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I'm renovating my old (1920s) house. One of the beams in the crawlspace which carries floor joists for the room above as well as a load bearing wall is an old rough-cut true 6x6. The beam is in good shape but only has a few 4x4s as posts with 7 foot spans between them.

I'm going to install jack posts to relevel and support the beam but am curious what kind of span that 6x6 can handle. The beam has surprisingly handled 7 foot spans well and the only issue is that the 4x4 posts have sunken an inch or two over the years due to inadequate size and footings.

I am planning on 3 foot spans with poured concrete footers and proper jack posts.

Any red flags you guys see?

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  • It depends on the size of the beam. 3 foot spans should be good/needed for a beam made from 2x4s. Sunken/sinking is usually caused by bad/no footings/not proper footings, not the span or size of the posts. Does the beam sag between posts?
    – crip659
    Nov 1, 2023 at 19:12
  • No real sagging between the posts. Inadequate post size and footings is (I believe) the cause of the issue. I just want to fix it correctly.
    – Lazarus
    Nov 1, 2023 at 19:21
  • Post size will depend on their length, so they don't bend. Short 4x4s okay, long ones will go to the 6x6 or steel posts
    – crip659
    Nov 1, 2023 at 19:27
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    Does this beam carry two floors? A floor, ceiling, and roof? What's the snow load? What are the dimension of the areas carried by the beam?
    – popham
    Nov 1, 2023 at 19:31
  • that's a lot of work to leave a drop beam in place. have you thought about temp supporting the joists and then pushing the beam up and using hangers for a flush ceiling? Nov 2, 2023 at 3:20

1 Answer 1

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A rough cut 6x6 sounds a lot like a header built up from 4 2x6s. You can size the beam under IRC Table R602.7(1) or IRC Table R602.7(2) for the modern size, then compare your beam to the modern size. Don't forget to take note of the lumber grade and species of the modern version versus whatever your 6x6 is made of.

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