[permaculture] Ferrocement water tank pix

Keith Johnson keithdj at mindspring.com
Sat Dec 15 01:02:39 EST 2007

The steel rebar and expanded metal lath give it strength and the mortar 
gives it rigidity. The two combined make it VERY strong. Very large (130 
f) ocean-going boats <http://www.ferrocement.org/> are made with this 
technique (the Brits built a 120 foot submarine) and their walls are not 
much thicker. Many homes are built with it.

This is my fifth tank and my second 10,000 gallon one. We intend to add 
onto the tank a ferrocement room that wraps around a third of the tank 
and will serve as a root cellar, storm shelter and spring house 
(utilizing the overflow). The tank will be bermed about 3 feet high 
around the rest of the circumference. Freezing has not damaged our 
tanks, though the coldest climates would require more extensive berming 
or partial burying.

The cylindrical shape itself is a principal source of strength as the 
outward pressure is equalized over the entire surface. The overall 
thickness is one to one and a half inches. The walls are not thicker at 
the bottom of the wall than the top of the wall. The roof is the same 
thickness. When empty, it rings like a bell when you whack it with a 
rubber mallet. If you sing in it, it echoes nicely. A really lovely and 
versatile material and well worth the embedded energy.







The stone gutter you refer to WAS essential to direct a large flow of 
water into a sinuous garden path that provided many infiltration points 
to prevent erosion in a very erodable landscape.

Lawrence F. London, Jr. wrote:
> Keith Johnson wrote
>> Peter and I recently finished laying pipe to plumb our water tank and 
>> have started to install the roof catchment parts of the system.
>> You can look at pix of the project at 
>> http://picasaweb.google.com/KeithDJPcA/FerrocementTankPix02
> Nice work. What design factors are required to give it enough vertical and circumferential structural rigidity to keep 
> it from bursting from hydrostatic pressure and is the concrete thicker at the base that near the top?
> http://picasaweb.google.com/lh/viewPhoto?uname=KeithDJPcA&aid=5141688084664055841&iid=5141688179153336402
> The stone gutter in this pic is just like downtown. I used to build some of these for landscape customers.
> If you have a lot of flow this feature is essential.

Keith Johnson
"Be fruitful and mulch apply."
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