Recommended test
Generate a gable-ended Mansard with roof layers and inspect both pitches and the eaves.
- In Build, choose Gable, Truss and Mansard; keep Gable ends and Manual for the first inspection.
- Set the upper pitch, lower pitch and slope-break distance, then apply and generate with sheathing, battens and gutters.
- Hide the covering to inspect rectangular battens, pitch-break joints, square eave cuts and the flashing's gutter lip.
- Use Roof Control to adjust the outer bargeboard and Wall Control to change upper/lower siding together.
- Save and reopen, then verify the live settings and roof shape.
Choose the end shape
In Build > Gable > Roof Structure > Truss, select Mansard truss. The type card shows the broken-pitch outline. Choose the roof ends in the dialog:
| End choice | Shape and current calculation workflow |
|---|---|
| Gable ends (gambrel) | Two pitches on each side and upright gable ends. Manual or preliminary Automatic truss sizing. |
| Hipped ends — full Mansard | Two pitches on all four sides. Manual framing with a separate experimental whole-roof analysis. |
The gable-ended form is commonly called a gambrel roof. The app keeps Mansard as the truss type name; the end selector determines the complete building roof. A standalone Truss Builder definition describes the cross-section, not the full hipped assembly.
Set the pitches and break
The building’s main roof angle is the upper pitch. Set the steeper lower pitch separately; its initial value is 60°. Slope break from wall starts at 20% of the span and accepts whole millimetres between 10% and 40% of the span.
The drawing and generated members use both pitches. Check the knee-post positions, collar height, floor level and clear room before applying. Manual member controls remain under Advanced settings. The current Mansard calculation uses its tapered heel; the A/W full-depth heel option is a different model.
Preliminary Automatic sizing
For Gable ends, Automatic uses Code_Aster with separate members for all four rafters, alongside the attic floor, posts and collar. It retains both pitches, the break, CC and the selected common 36/48 mm thickness. C30 is the new-design default; C24 can be selected.
Review snow, floor loads and restraints, then calculate and review the result before applying. Changing either pitch or the break requires recalculation. The supported building case is a rectangular single-storey layout without dormers, porches or edited roof members.
This is a preliminary assessment. In particular, local snow accumulation at the slope breaks is not verified. The pilot does not reduce snow because a lower slope is steep. Connections, bracing, floor vibration, wind and the complete load path also require separate checks. Full hipped Mansard cannot use this planar result as approval.
Roof layers and eaves
Sheathing, counter battens, tile battens, covering and trim follow all four gable-ended roof slopes and meet at the pitch breaks. Tile battens retain rectangular 48 × 30 mm sections and the selected spacing. Counter battens, sheathing and covering end square to the eave slope. The first tile batten sits on the actual trimmed counter-batten ends.
Eaves flashing includes a folded lip into the gutter. Gable outriggers use rectangular 48 × 98 mm stock independently of truss chord depth, with soffits fitted underneath. Lower bargeboards sit inside the upper outer boards; their square eave ends cover the gutter ends by default.
Use the normal roof layer and drainage settings in Build. Hide covering or sheathing temporarily to inspect support and junctions, then restore it for the finished view.
Live adjustments
In Live Control > Roof Control > Outer Bargeboard, Height multiplier moves the outer layer and Length multiplier (eave end) adjusts the free eave ends. Pitch-break joints remain fitted and the boards retain their stock section. Large overrides can uncover the gutter.
Covering thickness and offset retain the broken-pitch geometry. In Wall Control, Simple Panel pattern, board width, strength and contrast apply to both the upper gable and the wall below. Their courses align without an extra outline along the join.
Save and reopen to retain the supported live settings. Older generated roofs need one regeneration to acquire the corrected eaves, siding and bargeboard controls. Save a project copy first if you need to preserve manual edits.