A pigeon loft can be built in a number of shapes and sizes but several rules apply to any design. First and foremost is the loft must be dry. Second, the loft should be well ventilated but free of drafts. Third is to allow as much direct sunlight as possible to reach the birds.
Most lofts have separate pens for the cocks, hens and young birds. This will allow to keep the sexes separate during the fall and winter months when the shows occur. Then the pairs can be placed together for the breeding season which commences in spring and runs typically until the end of summer.
Some breeders prefer to keep each pair in a separate cage for breeding while others will keep multiple pairs in a pen that has been fitted with nest boxes. Either way is suitable.
Wood shavings or similar material should be placed in the pens to keep things dry and sanitary. An alternative would be to scrape bare floors daily to remove the droppings.
The size of the loft only depends on the number of birds that you wish to keep. A single pair could be kept comfortably in something the size of a rabbit hutch, two feet by three feet. However if you wish to raise youngsters form this pair you would need something larger. Many smaller lofts measure four feet by eight feet and work very well.
There are a variety of commercially prepared pigeon feeds available. The two main varieties are grain and pelleted rations. Pellets combine ground grains with added minerals into a single pelletized ration. Most pigeons do not prefer the pellets over a grain ration. The grain rations vary in the number of seed varieties and fat/protein levels. Protein should be 14-16% for breeding and molting. 12% is fine for winter maintenance. If feeding a grain diet, grit should always be given to supplement any mineral deficiency. The "red" type is best and the birds seem to prefer it the most.
Fresh water should be given daily, twice daily if possible. Optional vitamin supplements can be given in the water as well. Make sure whatever type of water vessel is used that it does not allow the birds to contaminate the water with droppings.