Definition
Trusses are pre-engineered roof frameworks—lightweight but extremely precise. Cutting or altering a truss can cause catastrophic roof failure because the entire system is engineered as a unit.
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Modern homes use manufactured trusses designed by engineers for specific applications. Trusses must not be altered or cut, as modification compromises their structural integrity. Common problems include broken web members (interior bracing), separation at bearing points, and sagging from water damage or inadequate support. Inspectors examine trusses from the attic, looking for cracks, deflection, water stains, and signs of movement.
Pro Tip
Never cut or modify manufactured trusses. If you need to run ductwork through the attic, consult an engineer for proper reinforcement methods.
Example
A home inspector in Ohio found that a homeowner had cut a truss web member to run HVAC ducts through the attic, creating a serious structural defect. The truss was no longer capable of supporting roof loads, requiring expensive repair involving sister-trussing or complete replacement.