Cat house for strays??

There are 5 semi-feral cats coming into house and who I feed everyday (mom, 1 brother, 2 sisters, 1 intruder). They took my house yard as their own place. They'd stay there like ALL day everyday especially after I got them fixed.  I love them so much (and they do too) and I treat them like my own. Anyways,  I noticed although they really like to stay here, they don't seem to find a good spot to sleep or rest in. They either sleep under a tree or somewhere on the floor. I'm living in a country with a usually very hot weather now its about 33C and in the summer its 40~47C. so I really want to provide them with a place that has average temperature. I'm thinking of building a small house on top of a cabinet. but then how can I be sure they'd use it?

btw my family don't want the cats inside the house ever or in any room so thats the only solution I could think of. Any opinions please? 

Depending on your financial situation, there are a couple of options.  You can buy a small shed or large doghouse and outfit it with cat doors.  Two would be best as it gives them escape routes, just in case.  Fill it with straw (not hay or blankets).  In a shed, you can also add shelves and or boxes mounted on the walls to give them vertical space.  If the place is big enough, you can feed them in there.

For winter, you can also construct snug shelters out of Rubbermaid totes.  Google "Rubbermaid cat shelter" for easy instructions.  These will give each cat their own "room" in case they don't want to share.  These can be tucked under trees or bushes or maybe even a deck.

Thank you for helping them - and especially for having them spayed and neutered.

Do a google search on feral cat shelters and check under images.  You might get an idea there.  Definitely you will want an entrance and exit so the cats don't feed trapped.  I have numerous shelters for my cats and often just use rubbermaid totes.  For winter I add a heat pad (outdoor approved) or you can add straw for warmth.  For the summer, I do keep a few of the shelters around so the cats can get out of the rain.  For extra protection from the rain, I sometimes use an extra lid that extends over the entrance/exit.  I just put a few bricks on top to keep it in place. 

To see pictures of my shelters, you can click on the link in my signature, but a google image search will  provide you with lots and lots.

Thank you for caring and especially for getting them all spayed/neutered!!!  Way to go!!!!!