I emailed him a few days after the Marion tornado to ask whether that home warranted such a high rating, given it wasn’t built on a traditional concrete-slab foundation like most high-end EF4 DIs are. He replied that DoD-10 typically applies to homes on slab foundations, implying Marion’s home shouldn’t have been rated as DoD-10.
I guess my question is why is being nailed to the wall bottom plate different from being nailed to the sill plate? Forgive me if I'm missing something, as I'm not an expert on this, but isn't the point of failure still a wood wall of sorts coming off an anchor?
Huh, I assumed he worked on the Marion survey himself, given it was an awarded EF4 from one of the offices (Paducah) that I assume doesn't have the "authority" to issue their own violent ratings.
Credit where credit's due, he has been responsible for some great calls (Jarrell and Greensburg being my personal favorites). Didn't researchers at the NIST try downgrading Jarrell to F3, which was never picked up by the NWS? It's a fascinating read and actually had some decent points, although the main flaw was not factoring in contextuals from the tornado and focusing only on structural damage.
I don't think he has as much of a negative impact as most think. Sure, he's made some decisions I vehemently disagree with, but other things are blamed on him that aren't really his fault. From what I gather, in Vilonia, he had the wool pulled over his eyes by John Robinson, while the infamous presentation that had the Goldsby photos was actually Jim LaDue, not Marshall.
Great question, and you’re right that in both cases, the studs are ultimately attached to both type of foundations the same way. The key difference lies in how the wind forces are transferred through the structure. When a home is built on a concrete slab, the wall bottom/sill plate is typically anchored directly to the slab using bolts or straps, creating a strong, direct load path that resists uplift and lateral forces more effectively. In contrast, homes with elevated floor systems have additional connection points. The sill plate is bolted to the foundation, but the floor joists are usually toe-nailed into that sill plate, and then the studs are nailed to the subfloor and/or header joists. That toe-nailed connection between joists and sill plate is significantly weaker under tension (uplift), and the multiple layers introduce more potential failure points. So while both involve similar stud to plate connections, the load path in slab-on-grade construction is much more robust, which is why those homes tend to withstand tornadic winds better.
This photo was by Jim Ladue, the presentation was by Tim Marshall in partnership with NOAA and the "Warning Decision Training Devision" (WDTB, aka NWS meteorologist training).
Ah, do you have a link to it? One of my buddies was around at the time and said it was LaDue
I mean it doesn't confirm that this is DOD 10 damage, just that its EXP construction. It still seems kind of illogical to basically make a DOD 10 impossible for a very common type of building. Just go LB DOD 10 at that point, no?
You’re right that toe-nailing of the floor joists is considered an adequate connection and falls under the EXP classification. However, he clarified that DoD-10 is typically reserved for homes built on concrete slab foundations, not those constructed on crawlspaces or elevated floor systems. That suggests the maximum applicable DoD for Marion’s home, and others like it, would be 9. Am I overlooking something in the slide? From what I can tell, it just shows two graphics, one of a home on an elevated floor system, and one on a concrete slab with direct stud-to-sill plate connection.
Here's the slideshow its ripped from: https://training.weather.gov/wdtd/courses/EF-scale/lesson2/presentation_html5.html (module 17)
While Tim stated that DoD-10 is typically reserved for homes on concrete slab foundations, I do think it should also apply to crawl space foundations, but only under certain conditions. For example, if the elevated floor system is completely torn from the foundation along with the home, like what we saw in Gary, South Dakota, then DoD-10 may be appropriate. But if the floor system remains intact and attached to the foundation, I agree that DoD-9 is the more appropriate ceiling.
I am glad to see you back. I am sorry if I was a real jerk to you last time.
just a heads up , DOD 10 in the new EF scale has been moved to DOD 13 (both base on greenfield survey and a other presentation)
The reason I think the tornado *may* not have been overestimated is because, per the DAT itself (not me), contextual damage around the house was solid: