How to calculate the quantity of materials for mortar and Ytong stones?

If I only build a wall (stone on stone), are 17.5 cm enough even if I want to mount wall shelves sometimes? Or should I use thicker sand-lime bricks?

And later, should I specially plaster the exterior walls again or is sand-lime brick initially sufficient for soundproofing/insulation/thermal regulation?

You can tap on sand-lime brick, it works great. We built some walls that high and never used the saw. Even 17 cm walls hold shelves securely. You can also use thicker ones. The processing was quick and easy, even for me as a masonry layman.

Hello, sorry, but what do you mean by "abklopfen"? At some point I wouldn't need a whole KS anymore, but would have to cut the sand-lime brick to size. Or did I misunderstand you?

Assuming you want to build a small garden shed measuring 6m x 4m (and 2.40m height - still without roof) on an existing concrete slab with Ytong (Ytong plan blocks 499x365x249mm) and later install a roller door (2632x2405) and a window (50x100cm).
Question:
- How do I calculate, for example, how much mortar and Ytong blocks I need? I would then have to take into account how high the mortar layers are each time.

Only those who plan poorly have a lot of sawing to do. Use KS blocks; you can leave them unplastered and save significantly on wall thickness (15 cm should even be sufficient here). The height won’t fit into whole rows, so it’s best to level it out with and in the base layer. You don’t need to calculate how many cubic meters of mortar you will need: the block manufacturers tell you how many bags you need. The small window (our office dog calculates in his head: that’s four blocks) I would simply "overmeasure." However, it will be a rather dark shed.

- How large should the door and window openings actually be after masonry to properly install the door and window? Would you simply calculate 2-3 cm more opening for sealing work?

You will get the window 2 cm under nominal size anyway, so 98 x 48 cm. You could even save money by taking a bigger one, meaning make the opening according to the window, then you can take it as a stock size / special offer. The lintel is then dimensioned accordingly, easiest as a prefabricated part and piece goods. Doors are often offered for installation behind the reveal, and the dependent dimensions are explained in the order catalogs.

Hello, sorry, but what do you mean by "tap off"? At some point, I wouldn't need a whole sand-lime brick anymore, but would have to cut the sand-lime brick to size. Or did I misunderstand you?

A bricklayer's hammer is your friend.

Ytong is not mortared, Ytong is glued, it does not add thickness.

I would then have to calculate how thick each mortar layer is.