How a Bay Window is Installed

Video Transcript

Video Transcript

This window is one of my favorite features in the house. The morning light coming through there is just beautiful. And it's a terrific place to sit and take in the view, and I think I found a way to make a good thing even better.

I'm going to install a bay window. Now that's going to do a couple of things for me. It's going to make this whole area even more inviting and make the living room actually feel larger. But there's one thing that's very important to me. I want this new window to complement the other windows in the house and look as though it's always been there.

I've been working with the folks at Pella Windows for years. So I decided to go to their website and see what's available, as well as what's involved in the installation of a window like this. After checking things out, and considering the size and weight of the unit I want, well, I've decided this is a job I'm leaving to the pros.

So I give the local dealer a call and the next day, Chad Bock stops by to take a look at the existing window, make some basic measurements, and go over the options with me. We settle on a style and size, and a few days later, Don Olson drops by to get more detailed dimensions and verify my order.

He also checks for any potential problems, and finds one. Dry rot on the sill. He'll let the installers know about this ahead of time. Don writes up the order and sends it off to the Pella factory, where my window will be custom made.

It arrives a few weeks later, along with the installers. Meet the Demers, Ron Sr. and sons Ron Jr., Rich and Robert. This family of contractors wastes no time in getting started. They begin by removing the sash stops holding the windows in place, first on the sides, then on top.

Then they pry loose the sash tracks, bend them inward and remove both sashes and tracks as one piece. Next, the storm windows are taken out from the inside. Then Ron Sr. loosens the large center pane by tapping it from the outside.

The boys tilt it inward, lift it out of the frame and carry it away. Now it's time to pry off the interior sill, and the window casings. Outside, Ron Jr. removes the last of the storm window frames. Then he and his brothers start taking off the exterior trim.

Now the whole family gets in the act, lifting the window frame out of the rough opening. Remember that dry rot that Don discovered during his first inspection? Removing a few of the shingles below the window gives some idea how extensive the damage is.

Right here, the plywood sheeting is in pretty bad shape, but the damage has not spread far. The fix involves cutting away a strip of sheathing -- and replacing it with a new section.

Probably the most crucial step in installing any window or door is creating a stable, flat and level surface upon which the frame can rest. A one-by-four, shimmed every few feet and screwed securely in place, will do the trick. The new window will be well sealed to prevent any moisture from getting inside.

As an additional precaution, this aluminum tape with a rubberized backing is applied to the bottom of the rough opening, and run up the sides a few inches.

Well, the old window's out, that dry rot has been repaired and the flashing tape's been put on to keep it from happening again. Now one of the great things about working with a team of pros is that this entire process took less than two hours and we're ready now to put in the new window.

All of the window panes and sashes have been removed from the frame to make it easier to handle. Still, it takes two -- uh, make that three -- sturdy installers to set the unit in place. While dad and the two younger sons hold the frame in position, Ron Jr. drives in some screws to temporarily fasten everything.

Outside, Robert attaches support cable clamps to the solid wood header above the window opening. Then, he threads a support cable through, and when the window deck is level, tightens the cable clamp. A second clamp and cable hold the other side.

With the frame attached and level, the center fixed window can be set in position and secured in place. The double-hung sashes just snap into the frame and tilt up. Finally, shims are inserted into the space between the top of the frame and the rough opening and the unit is screwed permanently into place.

Well, that pretty much completes the structural part of the installation. Now we're gonna be moving onto some framing work for the roof and some finish and trim work. Now up to this point, the total elapsed time is only about three and a half hours.

Ron and Rich Demers have framed up the roof cap and are ready to hoist it into place. Once it's in position, Ron Sr. and Rob attach it. Then the interior space is filled with fiberglass insulation and plywood decking is nailed to the rafters. Next, wood trim is applied and metal drip cap is nailed along the edge. Roofing paper, or some call it roofing felt, is then laid over the plywood sheathing and attached.

Notice how the paper is run up onto the wall a couple of inches. Rubber-backed metal tape is applied over the edge of the roofing felt, to seal it against the wall. The first, or starter, row of shingles is attached upside down, with a second layer placed on top, right side up.

Then each subsequent row overlaps the one below. As additional protection against leaks where the roof cap meets the wall, short sections of metal flashing called step flashing, are installed. These are put in place one at a time and alternated with the shingles.


Once the last course of shingles is in place, a strip of metal flashing is attached at the very top of the roof cap. When the wood wall shingles are reinstalled, they're placed on top of the flashing.

Next, strips of wood trim are attached to the bottom of the bay, forming a sort of box. Rigid foam insulation is pushed up into the cavity, and an outer plywood cover is nailed over it. Finally, decorative wooden braces or corbels are attached to the framing below the bay, giving it additional support and the replacement, pre-primed shingles are slipped into place.

Well, the guys are almost finished out here. Now notice how that shingle roof cap sort of ties everything into the house? I mean that's going to look like it's always been here. Now, let's go inside and see what the effect has been there.

Wow [LAUGHS] -- now I knew that that window was going to open up this end of the room, but I had no idea how much. I mean that actually looks like we've moved the entire wall out about two feet.

Now these windows are state-of-the-art when it comes to thermal efficiency. Two panes of insulated glass. And even though I've got all that efficiency, I've still retained a traditional look with these two divided lights.

Now this frame is wood. Now here's something I didn't know, but wood has over 1000 times the insulating value of aluminum. And so, the window itself is about as insulated as it could be. But it's also important to insulate the installation.

As you can see when we were outside, we insulated the roof cap up here and then also underneath the deck right here. But there's one more place that we have to seal up, and that's right here.

The space between the edge of the window frame and the wall framing is insulated with a spray foam sealant that will provide a barrier against heat loss and cold intrusion. Now for the icing on the cake. First, a pre-finished deck panel is laid in place and attached.

Then a similar panel gets installed overhead. Trim strips are attached to the sides of the frame and applied over any exposed joints. Finally, everything is finished with decorative casing. One of the things I really like about these windows is how very easy they are to clean.

Everything is done from the inside. Each sash is hinged at the bottom. I just tip them down to reach the outside panes, then snap them back in place. Out in my truck, I've got the screens. Now these are not your ordinary insect barriers. They're what Pella calls high transparency window screens. Once they're in place, they block almost no light and are practically invisible.

Now, if ever there was a case of having your cake and eating it too, well, I've got to think this bay window is it. It's energy efficient, got a low E coating on the glass to reduce fading on carpets and upholstery, it's practically maintenance free on the outside with that aluminum cladding and it's convenient to clean.

Now, to boot, I got that traditional look that I wanted. That window seems like it's always been there and I've opened up the room and brought in more light.

Learn how to repair dry rot and install a new bay window to make your room more inviting.

An existing living room window admits beautiful morning light and frames a favorite scene, bringing the charm of the garden inside this home while leaving the weather and wildlife outside. As much as the view, however, a window's size and style can add ambience and grace to any room. Follow this project as we replace a flat window and its accompanying dry rot with a state-of-the-art bay window to make the room feel larger and more inviting. The new window provides more insulation, enhances the inside decor and compliments the other windows as seen from the outside of the house. On completion, it looks as though it has always been there.

Determine What Is Involved in the Bay Window Installation
Step 1

Determine What Is Involved in the Bay Window Installation

Take careful measurements and send dimensions for the custom-made bay window to the factory. Research what is involved in an installation. The size, weight, and complexity of this installation along with dry rot repair require help from a professional contractor.

Remove the Wooden Trim Holding the Old Window and Screens
Step 2

Remove the Wooden Trim Holding the Old Window and Screens

Remove the sash-stops, sashes and tracks, storm windows, and the large center pane for disposal. Pry off the interior sill and window casings. Take off the storm window frames and exterior trim. Lift the window frame from the rough opening.

Pry off Shingles beneath the Window to Examine Dry Rot
Step 3

Pry off Shingles beneath the Window to Examine Dry Rot

Determine the extent of the dry rot beneath the shingles and plywood sheathing under the window. In this project, the dry rot is isolated. Cut away the damaged sheathing and replace it with a new section.

Create a Stable Level Surface for the New Window Frame
Step 4

Create a Stable Level Surface for the New Window Frame

Install a one-by-four base for the bay window frame to rest on, leveling it with shims and securing it with screws. Apply aluminum flashing tape to the bottom and sides of the rough opening to seal out moisture.

Position the New Bay Window in the Opening
Step 5

Position the New Bay Window in the Opening

Remove window panes and sashes from the bay window frame to reduce weight. Set it in place. Attach and tighten support cable clamps to the solid header above the window opening once the window is level. Add remaining window components.

Level and Secure the Bay Window Frame in the Opening
Step 6

Level and Secure the Bay Window Frame in the Opening

Insert shims between the top of the bay window frame and the rough opening to level it. Do this from the inside of the window. Secure the window permanently by driving screws through the shims and into the wall.

Frame and Install the Roof Cap for the Bay Window
Step 7

Frame and Install the Roof Cap for the Bay Window

Construct and install the bay window roof cap. Insulate the interior with fiberglass and waterproof it with drip caps, roofing felt, aluminum flashing tape, asphalt shingles, and step-flashing before replacing the wooden house shingles along the upper edge.

Finish the Bottom of the Bay Window with Insulation and Corbels
Step 8

Finish the Bottom of the Bay Window with Insulation and Corbels

Use strips of wood trim to form a shallow tray for rigid foam insulation at the bottom of the bay window. Secure an outer plywood cover with nails. Add decorative wooden braces/corbels for additional support. Replace the wooden wall shingles.

Insulate the Interior Space between the Bay Window and Wall
Step 9

Insulate the Interior Space between the Bay Window and Wall

Insulate the space between the window frame and wall framing with spray foam sealant that expands to form a barrier against heat loss and cold intrusion. It will be hidden beneath trim when the bay window installation is complete.

Trim the Bay Window Interior and Add High-transparency Screens
Step 10

Trim the Bay Window Interior and Add High-transparency Screens

Dress the bay window interior with a pre-finished top and bottom panel. Add trim at the sides and exposed joints and finish the edges with decorative casing. Finish with high-transparency window screens that block very little light and are nearly invisible.