[Strawbale]protecting earth plasters

[Rene Dalmeijer]

Marcel,

Just adding lime to earth/clay plaster can work but is not recommended. 
Whilst talking to various experienced people at the ISBBC 2004 this was the 
general opinion. Just adding lime to earthen plasters is to fortify them is 
not good practice as the lime can interfere with the clay bond if you don't 
get the mixture right. Too much lime will also not work. It is quite 
critical to add the right amount as too little lime can actually degrade 
the mechanical stability of the earthen plaster. As earth plaster is a very 
variable product it is difficult to give the right recipe without on-site 
tests. I personally would recommend the following approach.

Use earth plaster also in the final coat with sufficient overhangs. If you 
are sure this is still not enough protection chose one of the following 
options offering increasing levels of protection.

2. Apply lime wash over the final coat of earth plaster this is a 
traditional solution which has been used extensively in the past.
3. Apply a final finish coat of lime plaster over the first and body coats 
of earth plaster. This is tricky to do and requires a lot of practice to do 
correctly but can work very well.
4. Go all lime. This is expensive but does give good weather protection
5. Place light wooden weather boarding over the earthplaster. This is again 
a traditional solution and often used in our type of climate.

Regarding the above it is only necessary to apply extra weather protection 
to exposed walls ie in the Netherlands SW on open ground otherwise 
sufficient roof overhang (at least 600mm for a single story) is sufficient 
in most cases. Sticking to plain earth plasters has the advantage that it 
makes repair much easier.

At 07:36 AM 6/10/04, you wrote:
>ik ben aan het verbouwen en in huis werk ik met leem (wand- en
>vloerverwarming en zo) maar de aangebouwde nieuwe buitenmuren wil ik ook
>gaan bewerken met leem.
>dat moet ik dan wel aanpassen om het weersbestendig te maken. heb jij
>daarvoor een oplossing? kalk toevoegen?


Rene Dalmeijer