[Cob] new earthen floor on old concrete floor

[Raduazo at aol.com]

In a message dated 8/24/2006 6:15:42 P.M. Eastern Standard Time,  
ap615 at hotmail.com writes:

(by the  way, we could nail or screw our wood.  Ed, how did you fasten yours  
down?)



Regarding fastening earth floors to concrete: I knew that I was going to do  
an earth floor all along. (The concrete was just to keep the building 
inspectors  happy.) So, instead of hard troweling I brushed the surface with a stiff 
broom,  one or those two-foot wide push brooms. 
    However, poured adobe is pretty sticky. Again I  would suggest that you 
do a one foot squares with different formulas, seal them  with linseed oil and 
place the legs of a chair in the centers of the squares and  put your weight 
on them. A good earth floor should support your weight with  out denting and 
with out spalling. More sand makes the floor harder, more clay  makes the floor 
sticker and more straw or horse manure makes the floor more  spall resistant. 
You have to do testing because the clay you dig out of your  back yard is 
different from the clay in my back yard.
    I have heard of adding a little Elmer's glue to the  formula to improve 
hardness but I have never tried this on a floor and I am  unsure how this would 
affect penetration of linseed oil into the surface. This  is something you 
need get your surface hardness. I made one other mistake when I  did my floor. 
After the linseed oil I put on a layer of oil based urethane to  give me a 
glossy finish. Boy was that a mistake. The Urethane did not adhere  properly to 
the linseed oil in places so I have to peel it off and replace it  with paste 
wax.
    It is not as easy as just mixing and dumping  something out of a can, but 
it is worth it to test your materials before you  start.
Ed