Build your next coop with 1/2" hardware cloth EVERYWHERE so noting can get in.That is the same as my reply to OP was going to be. So I'm posting a reply to a reply, since it's in the same vein.
I'm not keeping chickens at the moment as a pine marten killed 2 of 3 on the first round and then a few weeks later, when I thought it was really secure and had got replacement chickens, it killed the lot. I don't want to keep chickens again until I'm sure I can keep them safer.
A neighbour has lots of chickens and says loosing some chickens from some predator is par for the course. So I guess I need to harden up a bit too. He said the martens etc can get through tiny holes/gaps but are only after the eggs. They get scared by the chickens' noise and flapping and so kill them in what they see as self-defense. He said I could put an egg in a humane trap near the coop to trap it then release it somewhere else. Not sure how effective that is as I presume the marten would just find its way back.
But for the moment, like you, I don't have any chickens. I have other building works going on, so a renewed chicken coop is low priority right now.