Questions about the wall structure of a Stelly prefab house from 1998

Hello I have currently been offered a property for purchase which I like very much. It is a Stelly prefabricated house from 1998. In 2001 Stelly was taken over by Talbau-Haus. Since I have read quite a bit and also a lot of negative things on the internet about the wall constructions of a prefabricated house, I wanted to ask here. I have the complete construction description. Can you tell me if the construction/quality is okay for a prefabricated house? How is the sound insulation with these walls? Do I have to worry about a musty smell from moisture in the walls at some point and how long does such a house last? Exterior walls: Total wall thickness 250mm (U-value 0.235 W/m2K) 3.00mm seamless synthetic resin plaster, troweled on 3.00mm reinforcing plaster (total thickness approx. 6mm) 40.00mm special insulating construction boards -> (whatever that is - anyone any idea?) 13.00mm wood-based panels V 100 G 165.00mm solid wood beams - frame construction made of dried quality softwood 150.00 stiffened mineral wool - insulation in frame construction 13.00mm wood-based panel V 20 E1 0.20mm foil as vapor barrier 12.50mm natural gypsum boards Interior walls: Sound and thermal insulated, particularly stable, shelves and cupboards can be attached without restriction to every wall. Total wall thickness 151mm 12.50mm natural gypsum boards 13.00mm wood-based panel V 100 G 100.00mm solid wood beams - frame construction made of dried quality softwood 100.00 stiffened mineral wool - insulation in frame construction 13.00mm wood-based panel V 100 G 12.50mm natural gypsum boards Floor/ceiling panels: Impact sound insulated ceilings with 220mm thick solid wood beams, total thickness depending on finishing stage up to 400mm Construction from top to bottom 25.00mm wood-based panel V 100 G 220.00mm solid wood beams - statically calculated made of dried quality softwood 120.00mm stiffened mineral wool - insulation in frame construction 0.20mm foil as vapor barrier 20.00mm substructure made of dried softwood 12.50mm natural gypsum boards Thank you very much and best regards Thomas

We have had a Stelly house since 1996, so I can answer the question. There was some trouble during the construction phase and afterwards some defects, which, however, seem typical for prefab houses. For example, the four outer corners in the attic were leaky, and a lot of assembly foam was needed to fix that. The load-bearing wall on the ground floor is partly (it consists of 2 parts) built crookedly. The roof had to be dismantled and re-covered again because the scaffolder (a local master roofer) found extreme installation defects.

The theoretical values for thermal insulation are calculated based on a wall without corners, windows, doors, floor, and ceiling connections. Defects such as gaps in the corners, missing silicone sealing at the windows, etc. are of course not taken into account.

The sound insulation is significantly worse compared to a solid house. This is not comparable due to the mass of the walls alone. The sound insulation inside the house is okay; the screed ensures that.

My conclusion: Never again a prefab house, never again a house built by a company from far away.

The advantages of the prefab house (fast construction time, low rental time plus financing) are, in my current conviction, far outweighed by the disadvantages.