Depending upon both the height and type of chickens (heavies?), you may have happier and healthier chickens, if they can FLY up, rather than walk up a ramp. Even a box to jump up on first, can be a better alternative.
This eliminates the mouse problem, also. Can't post pictures of several alternatives, but I no longer use ramps at all. It also makes it easier for you to care for the birds, not having to work around a ramp.