Most inventories stop at the back door. The spaces a tenant uses but the clerk skipped quietly become disputes you cannot win.
The loft
Photograph the access hatch, the inside of the loft if it is safely accessible, and any contents already there. Note whether it is boarded, insulated and lit.
Sheds and garages
A locked shed is still your responsibility to document. Get the key, take a few photos, lock it back up.
External condition
A quick walk-around of the building exterior — brickwork, gutters, fascias — takes five minutes and protects against later disputes about damage you could not previously have evidenced.
Treat the inventory as everything within the curtilage of the property, not just the rooms with carpet.
