Probably the worst I've seen (residential column deterioration)

[SinStrucEng]

This is a fun one, folks. We got a call today, late in the work day (basically at closing time), and the individual was panicked and worried. They claimed that during drywall works following a garage leak, a column had "disintegrated" and the house was about to collapse.

Right. At this point I am obviously worried, but having been through many such calls I was a little skeptical. I agreed to make an urgent after-hours visit. Strapped my boots and parka on, drove out to the site.

And. Holy. Crap. This is one of those rare instances when the individual is 100% truly correct in their cause for worry.

The house is a fairly large, 7 year old custom build probably around the $1.5M mark. Lower flat roof partially over the garage, and a main trussed upper roof over the rest of the structure. There are two bedrooms overtop of the garage. The second floor front exterior wall sits on a wide flange steel beam in the garage. This beam was installed onto built-up wood posts (5 ply 2x6). Well, one of the two posts (left side) just... "disappeared". This was the worst dry rot I've seen in a structure this new. I mean, I've been in 200 year old barns that weren't this bad.

The post was left with no structural integrity (obviously) and collapsed in on itself. The beam dropped accordingly and is currently bearing on nothing but a top plate, 3/4" OSB, and stucco. Honestly I'm surpprised there's not much damage on the exterior finish. I will explore more but didn't have time (or willingness) to poke around, especially without it being supported.

Occupants were told to immediately vacate the side/portion of the house supported by this beam (practically entire second floor, most of first floor) and to contact contractors for shoring ASAP. Repairs to come...

 

[ANE91]

Dry rot needs a consistent source of calcium to modulate the organic load. I know you said stucco, but I’m guessing that’s the left wall, because the front wall cladding looks like masonry or stone. Either way, there’s your sources of calcium…

 

[SinStrucEng]

Dry rot needs a consistent source of calcium to modulate the organic load. I know you said stucco, but I’m guessing that’s the left wall, because the front wall cladding looks like masonry or stone. There’s your source of calcium…

Yes, the front is stone. The left side is stucco once you turn the corner.

 

[SWComposites]

Yikes! Flat roofs - Ugh! Never again will I own a house with one.

 

[SinStrucEng]

Yikes! Flat roofs - Ugh! Never again will I own a house with one.

I don't even understand why they're still built in the northern US states or anywhere in Canada (in residential). In my experience it's not a question of if they'll fail, but when.

 

[Tomfh]

Why is that? What causes failure in those zones?

 

[jerseyshore]

Wow those are great photos. It certainly lived up to the hype. That's about as bad as I've ever seen from stud wall rot damage.

How bad is the floor above? I'm assuming the joists are now supporting the beam instead of the other way around.

 

[SinStrucEng]

Why is that? What causes failure in those zones?

Flat roofs are notoriously susceptible to ponding, for starters, so in states/provinces with frequent snow and rain that introduces countless complications. Plus the flat roof membranes are easy to install poorly, but difficult to install well. That leads you to a roof that 1) will likely have standing water on it at some point and 2) is likely to have sources for water ingress.

The thin membranes being used in my area are also prone to being punctured by accident fairly easily. A stray nail or screw from the siding contractor makes a pin hole and from there you have endless issues that are hard to resolve. It's not like you can simply find the missing or lifted shingle.

 

[SinStrucEng]

Wow those are great photos. It certainly lived up to the hype. That's about as bad as I've ever seen from stud wall rot damage.

How bad is the floor above? I'm assuming the joists are now supporting the beam instead of the other way around.

So what you're seeing are ceiling joists, simply for the garage drywall and fumeproofing. There are engineered joists running parallel to the beam, in the same plenum space, for the actual second floor. Thankfully too, because otherwise that floor would have been a death trap right now.

 

[XR250]

Wow! Def. worst I have seen in my 30 years.
Generally, when I see things similar to this it is a flat roof issue. Would not want one on my house.

 

[XR250]

Dry rot needs a consistent source of calcium to modulate the organic load. I know you said stucco, but I’m guessing that’s the left wall, because the front wall cladding looks like masonry or stone. Either way, there’s your sources of calcium…

Why are you calling this "dry rot"? It is likely from a roof leak.

 

[SinStrucEng]

Why are you calling this "dry rot"? It is likely from a roof leak.

This specific form of rot is commonly referred to as "dry rot". It's called dry rot because it leads to the wood becoming very brittle, dusted with red, and with a spongy texture. During growth it shows up as this grey/white "skin". At advanced stages it's almost like the wood has literally been dried out of existence. You can actually see this in the photos - left two plies are in more progressed stages while the right plies are earlier on in the process. The actual name is Serpula Lacrymans. Contrary to its name it obviously requires a high moisture content - typically 20% or more for a prolonged period of time.

 

[XR250]

"An explanation of the term "dry rot" circles around boatyards periodically. In the age of wooden ships, boats were sometimes hauled for the winter and placed in sheds or dry dock for repair. The boats already had some amount of rot occurring in the wood members, but the wood cellular structure was full of water making it still function structurally. As the wood dried out, the cell walls would crumble. In other words, the wood was already rotten and as the boat dried, the wood collapsed and crumbled, causing the workers in the yard to determine it was "dry rot", when in fact, the wood had been rotten all along"

From Wiki. Interesting.

 

[ANE91]

Why are you calling this "dry rot"? It is likely from a roof leak.

OP’s term.

 

[SinStrucEng]

OP’s term.

Where we work, everyone calls this dry rot. Next time I will call it "Serpula Lacrymans" as the biologists named it Although I am not sure if that would make it any clearer for folks on this forum

 

[ANE91]

@XR250

https://www.sciencedirect.com/science/article/abs/pii/S0964830500000895

 

[ANE91]

Technically, I try to make a distinction between white rot and brown rot, when I can, because the mechanisms are different. Ultimately, I’m not a microbiologist, so it’s just rot. If I ever said the word “hyphae” out loud, I think I’d scare off clients.

 

[GaStruct]

The other studs look to be okay. Is water wicking down the steel beam causing the localized rot?

 

[SinStrucEng]

The other studs look to be okay. Is water wicking down the steel beam causing the localized rot?

Very well could be, but we didn't get a good look because of safety concerns and don't know the exact entry point at this moment. The owners will need to explore the roof and exterior walls in detail once the structure has been safely supported.

 

[dik]

Complete replacement of the area.

Lumber can lose 25% of it's strength due to dry-rot (aka brown rot) without any loss of mass or change in appearance. It's pernicious and builds on past damage. Other than epoxy injection, there is no real fix or repair.