As a trainer in brickwork construction, you need to know the dimensions of the most common bricks and the joint widths.
A NF stone (according to German standardizations) has the following dimensions:
The bearing joint is 1.23 cm thick, the lateral joint between the stones is 1.0 cm.
This means that Sven requires 8 stones per meter wall length in each layer [100 cm / (11.5 cm + 1 cm)]. Per meter wall height he needs 12 layers [(100 cm / (7,1 cm + 1.23 cm)]. On top of that there is a rolling layer. For this purpose 12 stones are needed per meter length [(100 cm / (7,1 cm + 1.23 cm)].
Get more information: Brickwork dimensions (Germany).
Please note: Find out the different stone dimensions in your country. The measurements can differ very strongly from the German measurements. They are individually standardized in every EU country.