In English, we use the verb "to be" both when an action is performed ("The chapel was rebuilt by the city") and when describing the resulting condition ("The chapel is rebuilt"). Spanish clarifies this by choosing between ser and estar.
Actions with ser (Passive voice)
To describe an action happening to a subject, use ser + past participle. This forms the passive voice, often paired with por (by) to state who performed the action.
| The chapel was rebuilt by my grandfather. | La capilla fue reconstruida por mi abuelo. |
| While I was eating, the old arch was demolished. | Mientras yo comía, el arco viejo fue demolido. |
Resulting states with estar
To describe the condition left behind after an action is completed, use estar + past participle.
| That roof is already rebuilt. | Aquel tejado ya está reconstruido. |
| That arch has been demolished for a month. | Aquel arco está demolido desde hace un mes. |
In both structures, the past participle acts like an adjective. Its ending must agree with the gender and number of the subject (e.g., el arco demolido, la capilla reconstruida).
Putting it together
Here is the active event (ser), followed by the condition it leaves behind (estar).
| The house was destroyed, but now it is rebuilt. | La casa fue destruida, pero ahora está reconstruida. |
| The chapel was remodeled and is already finished. | La capilla fue remodelada y ya está terminada. |