What we see remaining of most castles is misleading if judged on that alone.
For a start; many castles were either adapted to less violent times and altered to homes not defensive works, or they were simply abandoned because they were no longer needed and too expensive to keep running/adapt. So what is left is nothing like they would have been in the 12th to 15th centuries
You don't see all the wooden buildings, barriers, roofs and ad hoc structures. Go and have a look at a castle, and where there are good walls standing, look for all the post holes in walls. A lot of these will be scaffolding related from the building but there will also be floor joist holes for wooden structures, supports for wooden parapet covers, supports for wooden rail fences on higher levels. Some of the scaffolding post holes could be reused for these purposes.
Some loonies in France rebuilding a castle with old methods - including wooden scaffolding.
The holes are known (anachronistically - 17th century) as putlocks. They were used for supports for hoardings and covered walkway construction as well.
So: yes you can have a lot of weather and general 'health and safety' features that you don't see today.
(I suspect the average Norman knight might not have appreciated a chat about the Working Time Regulations however).
Short answer - Humph can legitimately have his fence (might have made it of square section wooden beams stuck to the outside of the steps though- in putlocks).