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My garage has a 17' 2x8 ridge beam. The roof is a V, lowest in the center, with 2x4 rafters nailed to the sides of this ridge piece.

At some point the roof drain clogged, the roof turned into a swimming pool, and this ridge board/beam cracked/tore in the middle. (As I understand it, this failure means that it is a "beam"--a load-bearing piece?) Someone "fixed" it by propping the ridge up with a 4x6 post wedged under the damaged point.

I'd like to replace the post with a more permanent fix. I assume some kind of sistering/bracing would be the standard approach? It would not be extremely hard to put a full-length sister of the same size next to it, sitting on added jack studs. But if that approach is overkill, it would be nice to not have to wrestle with shortening all of the rafters on one side and removing all of those metal joist hangers.

EDIT: tweaked wording and added pics. The bottom one is an attempt to show the damage to the wood. There is a similar "tear" in the top half of the beam on the other side of it--sort of a mirror image.

back wall

enter image description here

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    At least it's only the garage. A house in my area was declared un-repairable when it was found both to have a cracked roof beam and to be of its foundation; nobody was willing to risk trying to fix either until the other was resolved. – keshlam Apr 3 '16 at 13:39
  • Do you have access to the studs in the walls at the ends of the ridge? – DrewJordan Apr 3 '16 at 17:41
  • Before this can be answered you would be wise to submit pictures to show how it is structured. If it is a ridge beam and not a ridge board will make a difference. If there are ceiling joists tied in at the bottom ends make a difference as well. I have seen ridge boards crack, never a ridge beam. If a ridge beam cracks, you got trouble... It would help to know the age of the house too. – Jack Apr 3 '16 at 23:32
  • @DrewJordan, yes, the ends are on 2x4 ("jack"?) studs. – Phil Esra Apr 4 '16 at 7:53
  • @Jack, the garage was built in 1928. The roof appears to be somewhat newer. There are no ceiling joists or collar ties or anything along those lines. I will post a pic tomorrow! – Phil Esra Apr 4 '16 at 7:55
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The right way to fix this is to have a local engineer size a LVL (laminated veneer lumber) beam for you (solid wood lumber won't meet modern standards for a span that long). It'll likely be taller than your current beam. You'll need to temporarily support all the rafters with a framed wall on each side, using double top plates. Keep them a few feet away from the beam to allow room to work. Remove the existing beam, the posts supporting it, and all metal hangers.

The new beam will likely be 2" thicker than the current one--LVL beams are often 1-3/4" thick per member, and they're usually doubled in cases like this. This will require trimming of the rafters on one or both sides.

Slide the new beam into place and support it a few feet from each end with temporary posts. Fit new posts using adequate lumber. Double 2x4s may be enough, but ask the engineer. Install the same hangers if they're appropriate, or use new ones.

Alternatively, you may be able to install your new beam directly below the existing beam. Of course, this dramatically reduces headroom. I expect a new beam to be sized at around 12" high.

  • Thanks, this sounds like the definitive answer! LVL is stronger per unit than wood (as a beam), right? I'm surprised at the gap between what exists now (a single 2x8) and modern code (~1.75x12", possibly doubled). No wonder it broke! – Phil Esra Apr 5 '16 at 15:45
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    No reputable builder would've used a single 2x8 there in the first place, even 50 years ago. It was probably a DIYer that didn't know better. – isherwood Apr 5 '16 at 16:07
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    LVL exists for the reason shown in your photo: One knot or weak point dramatically weakens a solid-lumber board as a system. By laminating several layers, uniform strength and stiffness, along with dimensional stability, are achieved. – isherwood Apr 5 '16 at 16:10
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    So the rough imperfection in the lower foreground was a likely weak point? I see now that the vertical tear traces it. Coincidentally this is the second house I have owned and the second one built in 1928 (the first was in San Francisco). I have been struck over and over by the lower quality of the original construction on this one! Decades of DIY have been unkind to this one also. – Phil Esra Apr 5 '16 at 23:17
  • This may be the right way to do this, but is it worth it for this building? Wouldn't there be some way of sistering on some 2x_ to each side (and maybe a 2x4 underneath) so you wouldn't have to disassemble the roof? What about steel strapping nailed on the underside (tension side) of the beam? – Jim Stewart Nov 18 '17 at 17:41

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