List of defects on mine that with the benefit of hindsight could have been picked up:
More rotten sash windows than I thought.
Inaccurate information about layout of drains in relation to neighbour – would consider a drain survey in future depending on house age and/or location.
Small cracks in render – actually let in quite a bit of water over time. Surprising amount of damage revealed when you remove failed render.
Naively we didn’t check the owner of a nearby retaining wall that has now collapsed. It is ownerless…
Bathroom extractor fans that aren’t actually connected to a vent, hard to check.