Building components · Terminations
Threshold Upstand
Explains the one upstand in a building that is deliberately walked over, and why where the external waterproofing stops at that line is settled before the door is chosen.
Educational reference entry. What this element has to do, and whether any particular arrangement of it is adequate, depends on the whole assembly, the loading, the exposure, local requirements, the manufacturer's instructions and qualified professional design.
Overview
What a threshold upstand is
A threshold upstand is where the waterproofing of an external deck, balcony or terrace turns up and stops at a door opening. It is the same principle as any other upstand — carry the layer above the level water can reach, then close its top edge — applied at the one position in a building where people cross the line.
Every other upstand terminates where nothing passes. This one terminates at a line people cross, so the top edge that closes the layer is also a surface that is trodden on, and the two demands are answered by different parts of the arrangement. The published door threshold entries set out how the level-access conflict is resolved; what this entry adds is that the external waterproofing has to stop somewhere within that resolution, and where it stops is decided before the door is chosen.
Boundaries
How it differs from nearby elements
The distinctions that keep this entry from being a restatement of its neighbours.
- It is not the upstand in general. The published upstand entry describes waterproofing turned up against a parapet, a wall or a kerb, where nothing has to pass over the top of it and the only question is how it terminates. A threshold upstand is an upstand that is deliberately crossed, and being crossed is the entire source of its difficulty.
- It is not the door threshold. The published door threshold is the base of the opening itself — the trafficked junction beneath and around the frame, where wear, thermal continuity and level access are resolved. The threshold upstand is the termination of the external waterproofing that arrives there. They are two elements that have to be connected to one another, and the connection between them is where the arrangement usually succeeds or fails.
- It is not the external door threshold system. That system is the complete arrangement at an external door, taking in the frame, the threshold, the drainage in front of it, the insulation line through it and the waterproofing either side of it; the threshold upstand is one element within that arrangement, namely the height to which the external layer is carried before it is closed.
Terminology
Common names and aliases
These names describe the same element. The library keeps one entry per component so that a trade term or a regional name never becomes a second, thinner page.
- door upstand
- threshold kerb
- balcony door upstand
Dependencies
What it depends on
What has to be right elsewhere for this element to do its job.
- What happens to water immediately outside the door — whether it is intercepted, drained away or simply arrives at the opening.
- How the top of the upstand is terminated and closed so water cannot pass behind the layer at the very position where the layer stops.
- How it connects to the door frame and to the floor build-up inside, since the layer has to hand over to something on both sides.
- Whether level access is required, because that removes height as an option and transfers the whole problem onto drainage and shelter.
Considerations
Topics that genuinely apply here
Subjects worth discussing about this element. These are discussion topics, never measured values, ratings or performance claims.
This is the position where an external waterproofing plane terminates at a hole in the building, which makes it one of the few places where the layer's end and an opening coincide.
Water can be driven up a face as well as standing against it, so exposure, shelter and the way the surface outside behaves in wind all bear on a position that is judged by height alone.
The height available is set by finished floor levels decided long before, so the room to resolve the conflict is commonly fixed by the time the detail is drawn.
Drainage in front of a level threshold is what makes it work, and that drainage is a channel or grating at floor level where debris arrives and stays.
Materials
Commonly formed from
Material families this element is commonly realised in. This states common practice only — it is not a statement that any of these materials suits this component in a particular building, which depends on the whole assembly and on qualified review.
Assemblies
Building systems this element is met in
The role this component fills inside each assembly. A role describes what the element does there — it is not a statement that this component suits that system in any particular building.
Related elements
Neighbouring components
Typed relationships to other elements. There is deliberately no generic “related” category: an edge that cannot be classified does not exist.
Clarifications
Commonly misunderstood
- That a level threshold means the waterproofing can be level too. The layer still has to terminate somewhere above the water it may meet; a level entrance changes where and how that is achieved rather than removing the requirement.
- That sealant across the junction does the work of an upstand. A sealed joint fills a gap and has no second line behind it; an upstand keeps the layer above the water in the first place.
Conversations
Questions for qualified professionals
Questions worth asking someone with the project in front of them. This page cannot answer them.
- How is water intercepted and drained immediately outside this door?
- To what level is the external waterproofing carried, and how is its top edge terminated and closed?
- How does the external layer connect to the door frame and to the internal floor construction?
- If level access is required here, what is providing the water exclusion that height would otherwise provide?
Go deeper
Related Build Design Hub guides
Planning guidance behind the decisions this element involves.
Preparation
Related planning checklists
Owner-side preparation before the conversation where this element comes up.
What this entry does not do
- This entry describes a position and a conflict. It states no upstand height, no step, no channel size, no fall and no performance rating, and none can be inferred from it.
- Level access and water exclusion are both governed by local requirements and are reconciled by qualified professionals for a specific opening; nothing here determines what is permitted or sufficient anywhere.
Terminations & Weathering
The elements where a plane stops, turns up, sheds water or is deliberately interrupted — parapets, upstands, flashings, drips, weeps and movement joints.
Browse all terminations entries →