Bay and bow windows in Chicago, where the opening is the whole question

A bay window projects out past the face of the wall, normally in three units set at angles. A bow does the same thing with four or more units in a shallow curve. In Chicago both matter more than a window type usually does, because on a bungalow the bay organises the entire front elevation, and on a two-flat or three-flat it repeats floor by floor. The National Park Service documentation for Chicago bungalows names four bay forms, flat, square, polygonal and curved, and describes the flat bay as "one set of ribbon windows in a grouping of three or four windows into a single architectural frame". Two consequences follow. A price per window means nothing here until you know how the estimator counted the group. And a bay is a piece of structure, not just glass, so the moment the job changes the opening it leaves Chicago's no-permit wording for in-kind replacement. Read at the National Park Service and chicago.gov, 2026-08-11.

This page sits under the window types hub, which works through every type against the openings Chicago's housing stock actually has. How every claim here is sourced, and what this site refuses to publish, is on our methodology page. One standing note for this page in particular: where it describes how a bay assembly is built, that is a general description of the form and is labelled so. It is not a code requirement and not a structural specification. Every Chicago rule and every dollar figure carries its source and the date it was read.

Bay against bow, and what Chicago actually built

The two words get used interchangeably in showrooms and they are not the same assembly. The table below is a general description of the two forms rather than a sourced Chicago claim, with one exception marked in the last row.

	Bay	Bow
Units	Normally three: a wider centre light with a unit angled back on each side	Four or more equal units
Geometry	Faceted. Distinct angles where the units meet	A shallow continuous curve
Usual operation	Fixed centre, operable flankers, though not always	Often all units matched, fixed or operable together
Interior effect	A deeper projection over a shorter run of wall, which is why bays get seats	A shallower projection over a wider run of wall
Documented in Chicago's bungalow record	Yes. Four forms named: flat, square, polygonal and curved	Not named in that documentation

The last row is sourced: National Park Service, Chicago Bungalows Multiple Property Documentation Form, prepared by Daniel Bluestone, University of Virginia, read 2026-08-11. The rest of the table is a general description of the two forms.

That last row is worth more than it looks. On the housing type that makes up roughly one third of Chicago's single-family stock, the bay is not a feature somebody added, it is part of how the building was documented. Swapping a documented bay form for a bow is a change to the composition of the elevation. It may still be the right call for your house. It is not a neutral substitution, and a quote should not present it as one.

The four bungalow bay forms, and the ribbon group inside them

The Chicago Architecture Center and the Chicago Bungalow Association both put more than 80,000 bungalows in the city, roughly one third of its single-family housing stock, in an arc four to seven miles from downtown. The federal definition describes a brick building of one to one-and-one-half stories with a full basement and a low-pitched roof with overhanging eaves, built between 1907 and 1930, though sources put the era out to the mid-1930s.

For a window job the important detail is that the front bay comes in documented forms. The National Park Service documentation names flat, square, polygonal and curved. Of the flat bay it says: "When paired with an offset porch, the flat bay generally features one set of ribbon windows in a grouping of three or four windows into a single architectural frame." Of the polygonal bay it adds that bungalows with one "often use the bay as a focal point on which to showcase art glass windows".

Three things fall out of that, and they are the ones homeowners find out too late.

• Your front elevation is one composition. Three or four units inside a single architectural frame is not the same as three or four windows in a wall, and no per-window price compares across quotes until you know how each estimator counted the group.
• Bungalow work is custom-size work. The association's list of things not to do includes "Enlarge or reduce window openings to fit a stock window frame or change the shape of the window frames". A quote built around stock sizes is quietly proposing the change that guidance names, on the elevation everyone sees.
• The art glass is often in the bay, and often behind a storm. The National Register nomination for the Portage Park Bungalow Historic District records that "Most of these art glass windows hang behind protective storm windows in the bays of the primary facade, featuring grids of metal muntins, abstracted florals, or Prairie-style motifs". Metal muntins, not wood. The layer that has failed is frequently the storm in front, not the glass behind it.

The association's positive list is equally specific: retain and repair original frames, "Maintain historic muntin/grille pattern", "Restore or recreate art glass windows", and "Add thin profile wood or metal storm windows and screens similar in size, shape and color to existing windows". Its list of things not to do also covers replacing double-hung or casement units with "single fixed glass picture or slider windows", which is the most common thing proposed for a bungalow bay centre light.

Chicago Architecture Center, Chicago Bungalow, and Chicago Bungalow Association, Chicago Bungalow; National Park Service, Chicago Bungalows Multiple Property Documentation Form, and Portage Park Bungalow Historic District nomination, NRHP reference 14000620; Historic Chicago Bungalow Association Design Guidelines dated 6/21/2012, read in full at a third-party mirror hosted by oldnorthend.org, with the association's own live windows page carrying the same language. All read 2026-08-11. The guidelines are cited from a mirror and we say so rather than hide it.

Bays on two-flats, three-flats and greystones

The Chicago Architecture Center describes two- and three-flat apartment buildings as a quarter of Chicago's housing, with more than 76,000 two-unit buildings alone, most completed between 1900 and 1918, typically with "an entry porch to one side, and a projecting bay of windows on the other, all surmounted by a more or less ornate cornice in brick or stone". A separate Center article widens the grouping to two-, four- and six-flats, puts that at more than 30 percent of the housing stock, and describes those buildings "usually with bay windows greeting the street through a facade of brick or greystone". Those are two different groupings measured two different ways, so this page reports both and blends neither.

The practical difference from a bungalow is repetition. The bay repeats on two or three floors, so one specification decision gets made two or three times over on the elevation everyone sees, and any inconsistency between floors is permanent and obvious from the sidewalk. Get the bay right once and the rest of the building follows it.

Not every bay is masonry. The city's East Village District landmark designation report cites "fine architectural details such as pressed-metal bay windows, cornices, and gracious entries". A pressed-metal bay is a genuinely different job from a brick one: different fastening, different flashing where the assembly meets the wall, and an assembly whose own condition may be the real problem. The same report documents greystone three-flats by address, including "the greystone three-flat at 814 N. Hermitage" and greystone three-flats on the 1100 block of North Winchester.

On a greystone the opening is the hardest version of this problem. Openings are cut into dimensional Indiana limestone with carved sills, lintels and surrounds, so the opening is itself a piece of the ornament, and greystone appears on workers cottages, two-flats, three-flats and row houses alike, which is why sizes are not standardised across the type. Trimming a limestone opening to reach a stock unit is visible from the street and permanent. An honest limit: greystone sash and bay specifics are documented here only through that city report covering the same era of brick and greystone flats, not through a greystone-specific guideline, so treat them as more thinly sourced than the bungalow material above.

Chicago Architecture Center, Two- and Three-flats, The tale of the Chicago two-flat, and Limestone; City of Chicago, East Village District landmark designation report. All read 2026-08-11.

A bay is a small piece of structure, which is why it is priced differently

Everything in this section is a general description of how a bay or bow assembly is built. It is not a Chicago code requirement, it carries no span, load or dimension, and no primary source for those was read for this site. It is here because it explains why a bay quote is not a window quote with a bigger number on it.

Part of the assembly	What it does	Why it shows up in the price
Head structure over the opening	Carries the wall above a wider opening than a single window needs	It is structural work in a masonry wall, not glazing work
Support under the projection	Holds the projecting box up, by brackets, knee walls, cables or a masonry base	A hidden item that varies hugely by building and is easy to leave out of a quote
Head board or small roof	Sheds water off the top of the projection	Roofing and flashing trades, not window trades
Seat board and skirt below	Closes the bottom of the projection and forms the interior sill or seat	Interior finish work that a per-window price rarely includes
Flashing at every junction	Keeps water out where the assembly meets the wall, roof and sill	The most common failure point, and the least visible line item
Insulation of the projecting cavity	The box is exposed on several faces, including underneath	In a Chicago winter this is the difference between a seat and a cold spot
The units themselves	The glass and sash most people think they are buying	Often the smaller share of a bay total

General description of the assembly, not a sourced claim and not a code statement. No structural figure appears here because none was read at a primary source.

There is a second consequence of the projection and this page will not pretend to answer it. A bay or bow sticks out past the exterior wall plane, which raises questions about setbacks, lot lines and the public way that a flat replacement never raises. Chicago has provisions on that. This site did not read them at source in this pass, so it publishes no dimension, no allowance and no rule about how far anything may project. If your bay is being enlarged, moved or added, ask the city directly and get the answer in writing before anyone orders materials.

The permit question, and the exact moment it changes

This is the section the brief for this page exists for, and it turns on one sentence of the city's own wording rather than on anything about bays specifically.

Chicago publishes a list of work that does not require a building permit. In a residential building up to four stories above grade it includes "Repairing or replacing (in-kind) an exterior window or skylight in the existing opening". The city defines in-kind replacement as replacement "of existing materials, objects, or elements using new materials, objects, or elements of the same type, size, and shape".

A separate list applies in any building at any height. It covers repairing damage to an existing window, replacing glass in an existing window sash, installing or removing a storm window or an insect screen, and replacing an existing ground-level window in kind including the frame, "provided that the work does not require cutting away or removal of any portion of an exterior wall". That last clause is the one that decides most bay questions, because changing a bay opening usually means exactly that.

The job	Inside the city's in-kind wording?	What follows
Same bay form back in the same opening, same projection, same unit count, same sizes	Yes. Same type, size and shape	On the no-permit list in a residential building up to four stories above grade
Sashes replaced inside a bay whose frame and structure stay put	Yes, on the same reading, and repair of an existing window is separately exempt in any building	The smallest version of the job, and the one least often quoted
Bay replaced with a flat window group, projection removed	No. The shape changes	Outside the exemption. Treat it as a permit job, and as a change to the elevation
Flat opening converted into a new bay	No. The size and shape change	Outside the exemption, and creating a new opening is expressly outside the Express Permit route
Bay opening widened, heightened or squared off to reach stock units	No. The size or shape changes	Outside the exemption, and named in the bungalow guidelines as something not to do
Bay kept, but the unit count or the centre light changes from operable to fixed	Unclear. The type of one unit changes while the opening does not. The city does not address it	Ask the Department of Buildings before ordering, and get the answer in writing
Bay swapped for a bow, or a bow for a bay	No, on any plain reading. The shape changes	Treat it as a permit job and as a documented change to the composition
Any of the above above four stories	The four-story exemption does not reach it	See the Express Permit Program route below
Any of the above on landmark property or in a landmark district	The city says its exceptions "may not apply". Settle that question before anything else

City of Chicago, work not requiring a building permit, exterior, read 2026-08-11. The wording in the middle column is the city's; applying it row by row is our reading, and the Department of Buildings decides permit questions. Both exemption lists appear in full on do I need a permit.

Where a permit is needed for a straightforward replacement, the city's Express Permit Program is the streamlined route. It covers "Replacing a window in an existing wall opening in a building up to 7 stories tall", and the same work in a taller building only "With drawings prepared by an Illinois-licensed architect or structural engineer". It expressly does not cover creating a new opening, a window that has or is required to have fire-rated glass, a window within 10 feet of a fire escape, or, in a building with more than three stories, a window in a wall within two feet of a lot line separating two properties. Every application needs at least one existing-condition photograph and an energy and water efficiency compliance form. Read at chicago.gov 2026-08-11, and covered in full on the Express Permit Program page. The energy requirement that attaches to a replacement is on the energy code page.

Put the two halves together and the practical rule for a bay is short. Keep the opening and you are probably on the no-permit list. Change the opening and you are in the permit system, plus a projection question this site does not answer, plus a structural scope that is not window work. That is not a reason never to change a bay. It is a reason to know which job you are buying before the first quote arrives.

What a bay or bow costs, with every band attributed

No source read for this site carries an attributed Chicago price for a bay or a bow. Every band below is national and is labelled national on its own row. Publishing a national figure as a Chicago figure is the specific error this site exists to avoid.

Source, author and date	Bay	Bow
Today's Homeowner, Elisabeth Beauchamp, reviewed by Amy DeYoung, September 3, 2025. National	$1,000 to $7,000	$2,000 to $4,000
Bob Vila, Katie Flannery and Evelyn Auer, June 10, 2024. National, and the oldest source here	$900 to $7,100	$1,500 to $6,500
Modernize, Catie Bonner, reviewed by Isabella Andersen, March 17, 2026. National	$1,700 to $3,859 or more, bay and bow priced together
This Old House, Stephanie Minasian-Koncewicz, June 23, 2026, from a November 2025 survey of 1,000 homeowners. National	$791 to $886 average, bay and bow priced together
This Old House wood guide, Stephanie Minasian-Koncewicz, April 13, 2026, citing RSMeans data from Gordian. National, wood only	$1,475 to $5,100, average $3,287.50	Not given
Any Chicago source with a named author and a date	None found. No Chicago bay or bow figure appears on this site

Every row above read 2026-08-11.

Three readings of that table, and we label which is which.

• The This Old House row is the outlier and we are leaving it visible. Its bay and bow average sits below its own casement average, which no other source comes close to agreeing with. Our reading is that it is measuring something narrower, probably a unit rather than an installed assembly. That is our inference, not a claim the publisher makes.
• Three of the four put a bay somewhere between roughly $900 and $7,100. That is not a budget, it is a warning. A spread that wide means the number depends almost entirely on the specification, which is why the checklist further down matters more than any range here.
• Nothing here prices the structure separately. Every band above is a window figure. Head structure, support, roof and seat boards, flashing and insulating the projecting cavity are the items that move a real bay total, and no source read breaks them out.

For scale, and clearly labelled as not a bay figure: the only Chicago band this site could attribute to a named author, a named reviewer and a date is for vinyl double-hung units, at $650 to $1,200 per window installed and $700 to $1,250 for an energy-efficient vinyl unit. The same page puts Illinois statewide at $575 to $1,100 and an Illinois whole-home job of 10 to 15 windows at $6,000 to $16,000, and splits Illinois jobs at roughly two-thirds materials to one-third labour. Modernize, "Window Replacement Cost and Pricing in Illinois (2026)", Isabella Andersen, reviewed by Catie Bonner, March 18, 2026, read 2026-08-11. Do not multiply a double-hung price by three and call it a bay. The assembly is the part those figures do not cover. Full type-by-type comparison, with the disagreements between publishers left visible, is on cost by window type.

Why per-window pricing breaks on a bay, and what to ask instead

This is where two honest contractors produce quotes thousands of dollars apart on the same house. Neither is wrong. They counted differently and scoped differently, and nothing on the page told you which.

Get these in writing, in numbers, from every contractor before you compare totals:

• The unit count for the bay, stated as a number, not implied by a line item. Three units and one assembly are two different ways of writing the same elevation.
• The overall frame dimension for the group, plus each individual unit size, so you can see whether anyone is proposing to change the composition.
• The projection depth and the bay angle, before and after. If either changes, the shape changes, and so does your permit answer.
• Whether any unit changes from operable to fixed, especially the centre light. On a street-facing bungalow elevation, a fixed picture unit replacing an operable one is the specific swap the bungalow guidelines name.
• Who does the structural work above the opening, and whether it is in this price or excluded to be priced later.
• What happens to the head board, roof, seat board and skirt, and who finishes the interior sill.
• How the projecting cavity gets insulated, including underneath. In Chicago this is the difference between a window seat and a permanently cold floor.
• Flashing at every junction, named as a line rather than assumed.
• The bay substrate, masonry, limestone or pressed metal, and what the quote assumes about its condition.
• Removal and disposal, stated as a line. This Old House prices removal and disposal at $55 to $65 an hour and rotted frame repair at $250 to $800 nationally (June 23, 2026, read 2026-08-11).
• Who pulls a permit, and on what grounds. If the opening is not changing, in a building up to four stories, and the property is not landmarked, ask which specific part of the work the permit line is for.
• The written warranty terms, on the units and on the installation separately. They are usually two documents from two different parties.

One more. Ask each contractor to price the bay as its own project, separate from the rest of the house. A bay buried inside a whole-house total is the easiest place for scope to disappear, and it is the one opening where the scope is most of the money.

You may not need a new bay window

This site is paid a referral fee when a homeowner asks to be matched with a window contractor, which is set out in full on how we make money. So these cases are worth stating plainly, because a bay replacement quote is never going to raise them.

• If the bay structure is sound and only the sashes have failed, that is a sash job. The city's East Village District landmark report classes replacing sash, in a landmark district context, among "changes considered minor and reversible". A sound assembly with tired units is the cheapest version of this problem and the one least likely to be quoted.
• One failed sealed unit is not a bay replacement. Replacing glass in an existing window sash needs no building permit in any building, at any height, on the city's own list.
• Repairs are on the same list. "Repairing damage to an existing window or exterior door" requires no building permit in any building. Painted-shut sash and failed hardware are repair conditions, not automatically replacement conditions.
• Storm windows are a real option, not a consolation prize. Installing, maintaining or removing a storm window needs no building permit in any building, and the Chicago Bungalow Association recommends adding "thin profile wood or metal storm windows and screens similar in size, shape and color to existing windows".
• If the art glass in your bay is intact, price the storm in front of it first. The Portage Park nomination records art glass hanging behind protective storm windows across that district, with metal muntins. The layer that failed is often the outer one.
• If the problem is cold at floor level rather than the glass, the projection may be the issue. General point, not a sourced one: an uninsulated projecting cavity behaves like an exposed box in a Chicago winter, and no new sash fixes that.
• If you are considering adding a bay for looks on a street-facing bungalow elevation, stop and read the guidance first. The association asks owners not to enlarge or reduce openings or change their shape, and that elevation is exactly what landmark review looks at where it applies.
• If you are in a condominium and have not read your declaration, stop. You may be pricing something that is not yours to decide.

City of Chicago, work not requiring a building permit, exterior, and East Village District landmark designation report; Historic Chicago Bungalow Association Design Guidelines dated 6/21/2012; National Park Service, Portage Park Bungalow Historic District nomination, NRHP reference 14000620. All read 2026-08-11. The repair decision is worked through in detail on repair or replace.

Condominiums, where the bay may not be yours to decide

Bays and bow assemblies appear on plenty of Chicago condominium buildings, including converted two-flats and three-flats, and ownership decides this before any city rule comes up.

The Illinois Condominium Property Act sets a default in Section 4.1(a), and that section opens with the qualifier that decides everything: "Except to the extent otherwise provided by the declaration or other condominium instruments". Under the default, "all portions of windows in perimeter walls shall be deemed part of the common elements", Section 4.1(a)(5) deems them a limited common element serving that unit exclusively, and Section 18.4(a) puts replacement of common elements on the board. Declarations very often move that cost onto the unit owner, which is exactly why the declaration, not the statute, answers this for your building. A bay makes the question sharper than a flat window does, because a projecting assembly involves structure, roof and flashing that no reasonable reading treats as belonging to one unit alone. Read the declaration, then talk to the board, then talk to a contractor, in that order.

Illinois Condominium Property Act, 765 ILCS 605, full text effective January 1, 2023, published by the Illinois Department of Financial and Professional Regulation, read 2026-08-11. This is a general description of a statute and not legal advice.

Landmark status overrides most of this page

Two designations get confused constantly, and on a bay the confusion is expensive, because the bay is the part of the building that faces the street.

The National Park Service is unambiguous about the federal side: "Listing in the National Register places no federal restrictions or requirements on a private property owner. You may do with the property as you wish, within the framework of local laws or ordinances." Chicago has 15 bungalow districts on the National Register, so this comes up constantly on exactly the housing type with the documented front bay.

Chicago Landmark designation is the one with teeth. The Historic Preservation Division "reviews all permit applications for work involving designated and proposed Chicago landmarks and landmark districts", the Commission's pre-permit document extends that to anything located within a designated or proposed Chicago Landmark District, and its submission requirements for alteration work expressly name windows among the exterior features you have to describe. The East Village designation report recommends as significant features "all exterior building elevations, including rooflines, visible from public rights-of-way", which is the language that puts a street-facing bay inside review. The city also states directly that its no-permit exceptions "may not apply" on landmark property.

National Park Service National Register FAQ; City of Chicago landmarks permit review page, Commission on Chicago Landmarks pre-permit submission requirements (2026), East Village District landmark designation report, Chicago Listings on the National Register of Historic Places as of October 31, 2025, and work not requiring a building permit, exterior. All read 2026-08-11. Full treatment on landmark buildings and districts.

What we could not confirm, and will not guess

• A Chicago price for a bay or a bow. Nothing read carries one with a named author and a date. Two Chicago contractor marketing pages had local numbers. One names no author, the other names neither author nor date and contradicts itself on the same page, so their figures do not appear here in any form.
• How far a bay may project past a wall, a lot line or the public way in Chicago. Real provisions exist. They were not read at source in this pass, so no dimension or allowance appears. Ask the city and get the answer in writing.
• Any structural figure. No header size, span, load or bracket spacing appears, because none was read at a primary source. The anatomy table is a general description of the assembly and says so.
• Whether changing one unit inside an unchanged bay breaks the in-kind exemption. The opening does not change and the type of one unit does. The city does not publish an answer, so neither do we.
• Egress and rescue-opening dimensions. Chicago's provision was not read at source, so no dimension appears anywhere on this site. That matters on a bay where a centre or flanking unit may become fixed.
• What a window job returns at resale in Chicago. A resale return figure circulates widely, attributed to the Journal of Light Construction Cost vs. Value Report. Both publishers returned HTTP 403 to this session, so nothing was read at source, and therefore no return figure is published here.
• How long a bay assembly lasts, and what it saves in energy. Both get quoted freely in sales material. No primary source for either was read, so no figure appears.

Related pages

• Double-hung windows, the units that usually sit inside a Chicago bay, and the type that keeps a like-for-like job inside the city's exemption.
• Do I need a permit, carrying both city exemption lists in full and the in-kind definition this page turns on.
• Window cost by type, where every band names its publication, its author and its date, and the disagreement between publishers is the finding.
• Casement windows, for the flanking units in a bay and the clearance question an outswing sash raises on a Chicago lot.

Sources

All read 2026-08-11: City of Chicago, work not requiring a building permit, exterior; Express Permit Program, exterior window or door replacement; landmarks permit review; East Village District landmark designation report; Chicago listings on the National Register, as of October 31, 2025; National Park Service, Chicago Bungalows Multiple Property Documentation Form; Portage Park Bungalow Historic District nomination; National Register FAQ; Chicago Bungalow Association, windows; Chicago Architecture Center, Chicago Bungalow; Two- and Three-flats; The tale of the Chicago two-flat; Illinois Condominium Property Act, 765 ILCS 605. Cost figures from Today's Homeowner (Elisabeth Beauchamp, reviewed by Amy DeYoung, September 3, 2025), Bob Vila (Katie Flannery and Evelyn Auer, June 10, 2024), Modernize (national page, Catie Bonner, reviewed by Isabella Andersen, March 17, 2026; Illinois page, Isabella Andersen, reviewed by Catie Bonner, March 18, 2026) and This Old House (Stephanie Minasian-Koncewicz, June 23, 2026, and the wood guide of April 13, 2026). No competitor page, contractor marketing page or search-engine summary informed any statement above.

If you want quotes to hold against these answers, the form below passes your details to an independent licensed window contractor working in your part of the city. What that relationship is, and is not, is set out on the about page.

Straight answers

Questions Chicago homeowners ask

What is the difference between a bay window and a bow window?

The number of units and the geometry they sit in. A bay is normally three units projecting past the wall, a fixed centre light with an operable unit angled back on each side. A bow uses four or more equal units set in a shallow curve, so it reads as a soft arc rather than a faceted box. That is a general description of the two forms rather than a Chicago rule. In Chicago the distinction matters less than the form your building already has, because on a bungalow the front bay is documented as part of the type. The National Park Service documentation for Chicago bungalows names four bay forms, flat, square, polygonal and curved, and none of them is a bow. If a quote proposes swapping a documented bay form for a bow, that is a change to the elevation, not a specification detail.

Do I need a permit to replace a bay window in Chicago?

It depends entirely on whether the opening changes. Chicago publishes a list of work that does not require a building permit, and in a residential building up to four stories above grade it includes "Repairing or replacing (in-kind) an exterior window or skylight in the existing opening". The city defines in-kind as replacement using new elements "of the same type, size, and shape". Putting the same bay form back in the same opening at the same size and shape is the clearest case that wording covers. Changing the projection, the unit count, the angle, the head shape or the overall frame dimension changes the size or the shape, so it sits outside the exemption wording. Read at chicago.gov 2026-08-11. Landmark property is carved out separately, because the city states these exceptions "may not apply" there. The Department of Buildings decides permit questions, not this page and not a salesperson.

Can I add a bay window where my house has a flat opening now?

You can ask, and you should expect it to be a permit job rather than a window job. Cutting a new opening or enlarging an existing one changes the size and shape, which is outside the wording of Chicago's in-kind exemption, and the city's Express Permit Program expressly does not cover creating a new opening. The any-building exemption for replacing a ground-level window is also conditioned on the work not requiring "cutting away or removal of any portion of an exterior wall". Read at chicago.gov 2026-08-11. On a bungalow there is a second reason to pause. The Chicago Bungalow Association's design guidelines tell owners not to "Enlarge or reduce window openings to fit a stock window frame or change the shape of the window frames" (guidelines dated 6/21/2012, read 2026-08-11). Adding a bay to a street-facing elevation is exactly the kind of change that guidance asks owners not to make.

What does a bay or bow window cost in Chicago?

No source read for this site carries an attributed Chicago price for a bay or a bow, so this page publishes none. The only Chicago band on this site with a named author, a named reviewer and a date covers vinyl double-hung units at $650 to $1,200 per window installed, and $700 to $1,250 energy-efficient (Modernize, "Window Replacement Cost and Pricing in Illinois (2026)", Isabella Andersen, reviewed by Catie Bonner, March 18, 2026, read 2026-08-11). That is not a bay price and should not be scaled into one. National bay bands run $1,000 to $7,000 (Today's Homeowner, September 3, 2025) and $900 to $7,100 (Bob Vila, June 10, 2024), with bow at $2,000 to $4,000 and $1,500 to $6,500 respectively. Two Chicago contractor pages did carry local bay and bow numbers. Neither names an author, one carries no date at all and disagrees with itself on the same page, so their figures are not published here.

My bungalow front is three windows in one frame. Is that one window or three?

It is one architectural opening holding several units, and settling that is the difference between comparable quotes and guesswork. The National Park Service documentation for Chicago bungalows describes the flat bay this way: "When paired with an offset porch, the flat bay generally features one set of ribbon windows in a grouping of three or four windows into a single architectural frame." Of the polygonal bay it adds that bungalows with one "often use the bay as a focal point on which to showcase art glass windows". Read at the National Park Service 2026-08-11. So a per-window price on that elevation is close to meaningless until you know how each estimator counted the group. Ask every contractor for the unit count, the individual unit sizes and the overall frame dimension for the front group, stated as numbers rather than implied by a line item.

My two-flat has a metal bay. Does that change the job?

Yes, and it changes who you should be asking. The City of Chicago's East Village District landmark designation report cites "fine architectural details such as pressed-metal bay windows, cornices, and gracious entries" (read 2026-08-11), so a pressed-metal bay is a documented Chicago condition and not an oddity. A pressed-metal bay is a different substrate from brick or limestone, which means different fastening, different flashing, and a metal assembly whose own condition may be the actual problem rather than the sash inside it. General point, not a city rule: on a metal bay it is worth establishing whether the failure is the windows, the metalwork, or the flashing where the assembly meets the wall, before anyone prices windows. A contractor who has not identified which bay substrate you have is not yet quoting your building.

My block is a landmark district. Does that change what I can do to the bay?

Very possibly, and the bay is the part most likely to be reviewed, because it faces the street. The Historic Preservation Division "reviews all permit applications for work involving designated and proposed Chicago landmarks and landmark districts", the Commission's pre-permit document extends that to anything located within a designated or proposed Chicago Landmark District, and its submission requirements for alteration work expressly name windows among the exterior features you have to describe. The East Village designation report recommends as significant features "all exterior building elevations, including rooflines, visible from public rights-of-way", which is the language that puts a street-facing bay squarely inside review. All read 2026-08-11. National Register listing is a separate thing and restricts nothing by itself: the National Park Service states that listing "places no federal restrictions or requirements on a private property owner". Find out which designation applies to your address before ordering anything.