The structure is strong, especially for something that uses zips and velcro for joining the parts together. The large version has enough room for two cats, probably would hold three cats. We have five cats and at least two of them got in the house within an hour of putting it together. The heat seems fine as far as I can tell. We keep the cat house indoors. As for outdoors use, I think the outer materials would hold up against the weather. The heating pad I doubt would do well. For one, it is electrical. Two, the material is like scag carpet. I imagine that is why there are heavy clear plastic flaps (think pet door) velcroed over both of the entrances, to block rain from getting inside. In the large version, there are two entrances that face each other. One entrance is on the "back" and the other is on the "front." This would be perfect for stray cats .