Updated August 2024 – We’ve now updated our astragal bar technology. Learn more about our new Integrated Conservation Bars and how they blend heritage aesthetics with high performance.
In the early days of window manufacturing, technology limited the size of individual glass panes. Glass was made by flattening blown globes, which created fragile sheets that could only reach around 0.3m². That’s barely enough to let in proper daylight.
To increase light without sacrificing structure, manufacturers built larger windows out of many small panes. These panes were separated by slim wooden glazing bars, often called Georgian bars, named after the era when they were most used.
Traditional glazing bars were solid timber sections. Joiners would mortise and tenon them into the window frame, then install individual panes using linseed oil putty. Bars were usually 20–30mm wide and shaped with decorative mouldings to soften the look.
As glassmaking advanced, windows evolved too. By the Victorian era, larger panes became available, and a single vertical glazing bar often replaced the older multi-pane look.
The introduction of double glazing created a challenge. Homeowners still wanted period-style aesthetics, but traditional glazing bars couldn’t support heavier, deeper modern glass units.
Several workarounds emerged:
Overbuilt timber bars: Some manufacturers enlarged the bars to hold double glazing. These can look overly bulky and lose the elegance of original Georgian profiles.
Dummy bars inside the glass: Mainly seen in uPVC windows, these bars sit between the panes. From a distance, they mimic the look but don’t hold up on close inspection and are unsuitable for heritage buildings.
Astragal bars: A modern solution. These mimic traditional bars using a warm-edge spacer inside the unit, aligned with timber mouldings bonded to the outside of both glass panes.
Astragal systems give the look of historic glazing bars without sacrificing energy efficiency. At Gowercroft, we bond a warm-edge spacer inside the unit and use specialist tape to apply timber-effect astragals on both sides.
We use Q-Wood (a durable timber composite) and a high-security, closed-pore glazing tape. This system is so reliable that we include it in our industry-leading 10-year guarantee. It offers:
Long-term performance
Slim sightlines
Reduced energy loss
Authentic Georgian and Victorian appearances
Compared to full pass-through glazing bars, astragals are more efficient, more affordable, and more visually accurate.
If you’d like to compare traditional bars, internal spacer-only options, and our modern astragal solution side by side, we’re happy to help. You can view samples, speak to our team, or request more technical details.
Contact us to arrange a visit or ask a question – we’d love to talk.