Help with adding a room on top of garage

Hello, I am new member here , Please help me with my question . I am planning to add a room on top of a garage, where garage is a drop down garage with 15 feet deep, so planning to add a media room on the top of garage , The dimensions of the garage are 20X20, I spoke to a construction guy, he told he is going to use 14 inch I-joist, with 12 inch apart, is that sufficient enough for a load bearing , I am not going to put any heavy furniture but just want to make sure , Any advise is greatly appreciated. I am also attaching a picture of garage. Thanks

Moderators are extremely busy people, so I'll save them the trouble... Read this: http://www.johnlsayers.com/phpBB2/viewtopic.php?t=3231 Resize the picture and add your location... As for your question, I have no idea, but hopefully you'll find some answers here.

Thanks for pointing me in the right direction, to give some more information, this is still in planning phase and i am discussing with a contractor right know, Just want to make sure that's the right way to do that job. Please let me know if i need to supply any additional information. Thanks

Yes.....14" wooden I-Beams spaced 12" OC will be strong enough for a 20 foot span. I will try to find my load table and post it here when I can. You can also find that online at Georgia Pacific site.

newbie wrote:

Thanks for pointing me in the right direction, to give some more information, this is still in planning phase and i am discussing with a contractor right know, Just want to make sure that's the right way to do that job. Please let me know if i need to supply any additional information. Thanks

If you do not get a professional involved in designing this floor system to be reviewed and passed or failed by your local building inspection department, you are asking for much trouble. Spanning a wood I beam 20 feet or loading with furniture is not even part of the equation at this point. Don't let someone convince you that nailing a band around the perimeter of these walls and setting your joist system on this band is sufficient to carry this live load. It is not.

Thanks for the great suggestions, I asked the contractor to get the city approval/permit before starting the work and get it inspected by city inspector after finishing the work. Will that be sufficient or do I need to hire a designer to design this room first and then talk to contractor? Thank you

newbie wrote:

Will that be sufficient or do I need to hire a designer to design this room first and then talk to contractor?

Some contractors have this as a provided service - design, drawing out the view of the new floor plan, how the load is carried etc.. that set of drawings will be agreed upon by the builder and town for the permit to do the work. There will be a couple or a few points where they will want to see proof of the work before proceding - framing and electric are two key points. You can't put wall board up and expect to just explain what you did to the inspector. For me - I like to have someone do one thing and do it well. That is why for our home addition we are set for contruction start this spring, I chose an architect to draw up plans after reviewing the property. My reasoning is that his entire career is devoted to doing this stage of the process and from working alongside contractors he knows what needs the contractors are going to have as well as the town and the home owner. Plus, any architect should have experience with several contractors and could recommend a few for the work based upon the needs. Then you can shop around and basically interview yourself to have differing opinions and price points on the work. But for construction higlighted in this forum for sound isolation, we're dealing with a different beast. That is why it's important for you to do research and/or find a contractor or architect that has some experience with what you are considering.

newbie wrote:

Thanks for the great suggestions, I asked the contractor to get the city approval/permit before starting the work and get it inspected by city inspector after finishing the work. Will that be sufficient or do I need to hire a designer to design this room first and then talk to contractor? Thank you

These questions can only be answered by your local inspection department. Most want drawings they can inspect to have an overall idea about what it is you are doing to a structure. In your case, I would think they will want these drawings and >could< even want to visually inspect your property before anything begins. Or could want you to remove the existing sheetrock to better understand the structure towards your intended purpose. Remember, you are not wanting just a floor. You want a floor that is overhead in an existing structure that may or may not be able to support it. And how this floor gets supported may be of some concern to the inspection department. This is not an area of isolation(well, it is...but), this is an overhead floor. Flanking is already built into your want of this design, decoupling is not going to happen;)

I have a garage with a room over it. There are 12" TJI joists spaced 12" apart. It spans 24'. The end caps are 2.5" wide. It seems to have enough support. If you have a TJI joist, there are several factors in it's design that go into making it's strength, including the thickness of the OSB, and the size of the end caps. But without knowing the details, it looks like you'd have more support than my floor does. As you read this forum, you'll see that an elevated wooden deck as a floor is not considered a good design for a soundproofed room. Rod says it is a mistake to put money into such a design in his book. But, like you, that's the space I have. Good Luck!