[Strawbale] Strawbale Digest, Vol 21, Issue 7

[Derek Roff]

Walls, made of any material, usually need foundations, if they are to 
continue to stand.  I would think that frost heave would be an issue in 
your location, as would resisting wind loads, so that the wall is less 
likely to fall over.

I'm a fan of earth bags, less so of gravel bags.  The earth in 
earthbags forms a solid block, rather like adobe, which will hold its 
shape and integrity even if the bag materials disappear.  Since gravel 
doesn't bond with itself to form an integral block, a gravel bag is 
held together primarily or totally by the bag material.  I don't like 
basing the integrity of the entire wall on a bunch of polypropylene 
rice bags.  An alternative is to fill the bags forming the sub-grade 
foundation and lower courses with a soil-cement stabilized earth.  With 
the right mix, these blocks will maintain their strength and shape, 
even if the bag degrades away, due to UV light or rodent attack.

Walls blow over with some frequency.  Buttresses can help (no need for 
flying buttresses, however).  Building the wall in a serpentine plan, 
rather than a straight line, can make a substantial difference.  It 
also makes the wall more interesting and produces microclimates 
conducive to different plant species growing along the undulations.

It would be great if the city could inspire most homeowners to do the 
regular maintenance needed for a lime or earth plaster.  That looks 
challenging to me, unless they received money for their labor, rather 
than just for supplies.  I would use mesh if a portland cement plaster 
is chosen.  With proper design, mesh can contribute to resisting wind 
loads.

Derelict


--On Wednesday, March 12, 2008 12:00 PM -0500 
strawbale-request at listserv.repp.org wrote:

> After years of trying to get the City of Ann Arbor to consider an
> earthen/strawbale project, I think I have finally stumbled onto one
> that they are interested in doing, but I have some questions.   First
> let me describe the project... The south side of Ann Arbor consists of
> low-income homes that sit directly next to the I-94 expressway.  I
> have proposed that we build earthen walls and involve the community
> so that we get buy-in, ownership and a sense of empowerment from the
> neighborhood.  I have been reading on-line that strawbale is not the
> way to go when you want to build earthen walls (especially in wet
> areas like S.E. Michigan.), unless you are willing to build them like
> a structure (ie. Roof, foundation, drainage, etc.)  I have also been
> reading about the use of earth bags in place of the straw, which I
> think is a wonderful idea for this climate, but I read that you don't
> need a foundation if the bottom bags are filled with gravel...is this
> true, and if so, would all of the bags under the ground level be
> filled with gravel??
>
>
>
> Some of my other concerns are with the structure and with the
> plastering...Does the fence need to have a wire mesh affixed to the
> earth bags prior to the plastering? Do we need flying buttresses along
> the wall for stability...and if so at what interval?  I was thinking
> that we could use an earthen plaster with a finished coat of lime
> plaster, however I am concerned about continued upkeep of the fence
> and the fact that the community will be in charge of maintaining their
> individual sections of the fence...Given this what are my
> alternatives? There was some discussion today that we could do some
> community education about upkeep issues and we could create an
> account that the community could utilize when they needed money for
> supplies.  I think the sense of ownership that each homeowner will
> have for their individual wall section, and continued support from
> the City should guarantee success...what do you think?
>
> Thanks,
>
> ~ Jon
>
>



Derek Roff
Language Learning Center
Ortega Hall 129, MSC03-2100
University of New Mexico
Albuquerque, NM 87131-0001
505/277-7368, fax 505/277-3885
Internet: derek at unm.edu