We hear it and teach it frequently: Building construction and fire behavior are areas in which firefighters and officers must be well versed.
However, we never really identify the specifics of those two topics, which are broad at best, leaving us with the same old classes of construction types and light-weight construction. It is high time we get specific with building construction and what it means tactically for firefighter and officers.
With the recent event involving a metal roof at a residential structure, it is a good idea to address some challenges when operating on and below metal roofs. Every type of construction and its components creates a different set of challenges that we must be prepared for.
Although, in this case, the residential structure was wood frame, it had components more commonly found on commercial buildings. The differentiation between residential and commercial construction methods is becoming much less obvious.
No matter what type of roof we are operating on there are some very basic tactics that should be employed.
- Use a roof ladder and operate off of it.
- Operate from the up-wind side.
- Have more than one way off the roof.
- Use full PPE including SCBA, and be on air when there is active fire below.
- Have the right tools to do the job; this may include saws, blades, hooks and axes.
- Communicate with the interior crew and command about your efforts and the effectiveness of those efforts.
- Get down as soon as your task is complete.
Residential metal roofs aren't all that new, but we are seeing an increase in their use, primarily due to the economics and durability of the material. These metal roofs are not those of your grandparents or great-grandparents where they were just plain metal or tin. Today's metal roofs are coated to withstand ultraviolet rays and harsh weather conditions and to allow for attractive colors.
What lies beneath
The real problem is not so much the metal roof as much as what lies beneath it. The unknown layers of asphalt shingles or other roofing material is what really creates the problems for us on the inside.
Not knowing what and how much material is below the metal roof means ventilation may take longer — and the need for multiple tools and blades is very real. We must expect problems when operating on these roofs and venting them.
Additionally, these materials insulate the attic spaces, like they are supposed to, and when these roofs try to off-gas this insulation creates more heat and gas that has nowhere to go. The metal roof does not off-gas and deflects the heat to the only place it can, down.
This forced downward pressure can cause the interior environment to change for the worse rapidly and unexpectedly for firefighters operating on the interior. There are only three ways to avoid this, don't make the interior, get to the fire fast to make a quick knock down and finally to ventilate the space to allow trapped heat and gases to escape.
Making the push faster is dependent upon the training and experience of the suppression crew and the number of firefighters moving the line. If we don't have the resources to move the line quickly on a progressing fire, we may have to alter our interior attack tactics until we can get appropriate resources or get the space vented.
Not going in is an option, but one we don't like, especially if the space is tenable when we arrive. But, any time we are making the push on the interior and deciding to put crews inside, we must consider what is going to happen minutes from now and plan for those expectations. That might mean that we keep crews out of the building.
Venting is a viable option if we can determine some characteristics about the fire and the roof.
- Do we know where the fire is?
- Do we know where the fire is going?
- Can we determine what type of roof assembly we are dealing with, such as truss versus legacy rafters?
- Do we have the resources to make an efficient, coordinated attack with ventilation?
We cannot blindly put firefighters on any roof. We must have a very good idea where the fire is in order to effectively perform vertical ventilation on any roof, especially a metal roof. Venting at the wrong location can contribute to fire spread and making conditions worse.
We also need to understand where the fire is going. For the same reasons we need to know where it is, we must have an educated idea of where it is going. We don't want to get crews trapped on a roof by fast advancing fire in an attic or upper level.
Obviously, we have more stability and mass to deal with when operating on a legacy-built roof as compared with engineered truss roof systems. It does buy us a little time, but don't get a false sense of security. If the roof sheeting becomes compromised, falling into the space below is a real hazard.
Finally, we must have the resources to perform the tasks. You may need to consider alternate tactics like horizontal ventilation due to the lack of resources to perform all of the functions of a well-coordinated attack.
While actually operating on a metal roof some hazards and extra challenges that you need to be prepared for are:
- Metal roofs can be slick even when dry, but especially so when wet or covered with ice and snow.
- They cover older roofing materials; take extra tools that will allow you to penetrate multiple materials.
- Look for discoloration on the metal as a sign of where the roof sheeting is very hot or compromised.
- Roof ladder hooks may not penetrate and grab the metal roofing material, extra effort may be needed to seat the roof ladder.
As with any tactic, training and knowledge are key. You must understand how these systems work and choose tactics based on that knowledge. Practice placing ladders and operating on pitches if at all possible and know the capabilities of your tools. Communicating that your progress is positive or negative is an absolute so that the interior crew can make a safe exit or alternative ventilation tactics can be deployed in a timely manner.
Train hard and learn the lessons from others and be productive. I'll see you next month, right here From the Fireground.