Bulkhead planning · Guide 2 of 5 · 4 min readUpdated
Flush vs. underneath bulkhead framing
Compare infill crosspieces with full-width underside battens, including the effect on cut lengths, wall ledgers and finished headroom.
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Choose where the bottom pieces sit
Under Framing & finish, set Framing material to Wood lumber, then choose Bottom framing position. Flush between sides fits the flat bottom pieces between the side frames, with the bottom faces aligned. Full-width underneath carries those pieces beneath the side ladders.
Both options use bottom crosspieces lying flat, 1½ inches deep. Wood presets describe actual 1½ × 1½, 1½ × 2½ or 1½ × 3½-inch stock. This option changes the assembly and cut list; it is not simply a change in the 3D colour.
Full-width underneath
Flush between sides
Check the crosspiece length
For two side frames, a flush crosspiece spans the clear distance between their inside faces. An underneath batten spans the outside frame width. With an outside frame width of 31 inches and 2½-inch-deep side frames, that is a 26-inch flush piece or a 31-inch full-width piece.
Along a wall, wood flush pieces fit between the wall ledger and outer frame. The ledger needs room of its own, so a very narrow enclosure can be invalid for the selected wood depth.
Flush crosspiece = outside frame width − 2 × framing depth Underneath batten = outside frame width
Understand when headroom changes
Across a room, both wood options use the same 1½-inch-deep bottom crosspiece below the entered obstruction clearance. Switching to flush makes the side ladders deeper and the crosspieces shorter; it does not gain headroom in that two-face model.
Along a wall, the underneath assembly stacks a 1½-inch ledger above a 1½-inch batten below the obstruction. Flush places them at the same bottom level. With unchanged obstruction and clearance inputs, the flush wall run is 1½ inches shallower.
The stock total can change even when finished drop stays the same. Longer vertical ladder pieces and shorter crosspieces affect how cuts share stock boards.
Verify the chosen detail before cutting
Use Section to check the clear space and 3D detail to see how the pieces meet. The planner spaces stations evenly at or below the selected maximum, so the displayed actual spacing may be less than 12, 16 or 24 inches.
Closed wood ends add top backing in flush mode and top plus lower backing in underneath mode. The modelled end crosspiece supplies the flush bottom edge. Connections, extra backing and attachment to the building require their own detail.
New plans start with flush wood framing. Older saved bulkhead files reopen with their original underneath assembly. Changing the option updates every run; download a separate project before comparing an alternative you want to keep.