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RE: GSBN:Lime and Cement Plaster

Dear Kelly,

Difficult to respond without knowing more about the properties of your
Californian lime. Guess its  white, in powder form which normally dries
rather long and is described in France as chaux airienne.

In the Netherlands we do have for example lime made of shells, which
consists naturally of 80% "airlime (sorry for that translation)" and 20%
hydraulic lime (also in powder form) which for moistures weather conditions
is rather effective.

In France I did use without any problems 80% chaux airienne and as my
hydraulic lime had run out 20% of portland cement, together 1 part and 3
parts sand, so 50:50 is applied for the first of three layers if the next
two are simply "airienne", however a continuous mix of 80% lime and 20 %
cement are also possible. If you use a 50:50 mixture through all the layers
moisture will not be able to leave from inside the house.

People who are experienced with clay plasters and usually work with their
bare hands need to use gloves. There are mechanical applications too
(tyriollenne and spraying the plaster).
I have not heard of any corrosion etc. due to the use of lime. I persume
otherwise it would not be sold in do-it-your-self-stores...

Limestuccos need to dry slowly. A week is fine for the first layer, the
second two weeks, ... sunshine provokes cracks.

Do you have time for testing your mixtures? Might be the best.

Success, Martin

-----Oorspronkelijk bericht-----
Van: GSBN [mailto:GSBN@...]Namens Kelly Lerner
Verzonden: dinsdag 4 december 2001 18:22
Aan: GSBN@...; CASBA Listserve
Onderwerp: GSBN:Lime and Cement Plaster

Hi All,
On a residential straw-bale project in Capitola, CA (coastal California
climate, but a protected site with little driving rain), I've specified an
exterior plaster 1 part cement: 1 part lime: 6 parts sand.

The plaster contractor, an great experienced plasterer say he thinks the
mix is just too "hot". He's worried about the mix being so alkaline that it
will eat up the stucco mould (around the windows and doors) and will be
dangerous for his guys to work with.

He's recommending a mix of 1 bag cement: 1/4 bay lime and 25 shovels of
sand. (this is all via the general contractor so I'm not sure of the
volumetric measurements of this mix - shovels compared to bags).

I'm looking for a very vapor permeable plaster - his mix doesn't sound like
enough lime to me.

What have your experiences been? Any problems being burned by a 1:1:6 mix?
Any complaints from contractors? Your thoughts please.