Type V Construction-Wood Frame

The next type of construction that we are going to talk about is Type V, or wood frame construction.  This is the most commonly used type of construction in most jurisdictions.  This type of construction is typically associated with residential occupancies, namely single-family dwellings, but many commercial buildings are now built using wood frame construction.

Years ago, wood frame meant real dimensional lumber. A 2×4 was really a two inch by four inch piece of wood.  Roof systems were stick built with rafters of dimensional lumber that were connected with a ridge beam.  We forget that this traditional type of construction is wood frame.  Balloon frame is also a type of wood frame.

We have just gotten so ingrained that wood frame mean light weight, or now commonly known as “low mass” construction.  This “low mass” construction uses engineered products that makes construction faster and cheaper to build. Although these components like engineered I-joists and roof truss systems are very strong for the engineered loads, they fail miserable during fire conditions.

We just need to remember the hazards and myths of this type of construction. One is that if one truss fails they all fail.  I like to ask the classes that I teach if any of them has seen a house constructed with wood truss systems with a part of the roof burnt off and the rest of it still intact?  The answer is always yes.

I am not saying that these truss systems are safe, quite the contrary. All I am saying is that we need to keep our firefighters educated about these systems. I know there are some chiefs and instructors upset with some of this, but we can operate on and under these roofs with some careful size-up and thoughtful tactics. One thing I have learned in the fire service; never use the words never or always.  There is always a circumstance or situation that will challenge both.

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Now, characteristics about this type of construction.  There are void spaces everywhere and these components use a lot of glue to help keep them together.  These buildings are getting bigger on the residential side and this construction type is very popular for many commercial buildings like fast food joints, restaurants and strip malls.

Something we need to keep in mind also is that some of these wood frame buildings look like masonry or brick, or type 3 buildings.  These are just veneers and we need to understand the challenges dangers associated with that.  Masonry and brick veneers can easily collapse of the foundation and still kill or seriously injure firefighters.

Pay attention to your area and be familiar with the buildings you may have to operate in. Know the different characteristics of the construction types and the challenges each one poses for us operationally.

Train hard and stay safe.

1 Comment

  • Don Lawrence says:

    Some comments regarding building materials:
    1) Isn't it true wood has a duration factor in regards to failure where steel does not? Are there any steel structures where part of the roof is burnt off and the rest is intact?
    2) Isn't it true wood products promote a sustainable resource where steel and concrete leave much more of a carbon footprint on our environment which is merely a shadow of the damage fires cause to wood structures?
    3) Is there any fire research done on heavy timber trusses as a more suitable building product. How about European CLT (Cross Laminated Timbers) in regards to fire protective values? Why not promote these types of products which are wood constructed yet still a sustainable resource? I don't see a "Type" classification for these products.
    4) Sprinkler systems in residential housing is almost always defeated without implementation due to costs. As long as people put money concerns ahead of appropriate fire protections, fires will continue to consume properties and lives.
    Thanks for considering. You guys are heros in my book.

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