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I am getting ready to put a new roof on our house (changing the structure and all) and I am wondering what the best and most affordable kind of lumber or material is for the job. I need to span a 26' distance with no supports except at both ends (we are using a structural ridge beam at the peek).

I have looked into dimensional lumber, but it isn't as affordable as I had hoped. I'm still unsure what size we will need, but it will likely either be 2x10s or 2x12s. The best price I have found on the 2x10s is $37.60 each and $46.27 each for the 2x12s (if you buy 100 or more). We will likely need around 80 rafters, so that adds up quickly.

Is there a better material to use besides dimensional lumber or is there are trick to getting better prices on it?

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2 Answers 2

up vote 2 down vote accepted

You may want to go with a TJI (truss joist) that is made by one of these companies (Weyerhaeuser, Georgia Pacific, etc.,). Unless you use a 2 lb foam in the rafter bays, you will need something 14" or taller to get enough insulation in the ceiling to meet code. Of coarse, this depends on the area you live in. Different regions have different R-value requirements.

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Thanks for the idea. I have considered TJI joists, but I'm not sure how affordable they will be. Also, we are hoping to use spray foam insulation which doesn't require as much space (from what I have heard). Also it seems like TJI joists would be harder to work with since you can't just notch the joist without compromising the strength of the joist. –  BWDesign Jun 26 at 16:41
    
TJIs may be the cheapest alternative still. 26 ft long sounds really long but in reality the span, which code and engineers go by, is the horizontal measure from the ridge to the bearing point of the rafter, not the diagonal measure. IBC will give you the info you need for the minimum requirements to carry that span, then you can beef it up from there to carry what you need for insulation, if necessary. –  Jack Jun 26 at 21:56
    
Ok. I will look into the TJI joists again and see if I can get some pricing information. –  BWDesign Jun 27 at 10:53

In those sizes, you might want to look at manufactured lumber such as a Parallam beam. Those can be made in arbitrary lengths (subject to shipping limitations), and they may be cheaper than a solid-wood alternative of the same strength.

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Thanks for the idea. Is that the same as LVL? –  BWDesign Jun 26 at 15:41
    
I did a little looking, Weyerhaeuser makes Parallam which is sort of like really thick OSB (Oriented Strand Board), some folks call it flake board, but the strength and grade of material in Parallam is much greater. I do not mean to diminish the strength of Parallam, I only use it as a material reference. They also make Microlam which is Laminated Veneer Lumber (LVL). –  Jack Jun 26 at 16:04
    
Ok thanks. I will look into it and maybe get in touch with Weyerhaeuser and see what they recommend and the cost. –  BWDesign Jun 26 at 16:43

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