Remove prefabricated house walls and ceiling panels for electrical installation

As nordanney says, with exterior walls (and possibly upper floor ceilings, if cold roof) you very likely have a vapor barrier right behind. It can all be patched up (house manufacturers have to do that too if any repairs are necessary), but if you don’t do it properly, then you actually cause damage and also open the door wide for the house manufacturer to refuse warranty.

One more question – what do you mean by "cold roof" – with an acquaintance who built with the same manufacturer, it was such that the ground floor ceiling offers a lot of space for recessed spotlights when you slide the cable over the beams with appropriate tools. It was probably more difficult in the upper floor ceiling because the distance to the vapor barrier was much smaller – but still possible (maybe only surface-mounted spotlights possible).

Is that what you mean?

A common version of the cold roof in timber panel construction is when the insulation is on the ceiling of the upper floor, so that the actual attic space (if present, of course not relevant for flat roofs) is not heated/insulated. Then the vapor barrier also lies directly on the upper floor ceiling.

Presumably, in your acquaintance’s case it is like ours: the ceiling on the ground floor is only clad with gypsum board, which is then attached to the wooden battens. Then you really have a lot of leeway to install things. Recessed spotlights are no problem as long as you don’t have a beam in the way.

On the upper floor, it is usually the case that the gypsum boards are attached to OSB boards and on top of that lies the vapor barrier. If you want to install recessed spotlights, you have to cut through both the gypsum boards and the OSB boards, and then you will usually also hit the vapor barrier. Then you have to install an airtight mounting box in this opening and connect it to the vapor barrier. Alternatively, you can have the mounting box for the spotlights prepared directly by the house builder, then he is responsible for the airtight execution (and also has to make sure no beam is in the way). You can then install the spotlights yourself.

But it can also look somewhat different; some manufacturers have an installation layer in the upper floor ceiling, etc. – you can see that in your construction drawings.

Ok, thanks - but do you see any chance that I can somehow get cables into the ceiling on the upper floor? Without damaging the vapor barrier? Assuming there is no installation layer? Presumably, you can't just slide it between the drywall and OSB

The cables in the upper floor are usually laid in the cold roof, meaning once upwards through the boards & vapor barrier (insulated with appropriate tape or sleeves, if there is no cable duct/riser with its own insulated penetrations), possibly loosely (under the insulation / over the beams) to the connection point, and then once downwards through the boards & vapor barrier (also insulated here with tape/sleeves). It’s really not rocket science – as long as you can move well in terms of height in the attic, it is even easier than on the ground floor.

Alternatively, as mentioned, you can install an airtight box at the connection point instead of a cable passage, then the cable is fed through the rubber seal, and you can install your recessed spotlight accordingly.

I am building with a prefab house manufacturer and will have the house delivered in the summer. I had the painting work removed from the construction services in order to have the chance to pull some cables in the ceiling myself. Apparently, this is possible with some effort and planning without removing the ceiling panels, as there are many cavities here and you can probably get over the rafters with appropriate cable-laying tools.

That sounds to me like the naive idea of trying to apply the logic of wooden house construction to the process of chasing out grooves. The boarding of a structural ceiling is also poorly comparable with the laying boards of a decorative suspended ceiling. Moreover, the question arises for me (and probably also for some readers) why one does not simply order a shell construction version in such cases. "Incomplete plus" is always easier to realize than "complete minus and back."

Your project is at least unusual. That raises questions: Do you already have a plan where which cables are supposed to go and for what purpose? Do you want / need to secure this wiring separately as well? How much space will you have in the fuse box? How do you get there? What impact will your intervention in the electrical system have on the warranty of the entire electrical installation?