Re: SB: Great Lakes mix

[Speireag Alden <Joshua.M.Alden.91@alum.dartmouth.org>]

Sgrìobh mklough:

>I have been told that Portland cement plaster is a not good because 
>it does not allow vapour to pass through it and therefore it will 
>not allow a wet bale to dry or indeed a bathroom to dry. I have been 
>told that a good mix for this part of  the world ( just South of one 
>of the greatest great lakes) would be a mix of Portland cement and 
>lime  with a clay pozzalan ( I hope I recall correctly). I have been 
>told that earthen floors are taboo in this part of the world and 
>earthen/clay plaster base coats virtually non existent here abouts.

     For that climate, a lime stucco under wide eaves should work just 
fine.  It's been used on the coasts of Scotland and Ireland for many 
centuries.  For an application over straw, Bill Steen has been 
advocating a thick coat of earthen plaster, topped by a single coat 
of lime, for protection.  He has far more experience now than I will 
ever have, so I pay attention when he pipes up.  Here's why he has 
made this point in the past:

     Earthen plasters aren't as tough as lime plasters, but breathe 
better.  However, they have one clear advantage over all cementitious 
substances:  earthen plasters are more hydrophilic than straw.  When 
the wall gets wet, the water will tend to stay in the plaster, and 
not migrate into the straw.  Lime and Portland cement, on the other 
hand, will give up water to straw, so when the wall gets wet the 
water migrates into the straw layer more readily.

     Mind you, this is not a huge deal.  In most circumstances, the 
wall dries out just fine either way.  But in borderline situations, 
earth has the advantage in that respect.  Then top-coat it with lime 
stucco to protect it.

>  I have been told that this whole plaster issue can be resolved 
>without slaking lime in 55 gal drums for 2 months by just buying 
>ready mixed plasters (or stucco).
>
>Should I be looking at a ready mix product in the first place? 
>Should/could this product be used over an eathen/clay base coat? 
>Should I even bother with a base coat with this product?

     Expensive and pointless.  You don't have to slake lime to get 
putty, if you buy it as Bagged Hydrated Type-S lime.  You just mix it 
with water and let it sit for at least 48 hours.  You can mix it in 
5-gallon buckets, which are easy to handle and commonly available 
cheaply or for free.

     If you want a copy of my primer on how to get lime stucco up on 
the wall from bagged hydrated type-S lime, let me know.  You may also 
be able to find it in the archives.

-Speireag.

-- 
Understanding a person does not mean condoning; it only means that 
one does not accuse him as if one were God or a judge placed above 
him. -Erich Fromm, psychoanalyst and author (1900-1980)

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