A surge in backyard chicken-raising is raising the bar on henhouse design, say two Bay Area men who have just published a new book called "Reinventing the Chicken Coop."

Kevin McElroy and Matthew Wolpe, both self-described "makers" who love to sketch and tinker, said coops are hybrid structures, "part outbuilding, part outdoor furniture, part sculpture."

"Chicken coops are becoming more and more prevalent and they're becoming kind of an accessory for people's yards. Rather than being a ramshackle thing, they have potential for being really cool and fun to make," said Wolpe, a furniture maker who works in the woodshop of the UC Berkeley architecture school.

He and McElroy were recruited to do a book for do-it-yourselfers by Storey Publishing after their Chick-in-A-Box, an homage to mid-century modern design with a butterfly roof and open-to-the outdoors-design, won the Editor's Choice award at the annual Maker Faire.

The book includes 14 original designs with step-by-step instructions for building a chicken coop you could also place in your front yard without fear of backlash from your neighbors... as long as their are no roosters in the henhouse.

But there are a few basics that are important to include in any design to keep your hens healthy, safe and laying.

* Space Requirements: There are many different breeds of different sizes. But the basic rule of thumb is to provide roughly eight to 10 square feet of space per chicken.

* It's not enough simply to provide a place for roosting and nesting. Chickens need access to outdoor space for ground contact, for scratching and grooming. So create an attached run that is tightly enclosed, including on top, so predators can't get inside.

* If you prefer your chickens to be free-range or want to enlist them to fertilize your yard, your run can be a simple fence of at least four feet high with no roof. But be aware that they can still be prey for winged predators. Make sure the coop is secure at night.

* Chicken Tractors: This is a popular way to move your brood about and use them to fertilize your bed or field. Make the coop mobile with no floor, allowing chickens to forage, peck and fertilize beneath it. This is best however, for larger properties.

* Roosts: Chickens roost while they sleep, so you'll need to build in roosting bars. The higher up in the coop, the happier your hens will be. Allow at least eight inches of horizontal roosting space on the bar per bird and 12 inches of height.

* Ventilation: This is essential to remove dust and moisture and prevent the build-up of ammonia from accumulated droppings.

* Nesting Boxes: Hens like to fee safe and secure when laying, so keep it dark with an enclosed feel. Some builders like to attach them as shed-like boxes coming out the side with doors to drop down or open for egg collection from the outside.