New Construction help...new thread with 3D plan

That looks pretty good. 16x21 should be good for two rows - 6 seats easily, maybe 8 (I'm never good at remembering how wide they run).

When you say 9 feet for the ceiling, is that at the entrance end, or the screen end? If the screen end, it might be worth looking into pushing up a little more, but that wouldn't be absolutely necessary.

Now that you've committed to a dedicated design, it's time to start considering sound isolation and HVAC. Especially with lots of activity nearby, keeping a low noise floor in the theater can be challenging. As you may have seen referenced around here, there is only so much dynamic range in a recording - to be able to experience all of it, the room needs to be very quiet. If it's not very quiet, you'll either miss the quiet parts of the recording, or find yourself jumping for the remote when the action kicks in. Any thoughts about sound isolation expectations? Do you know what sorts of HVAC equipment will be installed and where they will be (zoned system?)?

A lot of the theaters you will find on this forum use decoupling and damping in their sound isolation. How many of you will there be in the house? If you have kids, or expect to watch movies when your other half is already in bed, you might want to consider a more comprehensive design. what are the neighboring rooms like? Is this theater on a second floor, first floor, basement, etc?

As far as HVAC, a dedicated space will require more cooling capacity than most contractors will generally design for. On top of that, to keep the noise floor down, you want the air coming into the room to be moving slowly so that it's not noisy at the register.

Finally, where are you planning to put the door in that powder room? I can't tell if that's a hallway beside it or not in your model

With regard to the noise floor, that's just a $10 way to say you want it quiet in the room. Think about the last time you watched a movie when the dishwasher, or clothes washer, or dryer, or, or, or was running. You turn the volume up to hear the dialogue over the ambient noise in the room, but then a loud action scene follows and you're grabbing for the remote to turn it down and marking off a few more points on your hearing test the idea is to keep the ambient noise in the room as low as possible so the audio is not competing with it.

With the HVAC, you still need the flow to keep the room cool when it's packed full of people and a hot projector. However, you want the air moving slowly so that it doesn't generate noise as it enters the room. Again, turning up the volume to compete with the noise every time the AC turns on.

You might want to check the Pimp My Garage thread and get Brad's thoughts on soundproofing a detached room.

A few more thoughts and design considerations that you may not have run across...

When specifying A/C service, be prepared for running the system to cool the room pretty much year round (where are you ?). Each person produces heat more-or-less like a 100W bulb, plus the 250 or 300 watts in the projector, plus any other electronics or amps that might be in the room, or any lights left on (not generally recommended), so the room will warm quicker than you expect. There are a number of build threads where the details have been hashed out, but some guidelines include trying to turn over or replace the air in the room 6 times per hour - that's a lot. And as J_P_A said, keep the vent velocity down - shoot for 250 fpm or less to keep them quiet - that's much lower than normal.

Supporting both the idea of cooling the room and minimizing extraneous light, you might consider putting the AV equipment in a closet or rack outside the theater. Often, closets are designed so that the face of the equipment is accessible from within the theater to load discs or adjust settings, while the rear is outside and ventilated elsewhere. Equipment racks require their own considerations, but generally provide enough advantages to make it worthwhile.

You might also look into an acoustically transparent screen or the importance of masking systems or maybe constant image height with or without an anamorphic lens ("a-lens"). If you haven't read through a few build threads, it's definitely worthwhile to spend a few hours (days) browsing and seeking inspiration. If you check the sticky threads at the top of the dedicated theater construction forum, you'll see the index of "show me" threads, which are great collections of theaters you can search for ideas that suit your preferences.

Sometimes it's tough for us (me) to make recommendations without knowing what you like and expect. With such a blank canvas there are so many options (not to mention it's taken me about three or four years of reading this forum to accumulate the "knowledge" that I have), I could design the space for me but not necessarily for you.

Fred

I'd think the loft would be the most difficult sound containment problem. If there are kids in the rec room they will want to mess around in the loft too. They'll be making enough racket to disturb the space below.

16' may be a bit narrow for four seats across.

Where does the door behind the theater lead to? Can you incorporate that space into the theater? Or maybe tuck the bathroom back into that corner.

The kid loft could go above the kitchen area.

I'd like 2.5 to three feet on each end of a row to walk comfortably. 2.5 should be fine, IMO, but you'll want a little extra to make room for acoustic treatments mounted to the wall or maybe a column or surround loudspeaker. So 11.5 feet for the seats, plus another 6 to 7 for aisles and things on the walls. 18 would probably be totally reasonable, but closer to 20 would feel relaxed and comfortable.

For rows spacing, I'd shoot for 7 feet from the front of one row to the front of the next, if using recliners. Certainly not less than 6.