Dangers of Decks

By Jason Poremba 

We often take for granted the construction beneath us — but poorly built decks can pose a potentially lethal hazard to firefighters during incidents. It's easy to assume that the construction at some point was installed properly, and more importantly inspected by a building inspector.

It's hard to say for sure, but to me it's becoming more and more common to see sub-par deck constructions. In an effort to save money, some builders are pushing the limits of spans on deck joists. Often architects will specify specific framing anchors in drawings, but builders or clients will make their own judgment on site. This is not to say some architects are under sizing framing members and anchors as well.

You cannot always assume a deck has been constructed legally, too. Often people do not realize you need a building permit to build them. Decks are often built by a resident on their own as a weekend project. According to Simpson Strong Tie, it is estimated that there are millions of decks in the United States that are beyond their useful life and may be unsafe.

The problem with poorly built decks is that they are often overlooked, and not so obvious to find. Most often they are failing before they are determined to be unsafe. It is not the kind of thing we tend to inspect during our fireground operations.

Some of these decks are almost guaranteed to fail under fire load, but they should also be considered dangerous under live load. What is a live load? A live load is often referred to as the variable load on a structure. In structural design, this weight is added to the dead load to calculate the total load. This information in combination with the span is used to calculate the framing required.

In some areas there are specific requirements for hurricane and seismic detailing. Firefighters with tools and hose lines are that live load. It would be safe to say an architect or engineer does not plan for firefighters operating on a deck, but it is more likely they can plan for a number of people. Will the deck hold 10 people if we were going to have a party? Probably. But what if you put them all in fire gear, and add tools and a hose line. Maybe not.

Take a look at this first video of a group of people getting together to have a small party. The number of people here is not the amount you think would raise a flag. The most important thing I want you to note is that the deck boards are new. In our case, we may see new deck boards and assume new deck framing. Not necessarily so. Watch as these party goers get a surprise. Now consider three or four firefighters making an attack on that same deck.

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The second example we have is a fire in a two-story, wood-frame, single-family dwelling in Toronto. The balcony is under a heavy load while firefighters operate below. During the initial size-up, we need to determine if the deck or balcony is near the point of collapse. If deemed unsafe, we must operate out of the collapse zone and we cannot allow firefighters to operate near or on the compromised structure.


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Things to look out for during size-up include:

  • Long spans of deck joists
  • Decks that appear to sit on spindly legs
  • Large spans between deck posts
  • Inadequate framing for the span — are they framing 20 feet with 2x6?
  • Inspect teco or anchors for nailing - Builders will often only nail about half as many nails that are actually required
  • New deck boards on old framing
  • Decks that appear to sag under no load
  • Bouncy decks or decks that tend to rack under a live load

The third example is from Boston. Although I would never operate on top of this front-entry porch, I see no harm in operating under this. The posts and framing are not compromised. The only thing burning in this video is the roof shingles. A quick hit of water will put that to an end fast. It is all about size-up and making a decision based on the facts and your experience.


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The final example highlights a fire in a one-story, wood-frame dwelling that has worked its way from the interior to the exterior.


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The main thing to remember during incidents involving residential decks is to continually assess the situation. During your initial size-up, try to locate the potential problem areas and continually assess them during operations. If you have a deck that is questionable, seek alternate ways to attack the fire, and communicate over the radio. Let everyone know on scene there is a problem, even if it is a warning. An example would be, "Be advised we have a poorly framed deck on the 1,2 side — units in, operate with caution." Alternative plans will also allow firefighters to have a different egress point in the event the deck they came in on fails.

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