An opinion piece by Howard Moutrie, Accessible Building Solutions
A door threshold is the area of floor below a door. The term ‘threshold’ originates from times long gone when thresh (or straw) was used as a floor covering and a raised section of floor under the door was used to contain the thresh.
What is a threshold ramp? A threshold ramp is a small ramp at a doorway and is used to transition between differing floor levels in adjoining rooms, which may be a result of differing floor finishes or as a means of weatherproofing. The intent, from an accessibility point of view, is to remove a step which may be a trip hazard or an impediment to a person using a wheelchair or other mobility aid. AS 1428.1 provides the design requirements for an accessible threshold ramp.
AS 1428.1 does not provide any guidance on when a threshold ramp can be used, although it is assumed that they can be used at any doorway. However, the BCA Clause D3D16 (formerly D2.15) provides the following restrictions:
A ramp cannot be provided at any point closer to a doorway than the width of the door leaf unless:
- It is in a patient area of a Class 9a building and then the height is limited to 25mm
- It is in a resident use area of a Class 9c building and again the height is limited to 25mm
- In a building required to be accessible, the door opens to the outside and it is a threshold ramp or step ramp in accordance with AS 1428.1
The BCA for Class 1 and 2 buildings, under the Livable Housing Standard, not only allows for a threshold ramp at the entry door but also at internal doors. The maximum rise of the ramp is not stated, but it must be contained within the door jamb and have a gradient no steeper than 1:8, and on this basis it will not normally exceed 25mm in height.
In point C above, the BCA says that in a building required to be accessible you can have a threshold ramp complying with AS 1428.1, if the door opens to the outside. It also says that you can have a step ramp closer to the door than the width of the door leaf. The requirements for a step ramp in AS 1428.1 apply to a step ramp located anywhere and don’t say that a landing is required in front of the door. So, thinking about this, we go round in circles: the BCA is allowing a step ramp close to the doorway, but the building is required to be accessible. So a landing is required and the ramp cannot be close to the door, thus the original statement in the BCA cannot occur.
When certifiers started enforcing this BCA requirement, my first reaction was to go to the definition of a ramp. The BCA does not define ‘ramp’: a dictionary definition is a sloping surface joining two levels, which is not helpful as 1:100 would be deemed a ramp. So I returned to AS 1428.1 and concluded that a ramp was a sloping surface with a gradient steeper than 1:20 but no steeper than 1:8. I added to this a further definition, that it is a surface which you are required to traverse; that is, it is an accessway or pathway. On this basis, I concluded that a threshold ramp did not fall under the definition of a ramp as you did not travel up or down it (unless in a wheelchair). Therefore, I considered that a threshold ramp was not a ramp, and thus did not fall under the BCA Clause requiring a ramp to be further from a door than the width of the door leaf.
However, on further consideration, I decided that because subclause C refers to a threshold ramp in accordance with AS 1428.1, the BCA considers a threshold ramp to be a ‘ramp’. So, we are back to the situation that a threshold ramp can only be used on a doorway leading to the outside unless it is a doorway covered under the Livable Housing Standard (and limited to being located within the jamb) or it is in a Class 9a or 9c building and is limited to a height of 25mm. Going back to the definitions in AS 1428.1, a gradient of 1:40 is considered level for the purpose of a landing. If you used the dictionary definition of a ramp, this ‘level’ landing would be considered to be a ramp and would not be allowed. This clearly needs clarification in the BCA.
While discussing door thresholds, what about the floor track of a sliding door? This can apply to a level threshold where a drain is used to collect stormwater and to a ramped door track. As in the following examples:
Neither are mentioned in AS1428.1 and there have attempts to liken the situation to a grate, but that is not fair. A grate has a function to let water through to avoid flooding and the size of the holes can be dependent on the expected water flow rate – heavier rain or water flow, the larger the holes that are required. The design of the sliding door track also has functional requirements and they are not related to a grate. However, they both need to be accessible – that is, not impede a person using a wheelchair or the like, or a person who is ambulant and may be unsteady or use a cane for example. It should be noted that a grate can be anything in size from 100mm wide to 900mm or more. Sliding door track on the other hand is normally about 100mm though the current trend to use sets with multiple doors, the sliding door track can increase up to 400-500mm. The track is also influenced by whether the door is top hung or on bottom rollers. And, finally, they also have to comply with the relevant Standards for weather proofing, if they are external. The 2021 version of AS 1428.1 added requirements for timber decking as this too was not adequately addressed, and I would suggest that door tracks also be included in the next revision. Fortunately in recent years, sliding door manufacturers have gone a long way to making their track accessible.