A door upstand is the structural support beneath a door, sliding door or floor-to-ceiling window.
Its purpose is to transfer the loads from the frame into the building structure while also forming part of the threshold and floor construction.
Where the upstand is located within the building’s insulation layer, its thermal performance becomes particularly important.
Why Is a Door Upstand Needed?
Large doors and glazed elements require a stable and durable support beneath the frame.
The upstand must:
- support the door or window frame
- transfer loads into the structural substrate
- maintain the correct threshold height
- integrate with the internal and external floor build-up
- allow the waterproofing and airtightness layers to be connected correctly
Traditionally, door upstands have often been formed using concrete, masonry, timber or other structural materials.
While these materials can provide structural support, some can create significant thermal bridges if they interrupt the insulation layer.
What Is an Insulated Door Upstand?
An insulated door upstand combines structural support with thermal insulation.
Its purpose is to support the door or window frame while reducing heat flow through the threshold connection.
This is particularly important where the frame is positioned within or close to the insulation layer of the building envelope.
A well-designed insulated upstand helps maintain continuity between:
Floor Insulation → Door Upstand → Door or Window Frame
This can significantly reduce thermal bridging at one of the most critical junctions in the building envelope.
Why Does Thermal Bridging Matter?
A thermal bridge occurs where a material with relatively high thermal conductivity creates a path through the insulation layer.
At a door threshold, this can result in:
- increased heat loss
- lower internal surface temperatures
- increased risk of surface condensation
- reduced overall thermal performance of the building envelope
The effect is especially relevant with large sliding doors, entrance doors and floor-to-ceiling glazing, where the threshold can extend over several metres.
How Does Triotherm+ Work as a Door Upstand?
Triotherm+ is a structural thermal insulation material designed to combine load transfer with low thermal conductivity.
The door or window frame is supported by the Triotherm+ upstand, which transfers the load into the structural substrate below.
At the same time, the material forms part of the insulation layer beneath the threshold.
This allows the structural and thermal requirements of the detail to be addressed with one system.
Where Are Insulated Door Upstands Used?
Typical applications include:
- entrance doors
- sliding doors
- lift-and-slide doors
- bi-fold doors
- floor-to-ceiling windows
- large glazed elements
The required upstand dimensions depend on the frame depth, floor build-up, threshold position, structural substrate and position of the building’s insulation layer.
The Complete Detail Matters
The performance of a door upstand cannot be considered in isolation.
The complete threshold detail includes:
Door or Window Frame → Support Points → Upstand → Structural Substrate
as well as the connections to:
- floor insulation
- waterproofing
- airtightness membranes
- radon barriers where required
- internal floor finishes
- external paving or drainage details
A successful installation therefore depends on both the structural load path and the continuity of the thermal and waterproofing layers.
The Important Point
A door upstand is more than simply a block beneath a door.
It is an important part of the structural, thermal and waterproofing design of the threshold connection.
Using an insulated structural upstand such as Triotherm+ allows the door or window frame to be supported while reducing thermal bridging and maintaining continuity with the building’s insulation layer.