Min stairs width

[Hunt Stoddard]

Does anyone know what the local code says about minimum stair width for egress (getting in and out of house, I assume) stairs. I think it's usually something like 36 inches.

What are opinions on preserving wood stairs on under eaves exterior stairways? I'm thinking using ACQ lumber and wood preserver on stringers. You see a lot of exterior stairways that are rotted after only a few years.

Thanks.