This is a somewhat distorted picture. I took it to show somebody my panels. The wide lens messes with the proportion and makes the door look almost centered.
It is 24'X12', with an 18'X12' sitting area and 6'X12' Bath/Changing/Equipment area. I built it with untreated sandwiched 2X4 posts wrapped in painted metal, and made sure everything that could get wet was either treated, or covered either in vinyl or metal.
We love it and I'd highly recommend it.
I didn't do a very good job of tracking costs, and I was doing a deck and pergola at the same time, along with a septic line. I hired the concrete, framing and roofing done, mostly because the crew was between jobs and needed some fill work. Really not a hard construction.
Immediately to the right of the door is a wall that separates the bath/equipment area. I used a steel exterior door there, so that room is fully water tight. Bathroom is just a toilet and sink, along with a wire storage rack for towels, suits and clothes. I debated a shower, but along with a water heater it would use a lot of space. I cram it full every fall with everything from the pool and deck. I plan to add a ceiling over the bath area as a storage loft for my winter cover.
I have a ceiling fan with lights in the screened portion. The wall height was chosen at around 2ft to allow us to sit at the table and watch kids in the pool. That was a smart move, IMO, although it wouldn't meet fence code if it wasn't above grade. Screens are in aluminum frames and just siliconed into the spaces. Very easy to install, secure and cheap. I plan to eventually make some plexiglass windows to add in the fall, along with a small LP stove.
I routed a TV, phone, network and speaker cables from the house, just in case. The switch for the pool light is in there as well.
I designed the roof and rafters to use a large ridge beam so I didn't have to use collar ties. That gives me a full vaulted ceiling. Ridge vent is important. The equipment room has a rectangular vent right next to the pump. I need to add one up high there too for flow.
I put a drain in the floor right next to the filter to get rid of water when I winterize or service the equipment. Pool plumbing goes through the wall and then into the ground. I don't have gutters and downspouts yet, as I wanted to wait until after the solar was installed.
If I had it to do again, I'd add a drain right under the table to get rid of blown in water more easily. I'd also have extended the wall on the side opposite the glass door a few feet to make an area that would be almost weathertight against the dividing wall. I might also have considered an entrance directly into the equipment area and dividing that off from the bathroom. That way I could work on things when the kids have friends over.
We live on a farm, so fly-free, shaded sitting and dining was a priority.