Window Shape Guide
Shutters for Circular, Oval and Porthole Windows
A round window is the one shape that defeats every off the shelf product. Blinds cannot follow it, curtains look absurd on it, and film is permanent. A templated shutter is the only covering that treats it as a feature rather than a problem.
Fixed sunburst or split circle: the one decision that matters
A fixed sunburst is a single ring carrying louvres that radiate outward from a small centre boss. It is the classic look, it is the cheaper of the two, and nothing moves. It suits a high gable porthole or a stairwell circle that nobody will ever reach.
A split circle is two half moon panels meeting on a vertical or horizontal centre line, each hinged into the ring so the window behind can be opened, cleaned and ventilated. It is the right build for a landing window, a bathroom porthole, or any circle within reach of a hand.
Why the template matters more here than anywhere
On a rectangular window a few millimetres out of square disappears behind the frame. On a circle it does not, because the eye reads a circle against itself. A ring built 6mm undersized on one axis produces a visible crescent gap that no amount of packing will hide.
So we scribe the actual opening on site rather than working from a diameter. Brick built circles in the chapel and barn conversions around Frodsham and Daresbury are frequently ovals by a centimetre, and the template picks that up where a tape measure does not.
Material and finish for round work
The ring is the structural part, and it either holds its curve or the whole panel fails. Our guidance by size:
- Under 600mm in engineered MDF or, in a bathroom, ABS. Light, stable, inexpensive.
- 600mm to 900mm in MDF for a fixed sunburst, hardwood if it is a split circle carrying hinges.
- Over 900mm in solid hardwood without exception, since the ring is now carrying real weight around a long unsupported curve.
Colour follows the same rule as the rest of the house: match the existing joinery rather than the wall, so the circle reads as part of the architecture.
Where these windows turn up locally
Three recurring sources on our patch. Converted chapels and lodges across mid Cheshire, where the original rose or oculus window is often the room's whole character. Gable end portholes on interwar semis in Orford, Appleton and Penketh, usually small and usually on a landing. And feature circles on newer estates around Chapelford and Saxon Park, generally large, high and best left as a fixed sunburst.
400mm
Minimum Diameter
Fixed sunburst or split circle
Two Builds
Scribed on site
Templating
8 to 10 weeks
Lead Time
Common questions
Answers before you call
Can a completely round window have shutters?
Yes. There are two builds: a fixed sunburst, where louvres radiate from the centre and stay put, or a split circle where two half moon panels hinge open on a circular frame. The split circle is the one to choose if you ever need to open the window.
What is the smallest circular window you can shutter?
Around 400mm diameter. Below that the frame and stiles eat so much of the glass that the window stops working as a window, and a frosted film or a fitted blind is the more honest recommendation.
Do circular shutters need hardwood?
Anything over about 900mm diameter, yes. The ring has to hold a true circle for decades and hardwood does that better than engineered board. Smaller portholes are fine in MDF or ABS.
How do you measure a round window?
We template it on site. A circle that looks round is often 5 to 10mm out between axes on older brickwork, so we scribe the actual opening rather than taking a single diameter.
Where do you fit these most often?
Barn and chapel conversions across mid Cheshire, gable end portholes on 1930s semis in Appleton and Orford, and landing feature windows on newer estates around Chapelford.
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