Bulkhead planning · Guide 2 of 5 · 3 min readUpdated
Flush vs. underneath bulkhead framing
Compare flush and underneath bulkhead framing by fastening access, piece lengths and finished depth, including when flush framing really saves headroom.
Choose the connection and finished depth together
Flush crosspieces fit between the side assemblies, with their bottom faces aligned. This can be useful when you want the underside within that depth and can make the required end connections. It asks for controlled inside measurements and a workable fixing detail at each end.
Full-width pieces underneath can be convenient when side ladders are already established and there is useful access from below. They cross beneath the side assemblies, so check what that stacks below the obstruction. A straight finished underside is possible with either method. Choose for the actual connection, access and depth—not because one arrangement is always stronger or shallower.
Example: a wall-side bulkhead with tight headroom
In this planner’s wood wall-side assembly, flush framing puts the ledger and flat crosspiece at the same bottom level instead of stacking them; that saves 1½ inches. Across a room, the two wood versions have the same finished drop for the same inputs. The steel versions also retain the same drop. Compare the section for your mounting condition before expecting a headroom gain.
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 the linked typical section to check the clear space. In Whole-room 3D, turn on Show framing & obstruction and choose Selected run to see how its 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. Version 1 bulkhead files reopen with their original underneath assembly; later files retain their saved framing choice. Changing the option updates every run; download a separate project before comparing an alternative you want to keep.