I can't find the discussion, but @Mister D recently said he takes creatine, has gained weight, but attributes it to water weight. I mentioned he likely built muscle too. I ran across this article today that has a section on creatine.
4. Creatine
Creatine monohydrate is the most extensively researched supplement on the market. It has been proven to be a safe and effective method to increase muscular strength and size more than any other natural supplement available.
When taking supplementation the extra creatine gets stored within the muscle. In turn, this provides your body with extra ATP to fuel high intensity exercise.
One group of researchers assessed the effects of creatine supplementation on muscle growth, these researchers noted double the gains in muscle mass for the creatine group compared to the control group after a 12-week resistance training protocol9.
One review compiled several studies that looked at the effects of creatine + resistance training on lean muscle mass gains and found average lean body mass increases of 4.4lbs10. Finally, unlike other supplements, creatine has over 200+ studies showing it to be very safe and effective. If you lift weights or exercise, ensure creatine is a staple supplement in your regime.
You can take 5g of creatine per day pre or post workout. You can also load with 4x 5g doses for the first 5 days to increase your cells’ stores quickly and reap the benefits in just one week.