In article ,
"OG" writes:

As another question, "how safe is it to walk on the roof itself?"
When we had the TV aerial fixed a couple of years ago the guy used the
ladder to get onto the roof at gutter height and then walked up the tiles to
the chimney.

When I had my chimney repointed, the chap slid every other roof tile
up under the one above it, and then used the exposed battons to walk
all round the chimney.

I'd be concerned about 2 things, damage to the roof, but more significantly,
the risk of shoes losing grip and me ending as a jammy heap in the garden.

The other risk is that of losing your balance. This is easy to do
when the surface you are walking on is a long way from horizontal,
and you are more devoid of visible horizontal and vertical reference
points than you are used to when walking on the ground, so two of
the sensory inputs subconciously involved with balance are feeding
the brain misleading information.

--
Andrew Gabriel