Glulam Beam Rotting from the Inside Out?? 6

[UTvoler]

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?

 

[UTvoler]

And one of the roof system.

 

[XR250]

Replace with PT glulams

 

[ChorasDen]

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.

 

[dik]

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

 

[lexpatrie]

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?

 

[UTvoler]

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.

 

[Tomfh]

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.

 

[XR250]

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?

 

[dik]

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

 

[XR250]

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.

 

[IRstuff]

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.

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[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.

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

-Dik

 

[phamENG]

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.

 

[XR250]

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.

 

[UTvoler]

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.

 

[phamENG]

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.

 

[EdStainless]

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.

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[dik]

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

 

[XR250]

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.