Question about slippery roofs (rooves)

I have been placing a few buildings around intending to allow roof access and a couple of them (even one siege wall) were acting strangely. My character slides around above the surface.

I have made maps for a different game and this problem reminds me of when surfaces are not marked as 'floor' surfaces.
I was just wondering if you have encountered this problem and know how to fix it. I don't really want players skating around on thin air about 1m above the building!

1) How do I fix the slippery problem?
2) When I dig out a river myself the water is completely clear, it doesn't seem to have a water texture attached? How do I make the water look watery instead of invisible?

Thanks, I get the feeling that both problems are probably in some texture/surface editing section I haven't discovered yet.

[Edit: Pretty much all the objects I have added dont really seem very "solid", I'm slipping through bridges too. So I'm sure it's some important step I have not done..]

Both issues sound like you need to restart M&B and reload the map. Sometimes bugs crop up that can only be fixed by restarting the game itself. If not... try these solutions:

As for the water, did you make sure you are at least -1 terrain height or lower? If you lower the terrain and see a clear type water it's because you are in edit mode. Hit H to see the map in regular mode (note you cannot lay props while in this mode, just hit H again to revert to edit mode).

For rooftops, if the reset doesn't work you can add barriers which will allow players to walk on the barrier instead of the prop. Pretty sure the reset will fix it though.

Let me know if that works!

To elaborate: The rooftop bug is likely caused because you moved the buildings/walls etc after placing them. The game remembers only the collision meshes of your initial placement - if you move the prop after placing it, you need to reload the map for the game to realize that the collision now happens elsewhere.

As for the water, as Dave said, that's the edit mode making it clear. Which is actually very helpful for placing items under the surface.

Thanks guys, that was the problem.
All fixed now!