Hello,
Last week put some scratch coat onto my strawbale garage. The render mix that I have used for the inside was 4 parts coarse sand to 1 part pure clay to 0,5 part chopped straw. With this mix everything went perfect, no cracks appeared when the plaster dried.
For the outside scratch coat I used the same ratio plus added hydrated lime in powder to the mix. The ratio of the lime I tried to keep to around 5% of the mix. The outside plaster cracked a lot. I'm sure that the reason for the cracks was lime. There was little area outside where I did not put lime in the plaster, and in this area no cracks appeared when the plaster dried. What ratio of lime should I keep in the mix for the outside?
Regards,
Tomas