Cob: Sub flooring

[Darel Henman]

>............ snipped

This is for a cheap floor without a concrete underfloor that some adobe
floors use. 

> We should have more than enough palm fibre on hand!  I would never have
> thought to use this material, but I am awfully glad you mentioned it. 

They use it in southern Japan and probably Taiwan.  It's also used in
brushes and the tough fibres were used for door mats in the States. 
Might be to tough dry and need to soak it in the mud mixture to soften
it up and for the mixture to get used to itself.

> I will
> keep the lime, sand and clay mix in mind.  I had wanted to avoid cement if
> possible, and we surely will want to avoid using anything that encourages
> mold!!!
> 
> What do you think of using flagstones for the floor?  What is best (in a 1/2
> humid, 1/2 dry climate) to use as mortar in beetween the stones?  Thanks!
> 

1.) a well weathered soil (say from an old weathered granite soil at the
foot of a mountain) Which a decent clay content and little silt.
2.) some pebbles and sand if not in the soil above in about the same
amount
3.) hydrated lime  (lime made from shells can also be used) (= water +
lime)
4.) magnesium hydroxide  ( this comes from salt making and is natural I
believe)
    This may not be necessary, but its in the recipe I have.
5.) water to mix all of the above together till about a 20% content (by
Weight).  Mix well

Ramm it until water begins to rise to the surface.


Another mix was:
	1 part hydrated lime to
	4-10 parts soil which has a 20-30% clay content.

	mix till water content is about 15%

then ram till water starts comiing up to the surface.

Then set your flag stones on this.
This is not cement and should be given a minimum of a week or so to
harden.  Two or more weeks would be better.  The lime needs air to
harden. 


Another mix is
	a.) silica (from old dead planton is good)   68% of mix   ( or a good
content 20-30% clay soil)
	b.) hydrated lime                            14%
	c.) salt farm magnesium hydroxide	      4%
	d.) water				     14%
			----------------------------------
                				    100%
mix  and ram it.
Place flag stones on top.   Some stick pebbles on top for a harder
surface, like the entry way where shoes are taken off and put on.


Another mixture was:
	Clayish soil	50%		another is 	75% with clay soil + sand	and 65%
	hydrated lime   30%		"	"	25%			 	    35%
	river sand	20%
	---------------------			------------				--------
		       100%			       100%				   100%

mix with water until water content reaches  10 - 15%+- and ram.


Be sure to ram it as level as possible.  Let it dry and in a month is
should reach 90% strength 

I think the following is an example of such a floor.  Ignore the garbage
characters if you don't have a Japanese font and just look at the floor
in the picture.
     http://web.pref.hyogo.jp/eizen/ya_csr/csr_ya8.htm

and here's outside the entrance floor:  It says it has "lamp soot or　
lampblack" in it to give it a darker color, as lime usually whitens
things.
   http://web.pref.hyogo.jp/eizen/ya_csr/csr_ya3.htm


Here's a floor without flag stones: 
http://www.tv-asahi.co.jp/tatemono/img/p000701/04_b.jpg

Don't get the mixture too wet.  This is to be a rammed floor.  The water
will come to the top as it is rammed with a wide, but not need to be
real heavy, wood mallet

Pack the floor say to 12 cm  = about	4 3/4 inch
then ram down to       8 cm  = about    3 1/8 to 3 1/2 inches    the
final level
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
water should start emerging by this time in the ramming process.

Set your flagstones if you wish, or pebbles to make the floor stronger
to shoes.  Push them in.

This is a cheap floor, but is reported to work and has been used for
hundreds of years.  If you do the floor level enough it should be just
as good or better than concrete.

Darel Henman