Welcome!
You probably will need to wrap sides (at least wind sides) to keep excess rain out. Otherwise it does fine. I used deep littler in my 8x15 large fowl coop. Dirt floor. Very high water table in winter. The bit of dampness inside just invited things like worms, wood lice, and other insects to move in. Turned more into a live composting system on me. I'd toss in shavings occasionally. Poops under the roost were gone in a couple days so there was never much there. I only removed any in spring for fertilizer and not too much.
After the first year, when it was established, I never had dampness anywhere near the surface and no smell. No flies either.
If I had to restart it, I'd put down a lot more pellets than I did originally and layer it with stall dry. Then the shavings. Think that was my issue that first winter. Not enough material down.
As is, as soon as I get new chicks, I'll move them and my couple survivors back into that pen. Should be good to go.
My silkie pens are probably closer to the run you're doing. They are basically covered runs with houses for silkies to sleep in. I just add a thick straw layer in fall. I have to top up after a few months. Straw will only last 3-4 months for me before it's composted. It does slowly raise the soil level in there, which is good. Silkies are fully wrapped in winter with greenhouse tarps to keep all rain out and warmth in.
Water seeps up from underneath because of my water table issue. Straw keeps the idiots from making mud soup to dunk their crests in, which they absolutely will. One has dished water out of the can in summer to do it.