04-29-2007, 03:45 PM #1
Kerf cuts...a little more info please.
OK...I am till studying the ventilation section of the essentials book, and read that kerf cuts can be performed to determine the direction of fire spread. Little else was explained, so I was hoping for some schooling here.....
How long do these cuts get made?
Are they just the width of a chainsaw blade?
Are you actually looking for fire through these cuts, or just smoke?
How well do they work on peaked residential roofs?
04-29-2007, 03:54 PM #2
04-29-2007, 06:25 PM #3
So a kerf cut with no smoke coming through "could" indicate that there is little or no fire/smoke below that location?
And that is assuming the entire attic has not been decked with plywood like mine is? I'd have a hard time venting my attic/ceiling.
04-29-2007, 07:53 PM #4"The education of a firefighter and the continued education of a firefighter is what makes "real" firefighters. Continuous skill development is the core of progressive firefighting. We learn by doing and doing it again and again, both on the training ground and the fireground."
Lt. Ray McCormack, FDNY
04-30-2007, 08:02 AM #5
Ok, last question on this subject. Are the kerf cuts made in a way to minimize roof damage? Such as between the rafters if possible as opposed to across rafters?
I know it sounds silly to think about minimizing roof damage when there is a fire below it, but that is how most of the older guys on my dept look at things. I don't necessarily agree with that philosophy.
04-30-2007, 08:36 AM #6
A kerf cut made parallel and close to a truss is the easiest to repair. Simply sistering onto the side of the truss from inside the attic and re-attaching the sheathing is often all that is required to make the repair.
A truss or a rafter should never be cut across if it can possibly be avoided. Even if a vent hole needs to be made, it can (and should) be done without the saw ever touching any framing member.
04-30-2007, 08:52 AM #7
04-30-2007, 10:27 AM #8
- Join Date
- Nov 2006
- The Mistake On The Lake
Nothing wrong with using the back of a flat head axe to make a vent hole. It just isn't always the easiest way to go about making a vent hole.
04-30-2007, 10:38 AM #9
Yes it is a little more difficult with the axe, but we had a guy slip on the sawdust many years back and almost fall off the roof as he was walking back to the ladder, so now we use the axe. I have done it in training and it honestly does not take all that much more time. For trenching, or large venting applications, a saw would definitely be the better choice.
04-30-2007, 11:02 AM #10
One nice thing about using an axe, is that it always starts.
04-30-2007, 12:42 PM #11"The education of a firefighter and the continued education of a firefighter is what makes "real" firefighters. Continuous skill development is the core of progressive firefighting. We learn by doing and doing it again and again, both on the training ground and the fireground."
Lt. Ray McCormack, FDNY
04-30-2007, 05:15 PM #12
04-30-2007, 06:33 PM #13
And as one guy stated to me at a training session, if I am going to tote the axe up to sound the roof, there is not much sense to me to bring up yet another tool.
Keep in mind, we usee PPV way more than roof vents, and most of the few fires we do get usually vent themselves......
04-30-2007, 06:41 PM #14
04-30-2007, 08:06 PM #15
Start training........yeah....you're preaching to the choir. I push , but there are just way too many pushing back. The joys of a small rural vollie department......
05-06-2007, 05:08 PM #16
- Join Date
- Aug 2006
- Franklin, TN
A roof ladder goes a long way towards keeping people from slipping off the roof and it has been our experience that you are more likely to lose your balance swinging the axe than venting with the saw.
05-06-2007, 07:57 PM #17Co 11
Virginia Beach FD
Amateurs practice until they get it right; professionals practice until they cannot get it wrong. Which one are you?
'The fire went out and nobody got hurt' is a poor excuse for a fireground critique.
05-06-2007, 08:23 PM #18
How do you know where the roof supports are when you are on top of the roof that is covered in shingles?
05-06-2007, 10:35 PM #19
To find out the direction and location of roof supports or rafters, on our department we do two things. First of all as we access the roof, the cutter starts a diagonal hole across the roof until a rafter is felt and then it is rolled. We then complete the hole in a triangular shape that is about 12 to 18 inches on each size. This accomplishes two things, finding direction of support and telling us what the roof is composed of. Once we have made this discovery, we make our trek to the area we will ultimately cut our heat hole, cutting smoke holes and sounding as we go. Once we have determined where we will make our cut, we make what we call a 5 cut leuvre. While this isn't quite as good of a way to find the direction of the roof supports or rafters, it can be used to do so.
While this post makes sense to me, I'm sure some of you may have questions about my terminology and would be glad to answer them if I can.
Last edited by station75; 05-07-2007 at 03:25 PM. Reason: correct grammar
05-07-2007, 08:34 AM #20
Sound the roof with an ax head and when the sound changes to more of a dull thump thats a rafter.FireFighter/EMT
05-07-2007, 09:42 AM #21
05-07-2007, 10:09 AM #22
Sound for the trusses first, then cut vertically along the inside (the side of the truss where the hole will be made) of the first truss, from the top to the bottom of a full sheet of sheathing. Next, cut along the inside edge of the third truss. Finally, cut the bottom of the decking between the first two cuts, removing the saw completely about an inch, or two shy of the center truss on each side.
A little pressure on either the left, or the right side of the sheathing will cause the plywood to pivot on the center truss, bending the nails, and will open like a damper. The plywood will remain attached to the center truss by the nails, but will open completely to vent the attic below.
The trusses remain uncut and the structural integrity of the roof is not compromised any more than necessary.
(Edit) I want to clarify what I posted above...
It is possible to open a 4x4 vent hole with only the two vertical cuts I described, provided they are made from the top to the bottom of a full sheet of plywood.
The horizontal cuts are only necessary if the opening being made is either less than 4 feet from top to bottom, or it is encompassing more than one sheet of decking.
On roofs that are plank-decked, horizontal cuts are rarely needed unless the decking is tongue and groove.
Last edited by fireman4949; 05-07-2007 at 10:54 AM.
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