Here's some of the reasons I don't use Straw. Especially in areas that may get wet. My runs will be covered but open on the sides and front. Straw gets heavy, it harbors bugs and if it starts to decay before I can remove it the birds can gets sick or most likely die from the molds as it decays. It also has molds, even in dry straw. I have a bad back and I have come to the realization of what my family says. I'm not super woman.
I know some members are going to say. Just remove it quickly when wet. But here, that sometimes is not an option. I care for my elderly dad since mom died last October, as well as run my hubbys trucking company. In addition there's the household chores. My life is too busy.
The main coop alone is 20 coops with 20 runs. (40' building) Then there's 15 dog kennels (10x10x6) with coops and possibly adding another 5.
Inside gets shavings, outside gets sand.

Both are shop vac'ed. Shop vac'ing is the best for me. It's quick, easy and saves my back from heavy wet straw.
I just wanted to praise our evil old cat. Charlie. I accidently locked her in my brooder room and there's 4 chicks with a momma hen running around. She was in there all night until I opened the door. All chicks are A-OK.
I guess I have to rethink my opinion on her meanness.
Nah, she still bites me.