I am disappointed that I can't sit in the lower bed with a standard sized mattress.  I think it is designed for thin mattresses.  There isn't a height measurement from the lower bed platform to the upper bed platform.  Before I placed the order, I called the customer service but they wasn't able to find the measurement.  I decided to keep the beds because the return shipping is probably very expensive.  I do like the option of being able to put into two separate beds and I can sit in the upper bed with 9 foot ceiling.