beams, which in turn supported the walls and floor joists. The idea was to
leave the soil exposed under the house, to let it breathe, and thus
literally 'live lightly' on the earth. But we found that the building
regulations in Scotland require not only a damp-proof membrane (dpm) but
also a minimum 50 mm concrete screed. There is no good reason for this,
although the Building Control officers will argue differently, and it is a
pity to have to cover the ground needlessly with concrete. The reasons they
give are: to protect the underside of the house from moisture and dampness
given off by the ground and to prevent plant growth. But given that the
piers were to have been spaced quite widely (2 .5 m) and the ground beams
raised 300 mm above ground, giving very free air flow, moisture would
certainly not have been a problem. As for plant growth, with many caravans
on the site, none with dpms or concrete screeds, one need only look
underneath any one of them to discover that plants don't grow in the
dark!!!




                                The Eco-village Information Service
http://www.gaia.org
______________________________________________________________________________

Eco-Village auditing will provide a measuring rod for existing villages and
communities to compare their current status with ideal goals for
environmental, cultural, and social sustainability. The process of village
auditing will be an exploration of the qualities needed to bring mankind
through the 21st century.
Your community/eco-village is invited to participate in an audit or to just
take a look at the structure of the audit, we're looking for comments and
input.      http://www.gaia.org/thegen/evaudit/index.html

______________________________________________________________________________
                                            heidi@heronbay.demon.co.uk,
heidi@gaia.org 


__________________________________________________________________
This greenbuilding dialogue is sponsored by Oikos (www.oikos.com)
and Environmental Building News (www.ebuild.com). For instructions
send e-mail to greenbuilding-request@crest.org.
__________________________________________________________________