ᐅ Adding a crawl space extension

Hello to all forum members. I just registered today and would like to ask my questions to you experienced home builders. I own a single-story building from the 1920s, built with bricks (18m x 8m (59 ft x 26 ft), 24 cm (9.5 inches) external walls, with a 12 cm (4.7 inches) thick load-bearing wall in the center) and a shed roof made of fiber cement corrugated sheets. This is a typical bungalow construction with a foundation and slab-on-grade. I have uploaded a sketch showing all load-bearing elements as an attachment. The rooms are about 2.55 m (8 ft 4 in) high, and above them is a crawl space. At the highest point, the crawl space is 1.50 m (4 ft 11 in) high and at the lowest 0.5 m (1 ft 8 in) high. We would like to add a 4 x 8 m (13 ft x 26 ft) space and plan to add an upper floor on part of the house. So, we want to convert a quarter of the crawl space into 2 living rooms. I have attached 2 sketches. One of them shows roughly how it should look.

My first questions are: Is it possible to build up the external walls and the 12 cm (4.7 inches) central wall using aerated concrete blocks? How should the right external wall (see sketch) be designed? Is it necessary to build a load-bearing wall on the ground floor to support the upper right external wall, or can I support it on a beam that spans 3.80 m (12 ft 6 in) from the existing 24 cm (9.5 inches) rear external wall to the 12 cm (4.7 inches) central load-bearing wall? Is the 12 cm (4.7 inches) wall resting on the slab sufficient?

Thank you very much for any responses, ideas, and suggestions.

Doesn’t anyone have an idea or a suggestion?

You will need a building permit / planning permission for this. It also involves structural changes. I would recommend having an architect take a look.

No one in the forum can provide you with a reliable structural calculation. For that, you definitely need a) a building permit / planning permission – which means an architect who takes responsibility, and b) a structural engineer who confirms the load-bearing capacity and statics.

Thank you for the responses. I understand that a building permit / planning permission and an architect are required for this. I figured that descriptions and sketches alone wouldn't be enough to make progress.