Building Construction and Basement Fires

Quite often, we find websites to share with you that have some great info, which is the case with UL University. They have conducted a study on fires in Single Family Dwellings, in particular “Structural Stability of Engineered Lumber in Fire Conditions”.  I recommend that you log in and view this presentation with your shift, on your duty crew night, or just for your own knowledge. 


Basement Fires and Collapse:

One of the most compelling items I pulled from the presentation is the T.I.C. portion. If we asked 100 FF’s what they view as the most dangerous fires that they could encounter in a SFD, I would venture to say a majority would say “basement fires”. They are hard to find, they are hot, they create zero visibility, and if not put out quickly they turn into a FF’s nightmare.

So the UL did a study with two separate basement floor assemblies:


1: a 2 x 10 wood joist floor with hardwoods on top (common to older homes).

2: a lightweight floor assembly (new homes) with carpet on a subfloor.

*Both of the floors had no ceiling assembly so it would resemble the unfinished basement we often encounter. They had a furnace in the basement, which simulated the working fire directly under the floor.

*For the entire duration of the test a T.I.C. was aimed at the 1st floor, which would be similar to us walking through the front door.

*They placed two FF’s in full PPE, one standing and one crawling, directly above the basement, on top of the two different floor assemblies.

Basement Fire

Here are the results (all basement temps are from thermocouples / all 1st floor temps are from the T.I.C.):

              2 x 10 floor:

·      @ 1:45 minutes in: 845 degrees in the basement / 74 degrees on 1st floor      

·      @ 5 minutes in: 1383 degrees in the basement / 75 degrees on the 1st floor

·      @ 8.5 minutes in: 1296 degrees in the basement / 86 degrees on the 1st floor 

 Special note: The nail heads used to nail the floor onto the subfloor are the only items showing a heat signature

·      The floor collapsed sending the 2 FF’s into the basement at approximately 19 minutes from ignition.


       Lightweight Floor:

·      @ 1:45 minutes in: 1196 in basement / 71 degrees on 1st floor

·      @ 3.30 minutes in: 1330 degrees in basement / 73 degrees on 1st floor

·      @ 5: 30 minutes in: significant 1st floor deflection and smoke emitting

·      @ 5:55 minutes: 1286 degrees in basement / 85 degrees on 1st floor

·      The floor catastrophically collapsed sending the 2 FF’s in the basement at 5:55 minutes from ignition.


 So how do we take this info and use it for our daily operations or to teach those new FF’s we have coming in?  

One of the first things to remember with this test is that it is conducted in a controlled environment so you do not have the typical open/burned thru basement door or intact/broken out basement windows.  These factors can help or hinder the potential for collapse conditions in the basement and may effect collapse times.  They also can make it hard for us to determine where the fire is. Regardless of these facts, there is a lot of information that affects our strategy and tactics.

TIC’s:  T.I.C.’s are only a tool to aid us.  We must not take us away from employing those vital basic firefighter skills.

  •  The T.I.C. only picks up surface temps in the room and not a 1300 degree fire in the basement below. If you sweep the floor with the line before you went in, the temperature that the T.I.C. is reading is the surface temperature of that wet carpet or hardwood floor.
  • Know what you are looking at with the TIC and how to interpret it?  Would you recognize that the nail heads on the floor are producing the heat signature and what would you do with that info?

TIME:  While we know that time is really never on our side…We now have actual data to support the belief that when we go to fires in older homes that we do have longer to fight fire. Conversely, when we go to fires in newer homes that have Lightweight components, we now know that window of time is much smaller.

Of course, many variables play into this that demand our attention (renovations, how long before the fire was reported, etc.) This only stresses being “Combat Ready” and using your false alarms and medical locals as chance to see what the SFD’s in our 1st due homes are constructed of.

  • If we take the traditional 2-story colonial with a walk out basement with fire in the basement, does this info change the way we deploy handlines?  It should, at a minimum, make you think.  If we have one line go to the top of the stairs to protect the occupants (civilians, truck doing a search) and the other line to exterior entrance to advance and put the fire out consideration to basement construction should be given to this info gathered.  In older homes we probably can make the first floor, advance to the steps and hold the fire in check. Or, if conditions are favorable, advance down (depending upon staffing, exterior entrance access, etc).
  • If it is a newer home, we may have to hold the fire in check from an area just inside the front door. If you have not been on a basement fire in SFD with lightweight trusses that had an isolated collapse around the seat of the fire, you will.  Obviously, this changes how the Truck will search also (possibly up a ground ladder to 2nd floor instead of the stairs, etc).

TRAINING: Train in the environment that we operate, zero visibility. The fire in the lightweight resulted in an incredible amount of floor deflection that may not be easily detected by the overzealous firefighter who charges right through the front door. We have all probably heard a tale or two about the firefighter who realized after the fire he was standing on a floor that was only held up by the tack nails that was used to hold the carpet.  The morale of the story is to continually train in zero visibility so you will inherently focus your attention on your other senses (feel, hearing, etc.) when you go to work.

SHARE:  As was mentioned at the beginning, this website is one of many that exist out there that has good info to share. Feel free to respond with your best website for information that may save your brother’s life.

 Know your buildings, know how they are put together…IT MAY SAVE YOUR LIFE!  

If you like these and other topics, keep an eye on our website for a “Fighting Fires in Residential Buildings” seminar coming in soon.

Be Safe. 


2 Responses

  1. “Special note: The nail heads used to nail the floor onto the subfloor are the only items showing a heat signature”

    This is important to remember. In a NIST test on structural collapse, simulating a basement fire, manequins were placed on the main floor and thermal imaging cameras were setup, in addition to other monitoring and recording equipment. The TIC covering the manequins revealed heat along the joists, in some spots, and similar to Dan’s statment above. What it did not reveal was that the manequins were held up for almost five minutes by carpeting and padding alone, after the floor (support) had collapsed.

    It was determined that, in some applications, the subflooring materials act as an insulate and give a misleading view captured by the TIC.

  2. Dan makes some good points that we need to be very aware of especially when putting troops on the first floor of a structure with a fire in the basement. This is and continues to be a very tough situation and with the increased use of light weight building components we need to get a good look at the rear and what is happeniing in the basement.

    The NIST recently put on a program regarding TGI’s and asserted that they do not significantly lead to early failure. While I appreciate what they said I am going to rely on what I have seen in the past and work that has been done by Joe Berry in regards to lightweight components. Please read Joe’s articles in FireHouse he did an outstanding job researching his information. Also be on the look out for work that is being done through the IAFC with Chief Shane Ray and J Gordon Routley heading up an effort with an manufacturer of Wooden I beams where they are doing a comprehensive study of their response to fires…. Important information…..

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