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Glulam Beam Rotting from the Inside Out??
6

Glulam Beam Rotting from the Inside Out??

Glulam Beam Rotting from the Inside Out??

(OP)
Hello friends and experts!
A water park facility that I do some consulting work for has some issues with rot in a few glulam beams. The building structure is glulam framing with a transparent panel roof. The beams in question are horizonal girt members located in the eave of the roof, ~16-ft above finish floor. It's a water park, so obviously serious humidity/moisture/chemical issues in general inside the facility. This particular area is located behind a large duct sock, there are no eave vents, and so very stagnant air/little to no air movement.

The roof panels are fastened to the glulam with stainless steel lag bolts, and the interesting thing is that the rot appears to have started internally at the lags. No signs of leaks from the roof, and just a few inches away from the rotted areas the moisture in the wood reads ~6%.

My best guess is the some form of condensation at the lags concentrating moisture in the wood? Recommendation is probably to replace in kind, but not sure on how to address the root cause of the issue.

Any thoughts on cause?

RE: Glulam Beam Rotting from the Inside Out??

Replace with PT glulams

RE: Glulam Beam Rotting from the Inside Out??

Not certain where you are located at, from your profile, appears you're on the east coast. If so, you should have options for pressure treated glulam and/or pressure treated structural composite lumber. If you intend to continue to wood frame these areas, those would be your best options. I would advise caution when selecting the beam and treatment, however. You'll likely want a product that is pressure treated, ideally with some warranty related to minimum chemical retention for the service life of the member, and something that works with your fastener treatment to limit local corrosion at the fastener.

RE: Glulam Beam Rotting from the Inside Out??

I can suggest that the glulam beams have periodically been wetted and that the surface has allowed to dry leaving the interior with an increased moisture leading to brown rot (aka dryrot).

This occasionally occurs with railway ties, for a slightly different reason. For ties, occasionally the creosote embedment is reduced on the interior. In addition with ties, being cut from a single 'stick', if the original tree was 'damaged' most trees try to protect themselves by sending extractive 'chemicals' to the tree rings on each side of the damage to reduce effects of fungal deterioration. This is one of the reasons some are hollow.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

RE: Glulam Beam Rotting from the Inside Out??

I'm not remotely sure what we're looking at.

Here are the pictures in-line.



Is that water staining on the perimeter wood element indicative of condensation dripping onto it, and that's the source of the water? Would replacing the wood at the perimeter of the skylight and metal flashing with a drip edge do anything here to prevent a recurrence?

RE: Glulam Beam Rotting from the Inside Out??

(OP)
Yikes, it's been a week....

Thanks for the input folks!

@dik, could be. I'm still not sure whether there was/is a roof leak, or if this is strickly from the interior moisture.

@lexpatrie, what you're seeing in the top picture is taking a picture of the roof system as high as I could get my phone. Translucent roof panels, supported on aluminum frame supported on glulam structure. The aluminum brackets/standoffs are fastened to the glulam with SS lags. The second picture is the underside of the horizontal glulam you see in the pic above, and it is rotted out around the SS lags.

RE: Glulam Beam Rotting from the Inside Out??

It is likely galvanic rot. The fasteners reacting with the timber treatment, in the corrosive water park environment.

Probably condensation too, dripping water onto those locations.

RE: Glulam Beam Rotting from the Inside Out??

Quote (Tomfh)

It is likely galvanic rot. The fasteners reacting with the timber treatment, in the corrosive water park environment.

Have we determined these WERE treated members?

RE: Glulam Beam Rotting from the Inside Out??

I would suggest that if a waterpark structure, it was likely treated timber.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

RE: Glulam Beam Rotting from the Inside Out??

You'd think but it sounds like they were interior.
There is a townhouse complex near me that has un-treated, 20 ft. span glulams supporting their decks.
Guess how many have failed.

RE: Glulam Beam Rotting from the Inside Out??

PT wood at the local stores typically have incision marks on their surfaces that improve absorption of the chemical treatment, so these don't look like the typical PT wood. And they would typically no longer look like interior wood from a coloration perspective.

TTFN (ta ta for now)
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RE: Glulam Beam Rotting from the Inside Out??

XR... are the beams located over a pool? I've seen glulam beams delaminate likely caused by the high humidity caused by occupant load... no brown rot.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

RE: Glulam Beam Rotting from the Inside Out??

IRstuff - that has to do with the species. Here in Virginia (where OP is also located based on their profile), just about all our treated lumber is southern pine. Southern pine has high absorption rates for pressure preservative treatment chemicals so incising isn't necessary. A lot of firs and larches used on the west coast are harder to treat, and require incising to get adequate penetration. So a lack of incising is not necessarily indicative of no treatment.

RE: Glulam Beam Rotting from the Inside Out??

Quote (dik)

XR... are the beams located over a pool? I've seen glulam beams delaminate likely caused by the high humidity caused by occupant load... no brown rot.

Nope, just fully outside in the elements.

RE: Glulam Beam Rotting from the Inside Out??

(OP)
Jumping back in here, thanks for the dialog!

Galvanic rot sure looks like what I'm seeing in the field, however these are UNTREATED glulam with stainless steel fasteners, either of which would seem to eliminate that process. These beams are located INSIDE/INDOORS, just under the translucent roof system, but in a water park so very hot, humid, harsh environment. Could have been/be roof leaks, not sure but not enough volume of water to be confirmed if so.

RE: Glulam Beam Rotting from the Inside Out??

My guess:

1) Pool water evaporates, taking chlorine with it.
2) During winter months, the warm, wet, chlorinated air rises and contacts the framing and roofing.
3) The translucent roofing material is likely several degrees colder due to contact with outside air. Chlorinated condensate forms on the roof and, maybe on some roofing members that are cooler.
4) Chlorinated condensate drips/runs to connection points.
5) Stainless steel does not like chlorine. Many SS fasteners are made from 304, which doesn't handle it well. 316 can take about twice as much chlorine as 304 can, but can still be damaged by it. So the stainless fasteners in the wood are corroding and letting the water into the wood through the fastener holes.

RE: Glulam Beam Rotting from the Inside Out??

What smell in a pool isn't chlorine, it is volatile chloramines that form when Cl reacts with various organics.
These chloramines will eat the SS (304 or 316), attack Al, and cause real issues with wood also.
These are very reactive compounds and are why ventilation of pool rooms to eliminate condensation is so crucial.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: Glulam Beam Rotting from the Inside Out??

Quote (IRstuff - that has to do with the species.)


All PWF lumber (added preservative requirements, in this locale are incised for added resistance.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

RE: Glulam Beam Rotting from the Inside Out??

Quote (dik)

All PWF lumber (added preservative requirements, in this locale are incised for added resistance.
As Pham stated, in my area, they do not incise PT lumber.

RE: Glulam Beam Rotting from the Inside Out??

PWF, in these environs, has added preservative necessitating the incisions.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

RE: Glulam Beam Rotting from the Inside Out??

dik, we understand that, such is the nature of treating either Western Hemlock of Douglas Fir. These wood species require incision to increase the (very limited) amount of preservative treatment that these species are able to retain. Southern Pine, available all over the south and eastern part of the U.S., does not require incision, and is not incised prior to treatment. This is due to the shape and structure of the wood cells and how they accept and bind to copper based wood treatments. I image that AWPA and FPL have lots of literature discussing how the structure of Southern Pine differs from western species to allow this to occur.

RE: Glulam Beam Rotting from the Inside Out??

There's NO incising on the wood. C'mon.

NO. NOT all treated wood has incising.

If it isn't incised, it's either a) not DF (or other refractory species) and has a pressure preservative treatment (like southern Pine) that's not got a lot of color to it, or it's AC2 which doesn't have a lot of color to it. Or it's not preservative treated (my vote).

I'd wonder when it was built, but for this to have PPT I'd be surprised. Aluminum and Stainless don't exactly agree on the galvanic chart, but you need water. I think it is water causing the problem, the "bolt" is where the rot appears to be concentrated, but I'm not fully sold it's chlorine related or not. I'd expect corrosion if it were chlorine related. I don't quite see that here.

And yes, the "Chlorine" smell is Chloramines. Usually produced via reaction with uric acid which is in sweat, as well as other sources.

While there seems to be some condensation occurring, it appears limited to water staining of the wood.

Here's what I see - the skylight has an aluminum edge angle that traps any water (as condensation), it looks like there's debris/corrosion there (top photo), admittedly aluminum doesn't "corrode" like that. I wonder if there's a more modern edge treatment that doesn't accumulate/trap water and what looks like blocking underneath it needs to be replaced. Various metal compatibility should be considered in the replacement, but it doesn't look like it's getting wet enough to actually corrode like that. Unless the screws are dramatically corroded, you can't really see from the photo.

RE: Glulam Beam Rotting from the Inside Out??

Recommend submitting this issue to the APA as a question... they seem to be a resource with expertise... and/or maybe this would present a opportunity for study of Your phenomena.

APA Help Desk: Expert Support
The APA Product Support Help Desk, a free service, is available to answer your questions pertaining to the specification and application of engineered wood products and systems. Staffed by specialists who have the knowledge to address a diverse range of inquires related to engineered wood, the Help Desk receives hundreds of e-mails, faxes, and phone calls each week from a wide variety of users and specifiers of engineered wood products.
... ...
https://www.apawood.org/help

[i]APA Resource Library
APA offers an extensive collection of detailed, technical information for architects, builders, code officials, engineers, specifiers and others in the trade.
Register for Free Access to APA Resources
Registration is required to access APA publications. Other resources, such as videos and images, may be accessed without log in. Registration allows the download of APA publications in PDF format by entering your username (email address) and password. APA does not share your personal information with any other parties; see our Privacy Policy for further details.

... ...
https://www.apawood.org/resource-library?
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

BTW... Your photo of rotted wood and a 'lag bolt threaded-end' visible. lexpatrie (Structural)13 May 24 16:47

Weird... the photo seems to show a bolt with H28 coarse threads and a relatively 'flat-tip'... typically fastened with a washer/nut... NOT the wood-lag-bolt with pointed-tip on the thread-ends and sharp-piercing widely spaced wood-screw threads I expected to see, thus...



Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

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