Modifying Garage for New Lift

PorscheSki89 · 01-21-2008, 12:01 PM

I have a 2 car garage with engineered truss roof, 9ft ceilings. My idea is to convert one bay to ridge beam/rafter roof and then remove the parts of the existing trusses on that bay (the right bay) to leave a vaulted ceiling about 16 ft high at the peak. Attached is a more specific layout I put together. The big question i have is whether or not I need to put a post/pole under the long joist going down to the garage floor or whether the joist itself would be enough given the low weight of the roof. Thoughts? Ideas? Comments? BTW, I live in Georgia so snow weight is not an issue. Thanks for any feedback

Kevin

Danny_Ocean · 01-21-2008, 12:16 PM

Do you have a span table? There are a few for the asking on the Internet.

I would say "no" to the post, but a span chart may indicate differently. I have "stretched" a joist in certain situations where I can control what goes on overhead, but you're talking about a garage roof where you have no control over the occasional heavy snow or rain (or 350lb. roofer named "Bubba" walking around up there)...

Here is my latest project - 2 x 12's, 12" O.C. spanning 20' (background). Those are acceptable according to the span chart. In the foreground you see 2 x 10's spanning 19' 6". Span chart says "no", so I added two 3 x 6 posts as part of the stairway to cheat a little.

tcar · 01-21-2008, 12:48 PM

Can you continue the red cirlcled post to a pad under the floor? That's probably too long a span for 2x12's. Increasing the number of joists doesn't help much, it's the depth that counts.

Check headers over both windows - 3-2x10's (2x6wall). Make sure there are at least double studs on each side of each window.

You need a post under the bottom end of the up/down joist, between the garage doors. It can be inside the wall.

PorscheSki89 · 01:43 PM

Good points TCar and Mr. Ocean. I can in fact put in a footer and carry the post under the red circle all the way down to foundation. I know this is the safest, just don't like the idea of a post in the middle of the garage... although it would be useful for mounting things like... electrical cord coil, work light coil, air hose coil....

I will be checking the headers above windows and way go ahead and throw in a third 2x6 on each side of the windows. Good catch on a post under the joist between the garage doors.

BTW, Mr. Ocean... very nice operation you have going there. I'm very jealous.

EDIT: Just got to thinking... if I carry the post in the red circle all the way down to a pas in the floor, do I even need the long joist?

Kevin

DW SD · 01-21-2008, 01:54 PM

Why not convert existing flat ceiling trusses to a vaulted truss system? You could retrofit the new truss system and then cut out the old one? Have you talked to a truss company? They usually supply the engineering if you buy their trusses. You could have them cut the new pieces, which may include gussets in the corners.
We have vaulted roof trusses and the distance between the roof peak and the ceiling peak is not more than 4' with spans of 40'. I bet you could get 12' to 13' of ceiling height without that post and extremely simple retrofit.

I'd hate to have to work around that post in the middle.

Doug

PorscheSki89 · 01-21-2008, 02:14 PM

Well I certainly like that idea. I talked to a structural engineer about modifying to scissor trusses but he suggested modifying the existing trusses would be harder than going to a rafter/ridge beam setup. He also wanted $500 just for the plan. I haven't talked to a truss company, but will do so. I like the idea of just installing pieces and then cutting away what I don't need. I would be plenty happy with 12ft or higher. Great idea. Thanks.

Kevin

MotoSook · 01-21-2008, 03:38 PM

Check with the local code for pitch and height limits if you are going to romove the old roof trusses and roof. If there are no code limitations, then scissors trusses are cheap and safe. They can be ordered from local lumber yards and delivered to your driveway. You can get the engineering drawings from the company that supplies the local lumber or home improvement stores.

You can even request custom spans and heights, and they will provide you the loading numbers. In Georgia, you won't need the loading numbers that we need in the upper midwest...snow and ice.

I think I paid less than $400 bucks for the scissors trusses I needed for my 24X20 garage. I have 10" walls and the interior height limit with the scissors trusses is probably 13 feet. I contacted the company that makes them to get the truss specs for my permit.

I designed, permitted and acted as general contractor when I built my garage. You can do the same to modify your garage. Make sure you get to know the villiage/town inspectors and building director. Give them respect and ask lots of questions of you don't understand what you need. I found my building guys to be pretty helpful and good to work with. Of course I went in prepared and even offered to provide documents with a professional engineer stamps (which they didn't need).