Throughout North America we are experiencing a shortage of nursery and finisher space. The industry has expanded, and we have export markets to take our extra pork, but shortages of capital and environmental restrictions have limited our ability to meet the demand for new buildings. However, even well designed facilities of only a decade ago are finding themselves short on space as pigs back up in these ‘constipated’ barns. Why do we have this shortage of space? How can barns that accommodated the farm’s pigs when they were built find themselves inadequate today? There are at least three contributing factors, each of which adds to the problems created by the others. Increased sow productivity, increased days to market, and increased pig size; have all led to an increase in space needs by 13.8, 12.5 and 10.4%, respectively over the last decade. But what is the overall effect? If we were building a barn to accommodate the production of this unit how much more space would we need? The previous barn had 16 finishing rooms, each of which accommodated 253 pigs, at a floor space allowance of 0.67 m2. That resulted in 2,712 m2 of pig space in the finisher barn (excluding alleys etc.). Building today we would need 18 finishing rooms, accommodating 288 pigs, with a space allowance of 0.74 m2/pig. The total finishing pig area would be 3,836 m2. The combined effect of the three factors identified would be to increase finishing space requirements by 41.4%. Building more finishing space is an obvious means to correct the problem, but how would you do it? Adding two new rooms would address the issue of two extra weeks to market, but the existing rooms would remain overcrowded due to number of pigs and increased pig size. A change in pig flow is needed to accommodate the new standards of productivity the farm is achieving. I was recently asked to look at the plans for a new farrow-to-finish operation. Although productivity in the herd was about what I have described for our example barn, the producer had designed the barn to accommodate 30 pigs/sow/year and market weights of 140 kg. That decision will likely be best appreciated in 15 years time. Our example also shows that typical farrow-to-finish barns, with weekly finishing rooms, are not very flexible when it comes to coping with increased sow productivity or market weights. Alternative, more flexible pig flows, should be considered when setting up a new operation.