[Cob] Marlin's rubble trench

[Yun Que]

   Cat here!  Keep it simple keep it natural and it will last oh about
   500 years then if it falls down build another one! :)
   for the good of all C.
       ______________________________________________________________

     From: "Peter Ellis" <dukegavin at hotmail.com>
     To: Coblist at deatech.com
     Subject: Re: [Cob] Marlin's rubble trench
     Date: Tue, 01 Nov 2005 17:15:38 -0500
     >It seems to me that the material in that trench isn't chosen just
     >for its loadbearing character - in fact, might even not be
     primarily
     >for loadbearing qualities. I would expect that if it's not going
     to
     >be a monolithic waterproof block (say poured concrete with a
     >waterproofing coating) that it is very important for water to flow
     >through it readily.
     >
     >No matter how well the material can withstand compression, water
     >freezing and thawing within it *will* break it down.
     >
     >I would go along with Marlin on this one.
     >
     >Peter
     >
     >
     >>From: Marlin Nissen <marlin_nissen at yahoo.com>
     >>To: Mary Lou McFarland <louiethefifth at hotmail.com>,
     >>Coblist at deatech.com
     >>Subject: Re: [Cob] Marlin's rubble trench
     >>Date: Tue, 1 Nov 2005 08:21:38 -0800 (PST)
     >>
     >>We used 'river stone' or washed stone - 1 , 1 1/2
     >>inches usually...it's actually from glacial drop
     >>around here.
     >>
     >>I have read (and it made sense based upon experience)
     >>that crushed limestone (finds etc.) packs down and
     >>actually becomes a type of lime/mud. If you drive on
     >>country roads (and I know you do, you're probably
     >>happy that it's not just dirt roads where you live!)
     >>you see the limestone and fines break down into finer
     >>and finer particles on the gravel roads.
     >>
     >>I assume underground that small limestone particles
     >>pack down into this same fine mud. While that may be
     >>'weight bearing' for awhile it also concentrates
     >>water, possibly heaves and can become a mud flow
     >>instead of foundation. Eventually, even if it's
     >>decades, a foundation of crushed limestone/fines seems
     >>like it would become indistinguishable from the mud
     >>around the foundation. That's what road base becomes
     >>as it breaks down if you dig into it with backhoe.
     >>I've seen the underlayers of a gravel road and it
     >>didn't look like a good foundation to me. Potholes,
     >>ripples, trenches, heave cracks .....
     >>
     >>UNcrushable glacial washed stones will never (in our
     >>short lifetimes or human span) breakdown, drains water
     >>around them very well and supports and distributes
     >>weight very well. We even put landscape fabric around
     >>the sides of the trench to try to keep all
     >>organic/compactible matter out of the rubble trench
     >>itself. On a house I'd try bentonite or another
     >>barrier as a skirt going out from the foundation to
     >>make it dry and better insulated as well.
     >>
     >>BTW, a sandy/fines subfloor seems very different as
     >>it's not expposed to outside water (different drainage
     >>and temp shifts) so it's main function is to allow
     >>floor blocks to be layed or a thin layer of cob on top
     >>of it. When it's exposed to mud it becomes ONE with
     >>the mud. Sand still seems better then limestone as it
     >>too doesn't really ever breakdown and is excellent of
     >>nestling something into it like concrete or
     >>flagstones.
     >>
     >>Marlin
     >>
     >>--- Mary Lou McFarland <louiethefifth at hotmail.com>
     >>wrote:
     >>
     >> > Marlin you mentioned in your post that you like the
     >> > washed gravel over the
     >> > crushed limestone. Just wondering why you had that
     >> > preference. Hadn't
     >> > thought about it before but had assumed that I would
     >> > use the crushed stuff
     >> > because of it's greater stability when taking on
     >> > weight or impact like
     >> > floor or arena base or shoulders on secondary
     >> > highways. For clarification,
     >> > when you say crushed limestone, I am assuming that
     >> > you mean what we call
     >> > base gravel around here and it has all the fines in
     >> > it and that is what
     >> > gives it it's strength. Also wondered what size you
     >> > usually go with.
     >> >
     >> >
     >> >
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     >>
     >>
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