Thursday, March 28, 2013
Wednesday, March 13, 2013
|Nuform© walls/forms during installation.|
Note the internal webbing showing on each
side of the door.
On my most recent deployment to Afghanistan I had the opportunity to observe the construction of a concrete building using the Nuform© system. Nuform© uses a vinyl form that is set in place, filled with concrete, and then left to become both interior and exterior surfaces. The first time I ran into this system is when I read Christopher Alexander's A Pattern Language: Towns, Buildings, and Construction.
Alexander tackled the idea of concrete pored into stay-in-place forms in pattern number "218 Wall Membrane." (Alexander divided his chapters into "patterns" each pattern contained an idea, proofs for the idea, and conected patterns on both a larger and smaller scale.) His version used site constructed forms that would resemble conventional concrete forming, but with a material that would be suitable to leaving in place. Alexander recommended materials such as plywood, brick, and gypsum board as form/wall material. All of which I see as seriously flawed in this usage.
|A soldier sliding a Nuform© section to extend a wall.|
Additionally, Alexander advocated using chicken wire instead of rebar and lightweight concrete with wider walls to make up for the lower strength of the lighter concrete. In the Nuform© system it uses normal concrete on the runny side, rebar, and the vinyl of the forms creates an internal webbing that improves the bulging issues that are a construction nightmare on any concrete project.
I'm not saying that any of these points makes Nuform© a system I like. The 6 inch walls are just too narrow to get the concrete to settle. Even with the runniest concrete specifications allowed and dedicated beaters hitting the walls to shake the concrete down, empty spots were left in the forms when the concrete was cured. The echo in this building was the worst I have encountered in any construction project I have observed, the vinyl provided no noticeable sound dampening.
In either method, making the walls straight and avoiding bulges is difficult. The use of so much embedded energy with the concrete is also a concern, as is the potential for chemical burns on the workers skin from wet concrete being poured overhead. Especially low grade concrete from a developing nation.
I wonder if the concept of a stay-in-place form would be better applied to a rammed earth building or even cob (although I can't see how a form could improve cob.) With both of these earth construction systems I would use even thicker walls than Alexander recommended. A form material would have to be found to work with the earthen materials, vinyl has a high energy footprint, just like the concrete.
|Any vertical use of concrete requires heavy support and|
bracing until the concrete is set. The weight of the concrete
is enough to throw the whole project into a jumbled mess
without the extra help.
I'm not sure I will ever find solutions to the problems I am seeing, but by looking at them I become a better designer and a better problem solver. And if we are ever going to make the world a better place those are two things that all of us need.
Thursday, March 7, 2013
|A top bar hive ready to be loaded it to a car and be taken |
I attended my first beekeeping class a couple of weeks ago. The class was free to attend and sponsored by IFA, a regional farm and garden store. The fact the class was no cost and had a retail sponsor tells me something important: bees are mainstream.
Even at the hight of the back-to-the-land movement of the 1970's, I don't think there was so much interest in raising bees. I suppose it will end up being a fad, but I hope not. Bees are terribly interesting and are at so much risk right now that every new hive offers a better chance for their survival.
|Langstroth hives in several configurations|
sitting in the store.
By having many beehives in a neighborhood, there are a greater number of bees to make up for the dead hives caused by temperature variations, pests, and pesticides. Lots of urban bees in back yards can eventually provide replacement bees for the highly stressed bees used to pollinate commercial crops.
|Thanks to Chris Rodesch for coming in to |
teach us a great class!
I don't know how many beehives an urban or suburban acre can hold, but if you ever have a question whether your bees can be fed, call me and I will be more than happy to design a bee garden for you!