Adding a room on top of garage


Old 02-07-08, 04:25 PM
Thread Starter
Join Date: Feb 2008
Posts: 2
Adding a room on top of garage


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(approx),

i was talking to some contractor to build a room on top of garage , This is what he is proposing.

He is going to use 14 Inch I-Joists with 12 Inch apart for the floor and on the left side of garage he is going to build a small frame with 2X4's on the top of the existing concrete wall by removing the sheet rock and that is used to hold these I-joists. I think the existing framing is built with 2X6 frames.

As far on the right side of the garage where the solid foundation is their, he is going to use lug nut bolts to screw
down a wooden frame(2X14) to concrete foundation and put joist hangers to hang the floor(I-joists). With this option
i get 9 feet ceiling room.


Other option he is giving is to lay the I-joist's directly on to foundation, which is kind of raised floor, with this option
i will only get 8 feet celing room.

I asked him to get the city permit before he start the work, But i just want to make sure that is the right way to a build a room on the top of the garage, I am going to use this room as a media room so no heavy furniture but still want to make sure that is it OK to put the additional load on the left side foundation wall.

Also is 14inch I-joists is the way to go for 20feet span ?

Any advice or suggestions will be really helpful.

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Old 02-07-08, 04:44 PM
Join Date: Aug 2004
Location: midwest usa
Posts: 111
It sounds to me like the contractor knows what he is doing, and a good inspector will make sure everything has been done correctly. I do not know the span and load ratings for I-joists, but I would guess that a 20-foot span of 14-inchers at 12" OC will be just fine. I have a 12-foot span with 10-inchers at 16" OC, and that floor is very solid.
Old 02-07-08, 06:11 PM
Thread Starter
Join Date: Feb 2008
Posts: 2
Thanks for a quick resposne , I just attached some pictures here for the folks to get an a better idea.

Thanks in advance.


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