What is it?
The door leaf itself, the moving panel that opens and closes within the door frame, here formed with a metal (typically aluminium or steel) construction rather than timber or uPVC.
What does it do?
The door leaf provides the openable, closeable barrier at the opening: security, weather resistance, and thermal and acoustic separation between inside and outside, while still allowing access through. Metal door leaves are usually built as an insulated panel (an outer and inner metal skin either side of a thermal core) rather than solid metal, so the door itself doesn't become a weak point in the thermal envelope of the wall.
Where is it used?
External door openings where durability, security, or a specific appearance (slim sightlines, large glazed areas) favours a metal system over timber or uPVC. Commonly on commercial buildings and increasingly on higher-spec residential ones.
Types
Metal doors are broadly either aluminium (lighter, good corrosion resistance, the common choice for slim-framed glazed doors) or steel (heavier, higher security, often used where robustness matters more than sightlines).
How to specify
A metal door is specified as part of a complete door set with its frame, since the two are engineered together for weather performance, security, and thermal performance (expressed as a U-value). Hardware (hinges, locking, and any door closer) and glazing (if the design includes glazed panels) are specified alongside it, along with the required security rating where relevant.
Other considerations
Metal conducts heat far more readily than timber, so an insulated core and a thermally broken frame (where the inner and outer metal sections are separated by an insulating strip) are what stop the door itself undermining the wall's thermal performance around it.
Interacting elements
- EPDM: a synthetic rubbery membrane that is adhered to the door frame and structural opening to prevent wind and rain from passing through the gaps in the opening.
- Weathering strip: the door leaf cannot truly touch the floor as the floor is slightly uneven and the leaf would catch on the floor. A weathering strip forms a slight upstand to prevent surface water from being able to pass under the door leaf (door threshold)