There is a lot of background info and details that are lacking, but IMHO for ease of development & cash savings, what you might consider is getting the first 4.5 x 4.5 coop in place on legs where you want it to be, at the height you want, then take out one wall (can be re-used as a wall in the extended portion) and attach a second 4.5 x 4.5 (floor) structure to it, so you have an over-all structure ~4.5 x 9 feet. This will give you the square footage you need for 10 LF birds. If the birds will only really be in there at night for roosting, you could probably fit 15 birds in there as long as they all are a flock and get along.
Obviously, these dimensions are non standard as far as lumber is concerned, but since you already have a structure built, and want to incorporate it, this would be the easiest way to maintain uniformity. There are some other considerations obviously like nest box placement (to conserve floor area, I would make them external with outside access to collect eggs), roost placement (needs to be higher than the nest boxes, yet low enough so they have head room when roosting), where will you place feeders and waterers, and probably the most important, but least thought out; ventilation! You also need to consider human access to be able to comfortably access the interior for cleaning and such. You can keep floor space available by hanging the feeder and waterer (use a lidded bucket with nipples).
I was going to go in depth on A frames, but there are just too many variablesAnd of course if you just start fresh, you could always use the existing 4.5 x4.5 coop as a quarantine unit or as a broody coop for when you are raising broody chicks. Whatever you do, I hope it works out for you.
Thanks so much. We think the using it 1st one for broody birds and babies is the best idea and just do the new one for the flock... Thanks
