Aluminium Bifolding Doors Threshold Options

Our aluminium folding doors come with two different threshold options which are suitable for different applications. An ultra low threshold that is only 15mm high, and a standard threshold that provides improved weather peformance.

Our surveyor will be able to advise you on which option is most suitable for your application, however if you are purchasing aluminium folding doors as supply only, or you are currently building the opening the following information will be relevant to you.

When choosing a threshold for your aluminium folding door you need to consider:

• Weather peformance and exposure to wind and rain
• Internal floor height compared with external floor level
• Required stepover height (ie height of threshold above internal floor level)
• Door opening direction (open out vs open in)

The standard threshold provides improved weather performance over the ultra low threshold, however unless the folding doors are highly exposed to wind and rain then both options will be more than adequate for most situations. If your folding doors are highly exposed to wind and rain then the standard threshold would be more suited to that situation.

Both thresholds can be used with or without a cill. The ultra low threshold without a cill is suitable for situations where the internal floor level is similiar to the external floor level i.e. where you want to provide a seamless transition between the inside and outside.

However, in most situations the internal floor level is higher than the external floor level, so either the ultra low threshold or standard threshold sitting on top of a cill would be suitable. In approx 80% of all installations a standard threshold is chosen, as it provides better weather perforance and providing a proper survey is carried out the height of the threshold above the floor can be minimised accordinlgy.

The different threshold options are shown below and summarized in the following table:.

Ultra Low Threshold with cill

The ultra low threshold is 15mm high on top of a 25mm cill (making 40mm in total). The detail is the same whether the doors open inwards or outwards (apart from the sash profile being reversed). If the doors are open in then remember to leave enough height for a floormat if you plan to have one, or for uneven floor surfaces.

The internal floor level can be built upto the top of the threshold if desired, however it is normal for the threshold to sit 10-20mm above the internal floor level.

Ultra Low Threshold without cill

The ultra low threshold stands 15mm high. Either side of the threshold can be built upto this level to provide a seamless integration between the inside and outside space. However it is prudent to leave 10-20mm clearance to allow for uneven floor surfaces.

Standard Threshold Open Out (Panorama)

The inside height of a standard threshold (on an open out door) sits 60mm high on top of a 25mm cill (making 85mm in total). Although the internal floor can be built upto this level it is normal for the internal floor level to sit at least 20mm below the top of the threshold.

Providing careful measurements are taken a low 'stepover' can be achieved using a standard threshold by measuring the difference between the internal floor level and the bottom of the external cill.

Standard Threshold Open In (Panorama)

The inside height of a standard threshold (on an open in door) sits 30mm high on top of a 25mm cill (making 55mm in total). As the doors will open on the inside it is prudent to allow enough clearance for uneven floor surfaces (or for items such as floormats etc). Therefore the internal floor level should sit at least 20mm below the inside height of the threshold.