permaculture

["John Schinnerer" <john@eco-living.net>]

Aloha,

Thanks for the compliments.  Other stuff to come...eventually... ;-)

> ...I wonder if anyone has come up with a faster way than twisting
> with lineman's  or fencing pliers every 6" or so.

Yep, though I haven't seen the device myself - a guy built a couple FC
dwellings near Kalani eco-resort (formerly Kalani Honua) on the red road
(Puna, Big Island) and I was told he made a small device that fit into a
drill chuck and would grab the wires and twist them, zip! and it's done,
next please...with one person on one side placing wires and the other on
the other side with the drill it sounded pretty quick.

I used light 20 ga. galv. wire and could twist by hand to start, then a
quick twist or two with pliers to pull it all together.  Lotta zen work,
to be sure... :-)

> I wanted to discuss your footings a little bit more. Let me preface this
> that I am not a builder and have a lot to learn. It seems to me that the
> rebar which is pounded directly into the ground will rot (rust) away
> pretty quickly in a tropical environment, and that corrosion will travel
> up through the footers and into the walls of the structure. Was this
> something that you considered? Clearly, it's easier  and cheaper to
> pound in some rebar rather than building a whole perimter footer with
> rebar risers, but what has that choice done to the building's longevity?

Yep, thought about that quite a bit.  The rebar below the footers is
'sacrificial', I expect it'll rust off/away eventually.  It's not
structural, it was just the quickest/easiest way to get the rebar to stand
up while I put the footers around it and got the wire on.  Some don't go
through the footers - the ones on the solid sloping lava are just sitting
on that lava, cast into the footers.

They are extremely well drained, as they're simply poked into the packed
cinder driveway fill until they hit the underlying solid lava (most were
barely deep enough to stay upright).  It's rather different than putting
them into soil or a similar medium.  They may barely even be getting wet
down there, I don't know.  I could make a little excavation to check, I
suppose.

Whether oxidation will travel up the whole way through the footer via the
rebar and keep going, and how long it'll take if it does, remains to be
seen.

The only ungalvanized metal in the structure is the rebar, and the rebar
isn't necessary to the integrity of the structure.  In FC it's the
close-woven mesh layers in combo with the cement plaster that give the
strength.  The rebar is just an initial support for the mesh armature.  If
I could magically make all the rebar vanish, I doubt it would affect the
integrity of the structure.

If I wanted to avoid all rebar/ground contact, I would still use separate
'quick-formed' footers, but I would bend the bottom of the rebar
horizontal and keep it completely inside the footer pour.  This would
require multiple braces on every one to hold them up/in place.

In other words, I don't know (yet) but I'm not too worried.  What I do
still plan to do is put a moisture-sealing coating on the exterior to
limit  moisture penetrating to the mesh through the wall in general (from
humidity, rain splash near the bottom, etc.)

> I was curious as to why you did the three layers of poultry mesh.
> Certainly it adds strength, but would the expanded metal lath be enough
> on its own?

I was originally going to use just the mesh - I added the lath because
three layers of mesh wasn't tight enough to hold plaster well (lots of
sagging and dropping off, there's one small spot on the building that
shows this, where I tried my first plaster batch before adding the lath).

Most sources I found recommended five or more layers of mesh and didn't
mention lath at all.

I've heard of people using only lath.  A friend of mine made a goat shed
using only lath (that's how I came to think of it when I needed a better
plastering surface than three layers of mesh).  A few parts of my
structure (the arches over the front and rear doorways and the top portion
of the walls as they rise towards the front) are lath only.

For hand plastering I think it would be difficult to get the plaster to
"meet in the middle" of multiple layers of lath and fill all the voids
properly - I had a few small areas where lath overlapped and/or was on
both sides and it was difficult to get enough plaster to push through and
fill spaces in between.  I have heard (but not seen) that a sprayer will
penetrate five or more layers of lath no problem, if one is using a
sprayer.

The mesh can be gotten in much larger units and rolled on big areas all at
once.  It's quicker and easier to cut and less sharp and nasty to work
with overall, and can be shaped more freely as well.  For me, multiple
mesh layers with one lath layer was an excellent combination and probably
what I'd use again.  For small stuff that wasn't 3D-curvy I'd use just
lath, probably.

> Did you tie all four layers at once, or each one separately?

I put relatively few wires to hold each mesh layer in place as I rolled
them on, then wired all three together at once.  The lath I had to do
separately since I wasn't originally planning on using it...otherwise I
would have tacked it all up and then wired all four at once.

> And while we are on the topic of ferrocement, I wonder if anyone knows
> how to calculate the maximum dimensions of a safe ferrocement cistern. I
> would like to understand how to calucalte that, as sometimes I muse
> about putting a really large tank on my land.

How large?  I've seen 10K gallons at least, hand-built...that's pretty
large.  More than that and a pond or multiple tanks might be more
efficient...?


John Schinnerer, MA
-------------------------
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Cultural & Ecological Designing
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