Bay window replacement means taking out a projecting window unit, seat, head and all, and putting a new one in its place. We handle bay window replacement in St. Joseph for both bays and bows, on everything from Victorian parlors to 1960s ranch living rooms. Before anything is ordered we check the support, the roof over the unit and the framing under the seat, so the new window sits level and stays dry for years.
Bay windows and bow windows: what's being replaced
A bay window is usually three windows: a large center unit with two narrower side windows set at an angle, most often 30 or 45 degrees. A bow window is four or more windows of equal size joined in a gentle curve. Both stick out past the wall, so each one is really a small structure. It has a head board on top and a seat board at the bottom, a support system (cables to the framing above, or brackets underneath), and a roof or cap that has to shed water.
Replacement takes the whole assembly out and sets a factory-built unit in its place. The side windows can be fixed glass, or casements or double-hungs that open. In St. Joseph's older houses, casements were often built into bays and sun porches, and many bays on Victorian houses have their own metal roof.
When bay window replacement is the right call
- Sagging. The seat has dropped, a gap has opened along the top, or the window no longer looks level against the siding.
- Soft wood in the seat board, the sill or under the unit outside.
- Water stains on the ceiling or wall near the bay, which usually point to the roof or flashing above it.
- Fogged panels that have lost their seal.
- A cold seat. If you can feel the draft through the seat board in winter, there is little or no insulation under it.
Why bay windows fail
A bay hangs its weight off the side of the house. Over decades the support cables stretch, brackets loosen and the framing it hangs from settles, and the whole unit tips outward. The little roof over it is easy to forget, so flashing goes unchecked until water finds its way in. Many older bays were also built with no insulation in the seat or head, which is why they feel so cold.
Same style, or something different?
Most people replace a bay with a bay, or a bow with a bow, since the opening and roof are already set up for it. Swapping one for the other is possible when the widths work. Replacing a projecting unit with a flat window is also possible, but it means new wall framing, siding or brick patching outside, and new drywall or plaster inside. We'll lay out what each choice involves, and if your house is in Museum Hill or Hall Street, a change of style there goes to the Landmark Commission first.
What moves the cost of a bay or bow
- The overall width and height, and how many panels it has.
- Fixed side windows versus side windows that open.
- The roof: re-shingling or capping the existing one, or building a new one.
- Seat and head boards, and the insulation under and over them.
- Support: new cables or brackets, or framing repair found when the old unit comes out.
- Interior trim and exterior finish, and whether it's on the first or second floor.
For the flat windows around it, see vinyl replacement windows. If the bay looks out onto the back yard, the patio door nearby is often worth pricing at the same visit.
Bay window questions
How much does it cost to replace a bay window?
It depends mostly on the size, how many panels it has, whether the side windows open, and what the seat, roof and support need once the old unit is out. A bay costs well more than a flat window of the same width because it is several windows joined into one structure. We price it after seeing it, and the cost page covers what changes the number.
How long does it take to replace a bay window?
The install itself is usually a day for a typical bay or bow. The longer part is the wait for the unit to be built, since each one is made to the measurements of your opening. Extra framing, roof or siding work found when the old unit comes out can add time.
How hard is it to install a bay window?
Harder than a flat window. A bay hangs off the wall, so it has to be supported, flashed into the siding or brick, and roofed. The head and seat boards have to be insulated, and the angles have to close up tight. It is a job for an installer who has done them, not a weekend project.
Does a bay window increase home value?
A bay that is sound, sealed and good-looking helps a house show well, and a rotting, sagging one is something every buyer notices. There is no reliable St. Joseph figure for how much value a new bay adds, so we wouldn’t promise a number. Replace it because it needs it, or because you want the room it gives.
Have your bay or bow window looked at
We'll check the support, roof and seat, and give you the options in writing.
Request an estimate