Start from the section

The fastest way to understand a steel door is to look at the leaf in section: a steel skin outside, another inside, an internal frame between them, and a filler in its voids. Those elements, plus the formed steel frame that carries the leaf, determine how the door behaves. The rest is hardware and finish.

What separates a steel door from a timber or aluminium one is not simply that it is steel. A hollow steel leaf performs worse acoustically than a filled timber one. Performance comes from how the materials are arranged, not from the material name.

The skins

Leaf skins commonly use cold-rolled sheet in the 0.8–1.2 mm range. Gauge decides how the face answers impact, and below 0.8 mm the first hard contact dents permanently. Gauge alone is not a quality measure, though: the folds around the leaf edge contribute as much to stiffness.

Flatness is a separate matter. Raking light makes slight waves visible, which shows most on plain matt surfaces. On patterned leaves the light scatters in the relief and small irregularities disappear.

The core

  • Polyurethane foam: fills the void completely, helps the leaf behave as one piece, and performs well thermally.
  • Mineral wool: favoured for acoustics and where fire resistance is required, since it holds form at high temperature.
  • Honeycomb board: cheap and light, but it answers a knock like a drum. Not a choice for an external door with acoustic or thermal expectations.

Whatever the core, it must be bonded to the internal frame. A core that settles leaves a cavity at the bottom of the leaf, and that cavity passes both sound and heat.

The frame is the part that moves

The frame transfers leaf weight to the wall through the hinges, receives the lock bolts and closes the gap to the wall. Most door problems originate here rather than in the leaf, because the leaf stays as it was built while the frame is attached to the building and moves with it.

Frame depth follows wall thickness: a standard depth for apartments, 20–24 cm adjustable for entrance and villa doors. The frame is anchored at several points per side — foam insulates, it does not carry load. For export, send wall thickness and material, since build-ups differ by country.

Hardware

Lock case, cylinder, lever, escutcheon, hinges and gasket. For security, the decisive factor is not the badge on the cylinder but the configuration: how many directions the bolts throw, how deep they enter the frame, whether the keep plates are reinforced, and whether there are security pins on the hinge side. Multi-point systems pull the leaf into the frame on three edges, spreading load and compressing the gasket evenly.

The surface

Bare steel is never left exposed. PVC membrane is vacuum pressed onto the leaf and follows laser-cut relief. Laminate and ultralam surfaces give a firmer feel and better scratch resistance. Digital print produces realistic stone and timber veining. Powder coating suits single-colour matt specifications. This is a maintenance decision as much as an aesthetic one: textured matt surfaces hide fingerprints and hairline scratches, gloss flat surfaces display both. Colour ranges share the same standard sizes, so the choice imposes no dimensional constraint — the real difference between black steel doors and pale ranges shows up in surface behaviour.

What a steel door does not solve

Honestly, it does not fix everything. Acoustic performance depends on the gap under the leaf as much as on the leaf and gasket; a perfect leaf still passes sound underneath it. Thermal performance depends equally on the packing around the frame. Fire resistance is a different product altogether — a standard apartment door cannot stand in for a fire door, and our fire doors are built with different cores, seals and closers.

Standard sizes are fixed: 90 × 200 cm clear and about 108 × 210 cm overall for apartments; 145 × 215 cm clear and about 165 × 223 cm overall for building entrance and villa doors. Outside those figures the door is made to measure. Send your opening dimensions in centimetres and the application, and we will confirm the right construction and quote it, shipping from Istanbul.