LVL Crushing 1

[XR250]

Was in a crawlspace today of a 3 story, wood framed condo. Was there investigating continued complaints of sheetrock cracks. Based on my laser measurements, pier settlement seems to be the biggest offender. However, I also observed many instances of the 3-ply, 18" LVL beams in the crawlspace showing signs of crushing over their SYP wood blocks (see attached). I measured about 1/4" of crushing with a computed existing load reaction of about 7k or 200 PSI perp. to grain. The SYP appears unfazed by the load. WTF? I though the LVL design values were about 750 psi for perp. to grain loading.
The LVL brand is "Weldwood" which appears to have been bought out years ago. My guess is no help from the new owner.

The building is 10 years old and pretty consistently lightly loaded with retirees (trussed roof clear spans the crawlspace). As such, I doubt the load changes much. Do you think the crushing has done all it is going to do?

 

[jayrod12]

Have you run the numbers on the bearing. I don't know why I didn't think of this earlier but prior to forte there was a program to design lvl and lsl beams called TJBeam and it didn't check bearing

When forte came out with the bearing check included I know it was a shock for some people how often bearing was the controlling failure mode.

Is it possible that the original designer didn't check?

In my experience deep narrow lvls don't do well with bearing

 

[racookpe1978]

The 2x (2x10 ?) treated horizontal spacer is squished (picture 1 and 2) and the LVL is squished also (picture 2).

But the horizontal 2x10 is in a" safe" (flat) condition, isn't it?

But, the two seem to have squished "safely" in that they are not delaminating nor distorting across the web: Only the lower "flange" of the LVL is distorted - and that distortion is on the bottom of the lower flange. The upper flange appears un-distorted, doesn't it?

What do the other posts in the basement look like?

 

[XR250]

The upper portion of the LVL;s are fine. This is a crawlspace, not a basement. The situation is similar on about 50/% of the piers.

 

[jayrod12]

You said 3 storeys right?

Does this post only pick up a small portion of the main floor?

7k seems low for standard residential loading, at 60PSF total that's just over 100 sqft. A 3 ply 18" lvl should be more than capable of that.

 

[XR250]

@Jayrod12;

I based the numbers on the current loads - which are about 20 psf total (not the design loads). The girders do not span very far.
You use 60 for residential? I use 40 live and 10 dead. Even if the actual dead is higher, I know I the floor will never see 40 psf anyhow.

 

[msquared48]

This is definitely moisture related, and detail related.

The 2X member on which the LVL bears is not treated, and there is no building paper between the concrete aid the 2X plate to prevent moisture migration. The LVL is seeing moisture from the concrete through the 2X plate.

The LVL specs in the #TJ-9020 Specifier's Guide definitely say that they are not for use in a "wet" environment, however they do not allude as to what they consider "wet". Probably have to call Weyerhaeuser on that. The Fc Perp is 750 psi and cannot be increased for duration of loading, so a higher than allowed load should not be the problem here.

I would recommend jacking up the LVL to relieve the load to the 2X plate, pulling the plate out, installing 2 layers of 90# building paper over the concrete, and reinstalling the 2X plate. May have to temporarily disconnect the strap too. I would also recommend better ventilation in the crawlspace, even if has to be forced. This will not remove the deformation, but prevent more from occurring.

Mike McCann, PE, SE (WA)

 

[jayrod12]

Fair enough. But it is entirely possible it saw something closer to design loading at some point and the crushing occured. There's no rebounding from that.

and even at 1/4" of crushing that's still likely a tolerable amount if it doesn't progress further. I would be any damage seen above is 95% due to pier settlement and 5% others factors (I still wouldn't attribute the whole 5% to lvl crushing)

 

[XR250]

@Mike;

How do you know it is not treated - i bet it is.
Also, no one has every put anything between the 2x and the pier in any structure I have been in - just not a common practice around here.
I have already recommended a sealed crawlspace system.

@Jayrod - "But it is entirely possible it saw something closer to design loading at some point and the crushing occured"
I find this unlikely, but certainly possible. My money is on the moisture

 

[boo1]

I like Mike's hypothesis

 

[msquared48]

@ XR250: The plate looks like either DF or Pine, not Hem-fir, and has no PT indentations or discoloring at the periphery from what I see. Perhaps there is another photo?

Thanks boo1. I try to please...

Mike McCann, PE, SE (WA)

 

[Signious]

I am apologizing in advance for this - but I promised myself a long time ago I would speak up whenever I see something like this.

"Also, no one has every put anything between the 2x and the pier in any structure I have been in - just not a common practice around here."

This really irks me. It is a really easily accomplished task, and everyone knows why it is important. Saying no one does it is a really piss poor excuse not to require it yourself, it is a code item where I am, and I suspect a code item anywhere - wood in contact with soil-contacting concrete is P.treated or 6mil poly gets put down.

 

[msquared48]

Signious:

I fully agree...

Mike McCann, PE, SE (WA)

 

[XR250]

@Mike and Signius - Please take some chill pills!

Mike - Our PT wood is pine and it does not have indentations. Once it ages, you cannot tell the difference between PT and non-PT.
@Signious - my comment assumed that a PT sill plate was used - which it typical in all of our construction.

FWIW, I have been doing this since 1991 and have literally been in 250 crawlspaces per year since then (probably significantly more than anyone on this forum). Most of the homes I look at are 40 to 80 years old and have their pine or oak beams bearing directly on masonry piers. Few have any rot. The ones that do typically have a widespread problem as well. As such, the whole "don't let non-PT wood touch masonry" argument does not hold too much water with me (no pun intended) even though I adhere to that rule. Even in this particular case, some of the LVL beams were bearing directly on masonry. Their moisture readings were no different than any other beams and were actually in the best condition.

 

[msquared48]

Been there too over 40 years. To each his own. Good luck.

Mike McCann, PE, SE (WA)

 

[boo1]

What is a better hypothesis then?
Could wicked moisture be seasonal or one time, wetting the LVL leading to the localized crushing?

 

[XR250]

My guess is that in the summer, the MC is alot higher. Also, alot times the LVL's are very wet from sitting on the jobsite (despite the coating). So the crushing may have occurred during construction before they "dried out" . I am going to have them get the moisture under control. At that point we can discuss whether they want to spend the money to jack and re-shim for a larger bearing area.

 

[4thorns]

The 2x is appears to be a piece of treated southern pine. The green hue comes from the treating process. It's almost as hard as the concrete it sit's on! If you've ever tried to drive a nail thru it after its aged (even a short while)you know that you have a better chance of hitting the lottery. I put down at least a hundred miles of this stuff as exterior decking back in the day and it was hard to work with. Not sure where this building is but I'm on the eastern seaboard and it is(was)the material choice.

 

[4thorns]

Could wicked moisture be seasonal or one time, wetting the LVL leading to the localized crushing?

Just thought of this. Here's a thought based on my experience with this type of lumber. Most of the time we had full packs of pt lumber delivered to the job site based on the size of decks and such that we were building. If the packs had been exposed while stored at the lumberyard (uncovered) then the outer most pieces of the pack had started to dry and become hard and brittle. For the most part this type of lumber had an extremely high moisture content fresh out of the inside of the pack. I wonder if when this was constructed, was the piece of 2x overly wet and it "wicked" into the lvl. May not have been the only contributing factor but based on all the fluids that I wiped out of my eyes driving nails into this stuff it could be possible.

 

[XR250]

@4Thorns -
I hear you about the wet PT lumber. I think if that was the case, the LVL's would have slid off s the stuff can be like ice when wet
BTW, it is central NC

 

[Robbiee]

I'll go against some of the great ones here and vote against moisture being the suspect. I believe this is a result of differential settlement resulting in rotation in the beams and hence localized compressive stress at the edge of the bearing plate. I am wrong if the crushing is uniform under the beam. The two photos were not helpful enough.