Forensic Engineering who specializes in Trusses/wood
Forensic Engineering who specializes in Trusses/wood
(OP)
I have a few questions regarding how an engineer forensically exams trusses for heat damage. Are there any Forensic guys out there that specialize in trusses?
Wayne D. Smith, Jr., CBO, MCP, CEAP, LEED AP





RE: Forensic Engineering who specializes in Trusses/wood
As noted in the other forum, here's what I would look for:
1. Dimensional changes, mostly shrinkage due to drying
2. Distress in fasteners and plates. Have the plates pulled out? Have the plates lost engagement?
3. Amount of charring, depth of charring, and location of charring.
4. Comparison of surrounding materials to get an idea of exposure temperature (did it melt certain plastics? Did metals in the area expand or discolor?)
5. Did excessive temperature cause sap bleed? If so, how excessive?
6. Is there any dead load deflection as a result of the elevated temperatures?
7. Review fire department reports and records to discern time on site, involvement of the fire at first observation, approximate temperatures if measured, time it took to extinguish, whether water was continued on smoldering sections.
8. Spalling of concrete materials near or adjacent to wood.
9. Damage to metal straps/accessories for uplift.
10. Sample and observed cross sections of the wood under microscope to check for cellular structure affects.
I'm sure I've left off a few things, but these are things I've looked at in past evaluations of fire damage. Most recent was in February of this year...testified in Tallahassee on structural damage.
RE: Forensic Engineering who specializes in Trusses/wood
Heat causes changes to the wood itself. Initially the lumber is dessicated and then the constituents, primarily lignins and hemicelluloses start to break down. Initially non-flammable components are released and then the reaction becomes exothermic (it generates heat and the reaction progresses on its own). Do a web search of destructive distillation. The chemical progression is fairly well documented.
It is possible to for the extent of pyrolysis to be determined by chemical analysis and depending on how serious the case progresses, it is possible to use similar undisturbed samples and test them by using controlled 'baking'. This is getting into some 'heavy' and costly forensics. Once you have a copy of the report from the insurance company's engineer, you may have to go this route.
I don't know how the insurance company's engineer works and if there is any bias. When I do a report for an insurance company, I clearly state to the owner that although the report is for the insurance company that it is unbiased and that the report would essentially be the same had I been hired by the owner. If there is a bias and the report is flawed or biased, then you may have recourse through the professional licensing board (or whatever). I also inform the owner that the report is for the insurance company and that release of it is at their option. I have only had consistent difficulty with one insurance company. I'm driven by technical aspects and not client driven.
I note that Ron is licensed in your area and does forensic work. If you search the site, you can look to his other responses and he appears to be pretty knowlegable and thorough; you might consider retaining his services.
Dik
RE: Forensic Engineering who specializes in Trusses/wood
Wayne D. Smith, Jr., CBO, MCP, CEAP, LEED AP
RE: Forensic Engineering who specializes in Trusses/wood
Glad you're enjoying the weekend..Yep, St. Augustine's a nice place. From A1A Ale Works looking across the Bridge of Lions and the inlet at sundown....nice!
I'm sipping a Landshark and watching the Gators win!
Ron
RE: Forensic Engineering who specializes in Trusses/wood
RE: Forensic Engineering who specializes in Trusses/wood
RE: Forensic Engineering who specializes in Trusses/wood
RE: Forensic Engineering who specializes in Trusses/wood
Dik
RE: Forensic Engineering who specializes in Trusses/wood
RE: Forensic Engineering who specializes in Trusses/wood
You are correct about the lower temperature. The wood starts to dry out and the lignin and hemicellulose starts to break down. It's not until you get an additional couple of hundred degrees that the chemical reaction becomes exothermic and combustion proceeds. Up to the point of combustion the various components break down further until the reaction is 'self-sustaining'.
Dik
RE: Forensic Engineering who specializes in Trusses/wood
RE: Forensic Engineering who specializes in Trusses/wood
RE: Forensic Engineering who specializes in Trusses/wood
Wayne D. Smith, Jr., CBO, MCP, CEAP, LEED AP
RE: Forensic Engineering who specializes in Trusses/wood
Dik
RE: Forensic Engineering who specializes in Trusses/wood
RE: Forensic Engineering who specializes in Trusses/wood
Wayne D. Smith, Jr., CBO, MCP, CEAP, LEED AP
RE: Forensic Engineering who specializes in Trusses/wood
Dik
RE: Forensic Engineering who specializes in Trusses/wood
Sounds like they've engaged one of a couple of testing labs in your area that have primary experience in evaluating soil conditions in Polk, Hardee and surrounding counties. That's fine, as long as the person involved is capable of evaluating structural materials. One of those firms in that area has some reasonably good people and can do this type of evaluation. The other significant one does not. I hope you got the good one!
I'm waiting to see their report. Should be interesting.
Ron
RE: Forensic Engineering who specializes in Trusses/wood
Wayne D. Smith, Jr., CBO, MCP, CEAP, LEED AP
RE: Forensic Engineering who specializes in Trusses/wood
Do you have photographs of the damage? and have you taken any core samples or coupons? Things change with time. A significant part of the 'musty' burn smell is caused by a fungus that 'lives' in/on charred/burned material.
You might have a commercial truss engineer (possibly the people that supplied the truss) take a look, too and offer an opinion. He can direct you to the best place to take a sample without compromising the truss and you can likely get a 'plug' cutter drill from a local hardware store.
Your engineer might be into this and as a 'heads up'. I don't know about Ron's approach, but when I take samples, the first sample is one of the container/bag that I'm collecting stuff in... just to provide a 'background' if the issue of 'contaminating' samples comes up.
Dik
RE: Forensic Engineering who specializes in Trusses/wood
You are like the CSI of wood...
Wayne D. Smith, Jr., CBO, MCP, CEAP, LEED AP
RE: Forensic Engineering who specializes in Trusses/wood
Wayne, one other significant point you have to consider is that of real estate disclosure. If you ever decide to sell your house, you will have to disclose the damage if it is unrepaired. It will get flagged and highlighted in a "home inspection" report obtained by the buyer. Fire damage is sometimes a deal killer, even after cleanup. Unrepaired fire damage is a clear deal killer, so the insurance company is compromising your ability to receive fair market value for your house or to possibly even sell your house. Tell them to pay for the repairs or buy your house since you can't sell it!!
RE: Forensic Engineering who specializes in Trusses/wood
Photographs of the worst? truss damage and a macro of one of the most discoloured/damaged truss plates would be interesting.
NFPA also has a protocol for fire investigations... if your engineer isn't using it, he may take a gander.
Next to 'Reality Programs', CSI programs p*ss me off, big time, and I don't normally get riled. Worse than Rap music(?). I do, however, like the fraggles...
Dik
RE: Forensic Engineering who specializes in Trusses/wood
Wayne D. Smith, Jr., CBO, MCP, CEAP, LEED AP