Type IV Construction

We are continuing to look at the different types of construction and the characteristics of each.  This post will outline considerations of Type IV or Heavy Timber construction.

Heavy timber construction is a type of construction we don’t see popping up in new buildings very often. However, there are still a great many buildings that are or were Type IV construction in our jurisdictions.  We need to identify these buildings in both circumstances.

[View with PicLens]

True heavy timber construction does not have void spaces. It is built with masonry or brick exterior walls with large diameter, six inches and more, interior structural components.  There have been debates about how these large beams and structural elements hold up to fire and some have found the large diameter wood components to hold up longer than steel.  The reason for this is that the steel will elongate and deform at around 1000 degrees and is prone to failure at that point. The large diameter components may burn, but they hold their integrity longer than the time it takes for steel to deform.  Obviously, there are variables, but an interesting bit of information.

These fires burn hot and for a long time. These are typically large buildings and have an additionally large fire load, making extinguishment difficult.  Many times we find these buildings in more urban areas and in highly dense locals. However, churches and resort lodges are common places for this type of construction.  Exposure protection is of the utmost importance and establishing an effective collapse zone is important.

When these building get remodeled and are altered, they can then be considered Type III construction.  The reason for the Heavy Timber classification is the benefit of the extended time of burning and the lack of void spaces. We lose some of that as false ceilings and new framed walls and floors are added to create lofts or office space.  Just something to consider because you will need to plan accordingly for the interior changes that are being made to these types of buildings.

Train hard, master the basics and have plan before you go to battle. Stay safe.

Lodge picture from Vermont Timber Works, visit them at vermonttimberworks.com