OK- read all the posts & noone mentioned eavelights.
I <3 my 2’ eavelights probably more than any inanimate object deserves & wish I’d gone for 3’.
Along with skylights in the indoor, they let in so much daylight I seldom need to turn lights on in the barn or attached indoor.
Mine are translucent but they now come in clear lexan also.
Ditto on plenty of outlets - GFI! - and want to add I had the lights that light my aisle and the ones over the stalls set on separate switches right by the barn service door.
That way I can come in when it is pitchblack & turn on a light for me w/o levitating sleeping horses.
For lighting I chose cold-ballast fluorescent as I dislike the buzzing & warmup time that comes with halide.
Mine are on instantly except when humidity is really high - for some reason (I am no electrician) they take a minute to come on fully then.
Wish I’d added overhangs
My stalls open via dutch doors directly to the sacrifice paddock that surrounds the barn & from there to pastures.
When the rare East wind blows, it can rain or snow into the stall doorways.
Go for the widest gates you can afford. Pair two gates if you have to for maximum width.
I have a 12’ gate at the entrance to my barn and although vet & farrier can drive their trucks right in, it is a teeth-gnashing tight fit when my hayguy does the same with a loaded wagon.
Wish I’d gone with two 8’ gates there.
My aisle is 12’ and that is plenty room for most use, but makes for some breath-held moments when haywagon coasts through to unload.
Stalls & aisleway (center-aisle design) are floored with crusher-run gravel topped with tamped-down stonedust.
It has packed over the years to where I can easily sweep the aisle. There’s no unlevelness or pitting in the stalls (no mats) & it drains so no smell, but horses still leave shallow hoofprints in the aisle , so it has some give for them.
I bed with wood pellets and find they last a good long time.
Equine Fresh is my brand of choice for lasting power & absorbency.
I mist the pellets and do not find them dusty as they break down.
I can re-bed a stripped stall with 2 bags - not the mfr-recommended 6! - 3 for lush bedding, and that lasts at least 2 weeks before I need to add another bag to refresh.
My horses are out 24/7, coming in to eat or hang out, so YMMV.