Very sturdy. It did take my husband and I about 3 hours to construct ( we took our time). When putting it together pay attention to the top bunk base rails ( the ladder will go into only the one side) not a big deal but we had to switch it around.  I also suggest if you are first time bunk bed owners such as we were, to look into getting a set of bunk bed sheets for the top. Making it is kind of a pain. We may place a piece of thin board underneath the top bunk too as it is just the boards and it’s not a big deal but you can see the underneath of the mattress above etc. I just put a fitted sheet on the bottom to make it look more uniform. Again I am a little extreme with wanting things tidy and neat.