A lot of people say that you can't build muscle mass with bodyweight exercises, but that's because they're ignorant. There are several ways to build muscle mass with bodyweight exercise, and time/volume training is a good one. Nick Nilsson lays out a complete, easy-to-follow bodyweight workout program for trainers whose primary goal is building muscle.
... Time/Volume Training is relatively simple. I'll use back training for my example (chin-ups, specifically).
For working back, I use a 15 minute block of time (this will vary according to bodypart - less time for smaller parts - e.g. 10 minutes for biceps).
First, start by doing a set of 3 reps. Then stop and rest 10 seconds. Now do another set of 3 reps. Stop and rest 10 seconds.
Keep going using 3 rep sets and 10 seconds rest until you can't get 3 reps anymore. When you hit this point, now starting taking 20 SECONDS rest in between 3 rep sets.
Keep going using 3 rep sets and 20 seconds rest until you again can't get 3 reps anymore. then take 30 SECONDS rest in between your 3 rep sets. If you have to increase again, go to 40 seconds, and so on.
Keep going in this fashion until your 15 minutes are up. Read more