Overview
The slab of a composite door is essentially airtight - 44mm timber core, polyurethane foam and GRP skin. Any draught is coming from the perimeter seal, the threshold, or a hardware opening (letterplate, cylinder gap).
Symptoms
- Draught felt when standing near the door.
- Curtains moving in a closed room.
Common causes
- Perimeter seal.
- Threshold seal.
- Letterplate brush.
- Cylinder not flush.
When to call a professional
- Seal replacement.
Prevention
- Silicone-treat seals annually.