Bay Windows: Canted, Box, Oriel and Circle Styles

A bay window is a group of at least three windows that projects out from the wall, usually a fixed center window flanked by two windows that open, set at an angle to the wall ^{1 2}. The styles differ in two ways: the angle of the side windows, and how the unit is held up. A canted or full bay has angled sides, commonly 30 or 45 degrees; a box bay has sides at 90 degrees; an oriel is a bay that projects from the wall without reaching the ground; and a circle bay is a softer, rounded variant ^{1 2 3}.

The style you pick changes the support, the roof and the price. This Old House, citing Angi and Pella data, lists box bays at $750 to $1,400, full bays at $1,100 to $3,300, oriels at $1,300 to $3,800 and circle bays at $2,500 to $6,000 (updated June 5, 2026) ³. A like-for-like replacement keeps the structure already there, while a new opening or a change of style brings framing and roof work.

The bay window styles at a glance

The sources do not use every name the same way, so read the table as a guide and ask what a quote means by each term.

Canted or full bay

"Canted" simply means angled ¹. Andersen uses it as a general term, a synonym for bay window, and says a canted bay can be bracket-supported or extend to the floor, on any floor of the house, with flanking windows at any angle ¹. Fixr uses "full" or canted bay for a unit whose windows form 30 or 45 degree angles and that extends down to the ground; it says a full bay is typically more expensive than a box bay and requires first-floor installation ². In the common layout, a picture window sits in the center with double-hung or casement windows on the sides ².

Andersen says the 30 and 45 degree angles create a trapezoid shape that suits a more traditional house and preserves more yard space ¹. This Old House puts the side angles usually at 25 to 45 degrees ³, so confirm the exact angle on the quote. Because a full bay extends the floor, Fixr notes it needs new floor and ceiling covering, which adds to the cost ².

Box bay

A box bay turns its side windows at 90 degrees, which gives the flat front and square corners its name ¹. Andersen treats it as a type of oriel, supported by brackets, and says the 90-degree shape suits a more modern house and makes better use of the space if furniture will sit in the bay ¹. Fixr describes it as having no curves and as relatively easy to install ², and This Old House says it is smaller and often found in kitchens ³. Andersen adds that a box bay is sometimes used as a garden window ¹; garden windows explained covers that variant.

Oriel bay

An oriel projects from the wall without extending to the ground, so it can go on any floor ². Andersen says it is bracket-supported, commonly seen on upper floors, and historically associated with ornate Italianate, Victorian and Edwardian buildings ¹. Because nothing holds it up from below, it needs additional structural support, as This Old House notes ³, and Fixr says a box or oriel window needs proper support to take stress off the exterior wall, with added reinforcement if the oriel is to be used as a seat ². This Old House adds that steel-cable suspension systems have made upper-floor bays possible without costly foundations ³.

Circle bay

The sources describe the circle bay differently. Fixr says it resembles a bow, but with curved panes of glass ². This Old House describes large glass panes in each section with smaller panes above, and more intricate moldings than other bay types ³. Both point to a rounder, more detailed unit, and This Old House's range for it is the highest of the four styles ³. Ask a quote to say whether the glass is curved or flat. A bow, by contrast, builds its curve from flat windows: Andersen's are at least four casement windows set 10 degrees apart ¹.

How each style is held up

Andersen describes three ways to support a bay: brackets, cables anchored to the house for a cantilevered unit, and a knee wall under a unit that extends to the foundation ¹. Which one applies depends mostly on the style:

• Box and oriel bays hang off the wall on brackets or cables, so there is no foundation work, but Fixr says they need proper support to take stress off the exterior wall ^{1 2}.
• A full bay that reaches the floor needs a knee wall or framing down to the foundation, and adds floor area inside ^{1 2}.
• A canted bay on brackets sits in between: angled like a full bay, held up like an oriel ¹.

Every style also needs its own roof, because it projects past the wall ². The details of brackets, cables, the pseudo roof and the seat board are in bay vs. bow windows. When you replace a bay, Andersen says you choose whether to match the existing support or change it, and confirm the structure can carry the new type ¹.

Replacement or a new opening

Replacing an existing bay. The opening, support and roof are already in place, so the job is mostly the window unit itself. Fixr's window-only prices by size run from $1,140 to $2,074 for a 7 by 4 foot unit to $1,333 to $2,425 for 8 by 5 feet, with labor of $210 to $383 on top (updated August 29, 2025) ². Any style fits as long as it matches the width, projection and support you have; changing from a canted bay to a box bay, or to a bow, changes the projection and may mean new framing.

A new opening. Fixr says a replacement costs considerably less than a bay where none existed, because a new one involves the wall's roof, floor and structure, and the wall often has to be opened up more than the size of the old window ². This Old House says a bay needs at least 40 inches of wall ³. Whether the job needs a permit depends on your local building department and on what changes; do you need a permit to replace windows shows how cities draw that line. The cost surveys side by side are in bay and bow window cost.

Choosing a style

• Traditional house, room outside: a canted bay at 30 or 45 degrees ¹.
• Modern house, or furniture in the bay: a box bay ¹.
• Upper floor, or no foundation work wanted: an oriel or another bracket- or cable-supported bay ^{1 3}.
• A softer curve: a circle bay or a bow ^{1 2}.

When you ask for quotes, give each company the same style, side angle, which windows open, support method, roof and seat board, so the prices compare line by line. Is the installer licensed in your state? How to choose a window installer lists what else to check, and types of windows covers the other styles. When you are ready, you can compare quotes from window installers.

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About these figures

• ¹ Reported: Andersen's description of canted, box and oriel bays, the 30, 45 and 90 degree angles, bows of four casements 10 degrees apart and its support methods, checked October 26, 2026.
• ² Reported: Fixr bay window guide, styles (box, full or canted, oriel, circle), window-only prices by size, labor of $210 to $383, and notes on support, roof, seat and new openings, updated August 29, 2025, checked October 26, 2026.
• ³ Reported: This Old House bay vs. bow guide citing Angi and Pella data, prices by bay style ($750 to $1,400 box, $1,100 to $3,300 full, $1,300 to $3,800 oriel, $2,500 to $6,000 circle), 25 to 45 degree side angles, the 40-inch wall minimum and cable suspension for upper floors, updated June 5, 2026, checked October 26, 2026.