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Garage Conversion

Old 01-28-2013, 12:08 PM
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I am planning to add a steel beam in my garage so I can floor the attic. Adding the steel isn't a problem. Just looking for some input. Right now I have cheap trusses that I plan to beef up so they can hold a floor. There is just too much wasted space up there that I want to utilize. Here is my thinking.

1. Add steel beam. Of course this will also involve some steel columns as well.

2. Then I will sister some 2x8's along side the existing 2x4 trusses. Lay some plywood.

Question is, can I sister some 2x8's or 2x6's along side the "rafters" of the trusses, and then install collar ties at each rafter to loose the truss bracing? Seems doable, the only thing that I will not have is ridge board. Is there an easy way to get around that? Shoot some holes in my theory.....looking for some good feedback.
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Old 01-28-2013, 01:41 PM
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When you sister the rafters they should go all the way from the ridge poll to the top plate of the outer wall. Whether you use 2X6 or 2X8 depends on the span. The rafters are probably now 2X4 in the trusses so adding a 2X6 glued and nailed or screwed should be good up the about 13 ft. Over that go 2X8. The hard part is getting the 2X6 or 2x8 into the rafter bays. Usually have to remove the gutter, facia and maybe the soffit for access. After they are all in go ahead and install collar ties and remove the trusses 1 or 2 rafter bays at a time. Good luck.
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Old 01-28-2013, 02:13 PM
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Originally Posted by hottoddie View Post
When you sister the rafters they should go all the way from the ridge poll to the top plate of the outer wall. Whether you use 2X6 or 2X8 depends on the span. The rafters are probably now 2X4 in the trusses so adding a 2X6 glued and nailed or screwed should be good up the about 13 ft. Over that go 2X8. The hard part is getting the 2X6 or 2x8 into the rafter bays. Usually have to remove the gutter, facia and maybe the soffit for access. After they are all in go ahead and install collar ties and remove the trusses 1 or 2 rafter bays at a time. Good luck.
What you talk about is all fine and dandy, but we don't know if the rafters are on 16", 24" or 48" on center? We also don't know the pitch of the roof and we don't know what the trusses he currently has in there are rated for? Far too many variables to give him the answer he is looking for with the info provided.
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Old 01-28-2013, 02:16 PM
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post a pic of your attic--
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Old 01-28-2013, 02:36 PM
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SOmetimes on a project like this it may literally be easier and less $$ and time to saw the roof off and stick frame it to meet your needs. Might sound crazy but its probably 1 day to remove the roof and start anew....
Some pics would help too.
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Old 01-28-2013, 02:42 PM
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Did anyone say a permit was needed here?
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Old 01-28-2013, 04:14 PM
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12/12 pitch. The trusses are spaced at 24" OC. The trusses are 2x4 now. Garage is about 24' deep, so it will about 12' from beam to edge. I am out of town for work, will snap a pic this weekend. Thanks for all the input so far. Permit.....
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Old 01-28-2013, 04:27 PM
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In the code book as well as on the truss it specifically states an engineered truss is not to be altered.

For what it is and what you want cut the roof and start over. It will be a easier, simpler and better end product when complete.

I would strongly reccomend having an engineer tell you what you should do and not rely on some boater buds. An engineer stamp would only cost a couple hundred and could save you 10 thousand.
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Old 01-28-2013, 04:46 PM
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Have you considered pulling the roof and trusses, building a proper floor then walls and putting the trusses back on?
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Old 01-28-2013, 05:08 PM
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Ok before you get too carried away, what are you going to do with the attic space? Is it just storage, or are you converting to living space? What is the dimension of the garage along the length of the trusses and what is the length perpendicular to the trusses? I'm a licensed engineer and you probably don't need to mess with anything other than the bottom chords, adding the beam and posts. I need more info first. This will only work if you are leaving the intermediate truss chords intact.

Edit - I just re-read your post. It sounds like you are looking to remove the intermediate chords that run between the bottom chords and the roof chords, replacing them with a collar tie. If that is the case, then you really do need to have an engineer look at what you are doing. Double 2x6 collar ties work well if the "roof joist" portion is designed to handle the loads, but not if they are only 2x4.

In order to do that, you would need to essentially stick frame your open roof from the inside as if it were new construction, attach to the existing roof joists and floor joists, and then you could cut out the center chords. Again, you really need an engineer to help. The good news is that you may be able to avoid the beam and posts in the garage space.

Last edited by louiefl; 01-28-2013 at 05:30 PM.
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Old 01-28-2013, 08:39 PM
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yes all parts of trusses are 2x4 now. I was for the roof cords i was planning to sister a 2x8 beside them to beef them up. add collar ties and a knee wall. This is just an area for light storage. I have a PE that can run some calcs for me. I am a PM for a general contractor so I know the major do's and don't, just looking for some input from a large audience. Right now I am managing a project that is about $55 mil, the engineer and I are pretty good friends, I am sure he will look at it for me. Not going to remove the roof, if I can't remove the intermediate cords then that isn't the end of the world. just exploring some ideas.
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Old 01-29-2013, 05:17 AM
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Originally Posted by mymojo View Post
SOmetimes on a project like this it may literally be easier and less $$ and time to saw the roof off and stick frame it to meet your needs. Might sound crazy but its probably 1 day to remove the roof and start anew....
Some pics would help too.
Not a bad idea. Trusses are carefully designed tension/compression units, and removing the chords destroys the truss instantly. Plus you gotta have a large opening for the stairs, which must also be properly designed.

My take, based on the questions you've asked, is that you need professional design help!
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