Maybe I'm just blind today, but I can't seem to find where climb speed and other speeds are described.
Specifically, I wanted to understand the rules for climbing/walking on the ceiling.
Core Rulebook page 91 (Climb Skill's description) says that a ceiling with handholds only has DC 30, while perfectly smooth, flat vertical (or inverted) surfaces cannot be climbed at all.
This is alright for characters, but when I have a Spider or other creatures with climb speeds my question starts.
Spiders and other vermins may (in real life) walk on the ceiling, so it's alright with the above rules, though I'll make the exception that they can climb any wall, but how can I know if other creatures with a climb speed can do it like vermis or must follow the rules with no exception?
Climb speeds is listed under Special in the Climb skill page91.
"A creature with a climb speed has a +8 racial bonus on all Climb checks. The creature must make a Climb check to climb any wall or slope with a DC higher than 0, but it can always choose to take 10, even if rushed or threatened while climbing."
So a spider must still make the climb check when climbing any surface just like anyone else, but it can take 10. The giant spider in bestiary page258 has a climb skill of +16 so taking ten gives it a 26. So on any surface with a DC of 26 or less the spider climbs without a problem. So strictly by RAW without something else to help the spider out a giant spider could not traverse on a ceiling upside down.
Now then if you had a giant spider drop down from above on the party no player would have a problem with it happening. Unless the party did something like coat the walls in oil to make it harder for the spiders to climb I would not be too worried about the spider climbing on the ceiling. Plus another way would be to add webs to the ceiling easily adding the extra +4 it needs to hang on.
As I said above, spiders are no trouble for the same reasons you listed, but the problem comes when I have other kinds of climb-speed creatures.
For instance, a Girallon (climb speed 40) climbs like a human, with hands and feet, so of course it couldn't walk the ceiling like a spider, but what about something like a Choker (climb speed 10)? Can it play Spider-Man or does it also need something to hold itself to?
With a successful Climb check, you can advance
up, down, or across a slope, wall, or other steep incline
(or even across a ceiling, provided it has handholds) at
one-quarter your normal speed.Action: Climbing is part of movement, so it’s generally
part of a move action (and may be combined with other
types of movement in a move action). Each move action
that includes any climbing requires a separate Climb
check. Catching yourself or another falling character
doesn’t take an action.
So the average human (Speed 30) can climb 7.5 feet with a single move action, and go ahead and make that 3 squares (15 feet) with two move actions, each action requiring a climb check. Climbing is slow and hard. A high level monk, on the other hand, with a speed of 80, could climb 20 feet per move action.
A perfectly flat ceiling (your modern house) cannot be climbed by anything. There is nothing to hold onto. The ceilings in dungeons and caves tend to have bracing, beams, decayed out hand-holds, and more that make holding yourself upright possible, particularly for critters with a climb modifier above 20.
With a successful Climb check, you can advance
up, down, or across a slope, wall, or other steep incline
(or even across a ceiling, provided it has handholds) at
one-quarter your normal speed.Action: Climbing is part of movement, so it’s generally
part of a move action (and may be combined with other
types of movement in a move action). Each move action
that includes any climbing requires a separate Climb
check. Catching yourself or another falling character
doesn’t take an action.
So the average human (Speed 30) can climb 7.5 feet with a single move action, and go ahead and make that 3 squares (15 feet) with two move actions, each action requiring a climb check. Climbing is slow and hard. A high level monk, on the other hand, with a speed of 80, could climb 20 feet per move action.
A perfectly flat ceiling (your modern house) cannot be climbed by anything. There is nothing to hold onto. The ceilings in dungeons and caves tend to have bracing, beams, decayed out hand-holds, and more that make holding yourself upright possible, particularly for critters with a climb modifier above 20.
Isn't this the rule for climbing half speed (15 feet)?:
Accelerated Climbing: You try to climb more quickly than
normal. By accepting a –5 penalty, you can move half your
speed (instead of one-quarter your speed)
That's in the same p90 of Core Rules.