Hide Hinge Hardware (Concealed SOSS Hinges)
Concealed SOSS hinges hide their leaves and knuckles when a door is closed, but the fit depends on the exact hinge model and its current template. Check the door’s weight, frame, swing, clear opening, and any fire or accessibility rules before routing. Then install, adjust, and verify the door using the manufacturer’s instructions and local code.
If you want a clean door face without exposed hinge barrels, a SOSS hinge can be a good option. The hard part is not hiding the hardware; it is choosing a model that suits the door and machining both mortises in the right place and to the right depth.
I plan these installs from the door and frame outward. That means checking the opening’s purpose, the actual door weight, the hinge model’s published limits, and the required clearances before I pick up a router. A small layout error can keep a hinge from closing or leave a heavy door poorly supported.
Planning: Door, Frame, Rating, and Hinge-Model Selection
Definition: Planning means confirming that the door, frame, hinge model, and opening rules work together before cutting. SOSS models are not interchangeable: their dimensions and capacity vary. Use the current instructions and load table for the exact model you select, rather than relying on a general hinge count or a template from another model.
Start by recording the door’s height, width, thickness, material, and actual weight if available. Note whether it is solid, hollow-core, or built from a custom core, and check how the frame is built. A hinge needs sound material and secure fasteners at both sides; a thin jamb or a weak door edge may need suitable reinforcement.
Next, identify the hinge model using SOSS’s current published limits. Check the stated door size, weight, hinge count, spacing, and installation conditions. Do not treat a rating as a simple per-hinge figure, and do not assume that adding another hinge increases capacity in a straight line.
Make a short pre-cut checklist:
- Door dimensions, material, and weight
- Frame type and sound fastening locations
- Swing direction and nearby walls or trim
- Exact SOSS model and current template
- Required clear opening and any rating or access rules
If the opening is fire- or smoke-rated, stop before routing. The hinge must be permitted by the assembly’s listing and applicable code. A concealed hinge is not automatically suitable for a rated door, and field-routing a listed door or changing its hardware may affect the assembly’s compliance.
Access and Clearances: Swing, Reveal, Egress, and Accessibility
Definition: Clearances are the spaces a door needs to swing, close, latch, and provide its required passage. They include the reveal around the door and the clear opening when it is open. Check each against the door’s use and the rules that apply; no single reveal or opening dimension fits every project.
A reveal is the visible gap between the door and frame. A 1/8-inch reveal is a common design target, not a universal SOSS specification or code rule. Follow the selected hinge’s instructions and account for the door, frame, finish, and swing. Use a full-size template or mock-up to check the layout before routing.
Also check the door’s path. It must open without hitting a wall, trim, cabinet, or other obstruction, and it must close and latch as intended. Confirm the hinge orientation and swing from the manufacturer’s instructions; do not infer them from a photo of a different model.
Code checks depend on the project and adopted code edition:
| Opening type | Check before installation |
|---|---|
| Required egress door under the IRC | IRC R311.2 specifies at least 32 inches clear width and 78 inches clear height. Confirm the adopted edition and local amendments. |
| Egress door under the IBC | IBC 1010.1.1 generally calls for at least 32 inches of clear opening width. Height and exceptions depend on edition and occupancy. |
| Door covered by ADA Standards | Section 404.2.3 requires at least 32 inches clear width, measured with the door open 90 degrees. Also check maneuvering clearance under 404.2.4. |
Do not use the IRC height as a general IBC rule, or assume a door meets accessibility needs because it looks wide enough. Measure the actual opening in its required position and check the provisions that apply to your building.
Execution: Template, Mortising, Reinforcement, and Installation
Definition: Execution is the controlled transfer of the hinge layout to the door and frame, followed by routing, fastening, and fitting. The model-specific template sets the mortise location, size, depth, and clearances. Accurate work protects the door and frame while allowing the hinge to close through its full movement.
Mark the layout. Follow the current template for the exact SOSS model. Transfer its position to both the door and the frame, keeping the hinge orientation consistent. Check the layout against the planned swing and reveal. Do not use generic dimensions or estimate a mortise by eye.
Test before cutting. If the door is custom or the layout is unfamiliar, make a full-size mock-up or use the template to confirm the hinge’s position and movement. Check that the planned hinge locations fit the door and frame and do not conflict with trim, fasteners, or weak material.
Route the mortises. Secure the work so it cannot shift. Set the router and guide to match the manufacturer’s template and specified depth. Make controlled cuts, then test-fit the hinge. Avoid widening or deepening the mortise to “make it work”; an incorrect cut can weaken the edge or stop the hinge from closing correctly.
Check the fastener material. Keep screws in sound door and frame material. Use the specified fasteners and provide suitable framing or blocking where needed to support the load. Do not rely on a thin finish layer or unsupported edge to carry a heavy door.
Install and adjust. Fit the hinge and fasteners according to the manufacturer’s instructions. Hang the door carefully, then make only the adjustments the model allows. Close it slowly at first and watch for binding, uneven gaps, or contact with the frame.
Wear eye protection when routing, secure the work, and use dust control suited to the material. If the template, hinge, or frame does not sit as expected, pause and diagnose the cause before removing more wood. A clean, measured correction is safer than chasing the fit with repeated cuts.
Verification: Load, Operation, Clear Opening, and Rated-Assembly Compliance
Definition: Verification confirms that the installed door carries and moves as intended and still meets its opening requirements. It includes checking the hinge model’s conditions, the reveals, the latch, and the full swing. On rated or accessible openings, verify the rules and listing rather than relying on appearance alone.
Cycle the door through its full swing and check that it closes without rubbing, binds, or leaves an uneven reveal. Confirm that the latch works and that the hinge hardware remains secure. If the door sags, does not close, or feels unstable, stop using it until you identify the cause.
Compare the finished installation with the selected model’s published rating and installation conditions. The rating is specific to the model and stated setup. Do not assume the door is within limits because it opens once or because another project used the same number of hinges.
Where required, measure the clear opening with the door at 90 degrees. Check maneuvering clearances when ADA applies. For a fire- or smoke-rated opening, confirm that the complete assembly, including door, frame, hinge, fasteners, and installation, is allowed by its listing and applicable code. NFPA 80 may apply to fire door assemblies; follow the requirements adopted for the project.
Installation Scenarios: What to Check Before Cutting
Definition: These examples show how the same hinge can call for different checks on different doors. They are planning scenarios, not claims that one model or layout suits every project. In each case, the right next step is to compare the actual opening with the selected model’s instructions and applicable rules.
A custom interior cabinet-height door: I would first weigh the door and check the frame material, then select a model from its current load table. Before routing, I would use the supplied template on both parts and test the swing. A neat reveal is useful, but it cannot replace a correct mortise or sound fastening.
A required exit or accessible opening: I would begin with the opening rules, not the hinge. Check the adopted code, required clear width, and swing path. If ADA applies, measure at 90 degrees and review maneuvering clearance. If the door is rated, verify the assembly listing before changing its hardware or routing it.
Conclusion: Make the Fit Model-Specific
Definition: A dependable concealed-hinge installation starts with the correct model and ends with measured checks. Use the model’s current template and load table, protect the door’s structure, and confirm the opening’s use and rules. That process helps the hardware disappear without hiding a fit, support, or compliance problem.
Before cutting, confirm the door and frame, choose the exact hinge, and check the opening requirements. Route only from that model’s template, fasten into sound material, then test the swing and clear opening. For rated doors, verify compatibility before any field work.
Frequently Asked Questions
Definition: These short answers cover the most common questions about choosing, routing, and checking concealed SOSS hinges. Always compare the answer with the current instructions for your exact model and the codes adopted for your project, since neither hinge dimensions nor opening rules are universal.
Can I use one SOSS template for another model?
No. Use the current template for the exact model. Mortise size, depth, and location can differ.
Is a 1/8-inch reveal required?
No. It is a common design target, not a universal SOSS specification or code requirement.
How do I choose the hinge size?
Compare the door’s dimensions and weight with the exact model’s current load table and installation conditions.
Can I add hinges to increase capacity?
Do not assume capacity rises in direct proportion to hinge count. Follow the model’s published rating and placement guidance.
Can I install a concealed hinge on a fire door?
Only if the hinge and installation are permitted by the applicable assembly listing and code. Check before routing.
What clear width does an accessible door need under the ADA Standards?
Section 404.2.3 requires at least 32 inches, measured with the door open 90 degrees. Check maneuvering clearance too.
Does the IRC egress-door rule apply to every building?
No. IRC R311.2 applies where that code is adopted and relevant. IBC projects have separate, edition- and occupancy-dependent rules.
What should I do if the hinge will not close in its mortise?
Stop and check the model, orientation, template, and mortise depth. Do not remove more material until you find the cause.
Can a concealed hinge make a door meet egress or accessibility rules?
No. The hinge does not replace required clear width, height, maneuvering space, or other opening rules.
How do I check the finished installation?
Cycle the door through its full swing, inspect the reveal and latch, confirm secure fasteners, and measure any required clear opening.
(This article was written by one of our staff writers, Nathaniel Pierce. Visit our Meet the Team page.)
