Old log cabin (C) Daniel Friedman

Building Structural Trusses
Photo Guide to Residential Roof & Floor Trusses
     

  • TRUSSES, FLOOR & ROOF - Photo guide to types of roof trusses, wood and metal
    • Photo guide to types of floor trusses, wood and metal
    • Common roof truss defects, ID by visual inspection
    • Common floor truss defects, ID by visual inspection
    • Definition of Howe truss and Fink Truss - design sketches
    • Broken roof truss bottom chord: inspector falls into toilet
  • I-JOISTS, Wood Roof Floor - separate article
  • POST a QUESTION or READ FAQs about roof & floor trusses and truss contstruction specifications & practices
  • REFERENCES

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This article describes and illustrates the different types of roof and floor trusses used in residential construction. We describe common roof or floor truss defects that can be observed by visual inspection. This article series describes building framing materials used in different epochs of residential construction. Knowing when certain materials were first or last in common use can help determine the age of a building. Our page top photo shows modern floor framing details for a modular-constructed house.

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Floor & Roof Truss Materials used in Building Construction

Wood Floor & Roof Truss Photos

Truss example (C) Daniel Friedman Truss example (C) Daniel Friedman

Our photos show an attic view of modern roof trusses (above left) and floor trusses (above right).

Illustration of Howe Trusses & Fink Trusses

The illustrations below illustrate two common wood roof truss designs: the Fink Truss and the Howe Truss.

Howe Truss example (C) Daniel Friedman Fink Truss example (C) Daniel Friedman

Common defects observed when inspecting wood roof trusses in residential buildings

Roof truss plate (C) D Friedman

Some common defects we find when inspecting wood truss construction in residential buildings include:

  • Wood trusses were cut or modified, such as the removal of the bottom chord of a truss to install an attic stair
  • Wood truss connector plates or "gusset plates" that are damaged or disconnected. Sometimes you may need to look closely at the steel connector plates on wood trusses for signs of separation, or on occasion, a "repair" of loose truss plates using roofing nails.
  • Truss uplift, a cosmetic not a structural defect, is discussed separately at TRUSS UPLIFT, ROOF

Broken Truss Chord, Inspector Falls into Toilet

Watch out: the bottom chord of the roof truss is often used to support the ceiling below. But the bottom truss chords, especially with pressed-on gusset-plate wood roof trusses, may not support the weight of an inspector who walks on them. Worse, the bottom chord of the truss is often hidden from clear view, buried in attic floor insulation.

Hybrid roof and floor trust combination (C) Daniel FriedmanThe author [DF] standing on a truss chord while installing an attic fan, suddenly found himself one floor down, in the bathroom of an unsuspecting condominium owner who had no idea that a contractor was working in the attic over her head while she was using the toilet.

As the dust settled from this painful and embarrassing incident we investigated the broken roof truss bottom chord.

A large knot through the bottom 2x4 truss chord had not interefered with the truss function while the chord was in tension - it's usual load. But when walked-on and when the contractor stepped on to the chord right over the knot, it simply broke in two, leading to an accident.

Our wood roof truss photo at above left shows a design that would have been less likely to collapse when walked-on. The bottom chord of the roof truss is formed by a wood floor truss. The two trusses are bolted together at the truss ends using plywood gusset plates.

(History & dates of the design and use of site-built and factory-made roof trusses, king trusses, A-trusses, and web trusses are in process, contributions invited,CONTACT us)

Below our photos show details of finger-jointed wood truss web connections.


Truss example (C) Daniel Friedman Truss example (C) Daniel Friedman

Metal Floor & Roof Truss Photos

Our photos below illustrate the use of steel roof trusses below a flat poured concrete roof. At below right you can see that steel roof trusses are not completely immune to damage from water, leaks, and rust. We don't consider surface rust to be of structural significance on these trusses, but when the rust has advanced to flaking exfloiating steel rust then the integrity of the truss and thus the structure is questionable.

Truss example (C) Daniel Friedman Truss example (C) Daniel Friedman

Below our photograph illustrates a steel I-joist also used in roof and floor construction. Also see I-JOISTS, Wood Roof Floor.

Steel web Truss example (C) Daniel Friedman

See Framing Methods Age for the history and date ranges of various building framing methods. Also see NAILS & HARDWARE, AGE and SAW CUTS, TOOL MARKS, AGE for additional building age clues likely to be available when examining building framing materials. Also see ARCHITECTURE & BUILDING COMPONENT ID.

Also see I-JOISTS, Wood Roof Floor.




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