Mon, 23 May 2011|
Paul Dansbach takes a look at some of the features and hazards associated with townhomes that makes use of parallel chord and peaked roof truss construction.
Automatically Generated Transcript (may not be 100% accurate)
-- my name is all that's back welcome -- -- -- -- minutes today -- out at a construction site to look at the construction of some wood frame town hall. -- -- homes that are being constructed. Used parallel cord and peaked roof trusses in the bill. We're going to look at some of the construction features. Methods techniques and hazards associated with this type of construction. These buildings are being constructed in a fashion similar to platform -- Specifically. We have a bottom plate the bottom plates it's not a problem -- -- which sits on top of the -- court would trusses. The feature now we're interest in India is the method of platform framing -- that there was no vertical extension potential through the -- stud that. Furthermore as -- run vertically through wall. There is no vertical fire extension potential at the top of the -- -- Will we see -- DoubleTree by four -- It would -- walls that separate account house swelling units are constructed -- technique. Of using the bubbles bog wood frame -- -- -- wood frame war creates combustible void space. Once you -- forced bug. Air space equal to another to buy it works thought and then another two by four walls -- This space is a combustible -- space that is far stopped at every floor level. There's -- stopping in the wash system below. And -- stopping at the top plate to prevent the vertical extension of fire. Within the bubble -- war. One of the greatest concerns firefighters in this type of construction. Is the use of parallel -- Lightweight -- trusses as we see in this forces them. These trusses are space when he four inches on senate. Lightweight cord trusses. -- surface to mass ratio. Surface to mass ratio is key in determining the collapse potential of any structural element particularly forces. The lightweight parallel port floor trusses bear on the top plate over a wood frame wall what you notice here is far stopping. The -- stopping is placed in between. The floor -- the -- stopping is designed to prevent the horizontal spread a fire. Into the bubbles -- wall cavity and vertically through the building and horizontally. Into the next townhouse -- The lack of fire stopping -- the removal of -- stopping during construction. Will result in rapid vertical and horizontal -- spread. Through the trust base. The use of parallel coordinate. White way would trust is greatly increases the fire spread potential within the dwelling in our trusses as we mentioned a 24 inches on senate. The lack of solid material or solid wood -- would allow any fire that extends. Beyond the interior finish. Or originates in the combustible void space -- bread. Anywhere within the limit of the dwelling unit up to any fire stopping that might be present. If the building were constructed with -- -- -- -- joints installed sixteen inches on center. We would have a space between the -- fourteen and a half inches wide that would allow for horizontal fire extension. In the direction parallel to the floor joists the difference between. -- the construction at parallel -- would -- construction is these potential for fire extension. In -- for Boston will board space in the trust system the fire has almost no limits up to it reaches the -- -- -- line. And called required -- up. Another potential for fire extension in this type of construction. Is when plumbing lines are run through. -- combustible -- space created by the parallel port lightweight fortresses. Will we see here is -- plumbing line penetrating the floor. Any fire in the trust walked with a combustible void space below will -- up around. The opening in the floor that may not be properly fire stop. Resulting in fire extension to the floor above. We're on the top floor of the building and we're -- look at the root structure as mentioned the root structure is constructed with Pete wait -- roof trusses. Let's walk up and we can see we see our bottom quarter the trust we see the web members and we see the -- -- the trials. Also notice the large combustible void space. That will remain after the drywall has been installed on the underside of the bottom word of the trust's. If we look at the area of the we will motives are combustible void space between the bottom port of the truss to the peak of the rule will be between twelve and fifteen feet. The use of peak lightweight -- trusses create large combustible void spaces -- -- to grow extend. And overwhelm. That trust -- This view through the floor truss system clearly details the potential for -- awful fire extension through this area. Also noticed the electric utility installed in the trust's rates any mechanical or electrical equipment installed in the combustible void space. Brings the potential for ignition and fire to a car within the combustible void space created by. -- -- -- The use of white weight peaked roof -- create -- -- from Boston will -- space. Should the fire originate or extend into the combustible void space created by the white weight peaked roof trusses. The fire will grow in intensity -- motives for the firefighters operating below. The use -- white -- floor trusses and roof trusses in this type of construction. Constitutes an extreme hazards to firefighters. To the fire involved with the Boston -- white space a lot of the war for the roof -- Thank you for watching this session a fiery hearing training that.