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  • Trench Cut

    We were making a trench cut on a 3 story apartment building the other day on the fire side of a firewall. The problem we ran into was that the roofing material ran about 10" to 12" and after making the 2 parrell cuts 4' apart through the 2 foam layers of insulation and pea rock we tried to remove that material. At one point we had about 15 men on the roof working on this. We were only able to open several small holes-none large enough to apply a master stream. Since we don't do this everyday does anyone have any tricks or tips they might have on this.

  • #2
    We don't do it everyday either, but some tips. (and I don't know all the circumstances)

    1: 15 people on the roof??......Sounds like way too many.
    2: Fire side of a firewall??.....Since a trench is a defensive tatic, couldn't you have used it as your defensive starting point. But once again, I wasn't there.
    3: You weren't able to complete the task??.....Radio command of your problem and possibly change tatics. Maybe crews inside pulling celings with large caliber handlines in place might have done the trick.

    I'm not trying to bash you, your officers or your Department, But it sounds like a classic case of "Tunnel-Vision".

    [ 11-28-2001: Message edited by: Trkco1 ]

    [ 11-28-2001: Message edited by: Trkco1 ]


    • #3
      Trench cuts can be very effective if done right, at the right time, in the right place and with the right resources committed to them.

      First, it's difficult to stay ahead of the fire when trenching a "regular" ie: square or rectangular shaped building. Trench cuts came about as a tactic used in the throats of "H" and "U" shaped tenements in NYC during the war years. They could be done fairly quickly in the narrow throat thus confining the fire to one wing or the other. At least two saws and a bunch of truck apes with hooks are needed, 15? I dunno about that, OK if the roof's real solid and they're all working I guess. For God's sake be sure of the roof's integrity!

      Second, trench cuts are not ventilation holes per se, that is to say a main vent hole - 4'X 8' minimum snould be placed over the main body of fire first. Yes, that's a lot of cutting!

      Third, it's rarely, if ever, a good idea to put a master stream through any hole cut in a roof for ventilation or confining fire spread. Better to put a tower ladder stream through the top floor windows and let eat into the cockloft/attic, second choice would be one or two 2 1/2" lines with big smooth bore tips on the top floor. Again, be sure of the roof's integrity if you do.

      Without digging out some old lesson plans, that's a down and dirty take on the subject from a "throwback culture."

      [ 11-28-2001: Message edited by: NozzleHog ]


      • #4
        Just a couple of things from me and they have already been addressed in replies:
        1. A trench, or as I prefer to call them strip cuts, is a defensive tool to say OK fire you got that much but I hold the line here!
        2. When the master stream goes up, the walls come down. In other words, when you deploy a master stream it is now a defensive firefight and the should be no one inside the building or on the roof.
        3. Along with item #1, a strip cut is a wonderful tool to use when applied to pulling cieling inside and stopping the fire.
        I hope I made some sense and like my other fellow firefighters said, I wasn't there and I hate to monday morning quarterback. So, there may be some details that would make me respond with added information.

        Good luck and stay safe!
        Just my opinion, not my organization's, for what it is worth.


        • #5
          Just to clear up a few questions.
          2 am call. The fire was on all 3 floors near the center of this section of building(about 60 apts) when our unit arrived, about 5 to 10 mins after 1st units arrived. After knocking down the bulk of the main fire on all 3 floors all lines were pulled out due to questions on soundness of the structure. A large portion of manpower went to checking & double checking the 200 apts affected by the fire during most of this time. The roof in the main section buckled & the fire grew again. It then blew through the firewalls on each side of the stairwell to the west. As the fire grew command deceided to give up the next block of apts. to stop it at the next at the firewall. Thats when we attemted to make this cut about 200' away from the stairwell right at the firewall. When I said master streams I ment mounted on the ladders.
          The 15 men on the roof only worked a short time at once due to swiching out of men. It was quite easy to watch the progress of the fire with the smoke going west as we were on a north-south section. The cuts never did show smoke until near the end of the effort. The last of the crews were pulled off thinking that the effort was lost. For some reason the fire stopped short of there. Alot of water on that section of roof (about 3-4") went into the cuts, who knows.The roof was sound the whole time. As the fire worked the section to the south it was only some of the 2nd & the 3rd floor involved. The decision to leave the roof was by the officers on the roof based on how sucessfull we were(or were not) and that anything that was lost was not even remotely worth one of us(acouple of guys were ****ed but they got up near the end and were still full of **** & vinegar) We felt we had a great chance to stop the fire there but were frustrated at not being able to get that stuff off.
          So the question still stands, how do you get that stuff off quickly?

          [ 11-29-2001: Message edited by: jducharme ]


          • #6

            I don't think any of us will be able to answer your real question: how do you pull this stuff off. My first thought and the gist of what I have read so far is that venting (or trenching) that roof probably was not a viable option .I sounds like your officers made the right decision to pull everyone out until they could determine if the structure was sound. I think I would have gone with an intensive interior attack, pulling ceilings and holding the spread of the fire. At my base, most buildings are steel construction. We vent horizontally unless a pre-existing opening in the roof could be utilized such as vent shafts or elevator shacks. Trench cuts are not in the preplans. Just my $.02

            [ 11-29-2001: Message edited by: Mrtank ]

            Roy Colbrunn (Tank)
            IAFF Local F-88 Sec/Treas


            • #7
              I guess im gonna have to crack the books--The way I was taught to do a trench cut-(and did it once) was to make a cut the full with of the building , pull the men off the roof and either pull or blow down the ceiling and fight the fire from the unburned side with large handlines or portable monitors, usung the cut not as an acess opening, but a vent to vent the fire upwards, hopefully limiting the horizontal extension.
              And if the apt building is still sound, why not get with the rennovation crew and experment with different ways to remove the roofing materials?


              • #8
                this is totally unrelated but, what's happening Mrtank? it's LFD from the inland spills conference in Cinci. gimme a holler sometime there's big news out here on the homefront nothing bad, just typical "home" stuff


                • #9

                  It sounds to me like the roof was an EDPM membrane/ballast type assembly, which is typically used on steel framed, flat roof structures. I have only seen trench cuts performed on wood-frame construction. I once was on a fire in an auto-body shop that had the type of roof you have described, and our overhaul lasted HOURS due to the fact that the fire had gotten into the insulating material between the EDPM membrane and the asphalt/rock top layer - it took an extreme amount of work just to remove small sections of that roof assembly and, even though it was not a fast-working fire in that roof, it took a very long time to tear it up enough to completely extinguish the little bit of fire extension that we had in there.

                  Bottom line is, I don't think there is any easy/quick/efficient way to open up that type of roof (If there is, I'd be glad to hear it) and I agree with Mrtank, horizontal ventilation is about the only option available in that type construction.
                  An ounce of prevention is worth a pound of cure!


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