Bulkhead planning · Guide 1 of 5 · 6 min readUpdated
Measure and plan a basement bulkhead
Choose between a close-fitting enclosure, a continuous bulkhead or a lower ceiling area by weighing headroom, appearance, service access and finishing work.
Box only what needs boxing—or make the drop intentional
A close-fitting bulkhead preserves more full-height ceiling but can create steps and short corners around every change in a duct or beam. A longer, consistent run may use more material yet give the room a calmer ceiling line and a simpler finishing job. A lowered ceiling area can make sense where services are dense, at the cost of headroom across that whole area.
Start with the service envelope, required clearances and access, then choose the finished shape around it. Duct insulation, hangers, fittings and future maintenance need room too. A bulkhead beside a wall often needs only one exposed face; a run through the room usually has two. That difference affects both framing and drywall.
Example: a duct above the route into the room
Mark where people walk and where the bulkhead crosses the doorway. Compare a tight box with a continuous run along a nearby wall, using the proposed finished floor level for both. If clearance is poor, reconsider the room layout or have the service arrangement reviewed before hiding it inside a smaller-looking box.
Measure the complete obstruction
Choose Room & ceiling at the top of the planner to enter the overall room width, depth and Ceiling reference height. You can also select a wall directly on the plan. Measure ceiling height from the proposed finished floor to the underside of the structure supporting the enclosure. Include the planned floor buildup.
W · obstruction across and D · obstruction down describe everything inside the box: duct insulation, hangers, fittings, beams or pipework. Width goes across the run; drop goes vertically down from the ceiling. L · framing length follows the run. Measure several points and use an envelope containing the widest and lowest parts.
Enter the required side and bottom clearances separately. The example one-inch gaps are editable planning values, not equipment requirements. Keep access routes for valves, cleanouts, dampers and electrical junctions in the layout.
Match an irregular basement outline
In Room & ceiling, start with Rectangle, L-shaped, U-shaped, Angled or Wall recess. Overall width runs left to right on the drawing; room depth runs top to bottom. Changing these overall dimensions scales the outline while keeping bulkhead positions unchanged.
Drag numbered corners or enter their exact distances from the upper-left origin. Select a wall to enter its length; this moves its next corner along the current wall direction, so recheck the adjoining wall. Add corner on wall splits an edge for a jog or recess. You can use 3–24 corners; walls cannot cross or fold back on each other.
Apply room shape commits the outline; Cancel keeps the original. If a bulkhead now lies outside the perimeter, move it back inside using the plan or exact offsets. The room may have angled walls, while bulkhead runs follow the two plan axes. An angled bulkhead needs a separate field detail.
Choose how the run meets the room
| Mounting | What the planner encloses |
|---|---|
| Island · two exposed sides | Two side frames and an underside. The obstruction is centred between the faces. |
| Wall · top/left or bottom/right side | An outer frame and underside meeting a wall. Obstruction width is measured from that wall to the farthest obstruction edge. |
| Follow room · automatic | One face where a parallel wall meets the service envelope; two faces where that wall steps away. The whole run keeps one name and one service path. |
Support the enclosure from suitable building framing. A duct or pipe is not the bulkhead’s support.
When a duct passes a wall recess
A straight duct can sit beside a wall, cross the opening of a recess and meet the wall again. Keep that as one named run. Choose Follow room and align the service edge with the wall using the exact offsets or plan snapping. The planner marks wall, island and wall sections at the room corners, adding the second side only where the wall steps away.
Select a numbered section below the plan to compare its cross-section and finished width. The duct does not move sideways when the framing changes. The underside stays at the deepest assembly required by the run; any spare depth remains below the service. This is especially useful with underneath wood framing, where the wall ledger can require more depth than an island assembly.
Choose Adjust sections & transitions to retain the detected positions as editable starts. Each start is measured along the framing from the beginning of the run. Move a transition, add one, or choose Follow room, Wall or Island for an individual section. Reset to auto follows the room outline again. A forced wall condition without continuous matching wall contact produces a support warning.
Detection checks exact, parallel wall contact. A nearby or angled wall is not assumed to support the enclosure. Site measurements and a suitable connection detail still matter; the drawing does not verify the wall construction. Framing and bead remain section allowances, and transitions need backing and connection details before cutting.
Place straight runs in the room
Framing length is the length of the frame. Closing a start or far end adds one drywall thickness beyond that frame. At a closed end, the obstruction model stops short to leave room for the entered framing depth and side clearance; confirm the real service ends there.
For new runs, Left offset and Top offset locate the service envelope’s top/left edge across the run, and the finished start along it. Framing grows around this reference as support changes. Older project files keep their finished-box offsets until you change the support mode, which converts the reference without moving the service. Drag a run or use Exact position & direction. Snap offers 1-, 6- or 12-inch steps and room/service edge alignment; Off disables snapping. Arrow keys nudge the focused run; Shift uses one-inch steps. Rotate 90° switches the plan axes.
Add up to 12 named duct, beam or pipe runs. Select one on the plan or in the run list, then edit its measurements; Duplicate starts a copy in free space. Undo and Redo restore project edits. Runs may meet or cross, and the drywall allowance removes shared surfaces, including different drops. Framing and bead remain separate-run allowances: junction openings, connections and backing need a site detail before cutting.
Read the finished envelope
Finished width includes the side framing and side drywall. Finished drop includes the obstruction, bottom clearance, selected bottom framing and underside drywall. Clear below measures from the finished floor to the underside of that drywall.
Example: a 24-inch-wide obstruction dropping 10 inches, two wood 2×3 side frames, one-inch clearances, flush 1½-inch-deep crosspieces and ½-inch drywall produce a 32-inch finished width and 13-inch finished drop. From a 96-inch ceiling reference, the clear height is 83 inches, or 6 ft 11 in.
Clear below = ceiling reference height − finished bulkhead drop
Headroom is a dimension, not an automatic compliance check. Check the requirements for the actual room, route and project before fixing its height.
Read the plan and linked section together
Room plan opens first and keeps all runs visible. L is the whole finished run. For a run with changing sections, the plan labels its maximum width and numbers the sections. Select a section below the plan to see its actual finished width, framing, drop and clear height; the dashed line moves to that section. Focusing a dimension field highlights the corresponding drawing label. Obstruction inputs are smaller than the finished enclosure because framing, clearance and drywall are added.
Whole-room 3D shows all runs in the room outline. Click a bulkhead to select it, drag to orbit, and choose Fit room, From below or Selected run. Show framing & obstruction reveals the individual straight-run assemblies. Framing material, Bottom framing position, spacing and finish settings apply to every run; dimensions, location, clearances, mounting and end caps are individual.