How to Build a Bay Window? (Step-By-Step Tutorial)

Do you currently have a bay window in your home? If not, then you’re missing out on the cozy feeling that it provides. Regardless of the size of your house, a bay window can enhance the quality of life of its residents by letting in natural light and giving outdoor views.

If you want to take advantage of all that it has to offer, you may want to know how to build a bay window. Luckily for you, the process isn’t as complicated as some people think it is. Though you would want a helping as it isn’t a one-person job.

How to Build a Bay Window?

Follow these steps to build a bay window on your own:

Step 1: Gather the Supplies

At the cost of scaring you away, you need at least eighteen tools to build a bay window. All of them come handy during the manufacturing phase, so you shouldn’t skip any. Having cited this cautionary note, here are the supplies need to build a bay window:

Tape measure Roof shingles Circular saw
Hammer Lumber Nails
Support braces Level Shims
Screws Windows Insulation
Roof sheeting Shingles Plywood
Caulking Roofing paper Cap flashing

Step 2: Decide the angle of the window

You have the option to build bay windows at two ranges of angles. They include standard bay windows (40 to 50-degree angle) and box bay windows (90-degree angle).

Step 3: Go through your local safety code

If you don’t want to bury your head in statute books, consult your local building inspector. They are the best person to let you know more about the safety code requirements that you may have to follow when building a bay window.

Step 4: Remove the existing window

Remove the existing window

Go towards the outside-facing side of the window, and measure the area where you’re going to install a new one. Note down the measurements in a notebook. Then take off the sash, tracks, and sash stops of the existing window before removing it.

Step 5: Building and installing the frame

Building and installing the frame

If your existing window is smaller than that of the upcoming one, you’d have to enlarge the opening’s size so that it could accommodate the box window. If the need arises, make more room by cutting through the existing studs using a circular saw.

Once you’ve made enough space, the next step would be building the box window’s frame. Once you’ve created the structure and placed it in the opening, install blocks and studs for support.

Step 6: Adding the window to the frame

Adding the window to the frame

To install the window into the frame, install support braces to the sill of the frame. Once you’re sure that the braces are secure, lift the box window and place it on top of them. To make sure that the window is level, use shims. Then screw it into the frame.

Step 7: Making the roof frame

Making the roof frame

Start with constructing the roof frame and once you’ve built it, nail it to the frame of the bay window. Follow up by installing plywood decking. At this time, you’ll be able to see some space between the window and the roof frame. Fill it with insulation.

On top of the insulation, attach roof sheeting and then cover it with roofing paper. Follow it up by attaching shingles one after the other (in an overlapping pattern).

Step 8: Final Step

Final Step

As you already have the window in place, this step would involve applying caulking around its edges so as to make it waterproof and airtight. Do this step with extreme caution, or else, in the event of rain, water might come inside your home.

Types of Bay Window

Following are the common types of bay window:

1. Box Bay Window

Box Bay Window

Boosting a 90-degree angle, box windows have one big window in the center and smaller windows on both sides. More often than not, they are placed below your eye line. They are mostly used in kitchens and are very economical to build and to purchase.

Provided you want to open up space in your home but don’t have the stomach to reposition any walls, box bay windows are undoubtedly worthy of your attention.

2. Oriel Bay Window

Oriel Bay Window

In contrast to box bay windows which are mostly placed on the ground floor, oriel bay windows are commonly installed on upper stories. Most people put them over the entrance of their home.

They are usually supported by corbels, stone, or brick brackets. Provided you live in an area where the far view is better than the near one, oriel bay windows are a must-have.

3. Circle Bay Window

Circle Bay Window

On the one hand, circle bay windows are larger than the oriel style. On the other, they are more decorated than the box style. Also, since they have more panes than box bay, they can feature more intricate patterns.

Apart from being up to six feet high, these windows can jut outwards by up to three feet. It is this design that allows them to transmit maximum sunlight into your home.

4. Bow Bay Window

Bow Bay Window

In contrast to all the other bay window styles, bow windows ditch the straight-sided pattern in favor of a curved one. To build them, you’d have to attach four (or more) casement windows.

This bay window style provides two benefits. First, it increases the appeal of your building’s exterior. Second, it expands the building’s inner space while also brightening it up.


Whether you want to increase the appeal of your building’s exterior, looking for more light to make its way inside the building, or just want to expand its inner space, you need to know how to build a bay window on your own.

While the process is not easy as you have seen by now – as you to remove the existing frame, build two new frames, and attach shingles, among other steps – the benefits that a bay window will provide will make your entire effort worth it.

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