Collapsing Building
A building coming down is the dismantling of an old structure. Shocking as it is, it was read as clearing ground to rebuild — and getting out of the collapse is a good omen of misfortune turning to gain. It often appears when something you have endured a long time, a relationship or a job, has reached 'this cannot go on'. Clearing the rubble means the sorting has begun. Being pinned and unable to escape, though, signals carrying it alone — time to ask for help.
A building coming down shows the ground under you shaking. Traditional readings treat houses and buildings as the seat of a household and a position, so collapse was read as a change of standing. What happened after the collapse decides most of the meaning.
Readings by Situation
Escaping before it falls
The point of this scene is that your body moved before the thing came down. Something was noticed before you reasoned it out, so bring to mind a place that has felt off to you while you left it alone.
Trapped under the rubble
You are pinned under what came down from above. What collapsed is not you but the structure you were inside, so the question shifts from how much you can bear to whether that structure can be changed.
Watching someone else’s building fall
The point is that the building is someone else's. It is not yours, so there is no loss — but it does make you check whether you have anything built from the same material.
Rebuilding on the cleared ground
The rubble has been carted off and the frame is going up again. Tradition saw tearing down an old house and raising a new one as a household growing, and the grain of the dream splits on whether you keep the same lot or move it.
A collapse in a dream does not foretell a real accident. Unlike an earthquake, what comes down is usually something you stacked yourself, so look first at a schedule or a debt you piled on too high. Taking off a single layer tends to quiet the dream.