Chances are you’ll come up against some unfamiliar technical terms when reading about bi-fold doors. A glance down our short jargon buster may be able to help.

Quick guide to jargon used.

Building control

All eligible structural building works must be inspected and approved (signed off) by building control inspectors to comply.

Building regulations

Statutory regulated standards required for building work. Building regulations approval is required for most building work in the UK

  • Part L: regulations relate to conserving fuel and power
  • Part M: regulations relate to ensuring ease of access within buildings
  • Part F: regulations relate to standards for ventilation and air quality

Door Sill

The part of the door frame sitting directly on the floor foundation. It is typically hidden underneath the threshold. In an external door, the sill acts as the rainwater run-off and weatherproofing.

Door Threshold

The metal covering across the foot of the doorway. In an internal door, a threshold may allow different floor levels to transition smoothly e.g. laminate to carpet. Higher thresholds provide greater weather protection.


A non profit Competent Person Scheme that helps homeowners to comply with Building Regulations when choosing and installing replacement glazing from a supplier.

Finish floor level

The actual final level of a floor including any floor covering present such as tiles, engineered wood/laminate or carpet. Important for considering transition through bi-fold door thresholds.

Solar control glass

Specially coated glazing that has the ability to reflect heat energy from the sun. Solar control glass helps to keep temperature in rooms with large areas of glazing comfortable in summer whilst reducing the need for blinds or air conditioning.