Bifold door head flashing should connect the top of the opening to the wall's drainage plane in a layered, shingle-lapped path that moves incidental water down and out. The exact profile, membrane, sealant, and sequence must follow the door manufacturer's instructions and the project wall detail. Do not reduce the plan to “add caulk above the frame.” A sealant joint is one component; it is not a substitute for a coordinated drainage path.
Recent owner reports make the risk concrete. People describe water appearing at a door corner during heavy rain, recurring leaks after silicone repairs, and header leaks where a drip cap may be missing. Another homeowner widened a door opening and later discovered that the structural header did not clearly span the new width. These are different problems—water control, frame adjustment, and structure—but they meet at the same wide opening and must be assigned before installation.
The seven-step pre-install coordination guide
| Step | Decision to document | Evidence to keep |
|---|---|---|
| 1. Confirm the opening | Size, level, plumb, diagonals, header, sill, jambs, wall thickness | Survey, photos, structural documents |
| 2. Obtain system instructions | Frame type, flange or fin, head detail, anchors, tolerances | Current manufacturer installation document |
| 3. Identify the drainage plane | Housewrap, taped sheathing, liquid membrane, or other approved layer | Wall section and product data |
| 4. Define head flashing | Rigid drip cap or membrane, end conditions, slope, projection, sealant interfaces | Reviewed head section |
| 5. Lap the transitions | How head flashing connects over jamb flashing and under the drainage plane above | Sequence sketch and pre-cover photos |
| 6. Coordinate cladding | Clearances, trim, fasteners, end dams, drainage and drying gaps | Cladding detail and installer signoff |
| 7. Inspect and close | Hold points, sealant preparation, weeps, adjustment, controlled testing, warranty record | Checklist, photos, test record, closeout package |
1. Confirm both structure and geometry
A wide folding-door opening needs a verified structural opening and a frame-ready surface. Record width and height at multiple points, both diagonals, jamb plumb, head level, wall thickness, sill elevation, exterior paving, interior floor, and cladding thickness. Identify who verifies the final opening and who corrects work outside tolerance.
Do not ask the flashing assembly to solve structural movement. The header and supporting construction should be reviewed for the project before the frame is ordered or installed. Likewise, do not ask the door installer to infer hidden drainage layers after the cladding is complete.
2. Use the instructions for the exact door and wall
Obtain the current installation document for the selected frame configuration. A folding door may be finned, finless, recessed, face-drained, or paired with a proprietary sill and head profile. The wall may use mechanically fastened housewrap, taped exterior sheathing, a fluid-applied water-resistive barrier, masonry, stucco, or a rainscreen. Those conditions change the detail.
The active Senmit Bi-folding Window Door product page identifies a steel window-door product with glass, finish, and hardware information, but its catalog copy also lists the opening as “Pivot.” This article therefore does not claim a particular folding operation, head profile, drainage path, tested rating, or universal installation method for that listing. Confirm the exact requested configuration and its installation documents with Senmit before relying on the product title.
3. Locate the real drainage plane
The drainage plane is the wall layer intended to collect and direct water. It may sit directly behind the cladding or farther inward. Draw it continuously above, beside, and below the opening. Every flashing piece should return water to that plane or to the exterior without creating a hidden pocket.
The US Department of Energy's Building Science Education guidance for fully flashed openings calls for a properly lapped sequence: sill pan, unit, jamb flashing over the pan, head flashing over the jamb flashing, and integration with the drainage plane. It is a useful concept. Manufacturer instructions and project conditions still govern the exact materials and dimensions.
4. Define a head detail that sheds water
The head detail may combine a membrane and a rigid metal or formed flashing with a drip edge. Show slope, projection, upstand, end conditions, fasteners, seams, and how the top edge is terminated. Identify where sealant is required and where a gap must remain open to drain or dry.
The Building America guide to missing window and door flashing illustrates a metal head flashing that angles outward so water drops away from the trim rather than rolling back toward the opening. Treat that as water-management logic, not a one-size-fits-all profile.
5. Sequence the head, jambs, and wall layer in shingle fashion
Water should encounter upper layers that overlap lower layers. At the head, the drainage plane above generally needs to direct water over the head flashing, while the head flashing overlaps the jamb transitions below. Avoid reverse laps, unrolled tape, fish mouths, unsealed cuts, and fasteners through critical horizontal surfaces unless the approved detail addresses them.
Building Science Corporation's guidance on taped sheathing drainage planes documents a sequence in which jamb flashing precedes head flashing and the head transition is then terminated to the drainage plane. It also notes that awkward changes in plane can create wrinkles and bypasses. Plan those transitions before vertical furring or trim blocks prevent access.
6. Coordinate the cladding and trim
Show how siding, stucco, masonry, rainscreen furring, and trim meet the head flashing. Provide required clearance so the flashing can drain and be inspected. Do not bridge a drainage gap with mortar, foam, paint, or sealant because the finish looks incomplete. Confirm end dams or returns where wind-driven rain could move laterally.
Assign each trade. The door installer may set and seal the frame, the weather-barrier trade may integrate membranes, the sheet-metal trade may form a drip cap, and the cladding installer may complete the exterior. If no one owns the interfaces, every trade can finish its own work while leaving a discontinuity between them.
7. Inspect before cover-up and test deliberately
Use hold points after the opening is prepared, after membranes and head flashing are installed, after the frame is set, and before cladding hides the work. Photograph the entire head and both upper corners. Verify that designated drainage and weep paths remain open and that frame adjustment does not tear or compress the flashing.
If controlled water testing is required, follow the project protocol and begin only after the assemblies included in the test are complete. Water can travel from above or beside the apparent leak, so do not diagnose the source from the interior stain alone. Document weather, test location, duration, observations, and corrective work.
What to send before requesting a quote
Send the project location, opening survey, wall section, exterior and interior photos, desired panel configuration, finish and glass direction, drainage-plane type, cladding, sill elevation, structural status, and applicable performance requirements. Ask for the exact door configuration, installation instructions, included perimeter components, exclusions, and shop-drawing process. If the active product copy does not match your requested operation, resolve that discrepancy in writing.
Use the current product page to start a project conversation, then contact Senmit with the wall and opening information rather than relying on a generic flashing detail.
Bottom line
A dependable bifold door head detail connects structure, frame, flashing, drainage plane, and cladding in the right order. Confirm the opening, use the exact system instructions, identify the drainage plane, define the head flashing, lap transitions shingle-fashion, coordinate the cladding, and inspect before cover-up. Repeated surface caulking is not a substitute for that seven-step process.
All visuals in this article were generated for planning education. They are not Senmit product photographs, shop drawings, tested assemblies, installation instructions, or proof of code compliance.
