Octagon Window Replacement — Round and Eight-Sided Accent Windows
The octagon on the stair landing or the round window in the gable has fogged, gone soft along the bottom, or left a stain on the wall below it.
Reply within one business day. Or call / text 763-204-2099.
Octagon window replacement means measuring the eight-sided or round accent window, ordering a new unit made to that shape, removing the old one, and flashing each side of the octagon or the full circle before trimming inside and out. JMB Builders replaces octagon and round windows across the Twin Cities metro, alone or with other windows. Priced per opening. Send photos and we reply within one business day, or book a free in-home estimate.
- Priced per opening, window supplied
- Unit made to the shape, lead time on quote
- Each side flashed, trim cut to the angles
Octagons and circles are accent windows: on a stair landing, in a bathroom, in a gable end, beside a front door or over a tub. Most are small fixed glass, so they get ignored until the glass fogs, the frame softens along the lower sides, or a stain shows up on the wall under it. They are often the last original window in a house where the rest were replaced.
A shaped window is made to order, not taken off a shelf. Per the makers' lineups, Andersen lists specialty shapes in the 100 and 400 Series and custom shapes in the A-Series and E-Series, and Andersen is stocked at Minnesota ABC Supply branches. Pella 250 Series and ProVia Endure list shaped units too; for those we confirm the line with our ABC branch before the quote is final. Shaped units usually take longer to arrive. The lead time depends on the brand and is written on the quote.
An octagon has eight joints to flash and a circle has a curve that flat tape will not lie on, so flashing is the part that matters. Each side of an octagon gets tape lapped so upper pieces lay over lower ones; a circle gets tape that stretches to follow the curve. Outside, trim is PVC cut to the angles or aluminum bent to the shape. Inside, an octagon gets eight mitered pieces of casing and a circle gets a drywall return or curved trim.
Get a written quote for this job
Three photos and a sentence is enough: a reply within one business day, or ask for a free in-home estimate. Or text the photos to 763-204-2099.
What you supply
- A straight-on photo of the window inside and out, plus one with a tape across it
- Where it is: gable, stair landing, bathroom, beside a door
- Glass choice: clear, obscure for a bathroom, or tempered where the location calls for it
- Frame color, usually matched to the windows around it
What JMB supplies
- In-person measure of the shape, with a template if the opening is irregular
- The new octagon or round unit, ordered to that shape
- Removal and haul-away of the old unit
- Flashing tape lapped side by side, or stretched around a circle
- Exterior PVC trim or aluminum capping cut to the shape
- Interior casing mitered to eight sides, or a drywall return on a circle
- Ladders or staging for gable and stair-landing windows
- Painting quoted as a separate line
How it is priced: per opening
Quoted in writing from your photos, with a reply within one business day. What moves the number:
- Shape: octagon, full circle, oval or another custom shape
- Size, and which brand and line can build it
- Height: a gable or stairwell window needs ladders or staging
- Glass: clear, obscure, or tempered where required
- Exterior finish: PVC trim cut to the angles or aluminum capping
- Interior: eight-piece casing, curved trim or drywall return
- Replaced alone or in the same order as other windows
Send a straight-on photo with a tape held across the widest point, and one showing how high the window is off the ground.
How long it takes
One octagon or round window: about half a day to a day once it arrives. Shaped units take longer to arrive than standard windows, and the old one stays in until then.
How your project works
- 1
Send photos, get a written quote
Send three photos of the space and a sentence about what you want. You get a clear, itemized reply within one business day. Prefer a look in person? A free in-home estimate is always an option.
- 2
Pick materials, or bring your own
We help you choose profiles and materials that fit the house and the budget, or match your existing millwork exactly — or you buy the door or trim yourself and we install it. Everything is confirmed before the crew is scheduled.
- 3
Clean, precise installation
The crew shows up on time, protects floors and furniture, and installs with tight joints and consistent reveals. Photos of the finished work go in your job folder.
- 4
Walkthrough and invoice
We walk the finished work with you. If anything is not right, we fix it before we call the job done. Then one invoice, paid by check or direct deposit — no card fees, no payment links.
Situations and options
Octagon
Eight equal sides, usually fixed, often in a stairwell, bathroom or beside an entry. Each side is its own flashing joint and its own piece of casing.
Full circle
A round window, sometimes called a bullseye or oculus, in a gable or over an entry. Flashed with stretch tape around the curve; inside it gets a drywall return or curved trim.
Change the shape
Swap an octagon for a small square casement or awning that opens. The opening is reframed and siding and drywall are patched, so it is quoted as more than a window swap.
With the rest of the house
Ordered with your other windows so frame color and glass match: one measure, one order, one line per opening on the quote.
Octagon Window Replacement — Round and Eight-Sided Accent Windows: questions, answered
Can an octagon window be replaced?
Yes. The opening is measured, or templated if it is out of shape, and a new octagon is made to it. The old unit comes out, each of the eight sides is flashed, and the window is trimmed inside and out. Priced per opening.
How long does it take to get a round window?
Longer than a standard rectangle, because shaped units are built to order. The lead time depends on the brand and is written on the quote. The old window stays in until the new one is here, then the swap takes about half a day to a day.
Do octagon windows open?
Most octagon and round windows are fixed glass. Whether a venting version is made in the line, size and color you want is checked with the supplier before the quote is final. If you want air from that spot, a small square casement or awning in a reframed opening is the other route.
Why does water get in around a round window?
Flat flashing does not lie well on a curve, and an octagon has eight joints where tape has to overlap the right way. When either is done short, water gets behind the trim and shows up on the wall below. On a replacement, the curve gets stretch tape and each octagon side is lapped so water runs out over the window.
Should a fogged octagon window be replaced?
Fog means the seal between the panes has failed. If the frame is also soft or the wall below is stained, the whole unit should come out so the opening can be checked and flashed. Sometimes a repair is enough, and we will tell you at the measure.
Can a round window be swapped for a different shape?
Yes. The opening is reframed to the new window, the siding and drywall around it are patched, and the new unit is flashed and trimmed. It costs more than a same-shape swap because of the framing and patching, and those are separate lines on the quote.
Recent JMB work, from our job log
59 installs recorded across 30 Twin Cities communities since Dec 2025. Window and door installs for homeowners and the builders we work with. Counts come straight from our job log; no customer names.
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Read morePage reviewed October 9, 2026 · JMB Builders LLC, MN license BC809005 · All windows pages
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