Evaluate the purchase of a house with timber frame construction

thank you for your tips!

An aunt of my mother only sold a Streif Haus house from around 1970/75 a few years ago due to age reasons. Built on a slope on a solid basement, the upper garage was also solid. She had the living room extended towards it, placed a conservatory over part of the terrace (that is, on the solid part, adjacent to the prefabricated house), and had one weather side clad with sheets. The house is still in tiptop condition; personally, the kitchen would be too small for me nowadays, but no problems have occurred with the house or with the conversion and extensions. Every transition between different materials requires proper execution and certain connections, joints, etc.; this is basically the case between solid construction and prefabricated building.

Her sister and cousin, both very sensitive health-wise, also always enjoyed multi-day visits there. No noticeable odors or other indications of building biology problems, mind you, from the 70s. I fear even less for those from the 1990s; that was after asbestos and lindane.

I also do not know of any specific bad reputation regarding Streif Haus houses; they were long part of the Neckermann program, widely (and beyond) distributed nationwide.

This is a Streif house from 1992/1993

Our wooden frame (not prefabricated!) house from 1976 had some weaknesses in the exterior walls because they were made of chipboard and covered with wooden shingles, some of which were split and no longer overlapping. Therefore, on the southwest corner, we tore down the exterior walls and rebuilt them ourselves. We also replaced the shingles with proper wooden cladding. Apart from that, the beams we exposed inside and also the roof trusses looked as good as new, tip-top. The energy consultant who created the energy certificate for the previous owner was also a civil engineer and shared his impressions with us after the inspection; however, the previous owner paid for it, as he was responsible for the energy certificate. I would like to add that the inspection by an expert is unfortunately only conditionally meaningful because the expert can only see what is exposed. He does not tear open walls, remove cladding, or insulation... what is behind that can only be guessed. In our case, there were hidden issues such as milled-out window sills where the roller shutters were installed. Since the window sill was no longer a basin, water could run in from behind. As a result, the beams under the windows were partly rotted and decayed. You cannot see such things from the outside. And the window sills were installed by a professional company... so a bit of trust is also necessary. By the way, the climate in our house is absolutely wonderful. Even in the condition it was bought (1976 walls, etc.), there was not a bit of mold.