[papercreters] Re: Vault building--free PDF for construction

You make good observations, but I'd like to clear up a few semantic details that may not be clear to everyone.

Not every vault is a Nubian Vault.

As Charmaine's examples illustrated there are many different methods of building a vaulted structure. Or for that matter there are many different methods of building a dome structure too.

The vast majority of Nadir Khalili's superadobe dome designs use more of a corbelling technique as apposed to the Nubian dome technique. This may seem like a minor semantic difference, but the physics of how the forces are distributed through the structure are significantly different. A Nubian Dome, when built properly is entirely in compression on every block in the dome. This is critical for its structural stability. Khalili's domes depend partially on the tensile strength of barbed wire between courses to prevent each flatish horizontal ring layer from spreading out. His superadobe domes were not entirely in compression along all vectors.

This contrasts with a Nubian Dome that is entirely in compression. Each ring forming the dome angles more and more vertically keeping everything in compression. Each block in the dome is pressing against each of its neighbors. There are no tensile forces anywhere in a Nubian Dome.

To look at a Nubian Dome vs a Superadobe Dome, the average person might not be able to tell the difference visually, but the differences under the plaster or stucco are dramatic and important.

Didn't John Annesley use cattle panels and a ferrocement roof vault? Or am I remembering a different project?

The key to a successful Nubian Vault is to use techniques that keep all components in compression. Everything depends on it.

That means that the vertical support walls holding up a Nubian Vault MUST be thick enough and strong enough to not only hold up the weight of the vaulted roof, but to hold the vault in and prevent it from spreading. If a Nubian Vault spreads... it fails. The vertical walls need to be big and thick enough to hold that roof together in compression.

When done properly, a Nubian Vault has a sexy poetic beauty about it that is astounding.


My comments are not intended to imply any particular technique is right or wrong. Just different, and the way a builder must think about each type of structure is radically different.


As with most things, anyone wanting to attempt a vaulted roof would be very wise to attempt a small structure first. Try building a dog house with a vaulted roof. Or a tool/storage shed. It simply makes sense to figure things out and make your mistakes on something small, less hazardous, and less expensive in time and money before attempting a larger, more hazardous, more expensive, and more time consuming project where mistakes carry larger consequences. Once someone has mastered the techniques required to build a vault in a smaller scale, they will be able to move on with much greater skill and confidence to larger projects, and will almost certainly have greater chances of success.



--- In papercreters@yahoogroups.com, Charmaine Taylor <charmainertaylor@...> wrote:
>
>
> also the late *Superadobe* earth bag inventor --*Nader Khalili-*-started
> out with arched and dome shapes...and built several in Hesperia CA, and
> offers classes on that construction. He did a fired clay dome too..and has
> a book or on building adobe arches.
>
> papercrete blocks don't have the weight of adobe 50+ pounds vs 10 pounds,
> and during a quake or failure may not damage or kill as heavy adobes can.
> When the *city of Bam* collapsed in an earthquake a few years ago the
> beautiful adobes fell.
>
> I am happy too send anyone interested a couple pdf files..50 page booklets
> on construction of vaults... you need to be safe and engineer them
> properly. the fact the papercrete is so much lighter makes me wonder if it
> is safer to use as the pressure to maintain the vault is the weight of
> adobes...will pc blocks offer the same strength? anyone built a vault and
> know?
>
> -- just search the bold words to learn lots more if interested in vaults
> Vaulted Dome Roof Project November 4, 2008 — Annesley < same guy who does
> the clay coated burlap--see link I sent a few days ago
>



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