Arched transoms, circle-top windows, eyebrow windows, trapezoids and other custom shapes give a building its character. They are also some of the hardest openings to protect from hurricanes. Standard rectangular panels do not fit, roll-down shutters cannot follow a curve, and improvised plywood often leaves gaps exactly where debris can get through. This article explains the challenges and the options.
Why Shaped Windows Are Difficult
Most shutter systems are designed around rectangles. Tracks run in straight lines, panels come in standard widths, and roll-down curtains move vertically. When a window has a curved or angled top, there are three common shortcuts, and each has problems:
- Covering a larger rectangle. A rectangular shutter mounted over the whole area hides the shape of the window and can look heavy on the facade. It may also need to be anchored to parts of the wall that are not designed to take the load.
- Protecting only the rectangular part. Leaving the arched transom unprotected defeats the purpose; a broken transom lets wind and rain in just as easily as a broken main window.
- Cutting panels to approximate the shape. Field-cut panels may not match any tested configuration, leaving gaps and uncertain performance.
Shaped windows are often the most prominent feature of a facade, such as a front entry, a stairwell window or a church window, so a poor solution is also highly visible.
Common Window Shapes and Their Challenges
Half-round and circle-top windows
A half-round transom over a rectangular window or door needs protection that follows the curve and connects securely to the protection below it. The curved edge must be anchored at regular intervals to resist both impact and suction.
Eyebrow and elliptical arches
Flatter arches have long, gentle curves, which makes it harder to hide the edges of a shutter and to keep consistent spacing from the glass.
Trapezoids, triangles and gable windows
Angled tops are common in vaulted rooms and gable ends. They are often high on the wall, which makes removable protection especially difficult.
Skylights and sloped glazing
Skylights face the sky rather than the wind, but they can still be struck by falling debris and are hard to reach. Protection must be fixed in place and designed for the slope.
Large arched storefronts and church windows
Commercial and institutional buildings may have tall arched openings, sometimes with decorative tracery. These usually need custom engineering for both impact and wind pressure.
Options for Protecting Shaped Openings
Impact-resistant glass can be manufactured in many shapes, but replacing windows is expensive and may not be acceptable on historic buildings.
Accordion and roll-down shutters generally work only on rectangular openings, so shaped tops usually need a separate solution.
Removable panels can be cut to shape, but they must be stored, organized and installed before every storm, often on high windows.
Custom fabricated barriers are built to match each opening exactly and mounted permanently or on hinges, so the window is protected without changing its shape. Exeter developed STORM SHIELD to provide aesthetically pleasing in-place protection for circle top, arch top and custom shaped windows and skylights. Because the perforated InvisiPerf™ barrier is see-thru, the shape of the window remains visible from both inside and outside. See examples in the product selection guide and the commercial gallery.
How to Plan a Project With Shaped Windows
- Photograph and measure each opening. Record overall width and height, the rise of the arch (the height from the springline to the top of the curve), and any mullions or trim.
- Make a template for complex shapes. For irregular curves, a paper or cardboard template traced on site is the most reliable way to capture the shape.
- Check the mounting surface. Decide whether the barrier will be face mounted on the wall around the opening or inset mounted in the reveal. Arched masonry openings often have deep reveals that suit inset mounting. See mounting options.
- Confirm clearance from the glass. The barrier must stay far enough from the glass that it does not strike the window when it flexes under impact.
- Coordinate with the protection below. Where a transom sits above a door or window, plan how the two barriers meet so there is no gap.
- Verify approvals and engineering. Custom shapes still need to meet the impact and pressure requirements for the location; confirm how the manufacturer's approvals cover shaped units.
Questions to Ask a Supplier About Shaped Windows
- Do you fabricate barriers to the exact shape of the opening, or only in rectangles?
- How is the curved or angled edge anchored, and how many fasteners are used along it?
- How do the transom barrier and the barrier below it connect?
- What minimum distance from the glass does your system require, and can it be met in my window reveal?
- Will the barrier need to be removed for cleaning, or can it open on hinges?
- Can the finish color match my window frames or trim?
Clear answers to these questions help you compare proposals on more than price. A barrier that fits poorly or leaves gaps will not protect the opening, no matter how strong the panel is.
Appearance Matters
Owners invest in arched and shaped windows because of how they look. Protection that hides or distorts them undermines that investment, and homeowner associations and historic review boards may reject designs that change the character of the facade. See-thru barriers that follow the window shape and use narrow frames tend to be the least intrusive option. Read more in hurricane shutters for historic buildings.
Conclusion
Arched, circle-top and custom-shaped windows should not be the weak link in a building's hurricane protection. Rather than covering them with oversized rectangles or leaving the top unprotected, choose protection that is fabricated to match each opening, mounted securely, and approved for the loads at your site. Custom see-thru barriers protect the window while keeping its shape and view intact. To discuss shaped openings on your project, request a quote and include photos and measurements.