HVAC contractor needs to get an air handler into the attic of a truss-framed house.

STOP — DO NOT PASS INSPECTION AS-IS.

Cutting bottom chords and webs of trusses is a structural modification that requires engineering approval. Trusses are designed as integrated systems; removing members without analysis violates IRC Section R802.3 and IBC Section 2308, which require truss alterations to be designed by a registered engineer or pre-approved by the truss manufacturer.

Immediate actions:

1. Halt the sistering plan. Nailing 2x6s alongside cut chords does NOT restore truss capacity. Truss members are sized for specific loads in compression/tension — field repairs need calculated connection details and material matching.
2. Call a structural engineer to design a proper repair (likely steel plates, splice connections, or temporary shoring).
3. Notify the inspector that the work is incomplete and awaiting engineered plans. Do not attempt to pass inspection with an unapproved repair.
4. Contact the truss manufacturer — they may provide a field repair detail if the cut is within their repair policy.

Safety risk: Attic loading, wind uplift, or snow loads could cause failure. Trusses are not like rafters — field modifications are not allowed without engineering.

Bottom line: Tell the contractor the framer’s fix is inadequate and unsafe. Get an engineer involved before inspection. If none available, reschedule and remove the unit temporarily.

Cite: IRC R802.3.1, IBC 2308.9, and truss design standards (TPI 1).

Stop work. Do not cover this up. The framer's fix is structurally invalid and will fail inspection.

Why it fails:

1. Trusses are engineered systems. Cutting the bottom chord and a web destroys the load path. The bottom chord is in tension; the web transfers shear. Sistering 2x6s alongside the cut ends does not restore tension continuity across the gap—it creates a hinge.
2. No load transfer. The sistered lumber bears on nothing at the cut. The truss cannot transfer ceiling/live loads across the opening without a properly engineered header/girder truss system carrying the load to bearing walls.
3. IRC §R802.10.4 / IBC §2303.4.5: Field modifications to trusses require a design by a registered design professional (RDP). The truss manufacturer’s engineer must approve the repair before work proceeds.

Immediate Action:

1. Call the truss manufacturer NOW. Send photos of the cuts. They will issue a sealed repair detail (likely involving plywood gussets, steel plates, or a site-built girder truss with proper bearing).
2. Do not let the framer "sister and cover." If they insulate/drywall over the hack fix, you own the liability for a potential ceiling collapse.
3. Inspection: Tell the inspector the truth: "Unauthorized truss alteration; engineer repair pending." They will red-tag the rough framing. That is the correct outcome.

Cost/Time: Expect $500–$1,500 for the engineering + 1–2 days for the repair detail. Cheaper than a lawsuit.