joist weight

Hi All, I would like do to a semi-conversion of my loft to use it as an office space/man cave (tv, desk, etc.) and to store some boxes, and as any house owner does sooner or later, I worry that the ceiling will sooner or later come down for the weight (or worst, I will come down with the...

Guys can you just confim that these missing bits of floorboards should have been replaced with some new sections of pine planks with the same thickness and grade... New flat who ever installed the new heating system butchered the old floor then juat walked away no idea what he did with the...