This is from Ch 6 of the core book, under "Doors".
"Any character can batter a standard dungeon door in 3 turns if equipped with an axe. Simple wooden doors take only 1 turn to batter down, while sturdier (solid metal or stone doors) cannot generally be battered down without heavy equipment."
and
"A stuck door can be forced open with brute strength. Forcing
open a door requires a proficiency throw of 18+. Doors of
unusual material or size may impose a penalty on this proficiency
throw. In addition, for each point of Strength adjustment,
modify the result of the die roll by +/- 4. (A character with
Strength 18 thus opens doors with a proficiency throw of 6+). If
two characters cooperate to force open a door, use the stronger
character’s Strength adjustment +4. A roll of 1 always fails to
open a door. It takes only one combat round to force open a
door, and characters may try again if they fail.
So why would you ever batter a door down when you could just force it open?