Recommended test
Create a truss, check its dimensions and reuse a project copy through Build's type selector.
- Open Truss Builder, choose a supported template and enter a known span, pitch and eave.
- Keep Manual for a geometry check; inspect heel positions, member intersections and room dimensions.
- Toggle Connector plates and confirm that their appearance is a visual placeholder.
- Save the definition, add a copy to the model and measure its span.
- In Build, choose Gable, Truss and the saved definition. Check building-fit settings before applying.
Choose a template
Open Truss from the main toolbar. Truss Builder provides these families:
| Type | Layout and workflow |
|---|---|
| W-frame | Triangular roof with W webs. Manual and preliminary Automatic sizing for the supported layout. |
| A-frame / attic | Clear central room, knee posts and collar. Manual and preliminary Automatic sizing for the supported attic layout. |
| Lattice loft | Attic layout with a deeper floor girder made from two chords and diagonals. Manual and preliminary Automatic. |
| Mansard | Steep lower and shallow upper rafters on each side. Manual and preliminary Automatic for the gable-ended cross-section. |
Build’s type selector also shows planned families as disabled cards. They cannot be generated by selecting the illustration. Full Mansard hipped ends are a separate building-level option; see full Mansard roofs.
Define the shape
Enter the span, roof angle and eave overhang. Review the bearing/heel detail when interpreting span; full-depth A/W heels place reactions at the declared bearing centres. Eave overhang is separate from span.
New trusses start with a 100 mm tail plumb cut, bounded by the available rafter depth. Saved definitions retain their existing cut. A/W types offer Tapered heel and Full depth over wall; the latter raises the roof while retaining the bottom chord over the bearing.
Attic room dimensions describe clear space between the knee posts and below the collar, before finishes. Lattice girder depth changes the floor level and remaining headroom. Mansard adds a lower pitch and a slope-break distance. Use the preview to inspect the actual members; type-card illustrations do not define calculated sections.
Manual or Automatic
Manual uses the sections you enter. Automatic checks combinations of supported sections while retaining the selected shape, CC and declared bearings. New designs use C30; C24 is available, and older saved designs keep their grade.
Automatic requires an available cloud calculation service or the paired Windows local calculation engine, load inputs and a supported layout. It is preliminary member sizing, not complete structural approval. Start with the automatic sizing guide for snow, floor loads, restraint assumptions, candidate counts and result review. A Manual W-frame can also use the separate read-only analysis panel.
Add, save or use in Build
Add the current truss to the model or save a reusable definition. Measure the placed result and inspect its orientation. Library entries and already-placed geometry are separate: updating a definition does not reshape earlier objects.
In Build > Gable > Roof Structure > Truss, choose a type card or open Saved trusses. New project drafts inherit the editable preview’s span, pitch and overhang and the building’s CC. Advanced settings can explicitly retain a saved definition’s dimensions instead.
Choose Manual or Automatic, review the draft and Apply to building. Use Edit beside the selected type to return. Automatic attic and large-section results require review before application. The library original stays unchanged. Advanced settings > Edit in Truss Builder opens the detailed editor.
Generate the building to update the actual roof and cutlist. Changes to geometry, loads, CC or declared supports require a fresh Automatic assessment. Existing saved geometry is retained on load until you replace or regenerate it.
Connector plates
Connector plates toggles compact plates at supported joints. Plates are included with the truss assembly when selecting, moving or copying it. Unsupported joints or incompatible member thicknesses can remain unplated; cutting an eligible dormer opening removes plates at affected joints.
These are visual placeholders. Plate size, fasteners, joint slip and connection capacity are not calculated from their appearance. A passing member-sizing result does not approve these connections or the required bracing.