AvadacaDoorbra

You utter the name of the spell and point your finger or spell focus at a door, portcullis, gate, hatch or other similar opening cover. If that object is not made of more than 1 foot thick of wood, 8 inches of stone, 3 inches of common metal or half an inch of adamantine, the door is violently broken open in the opposite direction of you. Any creatures in a 15 foot cone from the door must make dexterity saving throws taking 6d8 peircing damage from the shrapnel of the door, half as much on a successful save.
The door can be no bigger than 10 feet on a side
At higher levels: when cast at level 4 or higher the damage increases by 2d8 per level higher than 3rd. The max size on a side increases by 5 feet for every level above 3rd.