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The California Residential Code (CRC) 2019 has a table of header sizes for various spans / building widths / roof loads: https://up.codes/viewer/california/irc-2018/chapter/6/wall-construction#R602.7

The size column list various combinations of double, triple and quadruple 2x materials (e.g. 2x8, 2x10, 2x12).

Why are there no 4x options (e.g. 4x8, 4x10, 4x12)? Does a different section of code cover that, and do they have different allowable spans?

Context: my local building department suggested I revise my plans from 'double 2x12' to 'single 4x12', and said "like the CRC requires". I'd like to comply with their wishes, but I'd like to fully understand them by reading them in the code. I'd prefer to use double 2x, as it's easier to get in place.

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    Just wondering if local building department has a stake in local lumber yard. Can read this question/answers for some info about 4x to double 2x. diy.stackexchange.com/questions/89117/…
    – crip659
    Commented May 2, 2022 at 18:14
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    Suggest to your local building department that you'll be happy to comply when they show you exactly where in the CRC the table is located.
    – FreeMan
    Commented May 2, 2022 at 18:24

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I can't speak to the CRC, so I'll respond more generally.

Four-by lumber is typically far more expensive than combinations of smaller lumber due to much lower sales volume, so LVL and other more stable and precise options become favorable.

Large timbers typically aren't milled to a precise size like standard lumber, nor will they usually be planed for safer handling.

Large timbers are much less stable than beams built from multiple components, so warping and checking are more likely.

Single-member beams aren't rated for as much load. By using multiple components the risk of weakness caused by a knots or other flaws is lessened.

Four-by timbers would need to be lifted into place as a unit, requiring more people or equipment. Beams constructed from several smaller members are more manageable.

For these reasons four-by timbers have become passé as beam options. It could be that they're simply not included because they're rarely considered appropriate.

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  • Thanks. I agree with all the reasons to prefer 2x, but I'm not sure about "It could be that they're simply not included because they're rarely considered appropriate." There are so many other entries in that table - they had room a for a few more! Also, I see other references online about 4x being typical in CA.
    – tom
    Commented May 2, 2022 at 22:22
  • @tom you do know the proper way to say "thanks" is to click the up-vote arrow, right?
    – FreeMan
    Commented Jun 2, 2022 at 12:49
  • @freeman. I chose not to upvote your answer as I don't think it actually answers the question, sorry. Your answer lists many valid cons for 4x material, however 4x headers seemingly are common in CA, so all those cons must be overridden by something. Hence the cons don't seem to be a good explanation for why 4x material is not listed in the code. Thank you for taking time to write an answer, it contains many true and useful statements, it just doenst answer the question.
    – tom
    Commented Jun 2, 2022 at 16:08
  • Not my answer, @tom, but fair enough.
    – FreeMan
    Commented Jun 2, 2022 at 16:09
  • I'd like to hear more about "seemingly common". Have you seen them implemented in recent construction? Are they readily available in lumber yards and home improvement stores? I'm not sure why that would be the case there and not here in Minnesota. I'm closer to Canada than you are. :D
    – isherwood
    Commented Jun 2, 2022 at 16:13

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