How To Get A Bigger Back

There is no single weight lifting exercise for total building of the back. Being one of the largest and most complex muscle groups of the human body; the back is involved throughout many movements, both in weight lifting and while performing everyday tasks. Therefore it makes sense to use a variety of different exercises when designing a weight lifting routine for complete development.
The first and most important step in creating a routine is to understand the functionality of both the upper and lower back. The upper back is roughly the same size as the chest and shoulders combined and contributes significantly to the overall appearance of both muscle groups. Developing this area has perhaps the most drastic effect on the upper body as it frames in the chest and pushes out the shoulders to create the desired V-shaped torso. Unlike other muscle groups, the upper back can grow both in thickness and width with exercises that involve pulling weight toward the body either horizontally or vertically relative to the body. Horizontal movements build thickness while vertical movements build width. The lower back is one of the strongest areas of the entire body and acts as a stabilizer during any exercise that involves bending over such as squats, deadlifts, and bent-over barbell rows. Both portions of the back must be developed to ensure a balanced and functional physique.
Armed with this knowledge, the next step is to learn the most effective weight lifting exercises for each portion of the back. Upper back thickness is developed with free weight, machine, and cable rowing exercises; the ultimate mass builder being bent-over barbell or dumbbell rows. Width is built with pull ups and machine or cable lat pull downs. Since the pull up is the the primary mass builder, consider using a weight belt to attach a plate or two if this exercise becomes easy. Deadlifts are by far the most effective exercise more lower back development and second only to the squats in terms of building overall muscle mass. Since it is a power exercise, the best rep range for the deadlift is 4-6 with as much weight as can be lifted with good form. Ensure that these mass builders are included fore each area and use machines, cables, and finishing exercises as icing on the cake.
Each portion of the back can be trained separately or together in a single workout. The advantage of splitting up this large muscle group is more concentrated attention can be placed individually on thickness, width, and lower back developement. In addition, each targetted routine is easily paired with other bodyparts. Upper back exercises pair very well with a chest and shoulder routine (thickness complements chest and width complements shoulders) while almost all lower back movements involve the hamstrings. Training the entire back will involve doing fewer exercises for each area (5 exercises total is often plenty) but is effective as long as pull ups, deadlifts, and bent-over barbell or dumbbell rows are included.

Upper Back Thickness

• Bent-over barbell or dumbbell rows 2-3x6-8
• Any machine or cable row 2-3x8-10
• Bent-over lateral dumbbell or cable raises 2x10-15
  

Upper Back Width

• Pull ups 2-3x6-8 (use a weight belt to pull up a plate or two if needed)
• Any machine or cable pull down 2-3x8-10
• Dumbbell or cable pull over 2x10-15
  

Lower Back

• Deadlifts 2-3x4-6
• Hyper extensions 2x10-15
  

Total Back 

• Pull ups 2-3x6-8
• Deadlifts 2-3x4-6
• Bent-over barbell or dumbbell rows 2-3x6-8
• Any two back exercises 2x10-15 (focus on areas that are underdeveloped)