Trapezoid Window Replacement — Gable and Clerestory Windows Up High
The angled windows high in your vaulted living room have fogged or leak at the corners, and nobody can reach them without a plan.
Reply within one business day. Or call / text 763-204-2099.
Trapezoid window replacement in a vaulted great room is mostly an access job: rolling scaffold inside on protected floors, a lift or ladders outside, and a new unit made to the exact angles of the opening. JMB Builders replaces trapezoid, angled-top and clerestory windows across the Twin Cities metro, flashed outside and trimmed inside. Priced per window, quoted from photos, with a reply within one business day.
- Priced per window
- Scaffold inside, lift or ladders outside
- Units made to the angles of the opening
Vaulted great rooms from the 1980s and 90s often have a row of windows at eye level and angled trapezoid windows above them, following the roof line up the gable wall. Clerestories are a row of windows set high on a tall wall. Most are fixed glass. They fog when the seal fails and leak at the sharp corners, and because they are fifteen or twenty feet up they get left that way.
Each shape is made to the opening. We measure the legs, the base and the angle, and template odd shapes, so the order matches what is in the wall. Inside, a rolling scaffold goes on floor protection with furniture moved out of the way. Outside, the gable wall is reached by lift where the ground allows, or by ladders and staging.
The new unit goes in on a sill pan, with flashing tape lapped at the angled head so water runs down and out at the low corner. Outside it is capped or trimmed in PVC. Inside, the jamb extensions and casing are reset or replaced. If the windows below are going too, they are measured and ordered in the same round so glass and color match.
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
- Photos of the whole wall inside and out, plus a close-up of the worst window
- The room cleared under the windows on install day, or help us plan around large furniture
- Your frame color and glass choices
What JMB supplies
- In-home measure of legs, base and angles, with templates on odd shapes
- The units ordered to shape, matched to the windows below
- Rolling scaffold inside on floor protection; lift, ladders or staging outside
- Old units removed and hauled away
- Sill pan, flashing at the angled head, exterior capping or PVC trim
- Interior jamb extensions and casing reset or new
- Painting quoted as a separate line — or leave it primed and paint it yourself
How it is priced: per window
Quoted in writing from your photos, with a reply within one business day. What moves the number:
- Height of the window inside and outside
- Lift vs. ladder and staging access outside
- Shape: trapezoid, triangle, pentagon or rectangle clerestory
- Size and weight of the glass
- Rot or water damage at the angled corners
- Whether the windows below are done in the same round
- Interior trim reset vs. new
Send a photo of the full wall from inside and outside so we can plan the scaffold and lift.
How long it takes
A gable wall of two to four high units: about one to two days once they arrive. Made-to-shape units take longer to arrive than standard windows.
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
Trapezoid over picture windows
The classic vaulted gable wall: angled units above a row of rectangles. Often replaced together so the glass matches.
Clerestory row
Rectangles set high on a tall wall or a shed dormer. Replaced from scaffold inside and a lift or roof staging outside.
Fixed to opening
Some high windows can be ordered as awnings or casements with an extended crank or a motorized operator for air at the top of the room.
Trapezoid Window Replacement — Gable and Clerestory Windows Up High: questions, answered
How do you reach a window that high to replace it?
Inside, with a rolling scaffold on floor protection. Outside, with a lift where the ground allows one, or ladders and staging. The access plan is set at the measure so the right equipment is there on install day.
Can you replace just the glass in a trapezoid window?
Sometimes. If the frame is sound and only the seal has failed, a new sealed glass unit can be made to the shape and set in the old frame. If the corners leak or the frame is soft, the whole unit is the better fix.
How are odd-shaped windows measured?
We measure the base, both legs and the angle of the top, and make a template on shapes that are not regular. The unit is ordered to those numbers. Because each one is made to shape, it takes longer to arrive than a standard window.
Do I have to move furniture out of my great room?
The area under the windows needs to be clear for the scaffold. We move what we can with you and cover the floor and what stays. Large pieces like a sectional are easiest moved before we arrive.
Can a high fixed window be changed to one that opens?
Often, yes. Awnings and casements can be ordered for high openings, with an extended crank pole or a motorized operator so they can be opened from the floor. A powered operator needs an outlet, wired by a licensed electrician.
Why is the glass in my high gable window foggy?
The seal between the panes has failed and moist air got into the space between them. It cannot be cleaned from outside. The fix is a new sealed glass unit or a new window, depending on the frame.
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.
Related jobs we do
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Read morePage reviewed October 9, 2026 · JMB Builders LLC, MN license BC809005 · All windows pages
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