How would solid wood joist looks when it fails

[SeanStructural]

I did a structural inspection on a 112-year old row house in DC. The property has 2x10 floor joists that deflected about 3-inch (12 - feet span.) The joists show no damage to the fiber. Two questions:
1- When would you say that you have a structural failure for solid wood joists? and does anyone have pictures to share?
2- Would you fail such floor?

 

[msquared48]

Sounds like the joists got wet under load, then dried under load, leaving a permanent deflection.

There should be no problems with 2X10's spanning 12 feet. Technically, the floor has not failed stress wise, shear or moment, but the deflection limitations have been exceeded. Serviceability as an occupiable and liveable space has been compromised.

The floor structure needs to be replaced to be occupiable.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[chicopee]

These floor joists must be rough cut. If the ends are not notched, you may be able to turn them upside down for reuse and may be reinforce them.

 

[MiketheEngineer]

Look up wood creep!!

Did they fail - probably not. Is the floor usable - probably not.

Once was in a 700 year old (verified) hotel in England. Walking around that room made me think I was drunk or had vertigo. Did I mind - NO - not for a couple of days - it was part of the "charm"

Would I have lived there - NO!!!!!!!!!!!

 

[denoid]

I live in the northern Midwest. About 10 years ago last December, while working for a former employer (therefore, no photos - sorry), I was called by a Contractor client to look at the roof of a hardware store in an older strip mall where there was evidence of water damage on a lay-in ceiling. Above the lay-in ceiling was an old gyp board ceiling, also wet. When he poked a hole in the gyp board we looked up and saw a 2x10 purlin which had snapped and deflected about 3 inches. We opened up more of the ceiling and there were 2 more cracked purlins either side of the first. This all happened about 2 weeks after a big snow storm, (more than 17 inches as I recall).
We went up on the roof, and there were 10 foot drifts behind a false parapet on the front shops of the strip mall. We started checking other stores, and found about 6 more stores with the same problem. Needless to say we got shoring in there ASAP, and some of the Contractor's crews were called in to start shovelling the roof.
That's what I would call a failed 2x_ member. I agree with msquared48 that what you have, while not a true failure, is more a serviceability issue and needs to be fixed.

 

[Ron]

Agree with both Mikes. Likely a creep condition exacerbated by moisture. You say the joists show no damage to the fiber.....you are only considering a visible manifestation of damage such as a crack. The "fiber" of the wood has undergone significant change and damage at its cellular structure level. This results in less ductility and more susceptibility to failure at less than the design load.

Repair it.

 

[shobroco]

Wood joists are nearly always sized for serviceability, not strength. Deflection will occur to far beyond acceptable levels long before almost any wood member will fail for strength. If you have seen failure like denoid saw (& I have), the deflection would have been multiples of what anyone would tolerate.

 

[racookpe1978]

So, assume you accepted this floor as "fit for service" ...

The contractor can't sell the building with that much curve, so he (obviously without telling anybody what he is doing to cover up his mistake!) fills in the 12 x ?? 3 inch deep "wading pool" with concrete leveling mud. Then puts the flooring on.

Now you have a floor failure issue with excessive weight from the concrete leveling mud.

 

[shobroco]

No, I'm saying it's not serviceable. That's the whole point: serviceability governs & will tell you the system is unacceptable long before it is unsafe.

 

[dhengr]

I’d leave it as it is, and rent it at a premium to a ball bearing assembler. The promotional hook is that they will always know about where to look for fallen parts.

 

[ishvaaag]

The house (maybe 200 year old) that was of my grandparents may have such deflection (on spans maybe a bit over 6 meters). No rectangular joists, old trunks tip alternating with base at around 24 cm diameter; the floors of course move more than that one would love but not yet to be fearful; every summer, my aunts, the older to be 88, still live there near two months. These floors were retained for the main dining room and attic floor; roof was dismantled in the sixties and remade prefab concrete joists since span maybe over 7 meters and (if they did do that) quite likely showing the need.

 

[MAeng]

Someone mentioned serviceability and that would probably qualify it as "failure". It's hard to imagine you could do much with such a room as things would be a bit cattywompous (sp?). Here in New England I see many such things which defy analysis and yet there they are....