Roof Trusses

Trusses Exposed To The Elements

Question: 

We are having a house built and on a recent visit we brought along a friend who builds houses for a living. He noticed that the trusses were wet and a bit moldy. The wood seemed warped, brown, and had white splotches on it. We are worried that it would later make the roof uneven. How could we tell how long the trusses have been exposed to the elements? What options do we have from here? Do we request new trusses, or can these be repaired?

Truss Span Tables And Details

Question: 

Are there any typical wood truss span tables for roofs and floors available? Standard framing details for use in preliminary design?

Structural Composite Lumber In Trusses

Question: 

The lumber used in most metal plate connected wood trusses is either visually- or mechanically-graded solid sawn dimensional lumber. However, the Truss Plate Institute's ANSI/TPI 1 allows the use of structural composite lumber (SCL) products such as laminated veneer lumber (LVL), laminated strand lumber (LSL) and parallel strand lumber (PSL). These engineered wood products can conceivably compete with sawn lumber and complement it in truss designs.

Allowable Quality Tolerances

Question: 

What tolerances are allowed for metal plate connectors in wood trusses? How do you take into account the possible presence of splits, waves and knots?

Jobsite Inspections

Question: 

Consider this statement from a set of construction contract documents: “The Truss Manufacturer is responsible for inspecting the truss installation, bracing, anchorage and bearings and preparing a letter of verification stating that trusses are installed and braced properly.” At first glance, it may seem that the truss manufacturer is the most logical party to perform such an inspection. They are the truss experts, are they not?

Truss Attachment Information

Question: 

Would you please inform me of the specified requirements of the size and the amount of nail attachments from the truss to the top plate?

Truss Failure And Repair

Question: 

I am a professional engineer looking for information concerning the failure of metal plate connected wood trusses and methods of repair. I am looking for this information with regard to developing recommendations for the repair of truss systems in the floor structures of two-story multi-family dwellings. I see frequent failure of truss systems of this type in both in bending and due to catastrophic failure at the gussets.

Installation Guidelines

Question: 

What are the requirements on the permanent bracing of bottom chords? Can gypsum board diaphragms be used?

Manufacturing Tolerances

Question: 

I am a structural engineer on a project with a wood trussed roof. I have noticed some variations in the peak height in a run of identical trusses. Do you have any information on tolerances for the final dimensions of manufactured trusses?

Lumber Species

Question: 

What type of wood is usually used for wood trusses? I live in Louisiana and I would guess pine, but I want to make sure.