Bow window replacement rebuilds the curved, multi-unit window assembly that projects outward from a wall, and it is most often needed by St Peters homeowners with older two-story colonials and ranch homes where the original sashes, head board, or support brackets have started to fail. Many bow units in the area sit above porch roofs or garden beds, so shifting soil and freeze-thaw cycles common across St Charles County can loosen the seat framing and break the insulated glass seals. Our crews measure the radius and mullion angles, evaluate the header and cable support, then set the new units with proper flashing, backer rod, and low-expansion foam so water is directed away from the sheathing. Scheduling is open through 2026, with spring and early fall being the easiest seasons for careful exterior work.
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Bow Window Service Overview
Bow window replacement is the process of removing a curved run of joined window units, correcting the framing and support beneath them, and installing new sashes with sealed insulated glass, and at St Peters Window Replacement Experts it includes structural inspection, radius layout, flashing detail, and interior trim finishing across St Peters properties. Work begins with a careful look at the head board, seat board, knee braces, and any cable or bracket support carrying the projection, since a bow unit adds real load to the wall. Trained technicians then remove the old assembly in sections, controlling glass safely and protecting floors and landscaping with drop protection. New units are set plumb and square, shimmed at the load points, sealed with flexible flashing and low-expansion foam, and finished with exterior capping that sheds water. We handle single-family homes, townhomes, condo units, and small commercial storefront bays, adjusting the approach to each structure. Our 2026 schedule builds in extra time for weather windows, because rushing exterior openings invites moisture damage. Every project closes with a post-job walkthrough so you can see the sealing, operation, and cleanup for yourself.
Call Us: 636-736-6132- Signs You Need Bow Window Replacement -
Sagging projection, fogged insulated glass, sticking sashes, and drafts along the seat board usually mean a bow window has failed. St Peters homes show these symptoms as seals break, support cables loosen, and moisture reaches the head board. Replacement corrects the framing and restores safe operation heading into 2026.
Click Me to Call: 636-736-6132When the seat board tilts or the exterior cap pulls away from the siding, the support cables, knee braces, or header carrying the bow assembly are losing capacity. That shifting stresses the glass and creates a real hazard, so a structural inspection comes before any glass work.
Cloudy panes and moisture between the layers show the insulated glass seal has failed, while drafts at the mullions and seat board point to deteriorated glazing tape and worn weatherstripping. Winter energy bills in St Peters climb quickly once this happens.
Casement or double hung units within the bow that bind, refuse to latch, or drip onto interior trim usually indicate rotted sill framing and flashing problems above. Damaged sheathing behind the trim spreads if the opening is not reworked properly.
// Bow Window Pricing Factors Explained //
Our Bow Window Replacement Process
Technicians measure the rough opening at multiple points, check the header and sill for rot or deflection, and confirm how the existing bow is supported by cables or knee braces. Radius, projection angle, and sash count are recorded so the replacement unit is built to fit. Findings are written down and shared before any order is placed.
Floors and furnishings are covered, glass is scored and removed in controlled sections, and temporary support is added when the old unit carries any roof or trim load. Debris is contained rather than dropped. Once the opening is clear, the crew inspects framing, flashing, and moisture damage, then repairs the substrate before the new unit goes in.
The bow assembly is set level and plumb, shimmed at the mullions, anchored to sound framing, and supported with cables or a seat board as the design requires. Insulation, backer rod, and exterior sealant close the perimeter, followed by flashing and trim capping. We then test each operating sash, review the finished work with you, and leave the site clean.
/// Bow Window Questions ///
Most bow window replacements are completed in one to two working days, since the multi-sash unit must be assembled, set, shimmed, and flashed as a single curved assembly rather than dropped into a simple opening. Lead time before that day depends on the manufacturing schedule for the custom radius and sash count. We confirm measurements first, then schedule installation once the unit arrives and passes inspection.
A bow window replacement includes removal of the old unit, inspection of the sill and header framing, installation of the new curved assembly with proper support brackets or cable systems, flashing, insulation of the perimeter gaps, and interior and exterior trim finishing. We also verify that each sash operates and seals correctly before the walkthrough. Written estimates list every included item so nothing is assumed.
Yes, most bow windows require verified header support and often roof cable or knee-brace support because the unit projects out from the wall and carries its own weight plus any seat board load. Our technicians check the existing header, load path, and any settling before the new unit goes in. Skipping that inspection is one of the most common causes of sagging and sash binding later.
Bow window pricing is driven by the number of sashes, the projection depth and radius, the frame material, the glass package, and whether the header or support system needs repair. Rotted sill framing, an oversized seat board, or a switch to insulated low-emissivity glass will all move the number. We provide an itemized written estimate after an on-site measurement so St Peters homeowners can see how each choice affects the total.
Clearing roughly six feet of floor space in front of the window and removing blinds, curtain rods, and anything from the seat board is all we ask. Our crew handles floor protection, dust containment, and safe removal of the old glazing, which matters because curved units come out in heavy sections. Pets and small children should stay in another room while the opening is open and tools are in use.
Missouri’s swing between humid summers and freezing winters puts steady stress on a bow window’s many joints and mullions, which is why seal failure and condensation between panes show up here more often than on single-sash windows. In St Peters we typically recommend argon-filled insulated glass with a low-emissivity coating and carefully sealed mullion joints to reduce heat transfer and drafts. Proper exterior flashing and a sloped head board also keep wind-driven rain out of the projection.
Bow window replacement can be done in cold weather when the crew stages the work properly, sealing the opening in stages and limiting how long the wall is exposed. Sealants and flashing tapes have temperature ranges, so we select products rated for the conditions on the scheduled day. Many St Peters homeowners book late-winter installations in 2026 to have new glass in place before summer cooling season.
Existing interior details can often be matched, including seat board depth, stain color, and trim profile, though the original pieces are rarely reusable once the old curved frame is removed. We measure the projection and interior return before ordering so the new seat board and jamb extensions line up with the wall. Photos of your current setup help our team specify the closest available match.
// Free Bow Window Estimates //
