Holy cow.... Rambo Raccoon...
You **can** keep them out but you do best if you think ahead. I used to have a terrible problem with them where I used to live. This is what we did that worked: We had a wooden pole structure made from railroad ties, inside this we built a cube of chain link fencing. So yes, that means on the floor and the ceiling too - a full cube. Then, the thickness of the railroad ties away, we built another cube of welded wire. It was 1" X 2" welded wire, I think they use that to build cages? Not sure. Anyway we used J-clips and hooked it all together along the seams really well. THEN we had the birds inside that. Once we did that we did not lose another bird. Raccoons are really strong. They can actually rip siding off a barn, if it's 1" siding. With the double wire they could not reach through to grab the birds. Raccoons can also actually tear chicken wire, so I agree with Scarlit! Don't use chicken wire. Anyway my DH referred to this structure as the Prisoner Of War Pen. But it worked and we stopped losing birds.
Think 3-dimensional and protect the ground AND the ceiling. The coop I'm currently using has cement poured all the way around, down to 3'. Nothing is going to dig through that in a night's time. You have to think "Fort Knox" to stop raccoons.