Install Concealed Hinges for a Flush Door

A concealed hinge can make a carefully detailed door appear to float within its frame. That effect depends less on the hinge being hidden than on the accuracy behind it. To install concealed hinges well, the door, frame, hinge geometry and routing process must be considered as one coordinated detail - particularly where shadow gaps, flush linings and premium finishes leave no room for error.

For architects, contractors and homeowners, this is not simply a fitting task. It is a decision that affects the opening angle, handle position, door weight, architrave detail, fire performance and the long-term feel of the door. The following approach focuses on concealed hinges for internal timber doors, while highlighting where cabinet applications require a different specification.

Start with the door set, not the hinge

The first question is not how many hinges are needed. It is whether the proposed door set can accept the chosen hinge. Concealed architectural hinges are mortised into both the door edge and the frame or lining. Their body depth, leaf dimensions and pivot geometry all need adequate solid material around them.

Check the door construction before any cutting begins. A solid-core timber door will usually provide a reliable fixing ground, provided the hinge positions avoid joints, lippings or weak areas. Engineered and hollow-core doors need more care, as their internal construction may not support the routed pocket or fixing screws. Veneered, lacquered and painted doors also need protection during machining, since chipped edges are difficult to disguise on a high-specification finish.

Frame depth matters just as much. A slim lining may not offer enough material for the frame-side leaf, particularly when there is a concealed closer, intumescent detail or an unusually deep reveal. Where a flush door is set within a flush frame, establish the finished wall build-up early. A perfectly fitted door can still look wrong if plaster, panelling or skirting later restricts the intended opening.

For fire-rated, acoustic or security doors, only use a hinge and doorset arrangement that is tested and approved for that purpose. The hinge must be specified alongside the door leaf, frame, seals and closer, rather than selected for its appearance alone. A concealed hinge is not automatically suitable for every performance requirement.

Choose concealed hinges for the intended movement

Architectural concealed hinges and cabinet hinges share the same visual ambition, but they are not interchangeable. Cabinet hinges are generally cup-mounted and designed for lightweight doors, overlay arrangements and adjustment within furniture construction. Concealed door hinges are engineered to carry a full-size door leaf through repeated use, often while maintaining a precise flush alignment.

For internal doors, assess the leaf height, width, thickness and weight, then use the manufacturer’s load tables to establish hinge quantity and spacing. Three hinges may be appropriate for a modest internal door, but taller, heavier or frequently used doors often require four or more. Do not treat an additional hinge as an aesthetic compromise. It can reduce deflection, spread load through the frame and help maintain a consistent reveal over time.

Opening angle is equally important. Some concealed hinges allow a wide opening, while others are limited by their geometry or by the surrounding wall condition. A door opening into a narrow corridor, against a return wall or beside a projecting handle needs to be drawn and checked at full swing. A hinge that promises 180-degree opening is of little value if the lever handle strikes a wall at 110 degrees.

Finish should be coordinated across the visible hardware scheme. Although the hinge is hidden when the door is closed, it becomes visible when the leaf is open. A satin stainless steel hinge may suit a contemporary technical palette; a dark bronze or black finish can support a more considered, tonal interior. The hinge is a small detail, but it should not be the odd finish in an otherwise coordinated specification.

Set out before you rout

Concealed hinges demand repeatable set-out. Mark a hinge datum from the top and bottom of the door, then transfer the same positions to the frame. Avoid setting hinges too close to the door ends, where stresses are concentrated and the timber is more vulnerable to splitting. Follow the hinge manufacturer’s dimensional guidance rather than relying on traditional butt-hinge positions.

Before machining the finished components, make a trial installation in offcuts of the same thickness where possible. This is particularly worthwhile for a first installation, a new hinge model or a bespoke frame profile. It confirms router depth, template position, screw clearance and the relationship between door and frame before an expensive leaf is committed.

A routing jig or dedicated template is the right tool for this work. It keeps the pockets square, repeatable and accurately located. Freehand routing can produce a serviceable recess, but even a slight variation in depth or lateral position is amplified at the door face. On multiple-door schemes, CNC preparation offers excellent consistency, provided the final hinge schedule, handing and frame details have been signed off before production.

The hinge pocket should be clean, flat and only as deep as required. Over-routing weakens the fixing area and can create a hinge that sits too low, making adjustment unnecessarily difficult. Use a sharp cutter, control the router carefully and clear waste progressively. Where square corners are required, finish them with a sharp chisel rather than forcing the hinge into a rounded recess.

How to install concealed hinges accurately

Fit the hinges to the door leaf first, unless the hinge manufacturer states otherwise. Position each hinge in its routed pocket, check that it sits fully flush and pilot-drill all screw holes. Piloting is essential in hardwood, dense engineered timber and near door edges, where an unprepared screw can split the material or pull the hinge out of alignment.

Use the fixings supplied or specified for the hinge. Substituting screws may change the head profile, engagement depth or corrosion resistance. Tighten them firmly, but do not overdrive them: stripped threads in a concealed pocket are awkward to repair and can compromise load capacity.

With the frame-side leaves fitted, support the door at its designed threshold clearance and offer it into position. A door lifter, wedges and a second pair of hands make this stage safer and more controlled. Connect the hinge mechanism according to its design, then test the swing slowly before allowing the leaf to carry its full weight.

Most premium concealed hinges offer three-dimensional adjustment. The exact arrangement varies, but it usually allows adjustment for height, side-to-side position and depth. Work methodically. First establish an even head gap, then set the vertical reveals, then bring the door face flush with the frame. Adjusting every axis at once tends to chase the problem around the opening.

A consistent 2-3 mm reveal is common in contemporary internal door details, but the correct dimension depends on the door system, finish thickness and architectural intent. More important than the number is consistency. Check the gap with the door closed and open, from both sides, under normal lighting. A visually uneven shadow line is often more noticeable than a slightly larger but uniform one.

Details that protect the finished result

Concealed hinges work best when they are allowed to do their job without interference. Check handles, latch cases, magnetic keeps, door stops, seals and closing devices as a complete assembly. A concealed hinge cannot compensate for a door stop placed in the wrong location or a latch that pulls the leaf out of plane.

If the door has a concealed closer, coordinate its pocket and fixing positions with the hinge layout before machining. Similarly, timber movement should be anticipated in humid rooms, new-build conditions and properties without stable heating. A door set close to a bathroom may need an appropriate finish and sensible clearances to avoid binding as moisture levels change.

After final adjustment, operate the door repeatedly. Look for rubbing at the head or jamb, listen for a strained latch, and check that the door remains stable at different opening positions. Recheck the fixings after the first period of use, especially on heavy leaves. A hinge that has settled slightly is easier to correct early than after it has marked the frame or damaged the finish.

Common problems and their likely cause

A door that sits proud of the frame is often the result of shallow routing, an incorrect depth adjustment or a frame that is not plumb. A leaf that drops on the latch side may indicate insufficient hinge capacity, loose fixings or a lining that has moved. If the reveals change noticeably as the door opens, examine the frame for twist before blaming the hinge.

Binding at the hinge edge usually points to incorrect set-out, an overly tight reveal or a door that is not square. Avoid the temptation to plane the door immediately. First confirm that the hinges are fully seated, correctly adjusted and positioned in line. Removing material from a finished leaf may hide the symptom while making the visual detail worse.

For a single feature door, careful on-site routing can deliver an excellent result. For a development, hotel, office or whole-house scheme, the better route is usually coordinated specification and factory preparation. ITFITZ can support the hardware detail from the hinge selection through to the wider ironmongery schedule, helping ensure the door looks as resolved in use as it does on the drawing.