What is truss uplift?
Truss uplift describes two completely unrelated conditions. The first truss uplift, as in truss arching, is one of the causes of Partition Separation. WTCA has a publication in our TTB series on Partition Separation that describes this occurrence and ways to prevent it. What the brochure does not emphasize is that when truss arching occurs it is because of a moisture content difference between the top chord and bottom chord of the truss. One easy way to avoid this is to ensure plenty of ventilation of the attic space, do not discharge household vents into the attic, and ensure that ventilation areas are not blocked by insulation. The second uplift describes the tendency of framing (trusses, rafters, joists, etc.) to lift off their supports due to wind forcing them upward, or due to multiple bearings or cantilevers. These uplift forces are generally listed on truss design drawings. In some cases, toe nailing the framing to the top plate does not provide enough resistance to the uplift f
