Below are some general guidelines on how a farmstead should be laid out. This list is by no means exhaustive.

Neonates, maternity, and nurseries should be in highly visible but low farm traffic areas. Sounds like an oxymoron, but if you have to put something near a residence this is it. The odor and fly pressure can be minimal and if an animal is ill or having a difficult time calving you should be able to pick up on it right away.

By the same token place manure storages, compost piles, and bunker silos/ feed centers as far away and downwind as practical. The odor and traffic associated with these facilities can be quite offensive. Access / haul roads should travel around the farmstead and not through it. Moreover, by placing these units on the periphery you leave open your options for future expansion. 

Speaking of traffic...traffic patterns should never interfere with each other. Granted with 4- and 6-row freestall barns you will have feed alleys intersecting with cow alleys to and from the parlor, but the milk truck shouldn't interfere with the feed truck which shouldn't interfere with the manure tanker which shouldn't interfere with the vet, etc., etc. You get the idea. 

Traffic to and from the parlor should be two-way. In fact, all farm lanes should be wide enough to accommodate two vehicles passing each other. 

The shop and fuel storage are often placed together for obvious reasons. They should be a safe distance away from residences, but well-lit and visible to discourage theft and vandalism.

The sick and lame cow pen should be near the milking parlor. This is usually at the end of or beside the holding area to minimize the distance the cow needs to travel. This area should be easily accessed by the vet, as well as, large equipment should an animal need to be lifted or a mortality removed. 

Space the buildings out! Adequate separation is necessary for ventilation, surface water drainage, snow removal and/or storage, fire prevention, and, of course, biosecurity. Since most of the livestock buildings are naturally (vs. mechanically) ventilated it's important to leave enough space between structures so as not to restrict air flow. A rule of thumb is to space naturally ventilated barns 5 to 10 times the ridge height of the upwind structure (trees included). The longer the barn or hedgerow the greater the separation required.

At a minimum, the plan should be for a doubling of the herd size. Be sure to include the downstream, ripple effect of increasing herd size, as well: more calf, heifer, and dry cow facilities; larger parlor; bigger feed storage bunkers, commodity sheds, and grain bins; and, of course, a larger manure handling and storage system. 

Figure in flexibility. It may be a heifer barn now, but as the operation grows its placement on the farmstead and interior design should allow it to be turned into another lactating facility. 

NEVER place a barn so that it has a dead end. You should always be able to drive through or along a building. It's one thing to back up a manure spreader 20' - 30' to get under a push-off ramp, but having to back up a mixer wagon 150' - 200' (or more) because the new freestall was butted up against the old stall barn is time consuming and inefficient. Moreover, this situation frequently compromises the ventilation of both structures. 

So there you have it -- some "rules of thumb" by which you can plan your next expansion.