[Cob] Cob no need for plaster

[Dean Sherwin]

Interesting, right now I am in the process of building a rammed earth 
wall.  Ramming it to be dense makes it much more resistant to erosion 
(I'm sincerely hoping, also based on what I've seen and know).  so 
maybe whacking the wall while damp has the same king of effect as ramming.

As far as cob buildings lasting hundreds of years unplastered, well 
sorta.  There are many freestanding walls that seem to have lasted a 
long time, maybe as long as a century, although 99% of houses were 
(are) lime rendered at least.  I've seen spectacular failures when 
the plaster becomes damaged, the wall will just melt away.   Remember 
it depends on there being good protection for the wall surface in the 
first place "Give'un a good 'at and a good pair o' boots"  ie good 
waterproof base and good roof overhang, they used to say in 
Devon.  .  Devonshire cob is a superior mix to others and more 
weather resistant in the first place, its only where the Old Red 
Sandstone of the Devonian measures occurs.  And rain in Devon is 
seldom hard enough to cause erosion per se, its more the constant 
damp that gets to a wall.

At 03:00 PM 10/16/2010, you wrote:
>There are a few places on my wall where I smacked it with a 2x4 while
>it was barely pliable and it becomes very resistant to erosion. No
>plaster, just cob. I suppose having some of the straw exposed might
>be a downside, but if there's no need to plaster why do it? Didn't
>some of the cob building in England last centuries unplastered?
>Damon



Dean Sherwin CPE
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