Visofold aluminium folding sliding doors can be supplied with a choice of two threshold options. The weathered threshold is designed for external bifold doors and will normally sit on top of a projecting cill. A low threshold is ideal for internal bifolding doors, such as between your house and conservatory as it is only 20mm high and if necessary can be sunk into the floor to provide a flush floor level.
The weathered threshold should always be specified for bi-folds that are being used as external doors whenever possible. The long leg(50mm)will face inside the building for doors that stack outwards and outside the building for doors that stack inwards. The most popular requirement is for folding doors that stack outwards to save space inside the room and it is usually possible to adjust your internal finished floor levels to achieve a minimum step over threshold. The aluminium cill is 25mm high so if this option is selected the height from underside of cill to the top of the threshold will be 75mm as shown below.
Projecting Cill Options
Although it is possible to sit your new folding sliding door threshold directly onto the brickwork most installations will require a 150mm or 190mm projecting cill. An 85mm stub cill is also available. All aluminium cills are 25mm high.
The low threshold can be used where your new bi fold door is being used as a room divider or for instance, between your house and conservatory. The threshold can be sunk into the floor to provide flush levels between the two floor areas. The image below shows the low threshold fitted with the optional wheel chair ramps.
Please note that whilst the low threshold can also be used in sheltered external applications it is not a weather-rated threshold as there is no rebate for the doors to seal against. When used externally the low threshold cannot be guaranteed to be fully draught proof and when fitted without a cill an external drainage gulley should also be installed to eliminate any build-up of rainwater.