Here’s an update on our progress in modular CEB construction. In a previous post we’ve seen the beginning of CEB columns and foundations. These are part of an experimental modular CEB construction method.
Final Construction 2010 from Marcin Jakubowski on Vimeo.
In the 10 days that were left, we were able to demonstrate how a section of roof can be mounted on columns. We abandoned the first tall column for later, since we figured that we could grow the columns right under the roof, with the roof in place on the ground. What you see here is the start of a single section of our workshop. We started to build the roof right on the concrete pads. We then propped up the roof on one side with a farm jack, put 2×4 supports underneath, and began to build up the 2 supporting columns. Once the columns were about 4 feet, we dropped the roof on them with the farm jack, and propped up the opposite side of the roof – so we could continue growing the columns as needed. We attached roof overhangs to the main roof section, so that the columns would be protected from the elements. We then put on the sheet metal for the roof, and that’s as far as we got within our window of opportunity.
Sean and his crew dropped in on the last day for an interview and to collect more footage for his forthcoming 8 minute documentary on Factor e Farm.
Regarding construction – we’re continuing where we left off on April 1 – towards our 3000 sq foot production facility – when the weather becomes favorable again. In the meantime, we’ve got a few things to keep us going – which we’ll report on next.
That concrete for the post foundation looks very wet. What is your mix? Concrete should be as dry as possible for maximum strength.
What does the roof structure weigh?
I do have some reservations about the plywood trusses and metal roofing. It would be nice to see a durable roofing system. If you get a leak, or another roof failure (which is inevitable with the materials you are using; it is a matter of when, not if), it could compromise the stability of your columns, and in effect, the entire building.
I think a ferrocement, laminated ferrocement, CEB vault, timbrel (tile) vault, reinforced concrete, acrylic concrete, or otherwise durable roofing system is in order here. They are many options to choose from, and nearly every single one is cost competitive with what you are currently using. Most of the mentioned systems will outlast a wooden truss/metal roof by a factor of 10 (many earthen roofs in existence for more than 1,000 years).
What are the columns filled with? What is their reinforcement? Do you plan to put on an external sealer or other weather protection for the columns?
Are you in an earthquake prone area? Do you have modifications for those who could replicate this in earthquake areas (the current module would not meet earthquake requirements)?
Good start on this, guys. I think you are moving in the right direction, for sure. Maybe consider some alternative ideas over the winter, especially for the roofing system. The weakest link in any shelter is the roof, and it should be where the majority of your time, money, and planning is spent.
The metal roofing has a 40 year warranty. The entire roof weighs about 800 pounds without the overhang. We will lime plaster the columns, which are solid. We will experiment with timbrel – it sounds like the way to go. If we opensource the entire tool and production chain of earthen roofing – then sustainable roofing solutions may become a practical alternative to modern standards. That would be a major accomplishment in the Age of Substitutability.
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Wow, yea timbrel would be pretty awesome. Check this link:
http://www.treehugger.com/files/2009/02/crossway-zero-carbon.php
I think we can agree that this roof (plywood, 2x4s, metal) is not ideal, but it was quick and easy. In the future we can test other methods like you said Abe.
Do you have skills in applying these roofing techniques?
Yeah, 40 years is kinda pathetic, considering earthen roofs last 10 centuries or more, and can end up costing 1/2 of the metal/plywood method. How long does the plywood last when wet? The failure point of the metal roof is not the metal itself, but the screw-holes and rubber grommets around the screws. Once it starts to leak (5-10 years), the supporting structure will begin to rot. Within another decade or so, things get kinda shaky up there, and one day a decent wind comes along and WOOSH!
Timbrel is one way to go, but getting the tiles will be your biggest issue. I tried finding a decent, inexpensive source within a 4 hour drive from me, and it was very difficult. In the end, ferrocement and laminated ferrocement won on cost and durability. Also, timbrels are tricky to get started, and require a decent level of quality to maintain integrity during construction. It is not necessarily a “learn as you go” technology.
Nubian vaults could be a way to go as well, but there is a learning curve involved.
I don’t really see that earthen roofs are closed source technologies, just mostly forgotten and unused in the USA. The majority of roofs around me are earthen roofs, and several are older than the USA. Everyone around me knows how to construct them, even the folks who can’t read and haven’t even heard of the internet.
Sure, making cement might be difficult, but CEBs could work for a nubian vault application.
For right away, ferrocement or laminated ferrocement panels would be the best way. Your durability would be measured in centuries, not decades.
You should be able to drive LifeTrac on top of your roof. That is real durability.
I think you have a great starting point here, but you could easily take it to the next level by replacing the roof. I would definitely consider an alternative for the Spring construction season.
Yes, I have installed several Ferrocement, earth, and concrete-type roofs over the years. I love them, and I feel that they are far better than any wood or metal structure roof (I’ve done lots of those kind of roofs, too).
Timbrels are interesting, but tile is an issue. I could never find a cheap, quality tile that would work.
For what you guys are doing, why not make thinner CEBs, and go with a Nubian Vault?
Pre-made laminated ferrocement panels would be the long term goal. You guys could easily build a small setup to manufacture those panels, and installation would be a breeze.
I’ve installed many FC roofs for under $1/sf, and they’ll last for 5 centuries or more. There is very little that can compete with that.
Can you link to some pictures of the ferrocement roofs that you have built at $1/sq.ft. ?
Here is one: http://velacreations.blogspot.com/2009/08/roof-and-water-catchment.html Follow the More photos link at the bottom.
From Abe:
https://mail.google.com/mail/#inbox/12ce890cb634cce8
From Abe:
Another way to do ferrocement roofs:
Question: Can you do the wooden form, tin under the form as a ceiling, then 4 inches of insulation, then ferrocement on top of that?
Answer: That is how we did it for one of the roofs. The tin and wood is a leave-in form system. You could use any material for this that then becomes the ceiling, as long as it will hold a person walking on it and the weight of the wet concrete.
There are lots of ways to do these roofs, and most people use removable formwork. We used the metal as a way to test for a leave-in form. Another way is to have rafters or vigas visible from below, then a layer of flat wood or river cane above them, and then your insulation, and then a FC cap on top.
Alternatively, you make panels on the ground and lift them into place. This would be the best method, cause you can really control the quality of the FC, and make it super thin (laminated FC can be 1/2″ thick)
Another way is use a removable formwork and create a FC sandwich, so FC will be your ceiling, and another layer as the roof. Here is some info on that:
http://www.flyingconcrete.com/movableform.htm
http://www.flyingconcrete.com/vconstruct.htm
I have enjoyed learning about alternative roof systems and can see they have clear advantages. If you DO use wooden joists, you can protect them against water leaks through the metal roofing by simply putting a thin layer of tar on the top of the joists and then laying a strip of tarpaper on top of that, leaving an inch or two of tarpaper hanging off each edge so that any water leaks are directed away from the wood until you have a chance to fix them. Then nail the metal roofing through the tarpaper.
The other issue with exposed wood is carpenter bees; if you have such bees in your area, watch for them in the spring because once they start drilling in your wood they can do significant structural damage over a period of several years. I know a guy who was seriously injured when re-roofing a barn and bee-weakened rafters broke. The bees drill into pressure-treated wood just fine. The only way I know to prevent them is to paint the wood.
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