Recommended test
Compare two geometry choices without overwriting a saved library original.
- Create an attic truss and inspect clear width, collar height and the chosen heel detail.
- Switch between tapered and full-depth heel; confirm the roof lift and unchanged floor/bearing elevation.
- Save the definition, reload it and use Save as new for a changed variation.
- Fit a project copy to a different building in Build and confirm the original library dimensions remain.
Attic room and web layout
A-frame Manual geometry allows mirrored post pairs and a collar. The Automatic attic layout has a defined supported arrangement; additional or altered posts may need Manual modelling and a separate analysis.
Use clear width between the posts and height below the collar to check the usable room. Height is measured above the floor chord before finishes. Lattice attic floors sit on the upper girder chord. The requested room is not reduced automatically to pass sizing, and a short span/low pitch may simply leave insufficient height.
W-frame controls position the web joints along the chords. Changing an explicit joint position changes the calculation geometry and invalidates an existing result. Mansard uses its own two-pitch geometry; lattice attic adds actual floor diagonals and a second chord.
Thickness and depth
Automatic uses a common 36 or 48 mm timber thickness across ordinary planar truss members. The dimension visible in the truss plane is the member depth, which can differ between rafters, floor chord, posts and collar. Different depths do not mean that members must have different thicknesses.
The current catalogue reaches 223 mm depth for 36 mm stock and 298 mm for 48 mm stock. Confirm grade, section and lengths with the supplier. C30 is the new-design default, with C24 also selectable. Changing grade requires recalculation; it is more than a material-label edit.
Heel choices for A/W trusses
Tapered heel keeps the previous taper towards the outer wall face. Full depth over wall retains bottom-chord depth across the bearing and moves the tapered joint outside it. This raises the roof envelope; it does not lower the floor or move the wall-top bearing elevation.
Advanced details expose bearing width, projection and derived heel height. Check that the eave has room for the selected detail and its plumb cut. New designs start with a 100 mm plumb cut, while older saved values remain.
Full depth is not a general vertical-web raised-heel truss, and selecting it does not establish connection or bearing capacity. It can change the governing member check. The current Mansard pilot uses its separate tapered-heel model.
Library and project copies
Update changes a reusable library definition. Save as new preserves a separate variation. Include span, pitch and type in names to make designs easier to identify.
The library is browser-local. A definition stored there, the project copy selected in Build and already-generated CAD objects are separate. Save the .strek project to preserve its building settings and geometry; do not assume a browser library will appear on another computer.
Build normally fits a new project draft to its editable building geometry. For a saved source, Advanced settings can explicitly keep the saved dimensions. Applying a project copy does not overwrite the library original. Legacy saved-span locks and fitting choices remain available for saved designs; review inherited dimensions before generation.
Automatic assessments belong to the exact supported inputs. Scaling, changing CC, moving an explicitly selected bearing or editing loads does not renew the assessment. Recalculate, review, apply and regenerate. Manual geometry and existing placed objects remain unchanged until you deliberately replace them.