The Trench Cut

[Jack]

On one of the "you make the calls'," ( I believe 31) a few readers suggested trench cutting the roof. Trench cutting a roof is a very labor intensive and manpower intensive tactic and is very often misused. In what situations should we trench cut a roof and where do we trench a roof? What type of construction, other alternatives, etc....

[Reverend]

jack said:

On one of the "you make the calls'," ( I believe 31) a few readers suggested trench cutting the roof. Trench cutting a roof is a very labor intensive and manpower intensive tactic and is very often misused. In what situations should we trench cut a roof and where do we trench a roof? What type of construction, other alternatives, etc....

More to follow on trench cuts, when I have more time. However, the fire in you make the call #31 dosnt need a trench cut. It needs its little brother. The well placed large productive vent hole. That is if conditions warrent doing so, hooking ceilings in the ajacent unit with a hoseline may just do the trick. Quick easy and alot less manpower. More to come.

[JDub]

I mentioned the trench in #31. The reason I said to use this, and correct me if I am wrong Rev, the used that on the Hunters Glenn job I guess a little over a year ago. I sorta used that to base my tactics on #31 because it was a similar type of overall construction.

[thelurker]

jack said:

On one of the "you make the calls'," ( I believe 31) a few readers suggested trench cutting the roof. Trench cutting a roof is a very labor intensive and manpower intensive tactic and is very often misused. In what situations should we trench cut a roof and where do we trench a roof? What type of construction, other alternatives, etc....

Trench cutting the roof should be done at the narrowest part of the roof, or at a choke point. This can be best applied in the H shaped tentaments found in North Jersey and New York City. In these buildings, the Cross Bar of the H is a hallway, and is only the width of that hallway. The purpose of this cut is to stop the lateral spread of flames through a common cockloft. The cut must be wide, from side to side, and you must also be able to pull the ceilings below your trench cut. Then proper defense of the cut is to position a hose team inside directing streams up from the unburnt side and a hose team on the roof directing a hose stream (or multiple) down into the trench, also from the unburnt side.

Remember, the trench cut is not actually a vent hole, but is a defensive removal of materials allowing for a "fire Break" and defensive position.

MTC 31 definitely does not need a trench cut.

[JDub]

Well at least I know what NOT to do for that MTC.....

[1900]

jdub said:

Well at least I know what NOT to do for that MTC.....

But hey better to learn it here then out there...thats what this site is for...that MTC 31 pry wouldnt even need a hole in da roof, but get the crews in place...

We have used trench cuts numerous times they have worked, but you gotta have guys that know what there doing...We have requested it done a buncha times...Im still waiting for three of them to be completed!!!

[Reverend]

jdub said:

I mentioned the trench in #31. The reason I said to use this, and correct me if I am wrong Rev, the used that on the Hunters Glenn job I guess a little over a year ago. I sorta used that to base my tactics on #31 because it was a similar type of overall construction.

The Hunters Glenn Job which you speak of did not recieve a trench cut, Jdub. When the Chief asked, he asked for the roof to be opened up. The job started with me solo on the roof then got one ff from 11's and one ff from 23's. Then some additional help. Having been schooled by Hunters Glen before I had an idea of what was happening with the job. So a large vent hole (4x15, Expanding Cut) was placed just over the fire wall. This immediatly lifted the heat of of the division 2 and aided in helping the brothers hook the ceilings. The hole was only down one side of the peak. However here is where the confusion lies. When describing the fire to news crews 2300 stated that crews trench cut the roof during fire attack. Not the case. This is a common misconception.

Furthermore, one of the common mistakes is that crews place the trech cut over the fire, or try to cut it to close. The trench cut needs to be in a cut off area or area where the fire can be stopped. Check Lurkers response for an example. The initial vent hole needs to be cut to buy time and start relieving conditions and as a reference point on worsening conditions. The trench cut can not be part of the initial ventilation cut, Big time foul ball.

[3105]

Now THIS is what I call good info....and why this site continues to be (IMHO) successful.

I'm no expert on truck ops...I will gladly take notes from the Rev and others when it comes to techniques. One aspect of trenching that is often misunderstood and Lurker alluded to is the distance it must be cut from the fire....I need to find the reference to be 100% certain, but I remember reading that fire will travel across the underside of a plywood sheathed roof at a rate of something like fifteen feet per minute (it may be even faster...the old neurons aren't firing on all cylinders this morning)....which means if you're gonna trench, you better move down the roofline a considerable distance or else you're just wasting time and effort.

Another reason to trench is combustible roof insulation, like the material covering the Motown Mall....the fire tends to run laterally in between the top membrane and steel decking...as Rev and Lurker mentioned, this is being done to create a fire break.

[chief3102]

Another little thing I like to do when using a trench cut is to make observation holes approx every 5 ft to check the progression of the fire toward your cut, since like stated above, you should be quite a distance away at a point where you can make a stand.
Also, as stated in various posts. this is a very labor intensive process. Ask any of the old boys who were at the Mtown Mall fire.
Shovel off the stone before you can even begin to cut. It's a bear and like every technique it has it's time and place. Just another tool for the tool box.

[shader101]

which mall fire 3105 the last one ?

[papacheese]

shader101 said:

which mall fire 3105 the last one ?

nah, this was .......years ago (times' fun when you're having a good fly..or something like that). 02 might be able to give a list of dates I could pick from; I made most but not all of them.

[daveconstantine]

Sorry for the time delay. The last fire, as with the others, a trench cut was used and the date was December 23, 1992 at 0802hrs.