I have found and read various threads here about bonus room conversions into dedicated theaters. Most talk about potential problems from angles in the ceiling following the roof line. I found a couple that talk about concerns isolating sound from the rest of the house. My concern, which I have not found a decent discussion on, is how do you go about treating the floor? Is having the room above the garage going to throw booming base out the garage doors to bother the neighbors? Is it necessary to build a box-in-a-box floor included?

In the case of a house I am considering making an offer to buy, it has a very nice bonus room over a 3-car garage. The room has about eight feet from the floor to the beginning of a slope, and has a flat section about 10-11 foot up across the middle 10' or so of the ceiling. It is about 16' wide, and about 20' long, plus an extra 10' or so of length for the entrance + closet + bathroom area. The space looks like a great place for a home theater, to my untrained eye. :) (do you agree?)

If I do buy this house, will having the HT over the garage cause big problems? You may have seen some of my previous posts indicating that my only concern (except good value for future resale) is having a great place to build a dedicated home theater. If a above-garage-room has some significant issues unique to that design, let me know. Thanks! :)

I'm not sure if the worry about the booming bass from the garage is warranted. Most if not all of the sound escaping from my bonus room HT is through all the window space in the room. The flooring on the other hand is over 12" thick with acoustical batting and then layers of drywall so you can hardly hear it when I'm in the garage. You can't hear it at all from the neighbours through the garage area rather the sound comes from above or the "window areas".
Just my experience with my bonus room HT.
Good luck with your build
Cheers
Calvin

While I don't have a room as you describe I have looked at some homes that did, One major consideration is HVAC. Some of the better rooms I saw actually had a dedicated unit for the bonus space.

Worst case is a supply off the end of the main trunk serving the bedrooms and no return located in the room. That's a formula for transmitting sound to the bedrooms and suffering from overheating when the door is closed.

off topic but we always reffered to that room as the FROG Family Room Over Garage

It is often called a "bonus" room as it is an option the house can be built with or with out the room. Haven't heard the FROG before but that makes sense if the room is not a builder option.

BIG,

Good point HVAC is always a serious concern any HT so good suggestion to take a hard look at that. No point losing sleep over the neighbours been kept awake if your doing it to your own family as well ;)

Cheers
Calvin

I will have to make a point of looking closely at the HVAC in the bonus area then, if I revisit this home. Right now it is #1 on my list. The thing that caught my eye on the bonus room layout is the extra height I would get, 8' at the side walls and an extra 2-3' for the center 50% or so, and the bathroom handily at the entrance area (not a bedroom/hall bath).

Do you think I would need to gut the existing space (remove drywall etc.) or if putting two layers of 5/8" drywall on top of the existing would be a reasonable way to go? The only shared wall with the rest of the house is the end that would include the entrance area, equipment closet, and bathroom. Would using isolation clips or a staggered/double stud wall for that one wall be sufficient? This would be back wall of the theater.

My previous HT was in a bonus room over a two car carage and it was great for it. There is some distance between it and the bedrooms, maybe 20' and I never had any real sound transmission issues to the bedrooms, although you have to be somewhat reasonable with the volume control. But overall very acceptable considering there wasn't any special building techniques (double dry wall, greeen glue, etc). Definately no issue with sound coming out the garage door. Of course it all depends on how loud you like to watch movies.

However as previously mentioned, you probably will need to look into HVAC. My bonus room is the only thing on the 2nd floor with just a single heat pump for the whole house. So it can get warm up there during the summer and cold in the winter.

The only other issue was the slope of the ceiling limited my screen size to 92", but my side walls are only 4' tall. Yours is much higher so you will be fine.
Also I had to block the only window up there with the screen.

An old pic just for fun.
(BTW it is a composite, wish I could get that bright of a pic w/ the lights on!)

What about garage noise - car engines, garage door opener, furnace systems, you futzing in the wood shop while the wife wants to watch her Tivo shows....

Building an HT for sound isolation is as much about what comes in as well as what goes out.

Yes HVAC is a must - usually the windows and gable ceilings and no HVAC in garage makes these rooms much hotter or colder than rest of the house. If there is any HVAC vents in the room it is likely insufficient once the room is sealed.

I sugget you go with a belt drive over a chain drive for sure for the garage doors but you knew that already ;)

Cheers
Calvin

Check out Mark P's thread - a four car garage bonus room conversion - with neighbors a mile a way - and a four driver infinite baffle in the ceiling. I think he might have mentioned something about drywall shaking loose and snowing on his car....picking up shingles from the driveway...

http://www.avsforum.com/avs-vb/showthread.php?t=566082&page=1&pp=30

After more old-thread-reading, I am really liking Mark P's technique to cut out the ceiling joists and beef up the rafters. The spaciousness of that theater room is awesome. And it gives so much more room to put in bass traps. But that leads to another question, of course. Can bass traps be anywhere in a room to function effectively? More importantly, will they effectively function being placed above ear-level, or do they need to be down near the floor? If I go do go with the bonus-room-over-garage-theater, then I will have much more space above the room than I need, but will be tight on space at ear level.