Threshold Options for Aluminium Casement Doors

A threshold is the part of the door that separates the outside from the inside, so when entering you would “cross the threshold”

Threshold seals are used to seal the gap between the bottom of the door and the floor.

Full frame threshold 

This means the bottom frame is same four sided door frame with the frame along the bottom. This option is the most weathertight and thermally efficient threshold possible as the door sits behind the frame on all four sides.  

Low frame threshold 

The bottom frame is a little bit lower than the full frame. The low frame threhsold provides more accessibility but the less weather performance than the full frame threshold. 

Low threshold 

A standard threshold with weather protection has the upstand, seals and gaskets so the base of your bifolds seals tightly against it. 

Low threshold is a wheelchair and pushcaire friendly, provides Part M compliancy. 

Flush threshold

Flush threshold provides step-free access as you move in and out of your home.

A brush or automatic bottom seal are used at the buttom frame. A drop seal is fitted to the bottom of a door  and drops down automatically when the door closes to form a firm seal

Weathertightness for threshold  

When specifying the threshold, you can take into account the following factors: 

  • Air permability  
  • Watertightness 
  • Resistence to wind load  
  • Thermal insulation 
  • Height 

Projecting Cill Options

Although it is possible to sit the door threshold directly onto the brickwork or concrete block, you can use projecting cill for drianage, aesthetics most installations will require a 150mm or 190mm projecting cill.  An 85mm stub cill is also available. All aluminium cills are 25mm high.

A minium cill projection should be specified to drain water away from the brickwork and on to the ground. If the water was to be allowed to drain on to the surface of the brickwork it can cause undesirable staining. Prolonged exposure to water can cause damage to the bricks themselves allowing this to enter into the interior of the building.


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