# Longest length for roof rafter



## lifestooshort81 (Sep 8, 2012)

Hi Folks,
I'm looking to add a roofed carport area to the front of my existing 12x20 shop. I basically want to add a roof area 20' long by 20' wide. It's hard to explain my idea without a picture but basically my plan is to use one wall of the existing structure (that's 20' long) and come out 20' with a pitched roof. 

That being said I will have to run this by an architect/licensed p.e., etc for exact specs on snow-loads, etc but before I even pick up a phone to speak to an architect/engineer I wanted some input from experienced builders as to what products I can look at using. The idea here is I would LOVE to have an open floor plan, no support members in the middle of the shop. I realize without a truss design this isn't particularly possibly BUT with LVL & TJI's I've see it done elsewhere and pretty certain it can be done. 

That being said, what is the longest span I can span with a TJI. I know they come in all different dimensions but if I wanted to span say 22' (total roof length) what size TJI can I use. Also if you just may happen to know a ballpark price on them that would be awesome too. It's not like I can just run down to Home Depot and price them out. Well, maybe I can but they're not exactly "on the shelf" and the lumber yards are closed. SO I figured id see if anyone had some input here. 

I'm really just trying to get my ducks in a row before I actually consult with someone about this. I can build the project no problem I'm just not experienced per-se in framing. I do more finish work... 

Thanks in Advance
Al


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## ScipioAfricanus (Sep 13, 2008)

A lot depends on the specifics of your design. Generally speaking, (very generally) you can span that distance with regular lumber rafters. It all depends on the pitch of the roof plane, on center distance you want, dead and live loads, and ground-snow loads as required by your local, etc.



I have used TJIs for low slope roofs over 26' long no problems, I don't have your snow load to contend with though. 

Andy.


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## m2akita (May 18, 2012)

I would think TJI would definitely span it. Check out Weyerhaeuser website ( http://www.woodbywy.com/ ). Look under their Truss Joist tab, there should be information there on installation. Also do a search for "Forte", that is their software program. I think you can do a free trail download of that. That should be able to give you actual specs of what size TJI to use.

Good luck


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## griz (Nov 26, 2009)

Look here:

http://www.bc.com/dms/wood/ewp/3_Guide_Resources/west_us/1_west_spec_guide/west_spec_complete.pdf


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## thom (Nov 3, 2006)

Since you dismissed engineered trusses I guess you want to store stuff up there. What you store determines the live loading. Without that you really can't move forward. Storage loads can be huge and can bring the whole thing down if not adequately sized. 

Either way, engineered trusses or engineered lumber, 20' is an easy span with normal loading characteristics.


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