Rusting Nails in OSB Sheathing

[HouseHacking]

Hi everyone,

I recently noticed that most of the nails in the OSB sheathing on my home are starting to rust. I live just under a mile from the ocean in Seal Beach, CA, yet the construction is only four years old.

My contractor says the code doesn’t require the nails to be galvanized because they’re behind the siding and WRB, not exposed on the exterior.
Does anyone know which code section I should refer to here?



This is the closest thing I could find:
CBC 2304.10.1.1 https://codes.iccsafe.org/content/CBC2018V2/chapter-23-wood

 

[ICE]

Do you have access to the approved plans for the project? Code would require the bottom row of nails that are nailed to preservative treated lumber to be galvanized but not the rest of it. I don’t have experience with construction near the coast. If the sheathing nails are rusted, it might be all of the nails. I know of a builder that uses hot-dipped galvanized nails for everything. They have superior withdrawl resistance. You can rip the heads off trying to pull a 16 sinker

 

[HouseHacking]

Yes, I have the plans, and they do include the requirement for galvanized nails where there is pressure treated lumber. However, because the house is a remodel and we re-used the old foundation and possibly-redwood sill plate, we don't think we have any pressure treated wood.

 

[Joe.B]

Why are the nails (and OSB) exposed?

 

[jar546]

Why are the nails (and OSB) exposed?

I was wondering the same thing. Four years is too soon for a new roof to go bad. I am going to make a guess that there is some sort of renovation going on, such as adding roof vents, installing a covered deck that ties into the existing roof, or simply a really bored homeowner who is curious what is under those shingles. Maybe there was damage from a falling tree that required repair. The possibilities are endless. Maybe a satellite dish was added and then it fell over, requiring a repair. Then I was thinking that maybe, just maybe, a piece of a satellite came crashing down and damaged the roof. Then again, maybe the roof was put on wrong, and it is now being replaced. Of course, it could be that they did not like the color and wanted to replace it. On the other hand, there could have been a manufacturing defect that was recalled, and now the replacement is being made. Do you guys get hail near Seal Beach? I thought about the possibility that a military exercise went awry, and a flare could have landed, damaging the roof. Sometimes I wonder if Santa Claus gets mixed up with his months in California because the weather is the same in that area, and some rusty rails from his sled could have damaged the roof, causing a necessary repair. I am going to rule out large, pink elephants walking on the roof, however. Yeah, I wonder.

 

[ICE]

I was wondering the same thing. Four years is too soon for a new roof to go bad. I am going to make a guess that there is some sort of renovation going on, such as adding roof vents, installing a covered deck that ties into the existing roof, or simply a really bored homeowner who is curious what is under those shingles. Maybe there was damage from a falling tree that required repair. The possibilities are endless. Maybe a satellite dish was added and then it fell over, requiring a repair. Then I was thinking that maybe, just maybe, a piece of a satellite came crashing down and damaged the roof. Then again, maybe the roof was put on wrong, and it is now being replaced. Of course, it could be that they did not like the color and wanted to replace it. On the other hand, there could have been a manufacturing defect that was recalled, and now the replacement is being made. Do you guys get hail near Seal Beach? I thought about the possibility that a military exercise went awry, and a flare could have landed, damaging the roof. Sometimes I wonder if Santa Claus gets mixed up with his months in California because the weather is the same in that area, and some rusty rails from his sled could have damaged the roof, causing a necessary repair. I am going to rule out large, pink elephants walking on the roof, however. Yeah, I wonder.

Drunk posting again?

 

[jar546]

Drunk posting again?

No, just a slow, boring Saturday morning.

 

[wwhitney]

I recently noticed that most of the nails in the OSB sheathing on my home are starting to rust. I live just under a mile from the ocean in Seal Beach, CA, yet the construction is only four years old.

How do you know that they are "starting" to rust, i.e. that the rusting has been progressing over the last 4 years? Another possibility is that when the nails were initially installed, there was a delay in installing the WRB over them, and that all the rusting you are seeing now occurred during that initial period of exposure.

Cheers, Wayne

 

[HouseHacking]

Now this is getting interesting! Thanks all for the humor and insight.

How do you know that they are "starting" to rust

Good point. The sheathing went up on August 3rd, 2020, but the WRB wasn’t installed until November 15th, a 3½‑month gap.

The rusty nails that we know about are in the sheathing on the sides of the home. I'm not sure about the condition of the nails on the roof, but we'll probably find out when we tear into that.

Why are the nails (and OSB) exposed?

Faulty flashing and gaps in the WRB and siding trapped water in the walls, which has led to mold, rot and we even have termites. We could practically host an Easter‑egg hunt for code violations. Some more pictures in the attached document.

 

[wwhitney]

Faulty flashing and gaps in the WRB and siding trapped water in the walls

Well of course the nails are rusting if they are being exposed to water like that.

I'm not an expert, but in the areas where the sheathing damage is minimal enough that replacement is not required, I expect the rusting to similarly be minimal enough to ignore.

Cheers, Wayne

 

[jar546]

In all seriousness, the OSB on this roof was left wide open to the weather for over three and a half months with zero protection. That’s not a minor issue. No OSB manufacturer is okay with that kind of exposure. These panels are rated Exposure 1, which just means they can handle short-term delays during normal construction, not full-blown sun, rain, and salt air for months on end. We’re talking about Seal Beach here, moisture in the air, UV exposure, salt, it’s a perfect storm for damaging untreated sheathing. The panels swell, edges curl, fastener strength drops off, and the whole thing starts to break down structurally.

I know there's concern about some surface rust on the nail heads, but honestly, that’s the least of the worries. Light rust on nails happens, but it’s cosmetic. The real issue is what’s happening to the sheathing itself. If the wood has absorbed water and started to swell or soften, it's not going to hold nails the way it should, and you’re risking long-term roof failure. If this roof is going to be finished properly and built to last, that sheathing needs to be thoroughly evaluated, and chances are, it needs to be replaced. No qualified builder or inspector is going to sign off on OSB that's been baking and soaking in the open for that long, but apparently some did.

 

[ICE]

No qualified builder or inspector

For starters Jeff, it's wall sheathing not roof sheathing. As to an inspector getting excited because the OSB has been out side for 3.5 months.... well as the inspector, I would not know that. What I would know is the condition on the day I see it. Plywood and OSB can be abused just so much before I condemn it.

Sometimes there's a tell:

 

[jar546]

Sometimes there's a tell:

The ROOF sheathing in your photo would not pass any inspection, and its not even OSB like the OP is discussing.

 

[ICE]

Picky you are. You been getting it wrong right up until a moment ago. When I read your drunk post I thought, Oh my goodness, did he bust it again! That last smack to the melon can have residual effects.

 

[wwhitney]

Sometimes there's a tell:

The only thing I can tell is that the roof sheathing needs nailing off. Seems plausible that the plywood is still fine

Cheers, Wayne

 

[ICE]

The only thing I can tell is that the roof sheathing needs nailing off. Seems plausible that the plywood is still fine

Cheers, Wayne

After the plywood was rained on for several hours the contractor covered the roof with Visqueen. The plastic was left on for days. The Sun raised the temperature and the plywood warped. There was no saving it.

 

[wwhitney]

After the plywood was rained on for several hours the contractor covered the roof with Visqueen. The plastic was left on for days. The Sun raised the temperature and the plywood warped. There was no saving it.

If it was fully nailed off and those conditions actually caused the nails to withdraw, I'll agree. Probably too much trouble to flip all the panels, wet them all down again and repeat the process to warp them back flat. : - )

Cheers, Wayne