A lot of houses in the Valley have something out back. Could be a casita that got built for the in-laws, or a guest house that turned into a home office a few years ago and never really turned back. And almost every time I'm out doing a design, the main house gets all the attention and the building in the back just sits there in the dark like it isn't part of the property.
The walk out there is the real problem
The first thing I look at is the path. Say somebody's mother-in-law is staying in the casita, and every night after dinner she walks forty or fifty feet across the yard to get there over pavers or gravel, maybe down a step where the grade changes, holding her phone flashlight out in front of her. That walk is what I'd light before anything else. Some low path lights along it and a step light anywhere the ground drops would do most of the work, and then I'd want something at the casita door so she isn't fishing around for a key in the dark.
I wrote a post in July about how outdoor lighting gets more important as you get older, and honestly casitas are where that whole post lives, because it's a walk somebody makes every single night and a lot of the time that somebody is seventy-five.
Power is usually the first thing to figure out
Low-voltage lighting runs off a transformer and the transformer plugs into an outdoor outlet. Easy at the main house. Out at the casita it depends on how the building was wired and how far it sits from wherever the main transformer is going to be.
If it's a long way from the house I'll usually put a second transformer out at the casita rather than running wire all the way back, because low voltage loses strength over distance and the fixtures at the far end come out dimmer than the rest. A transformer out there solves that, and it also lets the casita lights run on their own schedule if the guests keep different hours than you do. If there's no outdoor outlet on the building at all, that's a small separate electrical job before we start.
Guest house or storage shed
If family or guests actually stay out there I'd light it like a small house, which usually means the entry and the walk plus maybe a soft wash on the front wall so it looks like somewhere you'd want to go from across the yard.
If it's where you keep the pool chemicals and the Christmas boxes, please don't. I've seen people spend real money making a storage shed glow like a boutique hotel, and then from the patio it's the brightest thing in the whole yard and it's a shed. One fixture by the door on a photocell is plenty.
Pool houses land somewhere in between. Most of them are really just a casita with a bathroom and a pile of wet towels, and I usually light the path from the pool to the door pretty well since people are walking it barefoot and dripping, and then keep the building itself on the quiet side so it doesn't compete with the pool.
Detached garages and workshops
With detached garages, you want the ability to see who's back there, and you want to not trip over the hose when you walk out to grab something at ten at night. We will light the approach and the door, and sometimes graze the wall that faces the house so the building doesn't turn into a dark block in the corner once the sun goes down.
If somebody actually works in there at night, the light at the door matters a lot more than anything on the walls.
A couple things people forget
The view from the house, for one. Whatever you light out there you're going to be looking at from the kitchen window or the back patio every evening, so I always check the design from inside, and sometimes that moves fixtures around.
And glare into the casita windows. If somebody's sleeping out there, an uplight aimed at the front wall can end up shining right through the bedroom blinds, which your guests will be too polite to mention and will absolutely remember.
— Sam
Desert Outdoor Lighting has served the Phoenix Valley since 2004. We're licensed and bonded (ROC# 340142) and install landscape lighting and Gemstone permanent trim lighting in Gilbert, Mesa, Chandler, Scottsdale, Tempe, Queen Creek and across the Valley. Call (480) 809-7800 or request a free after-dark design visit.