How much does it cost to install or replace bay windows?

Bay windows dress up any part of the home they are installed in. They are defined as any type of window that protrudes from the exterior of the house, while forming a “bay” inside. Bay windows are usually made in angles of 90, 130, and 150 degrees, and can also include a seat or storage on the interior beneath the glass.

These types of windows make a stunning presentation on both the interior and exterior of the home. Because they offer a greater range of positioning and angles, they allow more light to enter the home, and give you a larger view into the outdoors.

For this discussion, we will consider the cost of installing a new full bay window of 4-foot, 8-inches by 4-foot, 6-inches, which averages $3,060. However, there are a number of different types and sizes of bay windows, which can affect the final cost of installation. The size of the window, the angle at which it protrudes, whether or not you include a window seat, the material the window is made of, and whether this is an existing window that you are replacing or new construction can all impact the final cost as well.

Location

Bay windows ¹ extend outward from the house, which means that they need additional support. When considering the location for your bay window ¹, you need to look not only at where you want it aesthetically, but also where it will fit functionally. The area you install your bay window ¹ in must have an eave ² or an overhang from the roof directly above it. If you do not have this eave ² already there, it will need to be built, which can dramatically increase costs of the final installation, by as much as $2000. The size of the eave ² will dictate what angle your window can protrude to. An eave ² measuring 12-14 inches can support a 30 degree bay, while an eave ² that is 16-22 inches can support a 45 degree bay; anything larger will require an eave ² at least 18-24 inches deep.

For aesthetic reasons, you’ll want to choose a location that offers the best views, not only from the interior as you sit and read the paper on the ledge, but also from the exterior. Bay windows ¹ can dramatically increase the curb appeal of your home, so you’ll want to ensure they can be seen from the street. Common rooms to add them to include:

• Living rooms
• Bedrooms
• Dens
• Libraries
• Family rooms

Types of bay windows

While it’s become commonplace to call any type of window that curves or extends outward from the house a “bay” there are actually different types:

Bow window

A bow window is three or more windows that curve outward from the house in a smooth line. They may or may not include any seat or ledge below them, and there is usually space or support between each of the windows. This type of window can be installed in more places than a traditional bay, because it requires less support. Bow windows cost between $1,500 and $3,500.

Box bay window

A box bay window ¹ extends outward like a traditional bay or bow, but does not curve or create an angle to do so. Instead, a “box” or square addition is put onto the home with three flat windows installed in a row at the front. A box bay extends the living space of the room slightly, and will usually have its own roof or eave ² installed above it. Expect to pay around $2,500 to $3,200 for a box bay window ¹.

Full bay window​

A full bay window ¹ involves three or more windows that extend outward, usually with a ledge or seat indoors. The windows on the side are generally set at an angle to the center window, which is installed parallel to the house. Full bay windows ¹ don’t increase living space, but do give you more use of the window area by including a seat or storage. Expect to pay $1,200 to $3,000 for a standard full bay.

Materials

The type of material your bay window ¹ is made from can affect its cost, its appearance, and its longevity. There are four basic materials that are used for bay window ¹ construction:

• Vinyl ³: vinyl ³ is the least expensive material for bay windows ¹, which makes it a popular choice with many homeowners. Vinyl ³ is also extremely low maintenance, requiring no painting, scraping, or other work, but both the interior and exterior frame is made of vinyl ³, which is not as aesthetically pleasing as some other materials. Vinyl ³ is not a good insulator, so cold weather climates may require additional insulation around the frame as well. Typical costs for a window measuring 4-feet, 8-inches by 4-feet, 6-inches are around $1,400.
• Wood: wood is always a popular choice for window frames for its beauty and versatility. You can have custom windows built in wood of any shape and size, and you can paint or stain the frames to match the rest of your decor. Wood is a better insulator than vinyl ³, but it does require a lot of maintenance including painting, scraping, and caulking ⁴ on a regular basis. Wood is generally mid-range in price, costing more than vinyl ³. Typical costs for a window measuring 4-feet, 8-inches by 4-feet, 6-inches are around $2,000
• Fiberglass ⁵: fiberglass ⁵ is one of the newest materials for window frames. It’s extremely durable, versatile, low maintenance, and a good insulator. It comes in more choices than vinyl ³, and some types can be painted for a more custom look. This is the most expensive choice for window frames, and it may not be available in every size window. Typical costs for a window measuring 4-feet, 8-inches by 4-feet, 6-inches are around $3,000.
• Aluminum: aluminum is also a very popular choice for windows, as it can help increase the value of your home once installed. Aluminum is low maintenance, durable, a good insulator, and comes in a wide range of sizes. Colors and styles may be more limited, however, than with wood or fiberglass ⁵. Aluminum is generally mid-range in pricing. Typical costs for a window measuring 4-feet, 8-inches by 4-feet, 6-inches  are around $2,500.

Labor

Most window installers can make the necessary arrangements to install a bay window ¹ on your home. Depending on the existing area, labor can be as simple as exchanging the windows, or as complex as cutting and reframing the walls of your home and building a new roof over the area. If you are also adding eaves ² or a roof to the area above the window, you may need to hire a roofer to finish the area as well. Expect to pay $500 to $700 for window installation if you have an existing bay or bow window you are replacing, and $1000 to $2000 for installation if this is a new bay window ¹, which requires support, framing, and finish work to complete. If you need to hire a roofer to complete the job, expect to pay $45 to $75 an hour for the work.​

New installation vs replacement

While you can convert any existing window into a bay window ¹, keep in mind that the more labor that needs to be done, the greater the final cost. Exchanging an existing bay window ¹ for a newer version with better insulated glass and frame will be the lowest cost and labor, while building out a new box window and roof will be the most costly. Expect new installation to take 2 to 3 days to complete; replacements can generally be done in 4 to 6 hours.

Enhancement and improvement costs

Removal, disposal, and cleanup

Depending on the extent of the project, you may need to factor in removal of old windows, construction debris, and cleanup of the property. For many replacement window jobs, this is included in the cost of installation. For larger jobs, such as the opening of a wall and the building out of a box, you may need to pay additional removal and disposal fees of $200 or more. Check with your installer to find out what may be included.

Opening up of a wall

If you are converting a single window to a bay window ¹, keep in mind that more serious construction will be necessary on your home. This will include locating studs and load bearing walls, relocating these if necessary, and opening up the existing wall to make way for the new window. Your home may be open to the elements for one to two days during this time, although plastic sheeting may be used to cover the area until the new window is installed. This type of work can increase costs by $500 to $1500.

Energy efficient glass

If you live in a cold climate, you may want to consider triple insulated glass with a low-e coating to help improve the energy efficiency of your home by 15 to 25%. Most windows are available with this option, at an additional cost of 25 to 30% - or between $300 and $600 more.

Interior trimming

If you do not already have an existing bay window ¹ you are replacing, you may want to trim and finish out the interior to complete the look. This includes things like building a window seat or storage bench, adding window frames, or ledges. You may need to hire a carpenter to do this work at a cost of $70 an hour, or $840 to $1680 to build a window seat.

Remodeling Terms Cheat Sheet

³ Vinyl: A synthetic plastic made from ethylene and chlorine. Vinyl has many applications in the construction industry and it is widely used in sidings, window frames, roofing and gutters, among others

⁴ Caulking: A chemical sealant used to fill in and seal gaps where two materials join, for example, the tub and tile, to create a watertight and airtight seal. The term "caulking" is also used to refer to the process of applying this type of sealant

⁵ Fiberglass: Plastic that is reinforced with glass fibers. The fibers may be mixed randomly throughout the plastic, or come in the form of a flat sheet, or be woven into a fabric