Fitting s cabinet to timber frame house

[Bo Diddley]

TBF, asking any FEO how you should attach a cabinet opens up a can of worms; they have probably done paper-pushing all their lives and get the shivers at the thought of some DIY.
So long as it's secure and they can't move it, or see any gaps where it is fixed to the floor or wall, crack on

 

[Nick-St]

I did this in a wooden garden office/outbuilding. Put additional joists in the gaps, Expamet mesh in the room, then plywood on top. Cabinets had coach bolts to floor and joists. Extremely strong & the police were more than happy.