Of course, one must not forget that the construction companies calculate the hours differently when you have that recalculated. Most of the time, they only remove entire trades, and then there’s so little left that it usually isn’t worth it. They won’t make a fuss over a few bricks, and the entire schedule could be thrown off because the ground floor ceiling can’t be installed due to your own work. The underfloor heating is the same; the tradesman will think you’re crazy if he’s supposed to take over your preparation. So much can go wrong there... That leaves painting and flooring (not tiles) work. They hardly ever come included anyway and can be done well in self-performance. One must not forget that 1-2 amateurs need 1-3 full weeks to completely wallpaper a house (depending on effort, skills, and material quality). Floor coverings add more time. For 50 sqm of laying laminate with foil underneath, with 3 people (1 experienced carpenter, 2 technically skilled), we needed 2 weekends, plus procuring the material and driving to the site. Extras in electrical work can be done super well in self-performance, e.g. network, TV, etc...