I kinda like the looks of having an ornamental brick frame around doors / windows and maybe at corners.
For a brick house it's easy as it's made of bricks.
But for a straw bale one, embedding some bricks could pose lots of problems.
One solution that crossed my mind was to use thin ornamental brick or make thin, 3/8 (2cm) brick slices, and use those as a sort of veneer.
However, since the bales are plastered in lime, i would have to also use lime mortar to fix these thin ornamental bricks.
But lime mortar has a pretty weak bond in this scenario.
I think it would be best to use full thickness bricks which would require a stable shelf/foundation to support them. As you indicated adhering veneer to lime mortar/plaster would have a weak bond. Are the bale walls already constructed and plastered?
One option for the veneer would be to cut back into the plaster/bales as needed and install some cement tile backer board. The backer board can be screwed into framing lumber and wood dowels can be driven into the bales through holes drilled into the backer board. Once the backer board in installed you could use fortified tile mortar to adhere the brick veneer slices.
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