This link will work.

Here is a link that might be useful:

Your plan sounds okay, except I don't think you have enough room. A twin mattress is 39x75; an "L" shape of (75+75+39" =15.75ft) Are bunk mattresses smaller?

I did a quick floor plan with the rectangle signifying a 32" x 60" treadmill. After making the plan I looked back and saw where you door was (oops!) so that will have to go elsewhere. The beds are sized in the plan at 42" wide x 78" long which include a HB which you won't be using. Anyway, this will give a quick visual. As calirose said, it will be tight. The concept sounds fun. I bet the kids would love it!

I think it is a creative idea, but I am wondering if you aren't limited the use of the space and the room arrangement by having such a huge amount devoted to built-ins that will only occasionally be needed for sleeping.

If it were me I would instead invest in three uber-comfy chairs that fold out into single beds. That way the room has regular seating that the kids can move as needed for playing and gaming, and yet when it comes time to crash for the night, can be used for sleeping. One large ottoman could serve as coffeetable and storage for the bedding. Or the sleeper chairs often come with matching ottoman for that purpose.

Something like this from JCP:

sleepy sleeper chair

Ikea also has fold-out chair beds.

Or, you could get one of those bunk beds that have a full size mattress on the bottom and a twin on top. I've even seen them that the full size mattress on the bottom folds into a sofa/futon. It may not be as attractive built ins might be but it would be easy to remove if you don't want it set up that way anymore.

Here is a link that might be useful: bunk bed

Thanks to all for your input. I am going to continue to consider all of the above options. The house is being built, so I still have another 6 months or so until I have to pull the trigger.

I think it is a very interesting concept, though I'd plan it more for built-in seating with seat and back cushions (plus lots of pillows) with storage drawers below. That way the kids would have a place to store all their gear and you could also use it for all the gaming equipment, bedding and pillows. When it comes time to sleep--some could sleep on the built-in sofa with sheets and blankets or put some cushions and inflatable beds on the floors. Kids and teens seldom need a "conventional" bed to sleep on--and love to sprawl about--esp. as this will be a vacation for them. I think making the built-in as wide as a twin will be less comfy to sit on plus make the room feel more closed in.

One of my best childhood memories was at my own grandma's house. She had a screened in back porch that ran the length of her house with a creek out back. She put twin beds the length of the porch and the grandkids would all sleep back there. It was heaven!

Another idea is to get a couple of daybeds--one with a trundle and put then at right angles to one another with a table in the corner. You should definitely plan for some tables and lamps as well to put stuff--including snacks and drinks--since eating often goes hand-in-hand with TV watching/gaming, etc. You could add a storage ottoman to function as a coffee table and store gaming equipment in it. And, again, lots of pillows on the daybeds to lounge about. This would be a less expensive, more versatile option.

I like the idea mentioned about making these builtins more like seating with backs. Maybe line back with pillows so they can be used to sit against, slept on or propped on floor. It is true that kids sleep all over the place. I have a sectional in my playroom and the kids like to sleep with their heads at the armrest ends and toes touching. Boys and girls both have done this and love it. You can make cushions yourself with foam from craft stores. They foam comes in many thicknesses and with 40% off coupons or wait for sale it can be pretty inexpensive. Get the pillows from discount stores too. End tables and a mini fridge and microwave could make this a fun place to make popcorn and have sodas/water onhand if you trust them to have that in that room. They will never leave the room.