June 10, 2021

Steel Glazing FAQ’s

Written by Rebecca Clayton

Banner Image of oversized steel framed glazing with a modern and minimal framing

Find the answers to our most asked questions about steel-framed glazing.


Steel glazing systems are extremely popular for achieving a modern industrial design, as well as preserving the original charm of more traditional properties. Glazing technologies have allowed us to engineer thermally broken steel frames, resulting in steel glazing systems that surpass modern performance requirements and achieve a comfortable internal living temperature.


Keep reading for our frequently asked questions on steel-framed glazing and discover how to incorporate these elegant systems into your glazing specification.


Contemporary rear extension with steel systems linking garden and home


What are the configuration options?


Steel glazing profiles are able to create a wide range of steel door openings including single doors, double doors, large patio door arrangements, pivot doors and bifolding doors. One of the most popular configurations for steel glazing is a bi-folding door, as the steel frames stack neatly to one side to reveal a completely open aperture and a casement door can be incorporated into the design as a traffic door.


Steel window possibilities including large steel-framed facades, slim framed fixed steel windows, side hung steel windows, top hung steel windows, vertical pivoting steel windows, horizontally pivoting steel windows and bifold steel windows. As the window frames are manufactured on a completely bespoke basis, a range of shapes and specialised designs can be achieved.




Arched steel windows with glazing bar designs


How does steel compare to aluminium glazing systems?


Steel is 3 times stronger than aluminium, which means it can offer slimmer sightlines on the outer frames. Although aluminium glazing offers extremely minimal sightlines, the frame parameter is concealed within the building finishes in these installations, so the outer frame is not visible. With steel glazing systems, the outer frame would be thinner due to the strength of the frame being able to support heavier glass. This can make steel more suitable for use in casement doors, where the entire frame will be visible.


Aluminium is typically more lightweight compared to steel and other window materials. Previously, steel was considered less thermally efficient due to the conductive properties of the metal, however, advances in modern glazing have allowed steel profiles to include a full thermal break. One of the advantages of specifying steel over aluminium is the truly traditional look, which can be replicated with aluminium but not exactly matched.


In some cases steel windows must be replaced with like for like windows, to meet listed building regulations. Both materials are known for their durability, with steel frames gradually changing in appearance over time for a rustic effect. Architects and specifiers may prefer the physical feel of steel glazing systems, which is heavier and therefore able to accommodate heavier glass units.



Steel framed glass box extension



Can you provide steel sliding systems?


No, steel is not the best material to engineer a sliding door system with due to its heavyweight properties. When clients are looking for a steel sliding door system, we recommend incorporating glazing bars into an aluminium framed design to create a steel look. Often, with the aluminium steel look systems, the difference is not visible to the naked eye. Glazing bar designs are completely flexible, to ensure the architect or specifier can create entirely unique designs.




What are the sightlines of steel glazing systems?


Our steel glazing systems have the slimmest sightlines of any thermally broken steel system on the market, from as little as 30mm for fixed frames. The steel bifolding door system has an impressive sightline of 42mm width across the connecting bifolding panes, whilst the meeting stile offers 56mm. The vent and frame sightline is 50mm, characterized by the slim sharp edged profiles. The slimmest possible sightline would be a steel system with fixed framing.




Rear facade design with steel double opening doors


What are the typical Uw values?


The steel glazing profiles we use are fully thermally broken, to ensure they achieve high levels of insulation when paired with insulated glass units. All Uw values are calculated on a project by project basis to offer accurate performance values, however, Uw values from 1.1-1.3W/m2K can be expected when specifying steel glazing systems. As a guide, you can achieve a Uw value of 1.1W/m2K when you use double glazing with Ug value 1.0 W/m2K.




What’s the difference between applied glazing bars and true glazing bars?


True glazing bars are part of the steel frame, with the glass panes fitted around them. This method of splitting the pane of glass to create smaller panes can result in reduced Uw values but is sometimes preferred for a traditional style. Applied glazing bars, also known as adhered glazing bars, are adhered to the glass pane after the glass is fitted to the frame, maintaining one glass pane. Where adhered glazing bars are specified, IQ Glass uses a dummy spacer bar to ensure the glazing bar looks like it is going all the way through the glass pane.



Steel framed doors and roof glazing in artistic studio home


Framing profiles – what is the uniformity between true glazing bars, adhered glazing bars and roof supports?

Depending on the desired finish, true and applied glazing bars can be specified in the same size. Whilst true glazing bars are less flexible in design, applied glazing bars can be adapted to match them if needed. Glass roof supports can be specified in the same steek finish and powder coated in the same RAL colour for a cohesive design, but the size and width of the steel supports will be dependent on the structure it needs to support. Where a uniform design is required, we can make adjustments and adaptations to achieve this.



How do the adhered and true glazing bars compare visually?


True glazing bars are typically thicker (35mm-60mm) depending on the glazing system used. Applied glazing bars are more flexible in design, as they can be adhered to the glass after installation, so whilst these are typically around 25mm they could be larger or smaller if needed.




Steel French doors with glazing bar designs and flush threshold


Does the finish on steel profiles change when exposed to the elements?


Depending on the chosen finish, the appearance of steel-framed glazing can change over time when exposed to the sun. Finishes such as architectural bronze and Corten will change, but these finishes are often specified when the desired aesthetic is ‘weathered steel’. Chemically blackened steel, which is often used for steel-framed internal glazing, will also change when exposed to the sun. If you’re looking for a finish that will not change, a galvanized steel frame PPC is the perfect choice as it is resistant to the effects of the suns UV rays.




How can I protect my steel-framed glazing from rust?


Although steel is more likely to rust than other metals, this can be prevented with the correct specification from a glazing expert. The base frame that IQ use is engineered from galvanized steel, which is then protected by a layer of zinc on the external face. The weak points are at the corners, where the profiles have been cut and welded together, and this can sometimes break the protective zinc covering. In these cases, IQ Glass uses a PPC to protect the frame. In harsher environments, we recommend stainless steel due to its hardwearing properties as a base material.



Highly glazed rear facade with steel glazing


What are the options for the threshold details?


Flush thresholds are a popular choice, as they create a seamless transition between indoor and outdoor spaces that allows the two to be merged when the systems are open. For external steel door systems that are hinged, IQ recommend a rebated threshold to create a weathertight seal that acts as a barrier against water and debris. Internal steel glazing does not require a threshold, whilst steel-framed window systems would have a normal windowsill.



How much extra is an architectural bronze finish on steel glazing systems?


As a guide for the cost of this specialist finish, IQ Glass recommend allowing an additional £2,000 per meter squared.



Slim framed steel windows



Can steel systems be used internally?


Yes, steel glazing can be specified as an internal glazing system. The system won’t be thermally broken when used internally as the performance requirements are different, but steel framed internal glazing is a great way to preserve historical or heritage buildings without obstructing the flow of natural light. Steel framed partitions or internal doors can be used to create a broken plan layout or separate zones within the home.


We hope you’ve found our steel glazing FAQ’s useful, but if you have any further questions before specifying steel systems please do get in touch with us at hello@iqglasssuk.com, where our technical team are on hand to answer any questions and assist with your glazing specification.