You've far more nest boxes than needed. Always have two then add a nest for every 5 birds. Two nest will handle up to 10, once 11-15 you should have 3, up to 20 birds 4 nest would do. I've a 4x7 coop on skids with three external mounted nesting boxes- bird access from inside, lid for collection. Currently have 11 birds in the coop. Had 14. Will cull cockerels/cock birds and sell a few hens this fall. Hatching now. Plan on keeping 10-12 layers and 2 breeding males. I don't put food or water in coop. It has two roosting bars at same height spaced evenly in the 4 ft dimension running entire length of coop. They are one foot above liter, 16 inches above floor. The venting is top of coop, slanted roof with vents entire 7 foot length bottom and top of slant. Openings covered with hard wire cloth.
The reason for 4x7 dimension was to only need 3 sheets of 3/8th decorative plywood. By keeping 7 ft had enough extra for nest box. 3/8 inch plywood keeps weight down. 2x3's for posts and floor also keeps it lighter and if you note I use 2x2's for corners and top. They are just needed to screw the plywood together. Covered entire top with hardwire cloth so I could use only tin for roof. The high hats of metal roofing act as vents and no weasel can get in. Keep it simple.
My birds do well in such a small coop as they have incredible run size. Are outside everyday. In winter I provide a lean to which is taller than the coop. Slopes from ground to just over coop. Prevailing wind side is covered with a tarp all the way to end of coop. This makes for ample shelter, no snow or freezing rain nor is there Northerly winds. From this structure I shovel paths to their favorite hang out spots and put down a thin bed of hay. They love hanging out under a bush so have a 30 ft path shoveled and scrap out under the bush to toss down hay. I make the small coop work and the chickens love the set up. The reason I do it this way is so spring, summer and fall the coop can be pulled about the yard by lawn tractor and moving a 164' electric fence every two to three weeks to new forage areas.
This is a three nest box. Nailers shown in above photo and box below. Then two scrap pieces of plywood tacked to middle nailers to complete the box. Three foot long box is screwed to outside nailers. Lid attached via a few hinges.
Almost forgot to show the clean out door.
I ended up putting a 1x6 longer than clean out door and held in place by the pine shavings for liter. That way I don't have an avalanche of liter everytime I need to grab a bird. It's not secured so can be lifted out when ready to shovel out liter and replace.
Edited by Egghead_Jr - 3/27/16 at 3:20pm