Norsound NOR400 Edge Fire-Rated Letterplate is a slim-profile, telescopic letterplate designed for installation within suitable fire-resisting timber doorsets.
The assembly combines a black plastic frame with finished metal flaps and concealed intumescent protection around the telescopic sleeve. This allows postal access through the door while helping protect the aperture under fire conditions.
The stocked range is available in four flap finishes:
The surrounding frame remains Black across all four variations.
Cutting a letterplate aperture through a fire door removes part of the tested door-leaf construction. An ordinary unprotected letterplate can therefore create a route for flames and hot gases through the door.
The NOR400 Edge incorporates an intumescent liner around the telescopic sleeve. When exposed to elevated temperatures, the intumescent material expands to help seal and protect the opening around the letterplate.
The product has been assessed for use within suitable timber-based doorsets requiring 30 or 60 minutes of fire integrity. The claimed performance belongs to the complete tested or assessed doorset rather than to the letterplate in isolation.
The NOR400 Edge has a lower faceplate height than the standard NOR400 letterplate.
Its approximate dimensions are:
The slimmer 68mm-high faceplate provides a more compact appearance while retaining an A4-compatible postal opening.
The required door cut-out is not the same as either the faceplate size or internal postal opening. The aperture must follow the current fitting template and doorset evidence.
The internal and external sections pass through the prepared door aperture and bolt together to create a telescopic assembly.
This construction:
Published product information identifies physical compatibility with suitable timber doors between approximately 40mm and 80mm thick. The accessible fire assessment assumes a minimum door-leaf thickness of 44mm, so the current evidence must be checked before relying on fire performance in a thinner door.
The assessed installation uses graphite-based intumescent material around the outside of the telescopic sleeve.
The liner must:
Any remaining voids around the letterplate aperture must be treated with the specified acrylic intumescent mastic where required by the approved installation detail.
The letterplate incorporates sprung flaps designed to open through approximately 180 degrees.
This allows each flap to move fully out of the way as letters and postal items pass through, helping reduce the likelihood of the flap being forced against a restricted stop.
After use, both flaps should return freely to their closed positions.
Published technical information identifies:
These test results relate to the tested product configuration. Routine inspection is still required to identify loose fixings, damaged flaps, corrosion or movement around the door aperture.
All variations are supplied with a fixed Black frame.
The NOR400 Edge must not be described as independently providing an FD30 or FD60 rating.
Fire performance depends on the complete arrangement, including:
The publicly available Warringtonfire assessment covering NOR400 Edge installations reached the end of its stated validity in November 2025. Obtain current evidence or confirmation of reappraisal before relying on it for a new certified project.
The NOR400 Edge is marketed as a fire-rated letterplate rather than an acoustic letterplate.
Do not assign it:
Where the door requires smoke or acoustic performance, verify that the complete doorset and letterplate arrangement have suitable supporting evidence.
Before ordering or installing, confirm:
| Product Name | Norsound NOR400 Edge Fire-Rated Letterplate |
| Product Reference | NOR400/EDGE |
| Product Type | Telescopic fire-rated door letterplate |
| Application | Suitable fire-resisting timber doorsets |
| Fixing | Bolted telescopic assembly |
| Frame Material | Plastic |
| Flap Material | Finished metal flaps |
| Frame Colour | Black |
| Overall Dimensions | Approximately 310 × 68mm |
| Internal Postal Opening | Approximately 278 × 44mm |
| Assessed Door Aperture | Nominally 264 × 48mm under the accessible Warringtonfire assessment |
| Published Door-Thickness Range | 40–80mm |
| Minimum Leaf Thickness in Accessible Fire Assessment | 44mm |
| Fire Performance | Suitable for supported 30- or 60-minute timber doorsets, subject to current evidence |
| Fire-Test Standard Referenced | BS 476-22 |
| Intumescent Protection | Graphite-based liner around the telescopic sleeve |
| Assessed Intumescent Arrangement | Two 2mm layers, providing approximately 4mm total thickness and a nominal 38mm width |
| Perimeter Treatment | Acrylic intumescent mastic within aperture voids and behind the mounting plates under the assessed arrangement |
| Maximum Installation Height | No higher than 1100mm from the threshold under the assessed arrangement |
| Flap Operation | Anti-snap flap opening through approximately 180 degrees |
| Postal Opening | A4-compatible |
| Durability | 20,000 operating cycles |
| Corrosion Resistance | Salt-spray tested to BS EN 1670 Class 5 |
| Standalone Fire Rating? | No — performance belongs to the complete tested or assessed doorset |
| Standalone Smoke Rating? | No separate cold-smoke classification should be assumed |
| Standalone Acoustic Rating? | No |
| Frame | Flap Finish | Product Code |
|---|---|---|
| Black | Silver Anodised | NOR400/EDGE/SA |
| Black | Polished Chrome | NOR400/EDGE/PC |
| Black | Polished Gold | NOR400/EDGE/PG |
| Black | Satin Silver | NOR400/EDGE/SS |
| Frame Options | Finish Options | Total Variations |
|---|---|---|
| Black | Silver Anodised, Polished Chrome, Polished Gold and Satin Silver | 4 |
The accessible Warringtonfire assessment includes the NOR400 Edge within its scope for suitable 30- and 60-minute timber doorsets.
That assessment states a validity date ending in November 2025. Before relying on the product for a current certified installation, obtain confirmation of:
Inspect the installed letterplate periodically for:
The NOR400 Edge must be installed in accordance with the current manufacturer instructions and the supporting evidence for the complete doorset.
Do not cut a letterplate opening into a certified fire door until the door manufacturer, certificate or assessment confirms that the product, aperture and proposed location are permitted.
Before beginning, confirm:
Check that:
Do not install a damaged or incomplete assembly.
Fit the supplied or specified graphite liner around the outside perimeter of the telescopic sleeve.
The accessible assessed construction uses two layers of 2mm graphite intumescent, giving an approximate total thickness of 4mm.
For the NOR400 Edge, the assessed liner is arranged in sections that overlap and abut at the corners. Follow the current fitting guide exactly for:
Do not omit, reduce or substitute the intumescent liner without supporting evidence.
Mark the letterplate position on the door in the location permitted by the doorset evidence.
Under the accessible assessed arrangement, the letterplate must be installed no higher than 1100mm from the threshold.
Check that the proposed aperture:
Use the current fitting template or confirmed doorset detail to determine the cut-out.
The accessible assessment identifies a nominal door aperture of 264 × 48mm for the NOR400 Edge, but this must be checked against the current product and doorset evidence before machining.
Do not use:
Cut the aperture using suitable equipment and produce clean, supported edges.
Remove all machining debris and loose door-core material.
The aperture should accommodate the protected telescopic sleeve without:
Under the assessed arrangement, any voids between the aperture and protected sleeve must be fully filled with a suitable acrylic intumescent mastic.
The rear faces of both mounting plates must also be bedded on the specified mastic.
Apply a continuous treatment without obstructing:
Insert the internal and external sections through the prepared aperture.
Check that:
Install the supplied through bolts and tighten them evenly.
Do not overtighten, as this may:
Remove only excess uncured mastic while retaining the continuous required seal behind the mounting plates and around the protected sleeve.
Do not substitute ordinary decorator’s caulk for the specified intumescent product.
Open and release both flaps several times.
Confirm that:
Verify that:
Inspect the NOR400 Edge as part of the fire-door inspection programme.
Replace or rectify the installation where there are:
The NOR400 Edge does not independently provide a fire-resistance period.
Performance depends on the complete doorset, approved aperture, graphite liner, intumescent mastic, through-bolted fixing and installation quality.
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