How to Choose the Right Door Seal for Glass and Steel Doors

The Right Door Seal for Glass and Steel Doors

When a door fails to achieve the required acoustic, smoke or fire performance, the seal is often the first thing people look at. In reality, the seal is usually the last piece of a much bigger picture.

Door type, frame construction, threshold details, hardware, intended use and performance requirements all influence which sealing system will work best. A seal that performs perfectly on a steel door set may be entirely unsuitable for a glazed meeting room door. 

Equally, a product designed to maximise acoustic performance may not be the right answer where weather resistance or smoke control is the primary concern. That means selecting the right seal is less about finding the "best" product and more about understanding the problem you're trying to solve.

Start With the Performance Requirement

Before looking at individual products, it helps to ask a simple question, what is the door expected to do? In most projects, the answer falls into one or more of four categories:

• Improve acoustic performance
• Control smoke leakage 
• Maintain fire resistance 
• Reduce air leakage, draughts or weather ingress

Many doors need to satisfy several of these requirements simultaneously, which is why modern sealing systems often perform multiple functions. The key is identifying which performance requirement is driving the specification.

What Seal to Choose If Acoustic Performance Is the Priority

Acoustics is often the starting point for glazed door applications. Meeting rooms, executive offices, healthcare consultation rooms and educational facilities all rely on effective sound separation. In many cases, the weakest point in the assembly is not the glass itself but the gaps around it.

For hinged glass doors, drop seals can dramatically improve acoustic performance by sealing the threshold gap when the door closes. Systems such as the Schall-Ex GSH range are designed specifically for glazed door applications. They can be fitted without compromising the clean appearance that designers and clients expect from glass installations. Depending on the model selected, acoustic performance can reach up to 40dB. 

For existing installations, retrofit solutions such as the Schall-Ex GSA improve acoustic performance without replacing the door. This can be particularly useful in occupied buildings where disruption needs to be minimised. 

Steel doors present a slightly different challenge. Here, acoustic performance is often achieved through a combination of threshold and perimeter sealing. Products such as the NOR810 and NOR710 have been incorporated into tested assemblies delivering high levels of acoustic performance while also contributing to smoke control requirements. 

What to Choose If You're Working With Sliding Glass Doors

Sliding doors deserve their own category because they create challenges that simply don't exist with hinged doors. The very mechanism that allows the door to slide also creates larger leakage paths around the perimeter. So achieving meaningful acoustic performance requires a more comprehensive sealing strategy.

For threshold sealing, products such as the Schall-Ex Slide GS-H and GS-A ranges are specifically designed for sliding glass applications. These systems help reduce sound transmission while maintaining smooth door operation. Some configurations can achieve acoustic performance approaching 50dB. 

Where acoustic privacy is particularly important, a four-sided sealing system may be worth considering. The Universal M-12 system, for example, is designed to provide effective sealing against sound, smoke, draughts and odours while remaining largely concealed when the door is closed. 

What Seal to Choose If Smoke Control Is the Main Concern

Smoke often poses a greater risk to life safety than flames during the early stages of a fire. This is why controlling smoke movement through buildings remains a critical part of many fire strategies.
The challenge is that smoke exploits the same gaps that allow sound and draughts to pass.

For steel door sets, smoke control is commonly achieved through a combination of perimeter seals and threshold sealing systems. Products such as NOR810, NOR820 and NOR710 have been successfully incorporated into smoke-tested assemblies and can help restrict leakage around the door perimeter and threshold. 

The important point is that smoke performance should never be considered in isolation. The seal forms part of the wider door set assembly and should always be selected with the overall design and test evidence in mind.

What Seals to Choose If Fire Resistance Is Required

Fire-resisting door sets introduce another level of complexity. Unlike acoustic performance, which is immediately apparent to building occupants, fire performance may only be called upon during an emergency. Nevertheless, the requirements are often among the most demanding.

In these applications, intumescent seals remain a fundamental part of the solution. During a fire, they expand to help close gaps and maintain compartmentation. Norseal supplies both fire-only and combined fire-and-smoke intumescent seals suitable for incorporation within tested door set assemblies. These products are typically specified alongside other sealing systems rather than acting as standalone solutions. 

The lesson here is simple: fire performance is rarely delivered by a single product. It is achieved through the interaction of the entire door set.

What To Choose If Weather Performance Matters

External steel doors face a different set of demands. Air permeability, wind loading and driving rain can all affect the long-term performance of the installation. In these environments, standard acoustic seals may not provide the required level of protection. Specialist weather-rated drop seals can help address these challenges by improving resistance to air leakage and water penetration while maintaining acoustic performance. 

For manufacturers of external steel doors, these products often provide a way of satisfying multiple performance requirements without introducing unnecessary complexity.

Don't Forget the Perimeter Seals

One of the most common mistakes in door sealing is focusing exclusively on the threshold.
The gap beneath the door is important, but it is only part of the story. Perimeter seals frequently make a significant contribution to overall performance, particularly in acoustic and smoke control applications. Brush seals, transparent glass edge seals, and self-adhesive perimeter seals each have a role to play, depending on the door type and application. A high-performing door set is almost always the result of several sealing components working together rather than a single product doing all the work.

The Best Door Seal Is the One That Solves the Problem

It sounds obvious, but there is no universal seal suitable for every glass or steel door application. The correct choice depends on the door type, performance requirements, installation method and the wider door set design.

That is why manufacturers increasingly consider sealing strategies at the start of the design process rather than at the end. The earlier these decisions are made, the easier it becomes to balance acoustics, smoke control, fire resistance, accessibility and aesthetics.

Need Help Choosing the Right Door Seal?

Norseal supplies a wide range of sealing systems for glass and steel doors, including drop seals, perimeter seals, intumescent seals, threshold systems and specialist sliding door solutions.

Whether you're preparing for testing, developing a new door set or looking to improve performance on an existing installation, our technical team can help identify the most appropriate solution.

Get in touch with Norseal or download our Glass Door and Steel Door brochures for further guidance.

FAQS

Why does a glass door fail an acoustic test when the glass itself has a high acoustic rating?

The glass is rarely the problem. In many cases, sound passes through gaps around the perimeter and threshold rather than through the glass itself. Even small gaps can significantly reduce the overall acoustic performance of the door assembly.

Are drop seals always the best option for improving acoustic performance?

Not necessarily. Drop seals are often highly effective at addressing threshold gaps, but acoustic performance usually depends on a combination of threshold and perimeter sealing. The most successful installations typically treat the door as a complete system rather than relying on a single product.

Can sliding glass doors achieve the same acoustic performance as hinged doors?

They can achieve impressive levels of acoustic performance, but they require a different sealing strategy. Sliding doors create greater potential for leakage, which often means using specialist threshold, side, and head sealing systems to achieve the desired result.

What's the difference between a smoke seal and an intumescent seal?

A smoke seal helps restrict the passage of smoke under normal conditions and during the early stages of a fire. An intumescent seal remains dormant during everyday use but expands (intumesces) when exposed to heat, helping to maintain compartmentation during a fire.

How early should door seals be considered during door set design?

Ideally, from the outset. Decisions about threshold details, perimeter gaps and sealing systems can affect fire, smoke and acoustic performance, making them difficult to change once testing programmes have begun.

Why do meeting room glass doors still leak sound when they look fully sealed?

Visual and acoustic sealing are not the same thing. A glass partition may appear completely enclosed, but sound can still travel through relatively small gaps around the door. Effective sealing is often the difference between a room that feels private and one that doesn't.

Do external steel doors require different seals from internal doors?

Often, yes. External doors may need to address weather resistance, air permeability and wind loading in addition to fire, smoke and acoustic performance. This usually requires a different approach from an internal door set.