This is what we've ended up with for an outdoor shelter this season. We try to improve on things every winter. There is an entrance in front where the wood meets the plastic, on the bottom right, and an emergency exit in the back area. You should always have an emergency exit in case their shelter is invaded by a new cat or other animal. The tarp is laid over a big piece of wood and secured by all the pieces of wood so it doesn't fly up. Inside the shelter are a heated water bowl, heated outdoor kitty pad, (you can see the electrical cords running to our outdoor outlet on the bottom right) and a kitty condo like this:
Rubbermaid storage bins are the best to use in building a shelter, and eRubbermaid.com has started a great not-for-profit called the Roughneck Homes Program - here is their mission statement: "eRubbermaid.com is proud to support the ongoing fight to maintain the overwhelming population of feral cats in the United States. Through our 'Roughneck Homes' program you will find resources to help build and maintain a safe living environment for feral cats in your area, as well as access to our popular Roughneck Containers at zero-margin prices/delivery for use in building your shelter or donating to a charitable organization." I plan on writing to Rubbermaid to express my support for this program. Click here to order the tubs at low cost, and instructions on how to make the shelters.
Tree House has a fantastic outdoor event every October at their 1212 W. Carmen Ave. location called the Feral Cat Colony Caretaker Fest where you can get free and low-cost colony and winterization supplies, including these outdoor shelters, insulation materials (Styrofoam sheets and straw), heated water bowls, and free cat food, They serve donuts and coffee and juice and everyone chats and has a good time. I highly recommend attending as heated water bowls and heated kitty pads can be really pricey. We make our condos just a little different than this pic - we line the tub with that pink insulation foam board and then just stuff it with straw, which you can get at Home Depot in the fall.
We don't use the fleece cover, it would just get filthy and covered in cat spray and I think possibly they get more heat off just sitting on the unit.
Interestingly, there IS a solar-heated water bowl if you are feeding cats that are not on your property, or where there is no outdoor electrical outlet available:
Though it would make me a little nervous that it would get stolen in the neighborhoods that I feed in at least...since it has to be out in the open.