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WOOD: "Economical Spacing of Rafters/Joists"

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I will probably get around to doing this myself but I thought maybe some of you have already been through the exercise and have your own opinions.

 

As far as roof and ceiling framing is concerned, I tend toward a “standard” 24 inch spacing for the rafters and joists, use No. 3 SYP is possible and choose depths accordingly. Contrary to what some here have opined regarding “wind uplift,” when you are doing a home in the Houston metro area, a rural location here gives you AT LEAST 110 MPH (3-second gust) and Exposure “C”, which can really kick the h*ll out of a rafter with a long span, so the depth becomes an issue. I tend to like 8’ nominal myself.

 

Anyway, just had an architect send back my plans, with the comment that “you’ve got 24 inch spacing, we always use 16 inch,” and “why are you using 8 inch deep rafters? 6 inch should always be ‘good enough.’” That was the essence of his complaints.

 

Of course, the latter issue is influenced by the former—he didn’t seem to have considered that at first, but as we talked he saw what I meant. However, to him, 24 inch is just “not done”. When I asked for his reasoning he said “roof deck spans better,” etc. ‘Course, if the roof deck is selected as per the code, this is a non-issue, but I don’t like to disappoint a client so I deferred to him on it.

 

My point was that I thought a 24 inch spacing is more economical, even if you use 8 inch joists as opposed to 6 inch.

 

I’d like some input from others here on this question, limited initially to the economic comparisons.

 

If you want to pontificate further on other issues as to why one spacing would be preferred over another, feel free.