Clay plastering a clay block (Porotherm)

Hello,

Does anybody have experience with clay plastering monolithic blocks like Porotherm? I have seen some internal walls examples but never on external walls.

Thanks.

If someone is building from Porotherm then there are a low chances that someone would like to use clay plaster, especially for the exterior. I would assume clay/earth plasters are used for 3 reasons:

-cheap and widely available material
-improving interior atmosphere of the rooms
-compatibility with earth buildings

In case of Porotherm it would be the first reason.
When I build from fired clay bricks I always use lime plaster. It adheres well, looks gorgeous and will last.

Cristobal Cristo wrote:If someone is building from Porotherm then there are a low chances that someone would like to use clay plaster, especially for the exterior. I would assume clay/earth plasters are used for 3 reasons:

-cheap and widely available material
-improving interior atmosphere of the rooms
-compatibility with earth buildings

In case of Porotherm it would be the first reason.
When I build from fired clay bricks I always use lime plaster. It adheres well, looks gorgeous and will last.

I'm changing to Porotherm from logs and reason is cost and woodworm. What I don't want to change is clay plaster even if like will be the chosen one in the end. All the excavation of the basement will give so much good clay and it will be a pity not to use it. But maybe I can use it in the interior and for exterior to go with lime.

A. Root wrote:But maybe I can use it in the interior and for exterior to go with lime.

Yes!

If you have so much of it you could also use it on the outside and use lime just in the last layer. Make a plaster with fiber and/or more coarse sand for the first layer and then use a mix with finer sand and lime for the last layer.

Benjamin Dinkel wrote:If you have so much of it you could also use it on the outside and use lime just in the last layer. Make a plaster with fiber and/or more coarse sand for the first layer and then use a mix with finer sand and lime for the last layer.

I forgot to mention that I limewash everything clay or lime or or brick. But you are talking about a proper lime layer. I have seen a post on wide internet of someone totally opposed to the idea.

Sometimes plastering with just one mix is difficult, because many variables affect the outcome and longevity.
The finished project may look great and the builder may feel ecstatic but after two years it will start falling off. Using two different plasters  - one on another, opens the vast area of possible wrong combinations. The most difficult is finding out if the plaster will last - moisture conditions in winter, permeability of wall material and plaster layers, capillary actions, temperature fluctuations, etc will slowly work to show the results in a few years. For exterior it will be much faster. The beauty of earth plasters is that they are fully natural and cheap but ugly part is that they are all different. and what work wonderfully for one builder may fail for another.
If you plaster interior with clay and exterior with lime things will be more predictable..