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Old 5/22/07, 10:39 AM
Berry T. Wilson Berry T. Wilson is offline
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Question Crack in Support Beam

Crack in main beam. Diagonal. Just barely goes through entire beam. (see images)

These were found when remodeling basement and owner is wondering if it is necessary to replace the beam.
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crack-support-beam-crack1.jpg   crack-support-beam-crack2.jpg   crack-support-beam-crack3.jpg   crack-support-beam-crack4.jpg   crack-support-beam-crack-othersize.jpg  

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Old 5/22/07, 3:04 PM
Richard A. Hetzel Richard A. Hetzel is offline
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Default Re: Crack in Support Beam

The first thing I would do is try to measure any deflection in the beam. Tack a piece of wood at one support, and another of identical depth at the other support, and stretch a string over the blocks, measuring from the bottom of the beam to the string. I would also check with a level held against the bottom of the beam.

If there is no deflection, I wouldn't think it would be necessary to replace the beam. For safety, it might be a good idea to nail a 2x board of matching depth to each side of the beam for the length of the span in which the crack exists. However, if that is done, it will not be possible to monitor the crack.

Diagnosing from pictures is risky, as you might imagine, but it doesn't look to me like a structural failure type of crack. It looks like a "check" gone wild, if anything.

Measuring the deflection will tell the story. Nornal maximum deflection is 1/360 of the span. Actual deflection is usually less than that much, usually in the range of 50% to 60% of maximum in the middle of a properly-designed beam

It looks very straight to me, but again, I'm only looking at a picture.
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Old 5/22/07, 3:10 PM
rwand1 rwand1 is offline
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Default Re: Crack in Support Beam

In my opinion these are the result of the wood drying out (checking), and do not appear to be structural in nature. I also agree with Richards other assessments.
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Old 5/22/07, 5:55 PM
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W. Michael Chris W. Michael Chris is offline
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Default Re: Crack in Support Beam

Viewing the photo(s) is risky as Richard stated, but it appears to be cracking (drying out) as both Richard and Raymand have stated and do not appear to be a structural concern - I also agree with Richards assessments and recommendations.
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Old 5/22/07, 7:21 PM
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Marcel R. Cyr, CMI Marcel R. Cyr, CMI is offline
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Default Re: Crack in Support Beam

The cracking is normal in large wood beams. When they dry out, they contract; when they take on moisture, they expand. This expansion and contraction will cause cracks, mostly in beams and posts, say, 6 x 6 and larger. There is nothing you can do about it

Shake - separation along annular rings,


Checks - longitudinal cracks - usually happen during seasoning process

All depending on how the wood was originally cut at the mill also makes a difference.
The surface of the wood in the width of the lumber is where the shrinkage will occur more.

I do not think there would be a reason for Structural alarm.
But we are looking at pictures.


Write it up like you see it is all I can say.

Marcel
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Old 5/22/07, 9:32 PM
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Peter C. Russell Peter C. Russell is offline
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Default Re: Crack in Support Beam

Here's a couple of pictures of my house, built around 1840, timber framed, many of the beams have been exposed, as you can see this beam has allot of checking but is solid as a rock.
Please note that it is also a vertical beam not horizontal.

Last edited by prussell; 11/27/07 at 9:07 PM..
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Old 5/26/07, 3:15 PM
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roconnor roconnor is offline
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Default Re: Crack in Support Beam

A split wood beam is a structural concern.

Once a wood beam completely splits (as opposed to just surface checks/shakes) there will be a significant loss of strength ... which can be up to 1/2 the original strength. So the split beam would likely not be adequate unless originally oversized. No way to tell unless you do some calcs to evaluate that.

Just measuring deflections doesn't help unless they are compared to calculated deflections based on known loads. It's easier to just calculate out the strength with the split and compare that to anticipated loads.

JMO



Robert O'Connor, PE
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Last edited by roconnor; 5/26/07 at 3:24 PM..
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