[Cob] purpose of straw in cob

[James from House Alive]

The primary role of straw in cob is to provide tensile strength, like many
thousands of mini re-bars.  Many fibers can be used in place of straw.  I
have used a variety of grasses and reeds, palm fronds, and coconut fiber.
You want something long, strong, and resistant to rot.

Good luck,
James


On 7/12/07, Damon Howell <dhowell at pickensprogress.com> wrote:
>
> What is the purpose of straw in a cob mix? Nobody seems to "really
> know" what the role of straw is anyway. Is it there to hold the cob
> together while the wall is still wet (like a free form), or to keep
> the wall from crumbling incase it cracks later (like reenforcement),
> or to allow air/water to move through the wall (because straw is
> hollow)? The problem is that nobody knows the reason they used straw
> because they didn't leave behind notes on how and why they built that
> way, and it's been a while since they lived here. What do they do in
> Africa? Do they use straw "in" the cob? Can any other plants be used
> as tensile such as long grasses? I'm almost ready to start cobbing
> but straw is just unavailable in GA right now, and what straw there
> is has a very high price on it. I'm not willing to pay three times
> the price for it if there's a substitution. I would love to just go
> out in the field and get some tall grass if it would suffice. It's a
> heck of a lot cheaper!
>
> Chow,
> Damon Howell
> North Georgia, US
>
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James L Thomson
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