Cladding wooden stud frame in prefab house

Good day,

we have a Massa Haus prefabricated house in timber frame construction, currently a contracted drywall installer is boarding the walls.
The wall structure according to Massa Haus is as follows:

Interior walls:
- Timber frame 10cm
- 40mm insulation in between
- Lower layer Fermacell 12.5mm
- Upper layer drywall 12.5mm

Exterior walls:
- Timber frame 16cm
- 160mm insulation in between
- Lower layer Fermacell 12.5mm
- Vapor barrier film SD = 100
- Upper layer drywall 12.5mm

Our drywall installer is currently installing the first layer of the interior walls with Fermacell boards; the spacing of the timber studs is not uniform but varies between 20cm and 55cm. As we have now seen, however, the Fermacell boards are not cut and fastened flush with the timber studs, but in some places the Fermacell boards protrude by about 20cm.
When asked, the drywall installer said this is not a problem with a double-layer boarding and that an “overhang” of up to 30cm is allowed, but we have never seen this before and also find nothing on the internet about whether this may be done.

Is this feasible or must we insist on having it corrected?

Thank you very much.

Our drywall installer is currently covering the first layer of the interior walls with Fermacell boards; the spacing of the wooden studs is not uniform but varies between 20cm and 55cm.

Do I understand correctly: even the non-load-bearing interior walls were left open on one side by the house manufacturer as part of their delivery and secured, and by the spacing you hopefully mean the gap (625 minus 76 mm), with the "20 cm" referring to bracing?

As we have now seen, however, the Fermacell boards are not cut and fixed flush with the wooden studs, but in some places, the Fermacell boards stick out by about 20cm. [...] Is this feasible or do we need to demand that it be corrected?

What are those alarming holes, does the drywall installer want to rivet the boards??? No, that is not professional, but the contractor will probably not be satisfactorily capable of rectifying this technically (which, unfortunately, you will probably have to allow him to try first). I don’t need an ounce of my construction knowledge to recognize that this guy hasn’t watched a single drywall video. This is a sad joke; where did you pick him up? It’s obvious that he is acting aimlessly here, and the "drywall installer" (I never thought I’d have to put that in quotation marks!) obviously has experience mostly in lame excuses. At this point, a warning to all builders: drywall installers belong to the trades that do not require a master’s certificate, so instead of craftsmen, you also find plenty of general service providers there. Here, the client unfortunately has to expect to first have to teach the contractor the necessary basic knowledge! The correct procedure is to start in the middle of a post, use a suitable fastening system! and then stagger the boards in the second layer accordingly (so that the joints no longer line up over 1-3-5... but over 2-4-6...). I hope you have at least not made a mistake with the sequence, and the electrician is not still coming :)

I also think the screws have been countersunk a little too deep ... if it weren't sad, it would be funny :-(

I also think the screws have been recessed a bit too deeply

It seems to me especially that the holes were pre-drilled from the back ...