[@Crimson Raven] I forgot to mention you in my post, but I edited it in so that you at least see it when you go to look.

This ought to be interesting.

EDIT: As a note. I'm willing to change how long it took him to carve and prepare the Runes if that amount of time is insufficient. As a note, if the runes are damaged the enchantment ceases to work. Oh, and if a significantly powerful spell hits the surfaces it will also fail. You could also use a spell that messed with magical energy, or one strong enough to damage/pierce iron to get out of the building.

This is not something he could just as easily cast in combat by the way as he would be very likely to get interrupted.